Evaluation of a QuECHERS-like extraction approach for the determination of PBDEs in mussels by immuno-assay-based screening methods

USDA-ARS?s Scientific Manuscript database

A sample preparation method was evaluated for the determination of polybrominated diphenyl ethers (PBDEs) in mussel samples, by using colorimetric and electrochemical immunoassay-based screening methods. A simple sample preparation in conjunction with a rapid screening method possesses the desired c...

Self-Referenced Smartphone-Based Nanoplasmonic Imaging Platform for Colorimetric Biochemical Sensing.

PubMed

Wang, Xinhao; Chang, Te-Wei; Lin, Guohong; Gartia, Manas Ranjan; Liu, Gang Logan

2017-01-03

Colorimetric sensors usually suffer due to errors from variation in light source intensity, the type of light source, the Bayer filter algorithm, and the sensitivity of the camera to incoming light. Here, we demonstrate a self-referenced portable smartphone-based plasmonic sensing platform integrated with an internal reference sample along with an image processing method to perform colorimetric sensing. Two sensing principles based on unique nanoplasmonics enabled phenomena from a nanostructured plasmonic sensor, named as nanoLCA (nano Lycurgus cup array), were demonstrated here for colorimetric biochemical sensing: liquid refractive index sensing and optical absorbance enhancement sensing. Refractive indices of colorless liquids were measured by simple smartphone imaging and color analysis. Optical absorbance enhancement in the colorimetric biochemical assay was achieved by matching the plasmon resonance wavelength with the chromophore's absorbance peak wavelength. Such a sensing mechanism improved the limit of detection (LoD) by 100 times in a microplate reader format. Compared with a traditional colorimetric assay such as urine testing strips, a smartphone plasmon enhanced colorimetric sensing system provided 30 times improvement in the LoD. The platform was applied for simulated urine testing to precisely identify the samples with higher protein concentration, which showed potential point-of-care and early detection of kidney disease with the smartphone plasmonic resonance sensing system.

A simple and rapid creatinine sensing via DLS selectivity, using calix[4]arene thiol functionalized gold nanoparticles.

PubMed

Sutariya, Pinkesh G; Pandya, Alok; Lodha, Anand; Menon, Shobhana K

2016-01-15

A new, simple, ultra-sensitive and selective approach has been reported for the "on spot" colorimetric detection of creatinine based on calix[4]arene functionalized gold nanoparticles (AuNPs) with excellent discrimination in the presence of other biomolecules. The lower detection limit of the method is 2.16nM. The gold nanoparticles and p-tert-butylcalix[4]arene were synthesized by microwave assisted method. Specifically, in our study, we used dynamic light scattering (DLS) which is a powerful method for the determination of small changes in particle size, improved selectivity and sensitivity of the creatinine detection system over colorimetric method. The nanoassembly is characterized by Transmission electron microscopy (TEM), DLS, UV-vis and ESI-MS spectroscopy, which demonstrates the binding affinity due its ability of hydrogen bonding and electrostatic interaction between -NH group of creatinine and pSDSC4. It exhibits fast response time (<60s) to creatinine and has long shelf-life (>5 weeks). The developed pSDSC4-AuNPs based creatinine biosensor will be established as simple, reliable and accurate tool for the determination of creatinine in human urine samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Simple, field portable colorimetric detection device for organic peroxides and hydrogen peroxide

DOEpatents

Pagoria, Philip F.; Mitchell, Alexander R.; Whipple, Richard E.; Carman, M. Leslie; Reynolds, John G.; Nunes, Peter; Shields, Sharon J.

2010-11-09

A simple and effective system for the colorimetric determination of organic peroxides and hydrogen peroxide. A peroxide pen utilizing a swipe material attached to a polyethylene tube contains two crushable vials. The two crushable vials contain a colorimetric reagent separated into dry ingredients and liquid ingredients. After swiping a suspected substance or surface the vials are broken, the reagent is mixed thoroughly and the reagent is allowed to wick into the swipe material. The presence of organic peroxides or hydrogen peroxide is confirmed by a deep blue color.

Colorimetric detection of trivalent chromium in aqueous solution using tartrate-capped silver nanoparticles as probe.

PubMed

Xu, Yunbo; Dong, Yangjun; Jiang, Xue; Zhu, Ningning

2013-10-01

This study describes a simple and highly selective method for the colorimetric detection of trivalent chromium (Cr3+) using tartrate-capped silver nanoparticles (AgNPs) as probe. The addition of tartrate to the initially prepared AgNPs gives tartrate-stabilized AgNPs ascribing to the electrostatic repulsion of the highly negatively charged tartrate ions covered on the surface of AgNPs. It is found that, in the presence of Cr3+ in aqueous solution, the aggregation of tartrate-stabilized AgNPs occurs. The color of AgNPs suspension changes from yellow to pink and the surface plasmon absorption band broadens and red shifts, which could be applied for the colorimetric detection of Cr3+ in aqueous solution. The utilization of tartrate-stabilized AgNPs as probe substantially increases the selectivity and sensitivity for colorimetric detection of Cr3+. Control experiments with the addition of over 14 other metal ions, such as Pb2+, Zn2+, Cr2O7(2-), Cd2+, Co2+, Cu2+, Al3+, Ni2+, Mn2+, Ba2+, Fe3+, Ca2+, Mg2+, Sr+ do not result in a distinct change in the color or in the spectrum of the suspension, indicating that these metal ions do not interfere with the colorimetric detection of Cr3+. Under the conditions employed here, A502/A393 (ratio of absorption value at 502 nm to 393 nm) is linear with the concentration of Cr3+ within a concentration range from 0.1 to 1.17 microM with a detection limit of 0.06 microM. This study may offer a simple, rapid and sensitive approach to colorimetric detection of Cr3+ in aqueous solution.

A simple and highly sensitive colorimetric detection method for gaseous formaldehyde.

PubMed

Feng, Liang; Musto, Christopher J; Suslick, Kenneth S

2010-03-31

A colorimetric detection method using amine-functionalized polymer films doped with a pH indicator has been developed for the rapid, sensitive, and quantitative detection of gaseous formaldehyde at concentrations well below the immediately dangerous to life or health (IDLH) limit. In 1 min, visible color changes are easily observed, even down to the permissible exposure limit (PEL) at 750 ppb. The limit of detection is below 50 ppb (7% of the PEL) after 10 min of exposure. This sensor is essentially unaffected by changes in humidity or temperature (4 to 50 degrees C) and is not sensitive to common interferents.

A highly sensitive and selective aptamer-based colorimetric sensor for the rapid detection of PCB 77.

PubMed

Cheng, Ruojie; Liu, Siyao; Shi, Huijie; Zhao, Guohua

2018-01-05

A highly sensitive, specific and simple colorimetric sensor based on aptamer was established for the detection of polychlorinated biphenyls (PCB 77). The use of unmodified gold nanoparticles as a colorimetric probe for aptamer sensors enabled the highly sensitive and selective detection of polychlorinated biphenyls (PCB 77). A linear range of 0.5nM to 900nM was obtained for the colorimetric assay with a minimum detection limit of 0.05nM. In addition, by the methods of circular dichroism, UV and naked eyes, we found that the 35 base fragments retained after cutting 5 bases from the 5 'end of aptamer plays the most significant role in the PCB 77 specific recognition process. We found a novel way to truncated nucleotides to optimize the detection of PCB 77, and the selected nucleotides also could achieve high affinity with PCB 77. At the same time, the efficient detection of the PCB 77 by our colorimetric sensor in the complex environmental water samples was realized, which shows a good application prospect. Copyright © 2017 Elsevier B.V. All rights reserved.

Detection of proteins using a colorimetric bio-barcode assay.

PubMed

Nam, Jwa-Min; Jang, Kyung-Jin; Groves, Jay T

2007-01-01

The colorimetric bio-barcode assay is a red-to-blue color change-based protein detection method with ultrahigh sensitivity. This assay is based on both the bio-barcode amplification method that allows for detecting miniscule amount of targets with attomolar sensitivity and gold nanoparticle-based colorimetric DNA detection method that allows for a simple and straightforward detection of biomolecules of interest (here we detect interleukin-2, an important biomarker (cytokine) for many immunodeficiency-related diseases and cancers). The protocol is composed of the following steps: (i) conjugation of target capture molecules and barcode DNA strands onto silica microparticles, (ii) target capture with probes, (iii) separation and release of barcode DNA strands from the separated probes, (iv) detection of released barcode DNA using DNA-modified gold nanoparticle probes and (v) red-to-blue color change analysis with a graphic software. Actual target detection and quantification steps with premade probes take approximately 3 h (whole protocol including probe preparations takes approximately 3 days).

Label-free detection of specific DNA sequence-telomere using unmodified gold nanoparticles as colorimetric probes

NASA Astrophysics Data System (ADS)

Qi, Yingying; Li, Li; Li, Baoxin

2009-09-01

A simple and sensitive label-free colorimetric detection of telomere DNA has been developed. It was based on the color change of gold nanoparticles (AuNPs) due to DNA hybridization. UV-vis spectra and transmission electron microscopy (TEM) were used to investigate the change of AuNPs. Under the optimized conditions, the linear range for determination of telomere DNA was 5.7 × 10 -13 to 4.5 × 10 -6 mol/L. The detection limit (3 σ) of this method has decreased to pico-molar level.

Fabrication of a Paper-Based Microfluidic Device to Readily Determine Nitrite Ion Concentration by Simple Colorimetric Assay

ERIC Educational Resources Information Center

Wang, Bo; Lin, Zhiqiang; Wang, Min

2015-01-01

Paper-based microfluidic devices (µPAD) are a burgeoning platform of microfluidic analysis technology. The method described herein is for use in undergraduate and high school chemistry laboratories. A simple and convenient µPAD was fabricated by easy patterning of filter paper using a permanent marker pen. The usefulness of the device was…

A Simple Assay for Ultrasensitive Colorimetric Detection of Ag⁺ at Picomolar Levels Using Platinum Nanoparticles.

PubMed

Wang, Yi-Wei; Wang, Meili; Wang, Lixing; Xu, Hui; Tang, Shurong; Yang, Huang-Hao; Zhang, Lan; Song, Hongbo

2017-11-02

In this work, uniformly-dispersed platinum nanoparticles (PtNPs) were synthesized by a simple chemical reduction method, in which citric acid and sodium borohydride acted as a stabilizer and reducer, respectively. An ultrasensitive colorimetric sensor for the facile and rapid detection of Ag⁺ ions was constructed based on the peroxidase mimetic activities of the obtained PtNPs, which can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce colored products. The introduced Ag⁺ would be reduced to Ag⁰ by the capped citric acid, and the deposition of Ag⁰ on the PtNPs surface, can effectively inhibit the peroxidase-mimetic activity of PtNPs. Through measuring the maximum absorption signal of oxidized TMB at 652 nm, ultra-low detection limits (7.8 pM) of Ag⁺ can be reached. In addition to such high sensitivity, the colorimetric assay also displays excellent selectivity for other ions of interest and shows great potential for the detection of Ag⁺ in real water samples.

Combined enzymatic and colorimetric method for determining the uronic acid and methylester content of pectin: Application to tomato products.

PubMed

Anthon, Gordon E; Barrett, Diane M

2008-09-01

A simple procedure for determining the galacturonic acid and methanol contents of soluble and insoluble pectins, relying on enzymatic pectin hydrolysis and colorimetric quantification, is described. Pectin samples are incubated with a commercial pectinase preparation, Viscozyme, then the galacturonic acid content of the hydrolyzed pectin is quantified colorimetrically using a modification of the Cu reduction procedure originally described by Avigad and Milner. This modification, substituting the commonly used Folin-Ciocalteau reagent for the arsenic containing Nelson reagent, gives a response that is linear, sensitive, and selective for uronic acids over neutral sugars. This method also avoids the use of concentrated acids needed for the commonly used m-phenylphenol method. Methanol, released by the action of the pectin methylesterase found in the Viscozyme, is quantified using alcohol oxidase and Purpald. This combined enzymatic and colorimetric procedure correctly determined the galacturonic acid and methanol content of purified, soluble citrus pectin. Application of the procedure to water insoluble pectins was evaluated with water insoluble material from apples and oranges. In both cases good agreement was obtained between this method and commonly used methods based on chemical pectin hydrolysis. Good agreement between these procedures was also found in the analysis of both soluble and insoluble pectins from several tomato products. Copyright © 2008 Elsevier Ltd. All rights reserved.

Real-time monitoring of enzyme-free strand displacement cascades by colorimetric assays

NASA Astrophysics Data System (ADS)

Duan, Ruixue; Wang, Boya; Hong, Fan; Zhang, Tianchi; Jia, Yongmei; Huang, Jiayu; Hakeem, Abdul; Liu, Nannan; Lou, Xiaoding; Xia, Fan

2015-03-01

The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications.The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications. Electronic supplementary information (ESI) available: Experimental procedures and analytical data are provided. See DOI: 10.1039/c5nr00697j

One-tube loop-mediated isothermal amplification combined with restriction endonuclease digestion and ELISA for colorimetric detection of resistance to isoniazid, ethambutol and streptomycin in Mycobacterium tuberculosis isolates.

PubMed

Lee, Mei-Feng; Chen, Yen-Hsu; Hsu, Hui-Jine; Peng, Chien-Fang

2010-10-01

In this study, we designed a simple and rapid colorimetric detection method, a one-tube loop-mediated isothermal amplification (LAMP)-PCR-hybridization-restriction endonuclease-ELISA [one-tube LAMP-PCR-HY-RE-ELISA] system, to detect resistance to isoniazid, ethambutol and streptomycin in strains of Mycobacterium tuberculosis isolated from clinical specimens. The clinical performance of this method for detecting isoniazid-resistant, ethambutol-resistant and streptomycin-resistant isolates of M. tuberculosis showed 98.9%, 94.3% and 93.8%, respectively. This assay is rapid and convenient that can be performed within one working day. One-tube LAMP-PCR-HY-RE-ELISA system was designed based on hot spot point mutations in target drug-resistant genes, using LAMP-PCR, hybridization, digestion with restriction endonuclease and colorimetric method of ELISA. In this study, LAMP assay was used to amplify DNA from drug-resistant M. tuberculosis, and ELISA was used for colorimetrical determination. This assay will be a useful tool for rapid diagnosis of mutant codons in strains of M. tuberculosis for isoniazid at katG 315 and katG 463, ethambutol at embB 306 and embB 497, and streptomycin at rpsL 43. Crown Copyright © 2010. Published by Elsevier B.V. All rights reserved.

Real-time monitoring of enzyme-free strand displacement cascades by colorimetric assays.

PubMed

Duan, Ruixue; Wang, Boya; Hong, Fan; Zhang, Tianchi; Jia, Yongmei; Huang, Jiayu; Hakeem, Abdul; Liu, Nannan; Lou, Xiaoding; Xia, Fan

2015-03-19

The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications.

Design of a dual-function peptide probe as a binder of angiotensin II and an inducer of silver nanoparticle aggregation for use in label-free colorimetric assays.

PubMed

Okochi, Mina; Kuboyama, Masashi; Tanaka, Masayoshi; Honda, Hiroyuki

2015-09-01

Label-free colorimetric assays using metallic nanoparticles have received much recent attention, for their application in simple and sensitive methods for detection of biomolecules. Short peptide probes that can bind to analyte biomolecules are attractive ligands in molecular nanotechnology; however, identification of biological recognition motifs is usually based on trial-and-error experiments. Herein, a peptide probe was screened for colorimetric detection of angiotensin II (Ang II) using a mechanism for non-crosslinking aggregation of silver nanoparticles (AgNPs). The dual-function peptides, which bind to the analyte and induce AgNP aggregation, were identified using a two-step strategy: (1) screening of an Ang II-binding peptide from an Ang II receptor sequence library, using SPOT technology, which enable peptides synthesis on cellulose membranes via an Fmoc method and (2) selection of peptide probes that effectively induce aggregation of AgNPs using a photolinker modified peptide array. Using the identified peptide probe, KGKNKRRR, aggregation of AgNPs was detected by observation of a pink color in the absence of Ang II, whereas AgNPs remained dispersed in the presence of Ang II (yellow). The color changes were not observed in the presence of other hormone molecules. Ang II could be detected within 15 min, with a detection limit of 10 µM, by measuring the ratio of absorbance at 400 nm and 568 nm; the signal could also be observed with the naked eye. These data suggest that the peptide identified here could be used as a probe for simple and rapid colorimetric detection of Ang II. This strategy for the identification of functional peptides shows promise for the development of colorimetric detection of various diagnostically important biomolecules. Copyright © 2015 Elsevier B.V. All rights reserved.

Silver nanoparticles-based colorimetric array for the detection of Thiophanate-methyl

NASA Astrophysics Data System (ADS)

Zheng, Mingda; Wang, Yingying; Wang, Chenge; Wei, Wei; Ma, Shuang; Sun, Xiaohan; He, Jiang

2018-06-01

A simple and selective colorimetric sensor based on citrate capped silver nanoparticles (Cit-AgNPs) is proposed for the detection of Thiophanate-methyl (TM) with high sensitivity and selectivity. The method based on the color change of Cit-AgNPs from yellow to cherry red with the addition of TM to Cit-AgNPs that caused a red-shift on the surface plasmon resonance (SPR) band from 394 nm to 525 nm due to the hydrogen-bonding and substitution. The density functional theory (DFT) method was also calculated the interactions between the TM and citrate ions. Under the optimized conditions, a linear relationship between the absorption ratio (A525nm/A394nm) and TM concentration was found in the range of 2-100 μM with correlation coefficient (R2) of 0.988. The detection limit of TM was 0.12 μM by UV-vis spectrometer. Moreover, the applicability of colorimetric sensor is successfully verified by the detection of TM in environmental samples with good recoveries.

A SIMPLE COLORIMETRIC METHOD TO DETECT BIOLOGICAL EVIDENCE OF HUMAN EXPOSURE TO MICROCYSTINS

EPA Science Inventory

Toxic cyanobacteria are contaminants of surface waters worldwide. Microcystins are some of the most commonly detected toxins. Biological evidence of human exposure may be difficult to obtain due to limitations associated with cost, laboratory capacity, analytic support, and exp...

Colorimetric determination of Timolol concentration based on localized surface plasmon resonance of silver nanoparticles

NASA Astrophysics Data System (ADS)

Amirjani, Amirmostafa; Bagheri, Mozhgan; Heydari, Mojgan; Hesaraki, Saeed

2016-09-01

In this work, a rapid and simple colorimetric method based on the surface plasmon resonance of silver nanoparticles (AgNPs) was developed for the detection of the drug Timolol. The method used is based on the interaction of Timolol with the surface of the as-synthesized AgNPs, which promotes aggregation of the nanoparticles. This aggregation exploits the surface plasmon resonance through the electric dipole-dipole interaction and coupling among the agglomerated particles, hence bringing forth distinctive changes in the spectra as well as the color of colloidal silver. UV-vis spectrophotometery was used to monitor the changes of the localized surface plasmon resonance of AgNPs at wavelengths of 400 and 550 nm. The developed colorimetric sensor has a wide dynamic range of 1.0 × 10-7 M-1.0 × 10-3 M for detection of Timolol with a low detection limit of 1.2 × 10-6 M. The proposed method was successfully applied for the determination of Timolol concentration in ophthalmic eye-drop solution with a response time lower than 40 s.

Copper-Based Metal-Organic Framework Nanoparticles with Peroxidase-Like Activity for Sensitive Colorimetric Detection of Staphylococcus aureus.

PubMed

Wang, Shuqin; Deng, Wenfang; Yang, Lu; Tan, Yueming; Xie, Qingji; Yao, Shouzhuo

2017-07-26

Cu-MOF nanoparticles with an average diameter of 550 nm were synthesized from 2-aminoterephthalic acid and Cu(NO 3 ) 2 by a mixed solvothermal method. The Cu-MOF nanoparticles can show peroxidase-like activity that can catalyze 3,3',5,5'-tetramethylbenzidine to produce a yellow chromogenic reaction in the presence of H 2 O 2 . The presence of abundant amine groups on the surfaces of Cu-MOF nanoparticles enables facile modification of Staphylococcus aureus (S. aureus) aptamer on Cu-MOF nanoparticles. By combining Cu-MOF-catalyzed chromogenic reaction with aptamer recognition and magnetic separation, a simple, sensitive, and selective colorimetric method for the detection of S. aureus was developed.

Simple and Rapid Determination of Ferulic Acid Levels in Food and Cosmetic Samples Using Paper-Based Platforms

PubMed Central

Tee-ngam, Prinjaporn; Nunant, Namthip; Rattanarat, Poomrat; Siangproh, Weena; Chailapakul, Orawon

2013-01-01

Ferulic acid is an important phenolic antioxidant found in or added to diet supplements, beverages, and cosmetic creams. Two designs of paper-based platforms for the fast, simple and inexpensive evaluation of ferulic acid contents in food and pharmaceutical cosmetics were evaluated. The first, a paper-based electrochemical device, was developed for ferulic acid detection in uncomplicated matrix samples and was created by the photolithographic method. The second, a paper-based colorimetric device was preceded by thin layer chromatography (TLC) for the separation and detection of ferulic acid in complex samples using a silica plate stationary phase and an 85:15:1 (v/v/v) chloroform: methanol: formic acid mobile phase. After separation, ferulic acid containing section of the TLC plate was attached onto the patterned paper containing the colorimetric reagent and eluted with ethanol. The resulting color change was photographed and quantitatively converted to intensity. Under the optimal conditions, the limit of detection of ferulic acid was found to be 1 ppm and 7 ppm (S/N = 3) for first and second designs, respectively, with good agreement with the standard HPLC-UV detection method. Therefore, these methods can be used for the simple, rapid, inexpensive and sensitive quantification of ferulic acid in a variety of samples. PMID:24077320

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation

NASA Astrophysics Data System (ADS)

Ragab, Gamal H.; Amin, Alaa S.

2004-03-01

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at λmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 μg ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

A C-di-GMP-proflavine-hemin supramolecular complex has peroxidase activity--implication for a simple colorimetric detection.

PubMed

Nakayama, Shizuka; Roelofs, Kevin; Lee, Vincent T; Sintim, Herman O

2012-03-01

Herein, we demonstrate that the bacterial signaling molecule, c-di-GMP, can enhance the peroxidation of hemin when proflavine is present. The c-di-GMP-proflavine-hemin nucleotidezyme can oxidize the colorless compound 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS, to the colored radical cation ABTS˙(+) and hence provides simple colorimetric detection of c-di-GMP at low micromolar concentrations.

Colorimetric assay of copper ions based on the inhibition of peroxidase-like activity of MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Chen, Huan; Li, Zhihong; Liu, Xueting; Zhong, Jianhai; Lin, Tianran; Guo, Liangqia; Fu, Fengfu

2017-10-01

The peroxidase-like catalytic activity of MoS2 nanomaterials has been utilized for colorimetric bioassays and medical diagnostics. However, the application of peroxidase-like catalytic activity of MoS2 nanomaterials in environmental analysis was seldom explored. Herein, copper ions were found to inhibit the peroxidase-like catalytic activity of MoS2 nanosheets, which can catalyze the oxidation of 3, 3‧, 5, 5‧-tetramethylbenzidine by H2O2 to produce a colorimetric product. Based on this finding, a simple sensitive colorimetric method for the detection of copper ions was developed. In the presence of copper ions, the absorbance and color of the solution decreased with the increasing concentration of copper ions. The color of the solution can be used to semi-quantitative on-site assay of copper ions by naked eyes. A linear relationship between the absorbance and the concentration of copper ions was observed in the range of 0.4-4.0 μmol L- 1 with a detection limit of 92 nmol L- 1, which was much lower than the maximum contaminant level of copper in drinking water legislated by the Environmental Protection Agency of USA and the World Health Organization. The method was applied to detect copper ions in environmental water samples with satisfactory results.

Use of a Simple, Colorimetric Assay to Demonstrate Conditions for Induction of Nitrate Reductase in Plants.

ERIC Educational Resources Information Center

Harley, Suzanne M.

1993-01-01

Nitrate assimilation by plants provides an excellent system for demonstrating control of gene expression in a eukaryotic organism. Describes an assay method that allows students to complete experiments designed around the measurement of nitrate reductase within a three-hour laboratory experiment. (PR)

Visual and highly sensitive detection of cancer cells by a colorimetric aptasensor based on cell-triggered cyclic enzymatic signal amplification.

PubMed

Zhang, Xianxia; Xiao, Kunyi; Cheng, Liwei; Chen, Hui; Liu, Baohong; Zhang, Song; Kong, Jilie

2014-06-03

Rapid and efficient detection of cancer cells at their earliest stages is one of the central challenges in cancer diagnostics. We developed a simple, cost-effective, and highly sensitive colorimetric method for visually detecting rare cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and linker DNAs stably coexist in solution, and the linker DNA assembles DNA-AuNPs, producing a purple solution. In the presence of target cells, the specific binding of HAPs to the target cells triggers a conformational switch that results in linker DNA hybridization and cleavage by nicking endonuclease-strand scission cycles. Consequently, the cleaved fragments of linker DNA can no longer assemble into DNA-AuNPs, resulting in a red color. UV-vis spectrometry and photograph analyses demonstrated that this CTCESA-based method exhibited selective and sensitive colorimetric responses to the presence of target CCRF-CEM cells, which could be detected by the naked eye. The linear response for CCRF-CEM cells in a concentration range from 10(2) to 10(4) cells was obtained with a detection limit of 40 cells, which is approximately 20 times lower than the detection limit of normal AuNP-based methods without amplification. Given the high specificity and sensitivity of CTCESA, this colorimetric method provides a sensitive, label-free, and cost-effective approach for early cancer diagnosis and point-to-care applications.

Surface plasmon resonance based selective and sensitive colorimetric determination of azithromycin using unmodified silver nanoparticles in pharmaceuticals and human plasma

NASA Astrophysics Data System (ADS)

Chavada, Vijay D.; Bhatt, Nejal M.; Sanyal, Mallika; Shrivastav, Pranav S.

2017-01-01

In this article we report a novel method for colorimetric sensing and selective determination of a non-chromophoric drug-azithromycin, which lacks native absorbance in the UV-Visible region using unmodified silver nanoparticles (AgNPs). The citrate-capped AgNps dispersed in water afforded a bright yellow colour owing to the electrostatic repulsion between the particles due to the presence of negatively charged surface and showed surface plasmon resonance (SPR) band at 394 nm. Addition of positively charged azithromycin at a concentration as low as 0.2 μM induced rapid aggregation of AgNPs by neutralizing the negative charge on the particle surface. This phenomenon resulted in the colour change from bright yellow to purple which could be easily observed by the naked eye. This provided a simple platform for rapid determination of azithromycin based on colorimetric measurements. The factors affecting the colorimetric response like pH, volume of AgNPs suspension and incubation time were suitably optimized. The validated method was found to work efficiently in the established concentration range of 0.2-100.0 μM using two different calibration models. The selectivity of the method was also evaluated by analysis of nanoparticles-aggregation response upon addition of several anions, cations and some commonly prescribed antibiotics. The method was successfully applied for the analysis of azithromycin in pharmaceuticals and spiked human plasma samples with good accuracy and precision. The simplicity, efficiency and cost-effectiveness of the method hold tremendous potential for the analysis of such non-chromophoric pharmaceuticals.

Blue emitting copper nanoclusters as colorimetric and fluorescent probe for the selective detection of bilirubin

NASA Astrophysics Data System (ADS)

R. S., Aparna; J. S., Anjali Devi; John, Nebu; Abha, K.; S. S., Syamchand; George, Sony

2018-06-01

Hurdles to develop point of care diagnostic methods restrict the translation of progress in the health care sector from bench side to bedside. In this article a simple, cost effective fluorescent as well as colorimetric nanosensor was developed for the early and easy detection of hyperbilirubinemia. A stable, water soluble bovine serum albumin stabilised copper nanocluster (BSA CuNC) was used as the fluorescent probe which exhibited strong blue emission (404 nm) upon 330 nm excitation. The fluorescence of the BSA CuNC can be effectively quenched by the addition of bilirubin by the formation of copper-bilirubin complex. Meanwhile the copper-bilirubin complex resulted in an observable colour change from pale violet to green facilitating colorimetric detection. The prepared sensor displayed good selectivity and sensitivity over other co-existing molecules, and can be used for quantifying bilirubin with a detection limit down to 257 fM. Additionally, the as-prepared probe was coated on a paper strip to develop a portable paper strip sensor of bilirubin. Moreover, the method was successfully applied in real sample analysis and obtained promising result.

New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

USGS Publications Warehouse

To, T.B.; Nordstrom, D. Kirk; Cunningham, K.M.; Ball, J.W.; McCleskey, R. Blaine

1999-01-01

A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) >> Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), AI(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 ??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II)???Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), Al(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2/??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.

Cyclen dithiocarbamate-functionalized silver nanoparticles as a probe for colorimetric sensing of thiram and paraquat pesticides via host-guest chemistry

NASA Astrophysics Data System (ADS)

Rohit, Jigneshkumar V.; Kailasa, Suresh Kumar

2014-11-01

We have developed a simple and rapid colorimetric method for on-site analysis of thiram and paraquat using cyclen dithiocarbamate-functionalized silver nanoparticles (CN-DTC-Ag NPs) as a colorimetric probe. The synthesized CN-DTC-Ag NPs were characterized by UV-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy, dynamic light scattering, and transmission electron microscopic techniques. The CN-DTC molecules provide good supramolecular self assembly on the surfaces of Ag NPs to encapsulate thiram and paraquat selectively via "host-guest" chemistry, resulting in red-shift in surface plasmon resonance peak of CN-DTC-Ag NPs from 396 to 530 nm and 510 nm and color change from yellow to pink for thiram and to orange for paraquat, which can be naked-eye detected. The present method shows good linearity in the range of 10.0-20.0 µM and of 50.0-250 µM with limits of detection 2.81 × 10-6 M and 7.21 × 10-6 M for thiram and paraquat, respectively. This method was proved as a promising tool for on-site and real-time monitoring of thiram and paraquat in environmental water, potato, and wheat samples.

A Simple Colorimetric Assay for Specific Detection of Glutathione-S Transferase Activity Associated with DDT Resistance in Mosquitoes

PubMed Central

Rajatileka, Shavanti; Steven, Andrew; Hemingway, Janet; Ranson, Hilary; Paine, Mark; Vontas, John

2010-01-01

Background Insecticide-based methods represent the most effective means of blocking the transmission of vector borne diseases. However, insecticide resistance poses a serious threat and there is a need for tools, such as diagnostic tests for resistance detection, that will improve the sustainability of control interventions. The development of such tools for metabolism-based resistance in mosquito vectors lags behind those for target site resistance mutations. Methodology/Principal Findings We have developed and validated a simple colorimetric assay for the detection of Epsilon class Glutathione transferases (GST)-based DDT resistance in mosquito species, such as Aedes aegypti, the major vector of dengue and yellow fever worldwide. The colorimetric assay is based on the specific alkyl transferase activity of Epsilon GSTs for the haloalkene substrate iodoethane, which produces a dark blue colour highly correlated with AaGSTE2-2-overexpression in individual mosquitoes. The colour can be measured visually and spectrophotometrically. Conclusions/Significance The novel assay is substantially more sensitive compared to the gold standard CDNB assay and allows the discrimination of moderate resistance phenotypes. We anticipate that it will have direct application in routine vector monitoring as a resistance indicator and possibly an important impact on disease vector control. PMID:20824165

Smartphone-based colorimetric analysis for detection of saliva alcohol concentration.

PubMed

Jung, Youngkee; Kim, Jinhee; Awofeso, Olumide; Kim, Huisung; Regnier, Fred; Bae, Euiwon

2015-11-01

A simple device and associated analytical methods are reported. We provide objective and accurate determination of saliva alcohol concentrations using smartphone-based colorimetric imaging. The device utilizes any smartphone with a miniature attachment that positions the sample and provides constant illumination for sample imaging. Analyses of histograms based on channel imaging of red-green-blue (RGB) and hue-saturation-value (HSV) color space provide unambiguous determination of blood alcohol concentration from color changes on sample pads. A smartphone-based sample analysis by colorimetry was developed and tested with blind samples that matched with the training sets. This technology can be adapted to any smartphone and used to conduct color change assays.

Evaluating the feasibility of using insecticide quantification kits (IQK) for estimating cyanopyrethroid levels for indoor residual spraying in Vanuatu

PubMed Central

2014-01-01

Background The quality of routine indoor residual spraying (IRS) operations is rarely assessed because of the limited choice of methods available for quantifying insecticide content in the field. This study, therefore, evaluated a user-friendly, rapid colorimetric assay for detecting insecticide content after routine IRS operations were conducted. Methods This study was conducted in Tafea Province, Vanuatu. Routine IRS was conducted with lambda cyhalothrin. Two methods were used to quantify the IRS activities: 1) pre-spray application of small felt pads and 2) post-spray removal of insecticide with adhesive. The insecticide content was quantified using a colorimetric assay (Insecticide Quantification Kit [IQK]), which involved exposing each sample to the test reagents for 15 mins. The concentration of insecticide was indicated by the depth of red colour. Results The IQK proved simple to perform in the field and results could be immediately interpreted by the programme staff. The insecticide content was successfully sampled by attaching felt pads to the house walls prior to spraying. The IRS operation was well conducted, with 83% of houses being sprayed at the target dose (20 – 30 mg AI/m2). The average reading across all houses was 24.4 ± 1.5 mg AI/m2. The results from the felt pads applied pre-spray were used as a base to compare methods for sampling insecticide from walls post-spray. The adhesive of Sellotape did not collect adequate samples. However, the adhesive of the felt pads provided accurate samples of the insecticide content on walls. Conclusion The IQK colorimetric assay proved to be a useful tool that was simple to use under realistic field conditions. The assay provided rapid information on IRS spray dynamics and spray team performance, facilitating timely decision making and reporting for programme managers. The IQK colorimetric assay will have direct applications for routine quality control in malaria control programmes globally and has the potential to improve the efficacy of vector control operations. PMID:24885084

A Colorimetric Process to Visualize Erythrocyte Exovesicles Aggregates

ERIC Educational Resources Information Center

Saldanha, Carlota; Santos, Nuno C.; Martins-Silva, J.

2004-01-01

A biochemistry laboratory class protocol is described in order to create an opportunity for students to apply by doing the theoretical concepts underlying biomolecules and vesicles properties, together with the principles of centrifugation and colorimetric methodologies. Through simple procedures the students will i) observe the segregation of the…

Highly Sensitive Colorimetric Biosensor for Staphylococcal Enterotoxin B by a Label-Free Aptamer and Gold Nanoparticles

PubMed Central

Mondal, Bhairab; Ramlal, Shylaja; Lavu, Padma S.; N, Bhavanashri; Kingston, Joseph

2018-01-01

A simple, sensitive and selective colorimetric biosensor for the detection of Staphylococcal enterotoxin B (SEB) was developed using SEB-binding aptamer (SEB2) as recognition element and unmodified gold nanoparticles (AuNPs) as colorimetric probes. The assay is based on color change from red to purple due to conformational change of aptamer in the presence of SEB, and the phenomenon of salt-induced AuNPs aggregation which could be monitored by naked eye or UV–vis spectrometer. Results showed that the AuNPs can effectively differentiate the SEB induced conformational change of the aptamer in the presence of a given high salt concentration. A linear response in the range of 50 μg/mL to 0.5 ng/mL of SEB concentration was obtained. The assay was highly specific to SEB as compared to other related toxins. The limit of detection (LOD) of SEB achieved within few minutes was 50 ng/mL visually and spectrometric method improved it to 0.5 ng/mL. Robustness of the assay was tested in artificially spiked milk samples and cross-checked using in house developed sandwich ELISA (IgY as capturing and SEB specific monoclonal as revealing antibody) and PCR. This colorimetric assay could be a suitable alternative over existing methods during biological emergencies due to its simplicity, sensitive and cost effectiveness. PMID:29487580

A continuous spectrophotometric assay method for peptidylarginine deiminase type 4 activity.

PubMed

Liao, Ya-Fan; Hsieh, Hui-Chieh; Liu, Guang-Yaw; Hung, Hui-Chih

2005-12-15

A simple, continuous spectrophotometric assay for peptidylarginine deiminase (PAD) is described. Deimination of peptidylarginine results in the formation of peptidylcitrulline and ammonia. The ammonia released during peptidylarginine hydrolysis is coupled to the glutamate-dehydrogenase-catalyzed reductive amination of alpha-ketoglutarate to glutamate and reduced nicotinamide adenine dinucleotide (NADH) oxidation. The disappearance of absorbance at 340nm due to NADH oxidation is continuously measured. The specific activity obtained by this new protocol for highly purified human PAD is comparable to that obtained by a commonly used colorimetric procedure, which measures the ureido group of peptidylcitrulline by coupling with diacetyl monoxime. The present continuous spectrophotometric method is highly sensitive and accurate and is thus suitable for enzyme kinetic analysis of PAD. The Ca(2+) concentration for half-maximal activity of PAD obtained by this method is comparable to that previously obtained by the colorimetric procedure.

The colorimetric analysis of anti-tuberculosis fixed-dose combination tablets and capsules.

PubMed

Ellard, G A

1999-11-01

The perceived need to demonstrate whether or not the actual amounts of rifampicin, isoniazid and pyrazinamide in fixed-dose combination tablets or capsules correspond to their stated drug contents. To adapt specific, robust and simple colorimetric methods that have been previously applied to measuring plasma and urinary rifampicin, isoniazid, pyrazinamide and ethambutol concentrations to estimate tablet and capsule drug contents. The methods were applied to the analysis of 14 commercially manufactured fixed-dose combinations: two capsule and three tablet formulations containing rifampicin and isoniazid; seven tablet formulations containing rifampicin, isoniazid and pyrazinamide; and two tablet formulations containing rifampicin, isoniazid, pyrazinamide and ethambutol. All the combined formulations contained near to their stated drug contents. Replicate analyses confirmed the excellent precision of the drug analyses. Such methods are not only rapid to perform but should be practical in many Third World situations with relatively modest laboratory facilities.

Colorimetric determination of sildenafil citrate (Viagra) through ion-associate complex formation.

PubMed

Amin, Alaa S; Moustafa, Moustafa E; El-Dosoky, Reham

2009-01-01

A simple, quick, accurate, and sensitive colorimetric method is described for the determination of sildenafil citrate (SLD). The method is based on the reaction of SLD with Congo Red, Sudan II, and Gentian Violet in buffered aqueous solutions at pH 2.5, 6.5, and 11.0, respectively, to give highly colored soluble ion-associate complex species; the colored products are quantitated colorimetrically at 523, 554, and 569 nm, respectively. The various experimental conditions were optimized. The stoichiometric ratio was found to be 1:1 for all ion associates; the calculated logarithmic stability constants were 8.51, 7.79, and 5.58, respectively. Beer's law was obeyed over the concentration range of 0.2-7.0 microg/mL, whereas the Ringbom optimum concentration range was 0.4-6.5 microg/mL. Values for molar absorptivity, Sandell sensitivity, and detection and quantification limits were also calculated. The proposed method was successfully applied to the determination of SLD in Viagra tablets and in serum samples by using the technique of standard additions with mean accuracy values of 100.06 +/- 1.14, 99.87 +/- 0.70, and 99.86 +/- 0.97% for Viagra tablets and 99.88 +/- 0.60, 99.90 +/- 0.90, and 100.24 +/- 0.80% for serum samples, respectively.

Reconsideration of the Zincke salt: An efficient colorimetric chemosensor for detection of ethylamines

NASA Astrophysics Data System (ADS)

Kim, Jong H.

2018-03-01

In this work, an efficient colorimetric chemosensor for the detection of ethylamines using a pyridinium salt (the Zincke salt) is reported. Highly sensitive and selective reactivity of the Zincke salt enables colorimetric response of the Zincke salt solution to the ethylamines by showing well-defined visible color changes from colorless to the deep red. Furthermore, the Zincke salt thin film exhibits discernable color changes in response to ethylamine gas as well, which allows fabrication of simple, fast and portable strip- and textile-type ethylamine sensors.

A Portable Smart-Phone Readout Device for the Detection of Mercury Contamination Based on an Aptamer-Assay Nanosensor.

PubMed

Xiao, Wei; Xiao, Meng; Fu, Qiangqiang; Yu, Shiting; Shen, Haicong; Bian, Hongfen; Tang, Yong

2016-11-08

The detection of environmental mercury (Hg) contamination requires complex and expensive instruments and professional technicians. We present a simple, sensitive, and portable Hg 2+ detection system based on a smartphone and colorimetric aptamer nanosensor. A smartphone equipped with a light meter app was used to detect, record, and process signals from a smartphone-based microwell reader (MR S-phone), which is composed of a simple light source and a miniaturized assay platform. The colorimetric readout of the aptamer nanosensor is based on a specific interaction between the selected aptamer and Hg 2+ , which leads to a color change in the reaction solution due to an aggregation of gold nanoparticles (AuNPs). The MR S-phone-based AuNPs-aptamer colorimetric sensor system could reliably detect Hg 2+ in both tap water and Pearl River water samples and produced a linear colorimetric readout of Hg 2+ concentration in the range of 1 ng/mL-32 ng/mL with a correlation of 0.991, and a limit of detection (LOD) of 0.28 ng/mL for Hg 2+ . The detection could be quickly completed in only 20 min. Our novel mercury detection assay is simple, rapid, and sensitive, and it provides new strategies for the on-site detection of mercury contamination in any environment.

A Portable Smart-Phone Readout Device for the Detection of Mercury Contamination Based on an Aptamer-Assay Nanosensor

PubMed Central

Xiao, Wei; Xiao, Meng; Fu, Qiangqiang; Yu, Shiting; Shen, Haicong; Bian, Hongfen; Tang, Yong

2016-01-01

The detection of environmental mercury (Hg) contamination requires complex and expensive instruments and professional technicians. We present a simple, sensitive, and portable Hg2+ detection system based on a smartphone and colorimetric aptamer nanosensor. A smartphone equipped with a light meter app was used to detect, record, and process signals from a smartphone-based microwell reader (MR S-phone), which is composed of a simple light source and a miniaturized assay platform. The colorimetric readout of the aptamer nanosensor is based on a specific interaction between the selected aptamer and Hg2+, which leads to a color change in the reaction solution due to an aggregation of gold nanoparticles (AuNPs). The MR S-phone-based AuNPs-aptamer colorimetric sensor system could reliably detect Hg2+ in both tap water and Pearl River water samples and produced a linear colorimetric readout of Hg2+ concentration in the range of 1 ng/mL–32 ng/mL with a correlation of 0.991, and a limit of detection (LOD) of 0.28 ng/mL for Hg2+. The detection could be quickly completed in only 20 min. Our novel mercury detection assay is simple, rapid, and sensitive, and it provides new strategies for the on-site detection of mercury contamination in any environment. PMID:27834794

A colorimetric detection of acrylamide in potato chips based on nucleophile-initiated thiol-ene Michael addition.

PubMed

Hu, Qinqin; Fu, Yingchun; Xu, Xiahong; Qiao, Zhaohui; Wang, Ronghui; Zhang, Ying; Li, Yanbin

2016-02-07

Acrylamide (AA), a neurotoxin and a potential carcinogen, has been found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple, cost-effective, and sensitive methods for the rapid detection of AA are needed to ensure food safety. Herein, a novel colorimetric method was proposed for the visual detection of AA based on a nucleophile-initiated thiol-ene Michael addition reaction. Gold nanoparticles (AuNPs) were aggregated by glutathione (GSH) because of a ligand-replacement, accompanied by a color change from red to purple. In the presence of AA, after the thiol-ene Michael addition reaction between GSH and AA with the catalysis of a nucleophile, the sulfhydryl group of GSH was consumed by AA, which hindered the subsequent ligand-replacement and the aggregation of AuNPs. Therefore, the concentration of AA could be determined by the visible color change caused by dispersion/aggregation of AuNPs. This new method showed high sensitivity with a linear range from 0.1 μmol L(-1) to 80 μmol L(-1) and a detection limit of 28.6 nmol L(-1), and especially revealed better selectivity than the fluorescence sensing method reported previously. Moreover, this new method was used to detect AA in potato chips with a satisfactory result in comparison with the standard methods based on chromatography, which indicated that the colorimetric method can be expanded for the rapid detection of AA in thermally processed foods.

A gas chromatography-mass spectrometry method for the determination of delta-aminolevulinic acid in plant leaves.

PubMed

Hijaz, Faraj; Killiny, Nabil

2016-05-20

Delta-aminolevulinic (δ-ALA) acid is an important intermediate for tetrapyrroles biosynthesis and it has recently received great attention in plant physiology and human toxicology. However, the colorimetric method which is the most common method for determination of δ-ALA is time consuming and is not specific. In this study, a method for determination of δ-ALA in plant tissues was developed based on the trimethylsilyl (TMS) derivative of the pyrrole formed from the reaction of δ-ALA with ethyl acetoacetate via Knorr condensation. The δ-ALA in the HCl extract was reacted with ethyl acetoacetate to form a pyrrole. Then, the pyrrole compound was extracted using ethyl acetate and the solvent was evaporated to dryness. The dried sample was derivatized to its TMS ester and analyzed using GC-MS. The concentration of δ-ALA in citrus leaves incubated with levulinic acid was also determined by the conventional colorimetric method. The linear range was 10-200ppm in the full scan mode and 0.1-20ppm in the selected ion monitoring (SIM). The limit of detection was 6ppm in the full scan and 0.05ppm in SIM mode, representing a four-fold increase in sensitivity compared to the colorimetric method. The GC-MS method developed in this study is simple, accurate, sensitive, and could also be used to measure δ-ALA in other biological samples. Copyright © 2016 Elsevier B.V. All rights reserved.

A simple analytical platform based on thin-layer chromatography coupled with paper-based analytical device for determination of total capsaicinoids in chilli samples.

PubMed

Dawan, Phanphruk; Satarpai, Thiphol; Tuchinda, Patoomratana; Shiowatana, Juwadee; Siripinyanond, Atitaya

2017-01-01

A new analytical platform based on the use of thin-layer chromatography (TLC) coupled with paper-based analytical device (PAD) was developed for the determination of total capsaicinoids in chilli samples. This newly developed TLC-PAD is simple and low-cost without any requirement of special instrument or skillful person. The analysis consisted of two steps, i.e., extraction of capsaicinoids from chilli samples by using ethanol as solvent and separation of capsaicinoids by thin-layer chromatography (TLC) and elution of capsaicinoids from the TLC plate with in situ colorimetric detection of capsaicinoids on the PAD. For colorimetric detection, Folin-Ciocalteu reagent was used to detect phenolic functional group of capsaicinoids yielding the blue color. The blue color on the PAD was imaged by a scanner followed by evaluation of its grayscale intensity value by ImageJ program. This newly developed TLC-PAD method provided a linear range from 50 to 1000mgL -1 capsaicinoids with the limit of detection as low as 50mgL -1 capsaicinoids. The proposed method was applied to determine capsaicinoids in dried chilli and seasoning powder samples and the results were in good agreement with those obtained by HPLC method. Copyright © 2016 Elsevier B.V. All rights reserved.

Colorimetric As (V) detection based on S-layer functionalized gold nanoparticles.

PubMed

Lakatos, Mathias; Matys, Sabine; Raff, Johannes; Pompe, Wolfgang

2015-11-01

Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable. Copyright © 2015 Elsevier B.V. All rights reserved.

The determination of N-nitrosodiethanolamine (NDELA) at trace levels in shampoos and skin creams by a simple, rapid colorimetric method.

PubMed

Telling, G M; Dunnett, P C

1981-10-01

Synopsis A technique is described for the rapid determination of N-nitrosodiethanolamine (NDELA) in shampoos, skin creams and similar products based on aqueous extraction, partition into ethyl acetate and colorimetric determination using the Eisenbrand-Preussman cleavage reaction. Recoveries of NDELA added at levels of 5-100 mug kg(-1) to a range of shampoo and cream types ranged from 90-101%. The limit of determination for the method is 2.5 mug kg(-1). Observations on the application of a thermal energy analyser linked to a gas chromatograph are also reported. Application of the technique to a survey of a wide range of shampoo and skin cream types showed that levels of total N-nitroso compounds were less than 30 mug kg(-1) in < 90% of samples and, in many cases, less than 2.5 mug kg-1.

When alcohol is the answer: trapping, identifying and quantifying simple alkylating species in aqueous environments

PubMed Central

Penketh, P. G.; Shyam, K.; Baumann, R. P; Zhu, Rui; Ishiguro, K.; Sartorelli, A. C.; Ratner, E. S.

2016-01-01

Alkylating agents are a significant class of environmental carcinogens as well as commonly used anticancer therapeutics. Traditional alkylating activity assays have utilized the colorimetric reagent 4-(4-nitrobenzyl)pyridine (4NBP). However, 4NBP based assays have a relatively low sensitivity towards harder, more oxophilic alkylating species and are not well suited for the identification of the trapped alkyl moiety due to adduct instability. Herein we describe a method using water as the trapping agent which permits the trapping of simple alkylating electrophiles with a comparatively wide range of softness/hardness and permits the identification of donated simple alkyl moieties. PMID:27188264

Hydrogen bonding recognition and colorimetric detection of isoprenaline using 2-amino-5-mercapto-1,3,4-thiadiazol functionalized gold nanoparticles

NASA Astrophysics Data System (ADS)

Khezri, Somayeh; Bahram, Morteza; Samadi, Naser

2018-01-01

In this paper, we describe a rapid, low-cost and highly sensitive colorimetric method for the detection of isoprenaline, based on 2-amino-5-mercapto-1,3,4-thiadiazol (AMTD) functionalized gold nanoparticles (AMTD-AuNPs) as a sensing element. Hydrogen bonding interaction between isoprenaline and AMTD resulted in the aggregation of AuNPs and a consequent color change of AuNPs from red to blue. The concentration of isoprenaline could be detected with the naked eye or a UV-visible spectrometer. Results showed that the absorbance ratio (A650/A524) was linear with isoprenaline concentrations in the range of 0.2 to 2.6 μM (R = 0.997). The detection limit of this method was 0.08 μM. The proposed method is simple, without using complicated instruments and adding salts for enhancing sensitivity. This probe could be successfully applied to the determination of isoprenaline in human serum samples and urine samples after deproteinization.

A Simple Laboratory Exercise Illustrating Active Transport in Yeast Cells.

ERIC Educational Resources Information Center

Stambuk, Boris U.

2000-01-01

Describes a simple laboratory activity illustrating the chemiosmotic principles of active transport in yeast cells. Demonstrates the energy coupling mechanism of active a-glucoside uptake by Saccaromyces cerevisiae cells with a colorimetric transport assay using very simple equipment. (Contains 22 references.) (Author/YDS)

Extractive colorimetric method for the determination of dothiepin hydrochloride and risperidone in pure and in dosage forms.

PubMed

Hassan, Wafaa El-Sayed

2008-08-01

Three rapid, simple, reproducible and sensitive extractive colorimetric methods (A--C) for assaying dothiepin hydrochloride (I) and risperidone (II) in bulk sample and in dosage forms were investigated. Methods A and B are based on the formation of an ion pair complexes with methyl orange (A) and orange G (B), whereas method C depends on ternary complex formation between cobalt thiocyanate and the studied drug I or II. The optimum reaction conditions were investigated and it was observed the calibration curves resulting from the measurements of absorbance concentration relations of the extracted complexes were linear over the concentration range 0.1--12 microg ml(-1) for method A, 0.5--11 mug ml(-1) for method B, and 3.2--80 microg ml(-1) for method C with a relative standard deviation (RSD) of 1.17 and 1.28 for drug I and II, respectively. The molar absorptivity, Sandell sensitivity, Ringbom optimum concentration ranges, and detection and quantification limits for all complexes were calculated and evaluated at maximum wavelengths of 423, 498, and 625 nm, using methods A, B, and C, respectively. The interference from excipients commonly present in dosage forms and common degradation products was studied. The proposed methods are highly specific for the determination of drugs I and II, in their dosage forms applying the standard additions technique without any interference from common excipients. The proposed methods have been compared statistically to the reference methods and found to be simple, accurate (t-test) and reproducible (F-value).

A gold nanoparticles-based colorimetric test to detect single nucleotide polymorphisms for improvement of personalized therapy of psoriasis

NASA Astrophysics Data System (ADS)

Marsella, Alessandra; Valentini, Paola; Tarantino, Paolo; Congedo, Maurizio; Pompa, Pier Paolo

2016-04-01

We report a simple, rapid and low-cost test, based on gold nanoparticles, for the naked-eye colorimetric detection of a signature of single nucleotide polymorphisms (SNPs) relevant for the personalized medicine of psoriasis patients. We validated the colorimetric assay on real-world DNA samples from a cohort of 30 psoriasis patients and we compared the results, in double-blind, with those obtained with two state-of-the-art instrumental techniques, namely reverse dot blotting and direct sequencing, finding 100% agreement. We demonstrated high accuracy, sensitivity and specificity of the colorimetric test that can be easily adapted for the genotypization of different SNPs, important for the pharmacogenomics of various diseases, and in other fields, such as food traceability and population structure analysis.

Rapid and selective lead (II) colorimetric sensor based on azacrown ether-functionalized gold nanoparticles

NASA Astrophysics Data System (ADS)

Alizadeh, A.; Khodaei, M. M.; Karami, Ch; Workentin, M. S.; Shamsipur, M.; Sadeghi, M.

2010-08-01

A gold nanoparticle (AuNPs)-based simple and fast colorimetric sensor for selective detecting of Pb(II) in aqueous solution has been developed. Monodisperse AuNPs (approx. 2.0 nm diameter) has been prepared facilely and further modified with an alkanethiol-bearing monoazacrown ether terminus. These AuNPs are shown to selectively sense Pb2 + through color change, which is visually discernible by an appearance of the surface plasmon band (SPB) at 520 nm. The recognition mechanism is attributed to the unique structure of the monoazacrown ether attached to AuNPs and metal sandwich coordination between two azacrown ether moieties that are attached to separate nanoparticles. This inter-particle cross-linking results in an aggregation and apparent color change from brown to purple. Additionally, TEM experiments support the optical absorption data proving the aggregation between azacrown ether-capped gold nanoparticles. This AuNP-based colorimetric assay is a facile and robust method and allows fast detection of Pb2 + at ambient temperatures. More importantly, the developed technique does not utilize enzymatic reactions, light-sensitive dye molecules, lengthy protocols or sophisticated instrumentation.

Tuning Sensory Properties of Triazole-Conjugated Spiropyrans: Metal-Ion Selectivity and Paper-Based Colorimetric Detection of Cyanide

PubMed Central

Lee, Juhyen; Choi, Eun Jung; Kim, Inwon; Lee, Minhe; Satheeshkumar, Chinnadurai; Song, Changsik

2017-01-01

Tuning the sensing properties of spiropyrans (SPs), which are one of the photochromic molecules useful for colorimetric sensing, is important for efficient analysis, but their synthetic modification is not always simple. Herein, we introduce an alkyne-functionalized SP, the modification of which would be easily achieved via Cu-catalyzed azide-alkyne cycloaddition (“click reaction”). The alkyne-SP was conjugated with a bis(triethylene glycol)-benzyl group (EG-BtSP) or a simple benzyl group (BtSP), forming a triazole linkage from the click reaction. The effects of auxiliary groups to SP were tested on metal-ion sensing and cyanide detection. We found that EG-BtSP was more Ca2+-sensitive than BtSP in acetonitrile, which were thoroughly examined by a continuous variation method (Job plot) and UV-VIS titrations, followed by non-linear regression analysis. Although both SPs showed similar, selective responses to cyanide in a water/acetonitrile co-solvent, only EG-BtSP showed a dramatic color change when fabricated on paper, highlighting the important contributions of the auxiliary groups. PMID:28783127

DNA aptamer-based colorimetric detection platform for Salmonella Enteritidis.

PubMed

Bayraç, Ceren; Eyidoğan, Füsun; Avni Öktem, Hüseyin

2017-12-15

Food safety is a major issue to protect public health and a key challenge is to find detection methods for identification of hazards in food. Food borne infections affects millions of people each year and among pathogens, Salmonella Enteritidis is most widely found bacteria causing food borne diseases. Therefore, simple, rapid, and specific detection methods are needed for food safety. In this study, we demonstrated the selection of DNA aptamers with high affinity and specificity against S. Enteritidis via Cell Systematic Evolution of Ligands by Exponential Enrichment (Cell-SELEX) and development of sandwich type aptamer-based colorimetric platforms for its detection. Two highly specific aptamers, crn-1 and crn-2, were developed through 12 rounds of selection with K d of 0.971µM and 0.309µM, respectively. Both aptamers were used to construct sandwich type capillary detection platforms. With the detection limit of 10 3 CFU/mL, crn-1 and crn-2 based platforms detected target bacteria specifically based on color change. This platform is also suitable for detection of S. Enteritidis in complex food matrix. Thus, this is the first to demonstrate use of Salmonella aptamers for development of the colorimetric aptamer-based detection platform in its identification and detection with naked eye in point-of-care. Copyright © 2017 Elsevier B.V. All rights reserved.

A simple highly sensitive and selective aptamer-based colorimetric sensor for environmental toxins microcystin-LR in water samples.

PubMed

Li, Xiuyan; Cheng, Ruojie; Shi, Huijie; Tang, Bo; Xiao, Hanshuang; Zhao, Guohua

2016-03-05

A simple and highly sensitive aptamer-based colorimetric sensor was developed for selective detection of Microcystin-LR (MC-LR). The aptamer (ABA) was employed as recognition element which could bind MC-LR with high-affinity, while gold nanoparticles (AuNPs) worked as sensing materials whose plasma resonance absorption peaks red shifted upon binding of the targets at a high concentration of sodium chloride. With the addition of MC-LR, the random coil aptamer adsorbed on Au NPs altered into regulated structure to form MC-LR-aptamer complexes and broke away from the surface of Au NPs, leading to the aggregation of AuNPs, and the color converted from red to blue due to the interparticle plasmon coupling. Results showed that our aptamer-based colorimetric sensor exhibited rapid and sensitive detection performance for MC-LR with linear range from 0.5 nM to 7.5 μM and the detection limit reached 0.37 nM. Meanwhile, the pollutants usually coexisting with MC-LR in pollutant water samples had not demonstrated disturbance for detecting of MC-LR. The mechanism was also proposed suggesting that high affinity interaction between aptamer and MC-LR significantly enhanced the sensitivity and selectivity for MC-LR detection. Besides, the established method was utilized in analyzing real water samples and splendid sensitivity and selectivity were obtained as well. Copyright © 2015 Elsevier B.V. All rights reserved.

In Situ Enzymatically Generated Photoswitchable Oxidase Mimetics and Their Application for Colorimetric Detection of Glucose Oxidase.

PubMed

Cao, Gen-Xia; Wu, Xiu-Ming; Dong, Yu-Ming; Li, Zai-Jun; Wang, Guang-Li

2016-07-09

In this study, a simple and amplified colorimetric assay is developed for the detection of the enzymatic activity of glucose oxidase (GOx) based on in situ formation of a photoswitchable oxidase mimetic of PO₄(3-)-capped CdS quantum dots (QDs). GOx catalyzes the oxidation of 1-thio-β-d-glucose to give 1-thio-β-d-gluconic acid which spontaneously hydrolyzes to β-d-gluconic acid and H₂S; the generated H₂S instantly reacts with Cd(2+) in the presence of Na₃PO₄ to give PO₄(3-)-stabilized CdS QDs in situ. Under visible-light (λ ≥ 400 nm) stimulation, the PO₄(3-)-capped CdS QDs are a new style of oxidase mimic derived by producing some active species, such as h⁺, (•)OH, O₂(•-) and a little H₂O₂, which can oxidize the typical substrate (3,3,5,5-tetramethylbenzydine (TMB)) with a color change. Based on the GOx-triggered growth of the oxidase mimetics of PO₄(3-)-capped CdS QDs in situ, we developed a simple and amplified colorimetric assay to probe the enzymatic activity of GOx. The proposed method allowed the detection of the enzymatic activity of GOx over the range from 25 μg/L to 50 mg/L with a low detection limit of 6.6 μg/L. We believe the PO₄(3-)-capped CdS QDs generated in situ with photo-stimulated enzyme-mimicking activity may find wide potential applications in biosensors.

When alcohol is the answer: Trapping, identifying and quantifying simple alkylating species in aqueous environments.

PubMed

Penketh, Philip G; Shyam, Krishnamurthy; Baumann, Raymond P; Zhu, Rui; Ishiguro, Kimiko; Sartorelli, Alan C; Ratner, Elena S

2016-09-01

Alkylating agents are a significant class of environmental carcinogens as well as commonly used anticancer therapeutics. Traditional alkylating activity assays have utilized the colorimetric reagent 4-(4-nitrobenzyl)pyridine (4NBP). However, 4NBP based assays have a relatively low sensitivity towards harder, more oxophilic alkylating species and are not well suited for the identification of the trapped alkyl moiety due to adduct instability. Herein we describe a method using water as the trapping agent which permits the trapping of simple alkylating electrophiles with a comparatively wide range of softness/hardness and permits the identification of donated simple alkyl moieties. Copyright © 2016 Elsevier Inc. All rights reserved.

[Colorimetric characterization of LCD based on wavelength partition spectral model].

PubMed

Liu, Hao-Xue; Cui, Gui-Hua; Huang, Min; Wu, Bing; Xu, Yan-Fang; Luo, Ming

2013-10-01

To establish a colorimetrical characterization model of LCDs, an experiment with EIZO CG19, IBM 19, DELL 19 and HP 19 LCDs was designed and carried out to test the interaction between RGB channels, and then to test the spectral additive property of LCDs. The RGB digital values of single channel and two channels were given and the corresponding tristimulus values were measured, then a chart was plotted and calculations were made to test the independency of RGB channels. The results showed that the interaction between channels was reasonably weak and spectral additivity property was held well. We also found that the relations between radiations and digital values at different wavelengths varied, that is, they were the functions of wavelength. A new calculation method based on piecewise spectral model, in which the relation between radiations and digital values was fitted by a cubic polynomial in each piece of wavelength with measured spectral radiation curves, was proposed and tested. The spectral radiation curves of RGB primaries with any digital values can be found out with only a few measurements and fitted cubic polynomial in this way and then any displayed color can be turned out by the spectral additivity property of primaries at given digital values. The algorithm of this method was discussed in detail in this paper. The computations showed that the proposed method was simple and the number of measurements needed was reduced greatly while keeping a very high computation precision. This method can be used as a colorimetrical characterization model.

Colorimetric detection of endogenous hydrogen sulfide production in living cells

NASA Astrophysics Data System (ADS)

Ahn, Yong Jin; Lee, Young Ju; Lee, Jaemyeon; Lee, Doyeon; Park, Hun-Kuk; Lee, Gi-Ja

2017-04-01

Hydrogen sulfide (H2S) has received great attention as a third gaseous signal transmitter, following nitric oxide and carbon monoxide. In particular, H2S plays an important role in the regulation of cancer cell biology. Therefore, the detection of endogenous H2S concentrations within biological systems can be helpful to understand the role of gasotransmitters in pathophysiology. Although a simple and inexpensive method for the detection of H2S has been developed, its direct and precise measurement in living cells remains a challenge. In this study, we introduced a simple, facile, and inexpensive colorimetric system for selective H2S detection in living cells using a silver-embedded Nafion/polyvinylpyrrolidone (PVP) membrane. This membrane could be easily applied onto a polystyrene microplate cover. First, we optimized the composition of the coating membrane, such as the PVP/Nafion mixing ratio and AgNO3 concentration, as well as the pH of the Na2S (H2S donor) solution and the reaction time. Next, the in vitro performance of a colorimetric detection assay utilizing the silver/Nafion/PVP membrane was evaluated utilizing a known concentration of Na2S standard solution both at room temperature and at 37 °C in a 5% CO2 incubator. As a result, the sensitivity of the colorimetric assay for H2S at 37 °C in the incubator (0.0056 Abs./μM Na2S, R2 = 0.9948) was similar to that at room temperature (0.0055 Abs./μM Na2S, R2 = 0.9967). Moreover, these assays were less sensitive to interference from compounds such as glutathione, L-cysteine (Cys), and dithiothreitol than to the H2S from Na2S. This assay based on the silver/Nafion/PVP membrane also showed excellent reproducibility (2.8% RSD). Finally, we successfully measured the endogenous H2S concentrations in live C6 glioma cells by s-(5‧-adenosyl)-L-methionine stimulation with and without Cys and L-homocysteine, utilizing the silver/Nafion/PVP membrane. In summary, colorimetric assays using silver/Nafion/PVP-coated membranes can be simple, robust, and reliable tools for the detection of H2S that can avoid the complicated and labor-intensive analytical approach used in conventional biology. In addition, we expect that this assay will demonstrate a powerful ability to study pathophysiological pathways that involve H2S.

A convenient method for synthesis of glyconanoparticles for colorimetric measuring carbohydrate-protein interactions

PubMed Central

Chuang, Yen-Jun; Zhou, Xichun; Pan, Zhengwei; Turchi, Craig

2009-01-01

Carbohydrate functionalized nanoparticles, i.e., the glyconanoparticles, have wide application ranging from studies of carbohydrate-protein interactions, in vivo cell imaging, biolabeling, etc. Currently reported methods for preparation of glyconanoaprticles require multi-step modifications of carbohydrates moieties to conjugate to nanoparticle surface. However, the required synthetic manipulations are difficult and time consuming. We report herewith a simple and versatile method for preparing glyconanoparticles. This method is based on the utilization of clean and convenient microwave irradiation energy for one-step, site-specific conjugation of unmodified carbohydrates onto hydrazide-functionalized Au nanoparticles. A colorimetric assay that utilizes the ensemble of gold glyconanoparticles and Concanavalin A (ConA) was also presented. This feasible assay system was developed to analyze multivalent interactions and to determine the dissociation constant (Kd) for five kind of Au glyconanoparticles with lectin. Surface plasmon changes of the Au glyconanparticles as a function of lectin-carbohydrate interactions were measured and the dissociation constants were determined based on non-linear curve fitting. The strength of the interaction of carbohydrates with ConA was found to be as follows: Maltose > Mannose > Glucose > Lactose > MAN5. PMID:19698698

Sensitive method to monitor trace quantities of benzanthrone in workers of dyestuff industries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, A.; Khanna, S.K.; Singh, G.B.

1986-03-01

Dyestuff workers coming in contact with benzanthrone (an intermediate used for the synthesis of a variety of dyes) develop skin lesions, gastritis, liver malfunctions, and sexual disturbances. A highly sensitive fluorometric method to monitor trace quantities of benzanthrone in urine, serum, and biological tissues for experimental studies, has been developed. Coupled with simple extraction and resolution, optimum fluorescence is obtained in an equal mixture of chloroform:methanol, detecting as low as 2 ng benzanthrone. This method is approximately 250 times more sensitive than currently available colorimetric assay.

Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Kang, Fei; Hou, Xiangshu; Xu, Kun

2015-10-01

Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core-shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H2O2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core-shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum.

A sensitive colorimetric assay system for nucleic acid detection based on isothermal signal amplification technology.

PubMed

Hu, Bo; Guo, Jing; Xu, Ying; Wei, Hua; Zhao, Guojie; Guan, Yifu

2017-08-01

Rapid and accurate detection of microRNAs in biological systems is of great importance. Here, we report the development of a visual colorimetric assay which possesses the high amplification capabilities and high selectivity of the rolling circle amplification (RCA) method and the simplicity and convenience of gold nanoparticles used as a signal indicator. The designed padlock probe recognizes the target miRNA and is circularized, and then acts as the template to extend the target miRNA into a long single-stranded nucleotide chain of many tandem repeats of nucleotide sequences. Next, the RCA product is hybridized with oligonucleotides tagged onto gold nanoparticles. This interaction leads to the aggregation of gold nanoparticles, and the color of the system changes from wine red to dark blue according to the abundance of miRNA. A linear correlation between fluorescence and target oligonucleotide content was obtained in the range 0.3-300 pM, along with a detection limit of 0.13 pM (n = 7) and a RSD of 3.9% (30 pM, n = 9). The present approach provides a simple, rapid, and accurate visual colorimetric assay that allows sensitive biodetection and bioanalysis of DNA and RNA nucleotides of interest in biologically important samples. Graphical abstract The colorimetric assay system for analyzing target oligonucleotides.

Colorimetric monitoring of solid-phase aldehydes using 2,4-dinitrophenylhydrazine.

PubMed

Shannon, Simon K; Barany, George

2004-01-01

A simple and rapid method to achieve colorimetric monitoring of resin-bound aldehydes, based on ambient temperature reaction with 2,4-dinitrophenylhydrazine (DNPH) in the presence of dilute acid, has been developed as an adjunct to solid-phase organic synthesis and combinatorial chemistry. By this test, the presence of aldehydes is indicated by a red to dark-orange appearance, within a minute. Alternatively, resins that are free of aldehydes or in which aldehyde functions have reacted completely retain their original color. The DNPH test was demonstrated for poly(ethylene glycol)-polystyrene (PEG-PS), aminomethyl polystyrene (AMP), cross-linked ethoxylate acrylate resin (CLEAR), and acryloylated O,O'-bis(2-aminopropyl)poly(ethylene glycol) (PEGA) supports and gave results visible to the naked eye at levels as low as 18 micromol of aldehyde per gram of resin.

A quick inexpensive laboratory method in acute paracetamol poisoning could improve risk assessment, management and resource utilization

PubMed Central

Senarathna, S.M.D.K. Ganga; Ranganathan, Shalini S.; Buckley, Nick; Soysa, S.S.S.B.D. Preethi; Fernandopulle, B. M. Rohini

2012-01-01

Objectives: Acute paracetamol poisoning is an emerging problem in Sri Lanka. Management guidelines recommend ingested dose and serum paracetamol concentrations to assess the risk. Our aim was to determine the usefulness of the patient's history of an ingested dose of >150 mg/kg and paracetamol concentration obtained by a simple colorimetric method to assess risk in patients with acute paracetamol poisoning. Materials and Methods: Serum paracetamol concentrations were determined in 100 patients with a history of paracetamol overdose using High Performance Liquid Chromatography (HPLC); (reference method). The results were compared to those obtained with a colorimetric method. The utility of risk assessment by reported dose ingested and colorimetric analysis were compared. Results: The area under the receiver operating characteristic curve for the history of ingested dose was 0.578 and there was no dose cut-off providing useful risk categorization. Both analytical methods had less than 5% intra- and inter-batch variation and were accurate on spiked samples. The time from blood collection to result was six times faster and ten times cheaper for colorimetry (30 minutes, US$2) than for HPLC (180 minutes, US$20). The correlation coefficient between the paracetamol levels by the two methods was 0.85. The agreement on clinical risk categorization on the standard nomogram was also good (Kappa = 0.62, sensitivity 81%, specificity 89%). Conclusions: History of dose ingested alone greatly over-estimated the number of patients who need antidotes and it was a poor predictor of risk. Paracetamol concentrations by colorimetry are rapid and inexpensive. The use of these would greatly improve the assessment of risk and greatly reduce unnecessary expenditure on antidotes. PMID:23087506

Needle Decompression of Tension Pneumothorax with Colorimetric Capnography.

PubMed

Naik, Nimesh D; Hernandez, Matthew C; Anderson, Jeff R; Ross, Erika K; Zielinski, Martin D; Aho, Johnathon M

2017-11-01

The success of needle decompression for tension pneumothorax is variable, and there are no objective measures assessing effective decompression. Colorimetric capnography, which detects carbon dioxide present within the pleural space, may serve as a simple test to assess effective needle decompression. Three swine underwent traumatically induced tension pneumothorax (standard of care, n = 15; standard of care with needle capnography, n = 15). Needle thoracostomy was performed with an 8-cm angiocatheter. Similarly, decompression was performed with the addition of colorimetric capnography. Subjective operator assessment of decompression was recorded and compared with true decompression, using thoracoscopic visualization for both techniques. Areas under receiver operating curves were calculated and pairwise comparison was performed to assess statistical significance (P < .05). The detection of decompression by needle colorimetric capnography was found to be 100% accurate (15 of 15 attempts), when compared with thoracoscopic assessment (true decompression). Furthermore, it accurately detected the lack of tension pneumothorax, that is, the absence of any pathologic/space-occupying lesion, in 100% of cases (10 of 10 attempts). Standard of care needle decompression was detected by operators in 9 of 15 attempts (60%) and was detected in 3 of 10 attempts when tension pneumothorax was not present (30%). True decompression, under direct visualization with thoracoscopy, occurred 15 of 15 times (100%) with capnography, and 12 of 15 times (80%) without capnography. Areas under receiver operating curves were 0.65 for standard of care and 1.0 for needle capnography (P = .002). Needle decompression with colorimetric capnography provides a rapid, effective, and highly accurate method for eliminating operator bias for tension pneumothorax decompression. This may be useful for the treatment of this life-threatening condition. Copyright © 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

A simplified approach to the determination of N-nitroso glyphosate in technical glyphosate using HPLC with post-derivatization and colorimetric detection.

PubMed

Kim, Manuela; Stripeikis, Jorge; Iñón, Fernando; Tudino, Mabel

2007-05-15

A simple and sensitive HPLC post-derivatization method with colorimetric detection has been developed for the determination of N-nitroso glyphosate in samples of technical glyphosate. Separation of the analyte was accomplished using an anionic exchange resin (2.50mmx4.00mm i.d., 15mum particle size, functional group: quaternary ammonium salt) with Na(2)SO(4) 0.0075M (pH 11.5) (flow rate: 1.0mLmin(-1)) as mobile phase. After separation, the eluate was derivatized with a colorimetric reagent containing sulfanilamide 0.3% (w/v), [N-(1-naphtil)ethilendiamine] 0.03% (w/v) and HCl 4.5M in a thermostatized bath at 95 degrees C. Detection was performed at 546nm. All stages of the analytical procedure were optimized taking into account the concept of analytical minimalism: less operation times and costs; lower sample, reagents and energy consumption and minimal waste. The limit of detection (k=3) calculated for 10 blank replicates was 0.04mgL(-1) (0.8mgkg(-1)) in the solid sample which is lower than the maximum tolerable accepted by the Food and Agriculture Organization of the United Nations.

Simple and specific colorimetric detection of Staphylococcus using its volatile 2-[3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl] propanoic acid in the liquid phase and head space of cultures.

PubMed

Saranya, Raju; Aarthi, Raju; Sankaran, Krishnan

2015-05-01

Spread of drug-resistant Staphylococcus spp. into communities pose danger demanding effective non-invasive and non-destructive tools for its early detection and surveillance. Characteristic volatile organic compounds (VOCs) produced by bacteria offer new diagnostic targets and novel approaches not exploited so far in infectious disease diagnostics. Our search for such characteristic VOC for Staphylococcus spp. led to the depiction of 2-[3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl] propanoic acid (ATMAP), a moderately volatile compound detected both in the culture and headspace when the organism was grown in tryptone soya broth (TSB) medium. A simple and inexpensive colorimetric method (colour change from yellow to orange) using methyl red as the pH indicator provided an absolutely specific way for identifying Staphylococcus spp., The assay performed in liquid cultures (7-h growth in TSB) as well as in the headspace of plate cultures (grown for 10 h on TSA) was optimised in a 96-well plate and 12-well plate formats, respectively, employing a set of positive and negative strains. Only Staphylococcus spp. showed the distinct colour change from yellow to orange due to the production of the above VOC while in the case of other organisms, the reagent remained yellow. The method validated using known clinical and environmental strains (56 including Staphylococcus, Proteus, Pseudomonas, Klebsiella, Bacillus, Shigella and Escherichia coli) was found to be highly efficient showing 100% specificity and sensitivity. Such simple methods of bacterial pathogen identification are expected to form the next generation tools for the control of infectious diseases through early detection and surveillance of causative agents.

A colorimetric probe based on desensitized ionene-stabilized gold nanoparticles for single-step test for sulfate ions.

PubMed

Arkhipova, Viktoriya V; Apyari, Vladimir V; Dmitrienko, Stanislava G

2015-03-15

Desensitized ionene-stabilized gold nanoparticles have been prepared and applied as a colorimetric probe for the single-step test for sulfate ions at the relatively high concentration level. The approach is based on aggregation of the nanoparticles leading to the change in absorption spectra and color of the solution. These nanoparticles are characterized by the decreased sensitivity due to both electrostatic and steric stabilization, which allows for simple, and rapid direct single-step determination of sulfate at the relatively high concentration level in real water samples without sample pretreatment or dilution. Influence of different factors (the time of interaction, pH, the concentrations of sulfate ions and the nanoparticles) on the aggregation and analytical performance of the procedure was investigated. The method allows for the determination of sulfate ions in the mass range of 0.2-0.4 mg with RSD of 5% from the sample volume of less than 2 mL. It has a sharp dependence of the colorimetric response on the concentration of sulfate, which makes it prospective for indicating deviations of the sulfate concentration regarding some declared value chosen within the above range. The time of the analysis is 2 min. The method was applied to the analysis of mineral water samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Analytical properties of some commercially available nitrate reductase enzymes evaluated as replacements for cadmium in automated, semiautomated, and manual colorimetric methods for determination of nitrate plus nitrite in water

USGS Publications Warehouse

Patton, Charles J.; Kryskalla, Jennifer R.

2013-01-01

A multiyear research effort at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) evaluated several commercially available nitrate reductase (NaR) enzymes as replacements for toxic cadmium in longstanding automated colorimetric air-segmented continuous-flow analyzer (CFA) methods for determining nitrate plus nitrite (NOx) in water. This research culminated in USGS approved standard- and low-level enzymatic reduction, colorimetric automated discrete analyzer NOx methods that have been in routine operation at the NWQL since October 2011. The enzyme used in these methods (AtNaR2) is a product of recombinant expression of NaR from Arabidopsis thaliana (L.) Heynh. (mouseear cress) in the yeast Pichia pastoris. Because the scope of the validation report for these new automated discrete analyzer methods, published as U.S. Geological Survey Techniques and Methods 5–B8, was limited to performance benchmarks and operational details, extensive foundational research with different enzymes—primarily YNaR1, a product of recombinant expression of NaR from Pichia angusta in the yeast Pichia pastoris—remained unpublished until now. This report documents research and development at the NWQL that was foundational to development and validation of the discrete analyzer methods. It includes: (1) details of instrumentation used to acquire kinetics data for several NaR enzymes in the presence and absence of known or suspected inhibitors in relation to reaction temperature and reaction pH; and (2) validation results—method detection limits, precision and bias estimates, spike recoveries, and interference studies—for standard- and low-level automated colorimetric CFA-YNaR1 reduction NOx methods in relation to corresponding USGS approved CFA cadmium-reduction (CdR) NOx methods. The cornerstone of this validation is paired sample statistical and graphical analysis of NOx concentrations from more than 3,800 geographically and seasonally diverse surface-water and groundwater samples that were analyzed in parallel by CFA-CdR and CFA enzyme-reduction methods. Finally, (3) demonstration of a semiautomated batch procedure in which 2-milliliter analyzer cups or disposable spectrophotometer cuvettes serve as reaction vessels for enzymatic reduction of nitrate to nitrite prior to analytical determinations. After the reduction step, analyzer cups are loaded onto CFA, flow injection, or discrete analyzers for simple, rapid, automatic nitrite determinations. In the case of manual determinations, analysts dispense colorimetric reagents into cuvettes containing post-reduction samples, allow time for color to develop, insert cuvettes individually into a spectrophotometer, and record percent transmittance or absorbance in relation to a reagent blank. Data presented here demonstrate equivalent analytical performance of enzymatic reduction NOx methods in these various formats to that of benchmark CFA-CdR NOx methods.

A quick inexpensive laboratory method in acute paracetamol poisoning could improve risk assessment, management and resource utilization.

PubMed

Senarathna, S M D K Ganga; Ranganathan, Shalini S; Buckley, Nick; Soysa, S S S B D Preethi; Fernandopulle, B M Rohini

2012-01-01

Acute paracetamol poisoning is an emerging problem in Sri Lanka. Management guidelines recommend ingested dose and serum paracetamol concentrations to assess the risk. Our aim was to determine the usefulness of the patient's history of an ingested dose of >150 mg/kg and paracetamol concentration obtained by a simple colorimetric method to assess risk in patients with acute paracetamol poisoning. Serum paracetamol concentrations were determined in 100 patients with a history of paracetamol overdose using High Performance Liquid Chromatography (HPLC); (reference method). The results were compared to those obtained with a colorimetric method. The utility of risk assessment by reported dose ingested and colorimetric analysis were compared. The area under the receiver operating characteristic curve for the history of ingested dose was 0.578 and there was no dose cut-off providing useful risk categorization. Both analytical methods had less than 5% intra- and inter-batch variation and were accurate on spiked samples. The time from blood collection to result was six times faster and ten times cheaper for colorimetry (30 minutes, US$2) than for HPLC (180 minutes, US$20). The correlation coefficient between the paracetamol levels by the two methods was 0.85. The agreement on clinical risk categorization on the standard nomogram was also good (Kappa = 0.62, sensitivity 81%, specificity 89%). History of dose ingested alone greatly over-estimated the number of patients who need antidotes and it was a poor predictor of risk. Paracetamol concentrations by colorimetry are rapid and inexpensive. The use of these would greatly improve the assessment of risk and greatly reduce unnecessary expenditure on antidotes.

L-Phenylalanine concentration in blood of phenylketonuria patients: a modified enzyme colorimetric assay compared with amino acid analysis, tandem mass spectrometry, and HPLC methods.

PubMed

De Silva, Veronica; Oldham, Charlie D; May, Sheldon W

2010-09-01

Phenylketonuria (PKU) is an autosomal recessive disorder caused by an impaired conversion of L-phenylalanine (Phe) to L-tyrosine, typically resulting from a deficiency in activity of a hepatic and renal enzyme L-phenylalanine hydroxylase. The disease is characterized by an increased concentration of Phe and its metabolites in body fluids. A modified assay based on an enzymatic-colorimetric methodology was developed for measuring blood Phe levels in PKU patients; this method is designed for use with undeproteinized samples and avoids the use of solvents or amphiphilic agents. Thus, the method could be suitable for incorporation into a simple home-monitoring device. We report here on a comparison of blood Phe concentrations in PKU patients measured in undeproteinized plasma using this enzyme colorimetric assay (ECA), with values determined by amino acid analysis (AAA) of deproteinized samples, and HPLC and tandem mass spectrometry (MS/MS) analyses of dried blood spot (DBS) eluates. Pearson correlation coefficients of 0.951, 0.976 and 0.988 were obtained when AAA-measured Phe concentrations were compared with the ECA-, HPLC- or MS/MS-measured values, respectively. A Bland-Altman analysis revealed that mean Phe concentrations determined using AAA were on average 65 μmol/L lower than values measured by our ECA. These results may be the result of minimizing the manipulations performed on the patient sample compared with AAA, HPLC, and MS/MS methods, which involve plasma deproteinization or DBS elution and derivatization. The results reported here confirm that Phe concentrations determined by our ECA method are comparable to those determined by other widely used methods for a broad range of plasma Phe concentrations.

Antibody modified gold nanoparticles for fast and selective, colorimetric T7 bacteriophage detection.

PubMed

Lesniewski, Adam; Los, Marcin; Jonsson-Niedziółka, Martin; Krajewska, Anna; Szot, Katarzyna; Los, Joanna M; Niedziolka-Jonsson, Joanna

2014-04-16

Herein, we report a colorimetric immunosensor for T7 bacteriophage based on gold nanoparticles modified with covalently bonded anti-T7 antibodies. The new immunosensor allows for a fast, simple, and selective detection of T7 virus. T7 virions form immunological complexes with the antibody modified gold nanoparticles which causes them to aggregate. The aggregation can be observed with the naked eye as a color change from red to purple, as well as with a UV-vis spectrophotometer. The aggregate formation was confirmed with SEM imaging. Sensor selectivity against the M13 bacteriophage was demonstrated. The limit of detection (LOD) is 1.08 × 10(10) PFU/mL (18 pM) T7. The new method was compared with a traditional plaque test. In contrast to biological tests the colorimetric method allows for detection of all T7 phages, not only those biologically active. This includes phage ghosts and fragments of virions. T7 virus has been chosen as a model organism for adenoviruses. The described method has several advantages over the traditional ones. It is much faster than a standard plaque test. It is more robust since no bacteria-virus interactions are utilized in the detection process. Since antibodies are available for a large variety of pathogenic viruses, the described concept is very flexible and can be adapted to detect many different viruses, not only bacteriophages. Contrary to the classical immunoassays, it is a one-step detection method, and no additional amplification, e.g., enzymatic, is needed to read the result.

Colorimetric Aptasensor Based on Enzyme for the Detection of Vibrio parahemolyticus.

PubMed

Wu, Shijia; Wang, Yinqiu; Duan, Nuo; Ma, Haile; Wang, Zhouping

2015-09-09

A simple colorimetric aptasensor system has been developed to detect Vibrio parahemolyticus. Magnetic nanoparticles (MNPs) are synthesized and conjugated with specific aptamers against target and used as capture probes. In addition, this method employs gold nanoparticles (AuNPs) as carriers of horseradish peroxidase (HRP) and aptamers, which served as signal probes. In the presence of target, a "sandwich-type" complex of AuNPs-HRP-aptamer-target-aptamer-MNPs is formed through specific recognition of aptamers and corresponding target. As a result, HRP molecules confined at the surface of the "sandwich" complexes catalyze the enzyme substrate, 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 and generate an optical signal. Under optimal conditions, the signals are linearly dependent on V. parahemolyticus concentrations from 10 to 10(6) colony-forming units (cfu)/mL in a logarithmic plot, with a limit of detection of 10 cfu/mL. Owing to AuNPs, a large amount of HRP could be loaded, resulting in an amplified signal, and the sensitivity would be improved. This strategy has the potential of being extended to the construction of simple monitor systems for a variety of biomolecules related to food safety.

Colorimetric recognition of 6-benzylaminopurine in environmental samples by using thioglycolic acid functionalized silver nanoparticles

NASA Astrophysics Data System (ADS)

Zheng, Mingda; He, Jiang; Wang, Yingying; Wang, Chenge; Ma, Shuang; Sun, Xiaohan

2018-03-01

A simple and selective colorimetric sensor thioglycolic acid capped silver nanoparticles (TGA-AgNPs) was developed for the detection of 6-benzylaminopurine (6-BAP). The synthesized TGA-AgNPs were characterized by UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopic (TEM) techniques. The TGA-AgNPs as a sensor for binding 6-BAP through hydrogen-bonding and π-π bonding that causes large conjugate clusters, resulting in a color change from yellow to reddish orange. The surface plasmon resonance (SPR) band of TGA-AgNPs at 397 nm is red-shifted to 510 nm, which confirms that 6-BAP induces the aggregation of TGA-AgNPs. Under the optimized conditions, a linear relationship between the absorption ratio (A510 nm/A397 nm) and 6-BAP concentration was found in the range of 4-26 μM. The detection limit of 6-BAP was 0.2 μM, which is lower than the other analytical techniques. Moreover, the proposed sensor was successfully applied for the detection of 6-BAP in environmental samples with good recoveries. The proposed assay provides a simple and cost-effective method for the analysis of 6-BAP in vegetable and water samples.

Spectrophotometric total reducing sugars assay based on cupric reduction.

PubMed

Başkan, Kevser Sözgen; Tütem, Esma; Akyüz, Esin; Özen, Seda; Apak, Reşat

2016-01-15

As the concentration of reducing sugars (RS) is controlled by European legislation for certain specific food and beverages, a simple and sensitive spectrophotometric method for the determination of RS in various food products is proposed. The method is based on the reduction of Cu(II) to Cu(I) with reducing sugars in alkaline medium in the presence of 2,9-dimethyl-1,10-phenanthroline (neocuproine: Nc), followed by the formation of a colored Cu(I)-Nc charge-transfer complex. All simple sugars tested had the linear regression equations with almost equal slope values. The proposed method was successfully applied to fresh apple juice, commercial fruit juices, milk, honey and onion juice. Interference effect of phenolic compounds in plant samples was eliminated by a solid phase extraction (SPE) clean-up process. The method was proven to have higher sensitivity and precision than the widely used dinitrosalicylic acid (DNS) colorimetric method. Copyright © 2015 Elsevier B.V. All rights reserved.

Colorimetric detection of biothiols based on aggregation of chitosan-stabilized silver nanoparticles

NASA Astrophysics Data System (ADS)

Mohammadi, Somayeh; Khayatian, Gholamreza

2017-10-01

We have described a simple and reliable colorimetric method for the sensing of biothiols such as cysteine, homocysteine, and glutathione in biological samples. The selective binding of chitosan capped silver nanoparticles to biothiols induced aggregation of the chitosan-Ag NPs. But the other amino acids that do not have thiol group cannot aggregate the chitosan-Ag NPs. Aggregation of chitosan-Ag NPs has been confirmed with UV-vis absorption spectra, zeta potential and transmission electron microscopy images. Under optimum conditions, good linear relationships existed between the absorption ratios (at A500/A415) and the concentrations of cysteine, homocysteine, and glutathione in the range of 0.1-10.0 μM with detection limits of 15.0, 84.6 and 40.0 nM, respectively. This probe was successfully applied to detect these biothiols in biological samples (urine and plasma).

Colorimetric detection of glucose based on gold nanoparticles coupled with silver nanoparticles

NASA Astrophysics Data System (ADS)

Gao, Yan; Wu, Yiting; Di, Junwei

2017-02-01

We have coupled gold nanoparticles (AuNPs) with silver nanoparticles (AgNPs) to assemble a plasmonic sensing platform for colorimetric detection of glucose. In this system, small AuNPs ( 4 nm) can act as glucose oxidase (GOD) mimic enzyme to catalytically oxidize glucose in the presence of oxygen, producing hydrogen peroxide, which dissolves AgNPs to lead the color changes. Glucose can be detected not only by naked eyes (from yellow to red) but also by spectrophotometer in the concentration range of 5-70 μM, with detection limit of 3 μM. More importantly, we found that L-cysteine added in the system can markedly improve the selectivity for the detection of glucose. The proposed method was used to application for the detection of glucose in human serum with satisfactory results. This system is simple and low cost without using any enzymes and organic chromogenic agents.

A label-free colorimetric aptasensor for simple, sensitive and selective detection of Pt (II) based on platinum (II)-oligonucleotide coordination induced gold nanoparticles aggregation.

PubMed

Fan, Daoqing; Zhai, Qingfeng; Zhou, Weijun; Zhu, Xiaoqing; Wang, Erkang; Dong, Shaojun

2016-11-15

Herein, a gold nanoparticles (AuNPs) based label-free colorimetric aptasensor for simple, sensitive and selective detection of Pt (II) was constructed for the first time. Four bases (G-G mismatch) mismatched streptavidin aptamer (MSAA) was used to protect AuNPs from salt-induced aggregation and recognize Pt (II) specifically. Only in the presence of Pt (II), coordination occurs between G-G bases and Pt (II), leading to the activation of streptavidin aptamer. Streptavidin coated magnetic beads (MBs) were used as separation agent to separate Pt (II)-coordinated MSAA. The residual less amount of MSAA could not efficiently protect AuNPs anymore and aggregation of AuNPs will produce a colorimetric product. With the addition of Pt (II), a pale purple-to-blue color variation could be observed by the naked eye. A detection limit of 150nM and a linear range from 0.6μM to 12.5μM for Pt (II) could be achieved without any amplification. Copyright © 2016 Elsevier B.V. All rights reserved.

A Simple and Green Route for Room-Temperature Synthesis of Gold Nanoparticles and Selective Colorimetric Detection of Cysteine.

PubMed

Bagci, Pelin Onsekizoglu; Wang, Yi-Cheng; Gunasekaran, Sundaram

2015-09-01

Gold nanoparticles (AuNPs) were synthesized at room temperature following a simple, rapid, and green route using fresh-squeezed apple juice as a reducing reagent. The optimal AuNPs, based on the particle color, stability, and color change suitable for colorimetric detection of cysteine (Cys), are synthesized using 5 mL of 10% apple juice, 1 mL of 10 mM gold precursor solution, and 1 mL of 0.1 M NaOH. Under this set of parameters, the AuNPs are synthesized within 30 min at room temperature. The average size (11.1 ± 3.2 nm) and ζ potential (-36.5 mV) of the AuNPs synthesized were similar to those of AuNPs prepared via the conventional citrate-reduction method. In the presence of Cys, unlike with any other amino acid, the AuNPs aggregated, possibly due to the gold-sulfur covalent interaction, yielding red-to-purple color change of the sample solution. The red-shift of the localized surface plasmon resonance peak of the AuNPs responsible for the color change was recorded by UV-vis spectrometer. The effect of other potential interferents such as glucose, ascorbic acid, K(+) , Na(+) , Ca(2+) , Zn(2+) , Ag(+) , Ni(2+) , Cu(2+) , Co(2+) , and Hg(2+) were also examined. The results show that AuNPs can be used to selectively detect and measure Cys with a linear dependency in the range of 2 to 100 μM and a limit of detection (signal-to-noise ratio > 3) of 50 nM. The results suggest that the green-synthesized AuNPs are useful for simple, rapid, and sensitive colorimetric detection of Cys, which is an essential amino acid in food and biological systems. © 2015 Institute of Food Technologists®

The colorimetric detection of Pb2+ by using sodium thiosulfate and hexadecyl trimethyl ammonium bromide modified gold nanoparticles.

PubMed

Zhang, Yujie; Leng, Yumin; Miao, Lijing; Xin, Junwei; Wu, Aiguo

2013-04-21

A simple, rapid colorimetric detection method for Pb(2+) in aqueous solution has been developed by using sodium thiosulfate (Na2S2O3) and hexadecyl trimethyl ammonium bromide (CTAB) modified gold nanoparticles (Au NPs). Na2S2O3 was added into the Au NP solution and thiosulfate ions (S2O3(2-)) were adsorbed on the surface of the Au NPs due to electrostatic interactions. Au atoms on the surface of the Au NPs were then oxidized to Au(i) by the O2 that existed in the solution in presence of thiosulfate. The addition of Pb(2+) (the final concentration was lower than 10 μM), accelerated the leaching of the Au NPs, and Pb-Au alloys also formed on the surface of the Au NPs. There was an obvious decrease in the surface plasmon resonance (SPR) absorption of the Au NPs. The lowest concentration for Pb(2+) that could be detected by the naked eye was 0.1 μM and using UV-vis spectroscopy was 40 nM. This is lower than the lead toxic level defined by the US Environmental Protection Agency (US EPA), which is 75 nM. In this method, CTAB, as a stabilizing agent for Au NPs, can accelerate the adsorption of S2O3(2-) on the surface of the Au NPs, which shortened the detection time to within 30 min. Moreover, this detection method is simple, cheap and environmentally friendly.

Non-crosslinking gold nanoprobe-LAMP for simple, colorimetric, and specific detection of Salmonella typhi

NASA Astrophysics Data System (ADS)

Bozorgmehr, Ali; Yazdanparast, Razieh; Mollasalehi, Hamidreza

2016-12-01

In this study, we developed a non-crosslinking gold nanoprobe loop-mediated isothermal amplification (LAMP) method for nanodiagnosis of bacterial typhoid fever source, Salmonella typhi. Therefore, a unique region in the S. typhi genomic DNA was targeted for LAMP amplification using a specific set of four precisely designed primers. Also, for specific colorimetric visualization of the amplicons, a thiolated oligonucleotide probe, complementary to the single-stranded loop region of the amplicons between F2 and F1C segments, was designed. The probe was bound to the surface of gold nanoparticles via covalent bonds. Increasing the salt concentration in the detection reaction medium led to aggregation of nanoprobes in the blank and the negative vessels in a time-dependent form. That was followed by a change in the surface plasmon resonance (SPR) leading to blue/black color that was observable by the naked eyes after about 5 min. Meanwhile, the original pink/red color was retained in the positive sample due to the large interparticle spaces and the stability against the ionic strength elevation which persisted for about 30 min. The whole process of DNA extraction, amplification, and detection took less than 2 h with a sensitivity of 20 CFU/ml. The developed gold nanoprobe-LAMP could serve as a simple, rapid, and cost-effective method for nanodiagnosis of S. typhi in point-of-need applications.

Absolute colorimetric characterization of a DSLR camera

NASA Astrophysics Data System (ADS)

Guarnera, Giuseppe Claudio; Bianco, Simone; Schettini, Raimondo

2014-03-01

A simple but effective technique for absolute colorimetric camera characterization is proposed. It offers a large dynamic range requiring just a single, off-the-shelf target and a commonly available controllable light source for the characterization. The characterization task is broken down in two modules, respectively devoted to absolute luminance estimation and to colorimetric characterization matrix estimation. The characterized camera can be effectively used as a tele-colorimeter, giving an absolute estimation of the XYZ data in cd=m2. The user is only required to vary the f - number of the camera lens or the exposure time t, to better exploit the sensor dynamic range. The estimated absolute tristimulus values closely match the values measured by a professional spectro-radiometer.

Methods for the isolation, culture and assessment of the status of anaerobic rumen chytrids in both in vitro and in vivo systems.

PubMed

Rezaeian, Mohammad; Beakes, Gordon W; Parker, David S

2004-10-01

Anaerobic fungi were isolated from both the rumen and faeces of nine sheep and a cow. A reliable and simple method for the isolation of anaerobic fungi using 24 h rumen incubated milled straw as the inoculum source was developed. We also evaluate the use of chitin measurements as an assay of rumen fungal biomass. Chitin levels were determined from various sample sources (milled barley straw used as the fungal culture substrate in vitro; plant particulate digests from the rumen (PLP) and centrifuged strained rumen fluid (CSRF) using both HPLC and colorimetric methods. Both methods were highly correlated and consequently the simpler colorimetric method was adopted for subsequent studies. There was also a high degree of correlation between anaerobic fungal cellulase activities with the assayed chitin content of milled barley straw cultures over 12 d of an in vitro experiment. The colorimetric chitin assay protocol was then used to assess the diurnal variation and abundance of rumen fungi in in vivo assays. We assessed the distribution of chitin (mg g(-1) dry matter) in various fractions of the strained rumen fluid (SRF) and PLP samples from the rumen of sheep. Chitin was detected in all fractions of strained rumen fluid but the main source of chitin in the samples may be attributed to the fungal biomass. We did not detect any significant differences in chitin levels over a 24 h sampling period. Finally, an SEM study on subsamples of milled straw and plant particulate matter used in the chitin assays, revealed that the pattern of the fungal development on substrate material differs from the culture medium to the rumen.

Colorimetric detection of copper ions in sub-micromolar concentrations using a triarylamine-linked resin bead.

PubMed

Thomas, Tony George; Sreenath, Kesavapillai; Gopidas, Karical R

2012-11-21

The triarylamine derivative ETPA reacts with Cu(2+) to give deeply colored, stable radical cations in acetonitrile solution. ETPA was immobilized on to a tentagel resin bead which was then used for the fabrication of a simple device capable of the colorimetric detection of submicromolar concentrations of Cu(2+) ions in water. The naked eye detection limit reported here for Cu(2+) is one of the lowest ever reported for small molecule sensors.

UV-vis spectroscopy and colorimetric models for detecting anthocyanin-metal complexes in plants: An overview of in vitro and in vivo techniques.

PubMed

Fedenko, Volodymyr S; Shemet, Sergiy A; Landi, Marco

2017-05-01

Although anthocyanin (ACN) biosynthesis is one of the best studied pathways of secondary metabolism in plants, the possible physiological and ecological role(s) of these pigments continue to intrigue scientists. Like other dihydroxy B-ring substituted flavonoids, ACNs have an ability to bind metal and metalloid ions, a property that has been exploited for a variety of purposes. For example, the metal binding ability may be used to stabilize ACNs from plant food sources, or to modify their colors for using them as food colorants. The complexation of metals with cyanidin derivatives can also be used as a simple, sensitive, cheap, and rapid method for determination concentrations of several metals in biological and environmental samples using UV-vis spectroscopy. Far less information is available on the ecological significance of ACN-metal complexes in plant-environment interactions. Metalloanthocyanins (protocyanin, nemophilin, commelinin, protodelphin, cyanosalvianin) are involved in the copigmentation phenomenon that leads to blue-pigmented petals, which may facilitate specific plant-pollinator interactions. ACN-metal formation and compartmentation into the vacuole has also been proposed to be part of an orchestrated detoxification mechanism in plants which experience metal/metalloid excess. However, investigations into ACN-metal interactions in plant biology may be limited because of the complexity of the analytical techniques required. To address this concern, here we describe simple methods for the detection of ACN-metal both in vitro and in vivo using UV-vis spectroscopy and colorimetric models. In particular, the use of UV-vis spectra, difference absorption spectra, and colorimetry techniques will be described for in vitro determination of ACN-metal features, whereas reflectance spectroscopy and colorimetric parameters related to CIE L * a * b * and CIE XYZ systems will be detailed for in vivo analyses. In this way, we hope to make this high-informative tool more accessible to plant physiologists and ecologists. Copyright © 2017 Elsevier GmbH. All rights reserved.

Colorimetric detection of Cr (VI) based on the leaching of gold nanoparticles using a paper-based sensor.

PubMed

Guo, Jian-Feng; Huo, Dan-Qun; Yang, Mei; Hou, Chang-Jun; Li, Jun-Jie; Fa, Huan-Bao; Luo, Hui-Bo; Yang, Ping

2016-12-01

Herein, we have developed a simple, sensitive and paper-based colorimetric sensor for the selective detection of Chromium (Ⅵ) ions (Cr (VI)). Silanization-titanium dioxide modified filter paper (STCP) was used to trap bovine serum albumin capped gold nanoparticles (BSA-Au NPs), leading to the fabrication of BSA-Au NPs decorated membrane (BSA-Au NPs/STCP). The BSA-Au NPs/STCP operated on the principle that BSA-Au NPs anchored on the STCP were gradually etched by Cr (VI) as the leaching process of gold in the presence of hydrobromic acid (HBr) and hence induced a visible color change. Under optimum conditions, the paper-based colorimetric sensor showed clear color change after reaction with Cr (VI) as well as with favorable selectivity to a variety of possible interfering counterparts. The amount-dependent colorimetric response was linearly correlated with the Cr (VI) concentrations ranging from 0.5µM to 50.0µM with a detection limit down to 280nM. Moreover, the developed cost-effective colorimetric sensor has been successfully applied to real environmental samples which demonstrated the potential for field applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

PubMed Central

Wang, Hui; Zhang, Ke-Qin

2013-01-01

Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

Giant Gold Nanowire Vesicle-Based Colorimetric and SERS Dual-Mode Immunosensor for Ultrasensitive Detection of Vibrio parahemolyticus.

PubMed

Guo, Zhiyong; Jia, Yaru; Song, Xinxin; Lu, Jing; Lu, Xuefei; Liu, Baoqing; Han, Jiaojiao; Huang, Youju; Zhang, Jiawei; Chen, Tao

2018-05-15

Conventional methods for the detection of Vibrio parahemolyticus (VP) usually need tedious, labor-intensive processes, and have low sensitivity, which further limits their practical applications. Herein, we developed a simple and efficient colorimetry and surface-enhanced Raman scattering (SERS) dual-mode immunosensor for sensitive detection of VP, by employing giant Au vesicles with anchored tiny gold nanowires (AuNW) as a smart probe. Due to the larger specific surface and special hollow structure of giant Au vesicles, silver staining would easily lead to vivid color change for colorimetric analysis and further amplify SERS signals. The t-test was further used to determine if two sets of data from colorimetry and SERS were significantly different from each other. The result shows that there was no significant difference between data from the two methods. Two sets of data can mutually validate each other and avoid false positive and negative detection. The designed colorimetry-SERS dual-mode sensor would be very promising in various applications such as food safety inspection, personal healthcare, and on-site environmental monitoring.

An instrument-free, screen-printed paper microfluidic device that enables bio and chemical sensing.

PubMed

Mohammadi, Saeed; Maeki, Masatoshi; Mohamadi, Reza M; Ishida, Akihiko; Tani, Hirofumi; Tokeshi, Manabu

2015-10-07

This paper describes a simple and instrument-free screen-printing method to fabricate hydrophilic channels by patterning polydimethylsiloxane (PDMS) onto chromatography paper. Clearly recognizable border lines were formed between hydrophilic and hydrophobic areas. The minimum width of the printed channel to deliver an aqueous sample was 600 μm, as obtained by this method. Fabricated microfluidic paper-based analytical devices (μPADs) were tested for several colorimetric assays of pH, glucose, and protein in both buffer and artificial urine samples and results were obtained in less than 30 min. The limits of detection (LODs) for glucose and bovine serum albumin (BSA) were 5 mM and 8 μM, respectively. Furthermore, the pH values of different solutions were visually recognised with the naked eye by using a sensitive ink. Ultimately, it is expected that this PDMS-screen-printing (PSP) methodology for μPADs can be readily translated to other colorimetric detection and hydrophilic channels surrounded by a hydrophobic polymer can be formed to transport fluids toward target zones.

Colorimetric detection of cholesterol based on enzyme modified gold nanoparticles

NASA Astrophysics Data System (ADS)

Nirala, Narsingh R.; Saxena, Preeti S.; Srivastava, Anchal

2018-02-01

We develop a simple colorimetric method for determination of free cholesterol in aqueous solution based on functionalized gold nanoparticles with cholesterol oxidase. Functionalized gold nanoparticles interact with free cholesterol to produce H2O2 in proportion to the level of cholesterol visually is being detected. The quenching in optical properties and agglomeration of functionalized gold nanoparticles play a key role in cholesterol sensing due to the electron accepting property of H2O2. While the lower ranges of cholesterol (lower detection limit i.e. 0.2 mg/dL) can be effectively detected using fluorescence study, the absorption study attests evident visual color change which becomes effective for detection of higher ranges of cholesterol (lower detection limit i.e. 19 mg/dL). The shades of red gradually change to blue/purple as the level of cholesterol detected (as evident at 100 mg/dL) using unaided eye without the use of expensive instruments. The potential of the proposed method to be applied in the field is shown by the proposed cholesterol measuring color wheel.

Integration of Novel Low-Cost Colorimetric, Laser Photometric, and Visual Fluorescent Techniques for Rapid Identification of Falsified Medicines in Resource-Poor Areas: Application to Artemether–Lumefantrine

PubMed Central

Green, Michael D.; Hostetler, Dana M.; Nettey, Henry; Swamidoss, Isabel; Ranieri, Nicola; Newton, Paul N.

2015-01-01

The availability of falsified antimalarial drugs can be reduced with effective drug regulatory agencies and proper enforcement. Fundamental to these agencies taking action, rapid identification must be made as soon as they appear in the market place. Since falsified antimalarials occur mostly in developing countries, performing drug analysis presents itself with unique challenges. A fundamental factor in choosing a useful technique is affordability and simplicity. Therefore, we suggest a three-tiered drug evaluation strategy for identifying a falsified drug in resource-poor areas. Tier I is a simple comparison of a tablet's weight and dimensions with official specifications. Tier II uses inexpensive photometric devices (laser and fluorescence) to evaluate a tablet. Suspicious samples from Tier I and II assessments are then subjected to a colorimetric assay for active ingredients identification and quantification. In this article, we evaluate a novel colorimetric assay for the simultaneous assessment of both lumefantrine and artemether in co-formulated Coartem™ tablets, and integrate the method with two novel, low-cost, fluorescence and laser photometric devices. Image analysis software is used for the assessments. Although artemether–lumefantrine is used as an example, the strategy may be adapted to other medicines. PMID:25897066

Integration of novel low-cost colorimetric, laser photometric, and visual fluorescent techniques for rapid identification of falsified medicines in resource-poor areas: application to artemether-lumefantrine.

PubMed

Green, Michael D; Hostetler, Dana M; Nettey, Henry; Swamidoss, Isabel; Ranieri, Nicola; Newton, Paul N

2015-06-01

The availability of falsified antimalarial drugs can be reduced with effective drug regulatory agencies and proper enforcement. Fundamental to these agencies taking action, rapid identification must be made as soon as they appear in the market place. Since falsified antimalarials occur mostly in developing countries, performing drug analysis presents itself with unique challenges. A fundamental factor in choosing a useful technique is affordability and simplicity. Therefore, we suggest a three-tiered drug evaluation strategy for identifying a falsified drug in resource-poor areas. Tier I is a simple comparison of a tablet's weight and dimensions with official specifications. Tier II uses inexpensive photometric devices (laser and fluorescence) to evaluate a tablet. Suspicious samples from Tier I and II assessments are then subjected to a colorimetric assay for active ingredients identification and quantification. In this article, we evaluate a novel colorimetric assay for the simultaneous assessment of both lumefantrine and artemether in co-formulated Coartem™ tablets, and integrate the method with two novel, low-cost, fluorescence and laser photometric devices. Image analysis software is used for the assessments. Although artemether-lumefantrine is used as an example, the strategy may be adapted to other medicines. © The American Society of Tropical Medicine and Hygiene.

Evaluation of colorimetric loop-mediated isothermal amplification assay for visual detection of Streptococcus agalactiae and Streptococcus iniae in tilapia.

PubMed

Suebsing, R; Kampeera, J; Tookdee, B; Withyachumnarnkul, B; Turner, W; Kiatpathomchai, W

2013-10-01

Streptococcus agalactiae and Strep. iniae are bacterial pathogens that cause streptococcosis in many fish species. An accelerated colorimetric loop-mediated isothermal amplification (LAMP) assay with pre-addition of calcein was established, and the transmission and detection of Strep. agalactiae and Strep. iniae in tilapia under natural aquatic environment were investigated. A positive reaction was observed by a colour change from orange to green through the naked eyes after completion at 63°C for 30 min with 10 times higher sensitivity than that of nested PCR assays and without cross-amplification with other fish bacterial pathogens. All sample types of Nile and red tilapia (broodstock, fertilized egg, fry) were Strep. agalactiae- and Strep. iniae positive by this new method, implying that they could be vertically transmitted. With its application for screening broodstock and fry before stocking and for monitoring fish health in grow-out ponds, the method would become very useful in fish farming industry. The application of colorimetric LAMP with pre-addition of calcein offers simple, rapid and sensitive technique with applicability for small field laboratories. This technique explored the possible vertical transmission mode of Strep. agalactiae and Strep. iniae under natural aquatic environment. It could be such preliminary data provided for the screening broodstock before breeding and/or the specific-pathogen-free production. © 2013 The Society for Applied Microbiology.

A highly selective colorimetric and fluorescent chemosensor for Al(III) based-on simple naphthol in aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Zhaodi; Xu, Huajie; Sheng, Liangquan; Chen, Shuisheng; Huang, Deqian; Liu, Jie

2016-03-01

A colorimetric and fluorescent chemosensor (L) for Al(III) was synthesized and fully characterized. L could be both used as a colorimetric and fluorescent chemosensor for the detection of Al3 + ions with low detection limit (8.87 × 10- 7 M) in CH3CN-H2O (1:1, v/v) solution. The binding ratio of L-Al3 + was determined from the Job plot (absorption and fluorescence spectra) and MALDI-TOF MS data to be 1:1. The binding constant (Ka) of Al3 + binding to L was calculated to be 4.8 × 105 M- 1 from a Benesi-Hildebrand plot. Moreover, the binding site of L with Al3 + was determined by 1H NMR titration experiment.

Determination of glucose and uric acid with bienzyme colorimetry on microfluidic paper-based analysis devices.

PubMed

Chen, Xi; Chen, Jin; Wang, Fubin; Xiang, Xia; Luo, Ming; Ji, Xinghu; He, Zhike

2012-05-15

In this work, we first employ a drying method combining with the bienzyme colorimetric detection of glucose and uric acid on microfluidic paper-based analysis devices (μPADs). The channels of 3D μPADs are also designed by us to get better results. The color results are recorded by both Gel Documentation systems and a common camera. By using Gel Documentation systems, the limits of detection (LOD) of glucose and uric acid are 3.81 × 10(-5)M and 4.31 × 10(-5)M, respectively one order of magnitude lower than that of the reported methods on μPADs. By using a common camera, the limits of detection (LOD) of glucose and uric acid are 2.13 × 10(-4)M and 2.87 × 10(-4)M, respectively. Furthermore, the effects of detection conditions have been investigated and discussed comprehensively. Human serum samples are detected with satisfactory results, which are comparable with the clinical testing results. A low-cost, simple and rapid colorimetric method for the simultaneous detection of glucose and uric acid on the μPADs has been developed with enhanced sensitivity. Copyright © 2012 Elsevier B.V. All rights reserved.

Colorimetric detection of uranium in water

DOEpatents

DeVol, Timothy A [Clemson, SC; Hixon, Amy E [Piedmont, SC; DiPrete, David P [Evans, GA

2012-03-13

Disclosed are methods, materials and systems that can be used to determine qualitatively or quantitatively the level of uranium contamination in water samples. Beneficially, disclosed systems are relatively simple and cost-effective. For example, disclosed systems can be utilized by consumers having little or no training in chemical analysis techniques. Methods generally include a concentration step and a complexation step. Uranium concentration can be carried out according to an extraction chromatographic process and complexation can chemically bind uranium with a detectable substance such that the formed substance is visually detectable. Methods can detect uranium contamination down to levels even below the MCL as established by the EPA.

Met-myoglobin formation, accumulation, degradation, and myoglobin oxygenation monitoring based on multiwavelength attenuance measurement in porcine meat

NASA Astrophysics Data System (ADS)

Nguyen, Thien; Phan, Kien Nguyen; Lee, Jee-Bum; Kim, Jae Gwan

2016-05-01

We propose a simple, rapid, and nondestructive method to investigate formation, accumulation, and degradation of met-myoglobin (met-Mb) and myoglobin oxygenation from the interior of porcine meat. For the experiment, color photos and attenuance spectra of porcine meat (well-bled muscle, fat, and mixed) were collected daily to perform colorimetric analysis and to obtain the differences of attenuance between 578 and 567 nm (A578-A567) and between 615 and 630 nm (A630-A615), respectively. Oxy-, deoxy-, and met-myoglobin concentration changes over storage time were also calculated using Beer-Lamberts' law with reflectance intensities at 557, 582, and 630 nm. The change of A578-A567 was well matched with the change of myoglobin oxygenation, and the change of A630-A615 corresponded well with the formation and degradation of met-Mb. In addition, attenuation differences, A578-A567 and A630-A615, were able to show the formation of met-Mb earlier than colorimetric analysis. Therefore, the attenuance differences between wavelengths can be indicators for estimating myoglobin oxygenation and met-Mb formation, accumulation, and degradation, which enable us to design a simple device to monitor myoglobin activities in porcine meat.

A Schiff-based colorimetric fluorescent sensor with the potential for detection of fluoride ions.

PubMed

Huang, Cheng-Yin; Wan, Chin-Feng; Chir, Jiun-Ly; Wu, An-Tai

2013-11-01

A simple Schiff-based colorimetric fluorescent receptor 1 was prepared. It exhibits a "turn-on-type" mode with high sensitivity in the presence of F(-). The change in color is very easily observed by the naked eye in the presence of F(-), whereas other anions do not induce such a change. Job plot indicated a 1:2 complexation stoichiometry between receptor 1 and F(-). The association constant for 1-F(-) in CH3CN was determined as 1.32*10(5) M(-2) by a Hill plot.

Efficient colorimetric and fluorescent detection of fluoride in DMSO-water mixtures with arylaldoximes.

PubMed

Rosen, Christian B; Hansen, Dennis J; Gothelf, Kurt V

2013-12-07

Fluoride detection through hydrogen bonding or deprotonation is most commonly achieved using amide, urea or pyrrole derivatives. The sensor molecules are often complex constructs and several synthetic steps are required for their preparation. Here we report the discovery that simple arylaldoximes have remarkable properties as fluoride anion sensors, providing distinct colorimetric or fluorescent readouts, depending on the structure of the arylaldoxime. The oximes showed exceptional selectivity towards fluoride over other typical anions, and low detection limits for fluoride in both DMSO and DMSO-water mixtures were obtained.

Accuracy of Blood Loss Measurement during Cesarean Delivery.

PubMed

Doctorvaladan, Sahar V; Jelks, Andrea T; Hsieh, Eric W; Thurer, Robert L; Zakowski, Mark I; Lagrew, David C

2017-04-01

Objective  This study aims to compare the accuracy of visual, quantitative gravimetric, and colorimetric methods used to determine blood loss during cesarean delivery procedures employing a hemoglobin extraction assay as the reference standard. Study Design  In 50 patients having cesarean deliveries blood loss determined by assays of hemoglobin content on surgical sponges and in suction canisters was compared with obstetricians' visual estimates, a quantitative gravimetric method, and the blood loss determined by a novel colorimetric system. Agreement between the reference assay and other measures was evaluated by the Bland-Altman method. Results  Compared with the blood loss measured by the reference assay (470 ± 296 mL), the colorimetric system (572 ± 334 mL) was more accurate than either visual estimation (928 ± 261 mL) or gravimetric measurement (822 ± 489 mL). The correlation between the assay method and the colorimetric system was more predictive (standardized coefficient = 0.951, adjusted R 2  = 0.902) than either visual estimation (standardized coefficient = 0.700, adjusted R 2  = 00.479) or the gravimetric determination (standardized coefficient = 0.564, adjusted R 2  = 0.304). Conclusion  During cesarean delivery, measuring blood loss using colorimetric image analysis is superior to visual estimation and a gravimetric method. Implementation of colorimetric analysis may enhance the ability of management protocols to improve clinical outcomes.

Accuracy of Blood Loss Measurement during Cesarean Delivery

PubMed Central

Doctorvaladan, Sahar V.; Jelks, Andrea T.; Hsieh, Eric W.; Thurer, Robert L.; Zakowski, Mark I.; Lagrew, David C.

2017-01-01

Objective This study aims to compare the accuracy of visual, quantitative gravimetric, and colorimetric methods used to determine blood loss during cesarean delivery procedures employing a hemoglobin extraction assay as the reference standard. Study Design In 50 patients having cesarean deliveries blood loss determined by assays of hemoglobin content on surgical sponges and in suction canisters was compared with obstetricians' visual estimates, a quantitative gravimetric method, and the blood loss determined by a novel colorimetric system. Agreement between the reference assay and other measures was evaluated by the Bland–Altman method. Results Compared with the blood loss measured by the reference assay (470 ± 296 mL), the colorimetric system (572 ± 334 mL) was more accurate than either visual estimation (928 ± 261 mL) or gravimetric measurement (822 ± 489 mL). The correlation between the assay method and the colorimetric system was more predictive (standardized coefficient = 0.951, adjusted R2 = 0.902) than either visual estimation (standardized coefficient = 0.700, adjusted R2 = 00.479) or the gravimetric determination (standardized coefficient = 0.564, adjusted R2 = 0.304). Conclusion During cesarean delivery, measuring blood loss using colorimetric image analysis is superior to visual estimation and a gravimetric method. Implementation of colorimetric analysis may enhance the ability of management protocols to improve clinical outcomes. PMID:28497007

A simple analytical procedure to replace HPLC for monitoring treatment concentrations of chloramine-T on fish culture facilities

USGS Publications Warehouse

Dawson, Verdel K.; Meinertz, Jeffery R.; Schmidt, Larry J.; Gingerich, William H.

2003-01-01

Concentrations of chloramine-T must be monitored during experimental treatments of fish when studying the effectiveness of the drug for controlling bacterial gill disease. A surrogate analytical method for analysis of chloramine-T to replace the existing high-performance liquid chromatography (HPLC) method is described. A surrogate method was needed because the existing HPLC method is expensive, requires a specialist to use, and is not generally available at fish hatcheries. Criteria for selection of a replacement method included ease of use, analysis time, cost, safety, sensitivity, accuracy, and precision. The most promising approach was to use the determination of chlorine concentrations as an indicator of chloramine-T. Of the currently available methods for analysis of chlorine, the DPD (N,N-diethyl-p-phenylenediamine) colorimetric method best fit the established criteria. The surrogate method was evaluated under a variety of water quality conditions. Regression analysis of all DPD colorimetric analyses with the HPLC values produced a linear model (Y=0.9602 X+0.1259) with an r2 value of 0.9960. The average accuracy (percent recovery) of the DPD method relative to the HPLC method for the combined set of water quality data was 101.5%. The surrogate method was also evaluated with chloramine-T solutions that contained various concentrations of fish feed or selected densities of rainbow trout. When samples were analyzed within 2 h, the results of the surrogate method were consistent with those of the HPLC method. When samples with high concentrations of organic material were allowed to age more than 2 h before being analyzed, the DPD method seemed to be susceptible to interference, possibly from the development of other chloramine compounds. However, even after aging samples 6 h, the accuracy of the surrogate DPD method relative to the HPLC method was within the range of 80–120%. Based on the data comparing the two methods, the U.S. Food and Drug Administration has concluded that the DPD colorimetric method is appropriate to use to measure chloramine-T in water during pivotal efficacy trials designed to support the approval of chloramine-T for use in fish culture.

A colorimetric indicator-displacement assay array for selective detection and identification of biological thiols.

PubMed

Qian, Sihua; Lin, Hengwei

2014-03-01

A simple, inexpensive yet highly selective colorimetric indicator-displacement assay array for the simultaneous detection and identification of three important biothiols at micromolar concentrations under physiological conditions and in real samples has been developed in this work. With use of an array composed of metal indicators and metal ions, clear differentiation among cysteine, homocysteine and glutathione was achieved. On the basis of the colour change of the array, quantification of each analyte was accomplished easily, and different biothiols were identified readily using standard chemometric approaches (hierarchical clustering analysis). Moreover, the colorimetric sensor array was not responsive to changes with 19 other natural amino acids, and it showed excellent reproducibility. Importantly, the sensor array developed was successfully applied to the determination and identification of the three biothiols in a real biological sample.

Colorimetric detection of copper in water using a Schiff base derivative

NASA Astrophysics Data System (ADS)

Peralta Domínguez, D.; Ramos-Ortiz, G.; Maldonado, J. L.; Rodriguez, M.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Santillan, R.; Farfán, N.

2013-09-01

Organic molecular sensors have the advantage of being used through an easy, fast, economical and reliable optical method for detecting toxic metal ions in our environment. In this work, we present a simple but highly specific organic ligand compound 5-Chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for ions in a mixture of acetonitrile/water (ratio 10:1, v:v). Binding interaction between L1 and various metal-ions has been established by ultraviolet-visible spectroscopic measurements that indicate favorable coordination of the ligand with selective metal ions, particularly, with copper. These results showed that the electronic transition band shape of L1 change after binding with copper in aqueous solution. L1 exhibited binding-induced color changes from yellow to pink one detected by the naked eye. This new sensor presented 2.5 × 10-6 M as limit detection, even under the presence of other metal ions.

Ultrasensitive colorimetric detection of heparin based on self-assembly of gold nanoparticles on graphene oxide.

PubMed

Fu, Xiuli; Chen, Lingxin; Li, Jinhua

2012-08-21

A novel colorimetric method was developed for ultrasensitive detection of heparin based on self-assembly of gold nanoparticles (AuNPs) onto the surface of graphene oxide (GO). Polycationic protamine was used as a medium for inducing the self-assembly of citrate-capped AuNPs on GO through electrostatic interaction, resulting in a shift in the surface plasmon resonance (SPR) absorption of AuNPs and exhibiting a blue color. Addition of polyanionic heparin disturbed the self-assemble of AuNPs due to its strong affinity to protamine. With the increase of heparin concentration, the amounts of self-assembly AuNPs decreased and the color changed from blue to red in solution. Therefore, a "blue-to-red" colorimetric sensing strategy based on self-assembly of AuNPs could be established for heparin detection. Compared with the commonly reported aggregation-based methods ("red-to-blue"), the color change from blue to red was more eye-sensitive, especially in low concentration of target. Moreover, stronger interaction between protamine and heparin led to distinguish heparin from its analogues as well as various potentially coexistent physiological species. The strategy was simply achieved by the self-assembly nature of AuNPs and the application of two types of polyionic media, showing it to be label-free, simple, rapid and visual. This method could selectively detect heparin with a detection limit of 3.0 ng mL(-1) in standard aqueous solution and good linearity was obtained over the range 0.06-0.36 μg mL(-1) (R = 0.9936). It was successfully applied to determination of heparin in fetal bovine serum samples as low as 1.7 ng mL(-1) with a linear range of 0-0.8 μg mL(-1).

Determination of colloidal and dissolved silver in water samples using colorimetric solid-phase extraction.

PubMed

Hill, April A; Lipert, Robert J; Porter, Marc D

2010-03-15

The increase in bacterial resistance to antibiotics has led to resurgence in the use of silver as a biocidal agent in applications ranging from washing machine additives to the drinking water treatment system on the International Space Station (ISS). However, growing concerns about the possible toxicity of colloidal silver to bacteria, aquatic organisms and humans have led to recently issued regulations by the US EPA and FDA regarding the usage of silver. As part of an ongoing project, we have developed a rapid, simple method for determining total silver, both ionic (silver(I)) and colloidal, in 0.1-1mg/L aqueous samples, which spans the ISS potable water target of 0.3-0.5mg/L (total silver) and meets the US EPA limit of 0.1mg/L in drinking water. The method is based on colorimetric solid-phase extraction (C-SPE) and involves the extraction of silver(I) from water samples by passage through a solid-phase membrane impregnated with the colorimetric reagent DMABR (5-[4-(dimethylamino)benzylidene]rhodanine). Silver(I) exhaustively reacts with impregnated DMABR to form a colored compound, which is quantified using a handheld diffuse reflectance spectrophotometer. Total silver is determined by first passing the sample through a cartridge containing Oxone, which exhaustively oxidizes colloidal silver to dissolved silver(I). The method, which takes less than 2 min to complete and requires only approximately 1 mL of sample, has been validated through a series of tests, including a comparison with the ICP-MS analysis of a water sample from ISS that contained both silver(I) and colloidal silver. Potential earth-bound applications are also briefly discussed. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Colorimetric method for the detection of melamine using in-situ formed silver nanoparticles via tannic acid

NASA Astrophysics Data System (ADS)

Alam, Md. Fazle; Laskar, Amaj Ahmed; Ahmed, Shahbaz; Shaida, Mohd. Azfar; Younus, Hina

2017-08-01

Melamine toxicity has recently attracted worldwide attention as it causes renal failure and the death of humans and animals. Therefore, developing a simple, fast and sensitive method for the routine detection of melamine is the need of the hour. Herein, we have developed a selective colorimetric method for the detection of melamine in milk samples based upon in-situ formation of silver nanoparticles (AgNPs) via tannic acid. The AgNPs thus formed were characterized by UV-Visible spectrophotometer, transmission electron microscope (TEM), zetasizer and dynamic light scattering (DLS). The AgNPs were used to detect melamine under in vitro condition and in raw milk spiked with melamine. Under optimal conditions, melamine could be selectively detected in vitro within the concentration range of 0.05-1.4 μM with a limit of detection (LOD) of 0.01 μM, which is lower than the strictest melamine safety requirement of 1 ppm. In spiked raw milk, the recovery percentage range was 99.5-106.5% for liquid milk and 98.5-105.5% for powdered milk. The present method shows extreme selectivity with no significant interference with other substances like urea, glucose, glycine, ascorbic acid etc. This assay method does not utilize organic cosolvents, enzymatic reactions, light sensitive dye molecules and sophisticated instrumentation, thereby overcoming some of the limitations of the other conventional methods.

[Photometric determination of captopril using label-free silver nanoparticles].

PubMed

Li, Rui; Yan, Hong-Tao

2013-04-01

A simple, rapid and sensitive colorimetric method for the determination of captopril is presented in the present paper. It is based on the fact that captopril can induce the aggregation of AgNPs, thereby resulting in their yellow-to-red color change and the absorbance decrease at lambda395 nm. The mechanism of the aggregation effect was discussed in detail. Under the optimized conditions, the linear range of determination of captopril was 1-35 microg x mL(-1) with correction coefficient 0.998 4. The detection limit of the method for captopril was 0.7 microg x mL(-1). The method has been applied to the determination of captopril in tablets with satisfactory result.

Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification

NASA Astrophysics Data System (ADS)

Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

2015-02-01

A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg2+) detection was demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg2+ and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg2+, all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg2+, thymine bases of H0 could specifically interact with Hg2+ to form stable T-Hg2+-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N = 3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg2+-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.

Comparison of macro-gravimetric and micro-colorimetric lipid determination methods.

PubMed

Inouye, Laura S; Lotufo, Guiherme R

2006-10-15

In order to validate a method for lipid analysis of small tissue samples, the standard macro-gravimetric method of Bligh-Dyer (1959) [E.G. Bligh, W.J. Dyer, Can. J. Biochem. Physiol. 37 (1959) 911] and a modification of the micro-colorimetric assay developed by Van Handel (1985) [E. Van Handel, J. Am. Mosq. Control Assoc. 1 (1985) 302] were compared. No significant differences were observed for wet tissues of two species of fish. However, limited analysis of wet tissue of the amphipod, Leptocheirusplumulosus, indicated that the Bligh-Dyer gravimetric method generated higher lipid values, most likely due to the inclusion of non-lipid materials. Additionally, significant differences between the methods were observed with dry tissues, with the micro-colorimetric method consistently reporting calculated lipid values greater than as reported by the gravimetric method. This was most likely due to poor extraction of dry tissue in the standard Bligh-Dyer method, as no significant differences were found when analyzing a single composite extract. The data presented supports the conclusion that the micro-colorimetric method described in this paper is accurate, rapid, and minimizes time and solvent use.

Colorimetric determination of glutathione in human serum and cell lines by exploiting the peroxidase-like activity of CuS-polydopamine-Au composite.

PubMed

Wang, Yanying; Liu, Yaqin; Ding, Fang; Zhu, Xiaoyan; Yang, Li; Zou, Ping; Rao, Hanbing; Zhao, Qingbiao; Wang, Xianxiang

2018-06-07

In this study, we developed a simple colorimetric approach to detect glutathione (GSH). The proposed approach is based on the ability of CuS-PDA-Au composite material to catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to ox-TMB to induce a blue color with an absorption peak centered at 652 nm. However, the introduction of GSH can result in a decrease in oxidized TMB; similarly, it can combine with Au nanoparticles (Au NPs) on the surface of CuS-PDA-Au composite material. Both approaches can result in a fading blue color and a reduction of the absorbance at 652 nm. Based on this above, we proposed a technique to detect GSH quantitatively and qualitatively through UV-Vis spectroscopy and naked eye, respectively. This approach demonstrates a low detection limit of 0.42 μM with a broad detection range of 5 × 10 -7 -1 × 10 -4  M with the assistance of UV-Vis spectroscopy. More importantly, this approach is convenient and rapid. This method was successfully applied to GSH detection in human serum and cell lines. Graphical abstract A colorimetric approach has been developed by exploiting the peroxidase-like activity of CuS-polydopamine-Au composite for sensitive glutathione detection.

Rapid recognition of volatile organic compounds with colorimetric sensor arrays for lung cancer screening.

PubMed

Zhong, Xianhua; Li, Dan; Du, Wei; Yan, Mengqiu; Wang, You; Huo, Danqun; Hou, Changjun

2018-06-01

Volatile organic compounds (VOCs) in breath can be used as biomarkers to identify early stages of lung cancer. Herein, we report a disposable colorimetric array that has been constructed from diverse chemo-responsive colorants. Distinguishable difference maps were plotted within 4 min for specifically targeted VOCs. Through the consideration of various chemical interactions with VOCs, the arrays successfully discriminate between 20 different volatile organic compounds in breath that are related to lung cancer. VOCs were identified either with the visualized difference maps or through pattern recognition with an accuracy of at least 90%. No uncertainties or errors were observed in the hierarchical cluster analysis (HCA). Finally, good reproducibility and stability of the array was achieved against changes in humidity. Generally, this work provides fundamental support for construction of simple and rapid VOC sensors. More importantly, this approach provides a hypothesis-free array method for breath testing via VOC profiling. Therefore, this small, rapid, non-invasive, inexpensive, and visualized sensor array is a powerful and promising tool for early screening of lung cancer. Graphical abstract A disposable colorimetric array has been developed with broadly chemo-responsive dyes to incorporate various chemical interactions, through which the arrays successfully discriminate 20 VOCs that are related to lung cancer via difference maps alone or chemometrics within 4 min. The hydrophobic porous matrix provides good stability against changes in humidity.

Infrared and colorimetric characterization of discolored kiln-dried hard maple lumber

Treesearch

Benjamin E. Dawson-Andoh; Michael Wiemann; Laurent Matuana; John Baumgras

2004-01-01

Discoloration of hard maple lumber commonly occurs during kiln-drying. In this study, discolored andnondiscolored kiln-dried hard maple lumber boards were characterized using a colorimetric method and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). Colorimetric measurements (L*, a*, b*) were found to be in good agreement with visual...

Highly sensitive and specific colorimetric detection of cancer cells via dual-aptamer target binding strategy.

PubMed

Wang, Kun; Fan, Daoqing; Liu, Yaqing; Wang, Erkang

2015-11-15

Simple, rapid, sensitive and specific detection of cancer cells is of great importance for early and accurate cancer diagnostics and therapy. By coupling nanotechnology and dual-aptamer target binding strategies, we developed a colorimetric assay for visually detecting cancer cells with high sensitivity and specificity. The nanotechnology including high catalytic activity of PtAuNP and magnetic separation & concentration plays a vital role on the signal amplification and improvement of detection sensitivity. The color change caused by small amount of target cancer cells (10 cells/mL) can be clearly distinguished by naked eyes. The dual-aptamer target binding strategy guarantees the detection specificity that large amount of non-cancer cells and different cancer cells (10(4) cells/mL) cannot cause obvious color change. A detection limit as low as 10 cells/mL with detection linear range from 10 to 10(5) cells/mL was reached according to the experimental detections in phosphate buffer solution as well as serum sample. The developed enzyme-free and cost effective colorimetric assay is simple and no need of instrument while still provides excellent sensitivity, specificity and repeatability, having potential application on point-of-care cancer diagnosis. Copyright © 2015 Elsevier B.V. All rights reserved.

Green Synthesis of Silver Nanoparticles Stabilized with Mussel-Inspired Protein and Colorimetric Sensing of Lead(II) and Copper(II) Ions

PubMed Central

Cheon, Ja Young; Park, Won Ho

2016-01-01

This articles reports a simple and green method for preparing uniform silver nanoparticles (AgNPs), for which self-polymerized 3,4-dihydroxy-l-phenylalanine (polyDOPA) is used as the reducing and stabilizing agent in aqueous media. The AgNPs functionalized by polyDOPA were analyzed by UV–Vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectrophotometry, and X-ray diffraction (XRD) techniques. The results revealed that the polyDOPA-AgNPs with diameters of 25 nm were well dispersed due to the polyDOPA. It was noted that the polyDOPA-AgNPs showed selectivity for Pb2+ and Cu2+ detection with the detection limits for the two ions as low as 9.4 × 10−5 and 8.1 × 10−5 μM, respectively. Therefore, the polyDOPA-AgNPs can be applied to both Pb2+ and Cu2+ detection in real water samples. The proposed method will be useful for colorimetric detection of heavy metal ions in aqueous media. PMID:27916894

Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

PubMed

Song, Kai; Huang, Peng; Yi, Chenglin; Ning, Bo; Hu, Song; Nie, Liming; Chen, Xiaoyuan; Nie, Zhihong

2015-12-22

There is a high demand on a simple, rapid, accurate, user-friendly, cost-effective, and nondestructive universal method for latent fingerprint (LFP) detection. Herein, we describe a combination imaging strategy for LFP visualization with high resolution using poly(styrene-alt-maleic anhydride)-b-polystyrene (PSMA-b-PS) functionalized gold nanoparticles (GNPs). This general approach integrates the merits of both colorimetric imaging and photoacoustic imaging. In comparison with the previous methods, our strategy is single-step and does not require the signal amplification by silver staining. The PSMA-b-PS functionalized GNPs have good stability, tunable color, and high affinity for universal secretions (proteins/polypeptides/amino acids), which makes our approach general and flexible for visualizing LFPs on different substrates (presumably with different colors) and from different people. Moreover, the unique optical property of GNPs enables the photoacoustic imaging of GNPs-deposited LFPs with high resolution. This allows observation of level 3 hyperfine features of LFPs such as the pores and ridge contours by photoacoustic imaging. This technique can potentially be used to identify chemicals within LFP residues. We believe that this dual-modality imaging of LFPs will find widespread use in forensic investigations and medical diagnostics.

Discrimination of honeys using colorimetric sensor arrays, sensory analysis and gas chromatography techniques.

PubMed

Tahir, Haroon Elrasheid; Xiaobo, Zou; Xiaowei, Huang; Jiyong, Shi; Mariod, Abdalbasit Adam

2016-09-01

Aroma profiles of six honey varieties of different botanical origins were investigated using colorimetric sensor array, gas chromatography-mass spectrometry (GC-MS) and descriptive sensory analysis. Fifty-eight aroma compounds were identified, including 2 norisoprenoids, 5 hydrocarbons, 4 terpenes, 6 phenols, 7 ketones, 9 acids, 12 aldehydes and 13 alcohols. Twenty abundant or active compounds were chosen as key compounds to characterize honey aroma. Discrimination of the honeys was subsequently implemented using multivariate analysis, including hierarchical clustering analysis (HCA) and principal component analysis (PCA). Honeys of the same botanical origin were grouped together in the PCA score plot and HCA dendrogram. SPME-GC/MS and colorimetric sensor array were able to discriminate the honeys effectively with the advantages of being rapid, simple and low-cost. Moreover, partial least squares regression (PLSR) was applied to indicate the relationship between sensory descriptors and aroma compounds. Copyright © 2016 Elsevier Ltd. All rights reserved.

Simple and Sensitive Colorimetric Assay for Pb2+ Based on Glutathione Protected Ag Nanoparticles by Salt Amplification.

PubMed

Chen, Zhang; Li, Huidong; Chu, Lin; Liu, Chenbin; Luo, Shenglian

2015-02-01

A simple and sensitive colorimetric assay for Pb2+ detection has been reported using glutathione protected silver nanoparticles (AgNPs) by salt amplification. The naked AgNPs aggregate under the influence of salt. Glutathione (GSH) can bind to AgNPs via Ag-S bond, helping AgNPs to against salt-induced aggregation. However, GSH binding to AgNPs can be compromised by the interaction between Pb2+ and GSH. As a result, Pb2+-mediated aggregation of AgNPs under the influence of salt is reflected by the UV-Visible spectrum, and the qualitative and quantitative detection for Pb2+ is accomplished, with the detection range 0.5-4 µM and a detection limit of 0.5 µM. At the same time, Pb2+ in real water sample is detected. Furthermore, the high selectivity and low cost of the assay means it is promising for enviromental applications.

Molecular recognition and colorimetric detection of cholera toxin by poly(diacetylene) liposomes incorporating G{sub m1} ganglioside

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, J.J.; Charych, D.

1997-03-19

Molecular recognition sites on cell membranes serve as the main communication channels between the inside of a cell and its surroundings. Upon receptor binding, cellular messages such as ion channel opening or activation of enzymes are triggered. In this report, we demonstrate that artificial cell membranes made from conjugated lipid polymers (poly(diacetylene)) can, on a simple level, mimic membrane processes of molecular recognition and signal transduction. The ganglioside GM1 was incorporated into poly(diacetylene) liposomes. Molecular recognition of cholera toxin at the interface of the liposome resulted in a change of the membrane color due to conformational charges in the conjugatedmore » (ene-yne) polymer backbone. The `colored liposomes` might be used as simple colorimetric sensors for drug screening or as new tools to study membrane-membrane or membrane-receptor interactions. 21 refs., 3 figs.« less

Colorimetric Detection of Plasmodium vivax in Urine Using MSP10 Oligonucleotides and Gold Nanoparticles

PubMed Central

Alnasser, Yossef; Ferradas, Cusi; Clark, Taryn; Calderon, Maritza; Gurbillon, Alejandro; Gamboa, Dionicia; McKakpo, Uri S.; Quakyi, Isabella A.; Bosompem, Kwabena M.; Sullivan, David J.; Vinetz, Joseph M.; Gilman, Robert H.

2016-01-01

Plasmodium vivax is the most prevalent cause of human malaria in the world and can lead to severe disease with high potential for relapse. Its genetic and geographic diversities make it challenging to control. P. vivax is understudied and to achieve control of malaria in endemic areas, a rapid, accurate, and simple diagnostic tool is necessary. In this pilot study, we found that a colorimetric system using AuNPs and MSP10 DNA detection in urine can provide fast, easy, and inexpensive identification of P. vivax. The test exhibited promising sensitivity (84%), high specificity (97%), and only mild cross-reactivity with P. falciparum (21%). It is simple to use, with a visible color change that negates the need for a spectrometer, making it suitable for use in austere conditions. Using urine eliminates the need for finger-prick, increasing both the safety profile and patient acceptance of this model. PMID:27706158

Comparison of serum copper determination by colorimetric and atomic absorption spectrometric methods in seven different laboratories. The S.F.B.C. (Société Française de Biologie Clinique) Trace Element Group.

PubMed

Arnaud, J; Chappuis, P; Zawislak, R; Houot, O; Jaudon, M C; Bienvenu, F; Bureau, F

1993-02-01

An interlaboratory collaborative trial was conducted on the determination of serum copper using two different methods, based on colorimetry (test combination Copper, Boehringer Mannheim, Mannheim, Germany) and flame atomic absorption spectrometry (FAAS). The general performance of the colorimetric method was below that of FAAS, except for sensitivity and linear range, as assessed by detection limit (0.44 versus 1.32 mumol/L) and upper limit of linearity (150 versus 50 mumol/L). The range of the between-run CVs and the recovery of standard additions were, respectively, 2.3-11.9% and 92-127% for the colorimetric method and 1.1-6.0% and 93-101% for the FAAS method. Interferences were minimal with both methods. The two techniques correlated satisfactorily (the correlation coefficients ranged from 0.945-0.970 among laboratories) but the colorimetric assay exhibited slightly higher results than the FAAS method. Each method was transferable among laboratories.

Visual and light scattering spectrometric method for the detection of melamine using uracil 5‧-triphosphate sodium modified gold nanoparticles

NASA Astrophysics Data System (ADS)

Liang, Lijiao; Zhen, Shujun; Huang, Chengzhi

2017-02-01

A highly selective method was presented for colorimetric determination of melamine using uracil 5‧-triphosphate sodium modified gold nanoparticles (UTP-Au NPs) in this paper. Specific hydrogen-bonding interaction between uracil base (U) and melamine resulted in the aggregation of AuNPs, displaying variations of localized surface plasmon resonance (LSPR) features such as color change from red to blue and enhanced localized surface plasmon resonance light scattering (LSPR-LS) signals. Accordingly, the concentration of melamine could be quantified based on naked eye or a spectrometric method. This method was simple, inexpensive, environmental friendly and highly selective, which has been successfully used for the detection of melamine in pretreated liquid milk products with high recoveries.

Colorimetric detection of ammonia using smartphones based on localized surface plasmon resonance of silver nanoparticles.

PubMed

Amirjani, Amirmostafa; Fatmehsari, Davoud Haghshenas

2018-01-01

In this work, a rapid and straightforward method was developed for colorimetric determination of ammonia using smartphones. The mechanisms is based on the manipulation of the surface plasmon band of silver nanoparticles (AgNPs) via the formation of Ag (NH 3 ) 2 + complex. This complex decreases the amount of AgNPs in the solution and consequently, the color intensity of the colloidal system decreases. Not only the variation in color intensity of the solution can be tracked by a UV-vis spectrophotometer, but also a smartphone can be employed to monitor the color intensity variation by RGB analysis. Ammonia, in the concentration range of 10-1000mgL -1 , was successfully measured spectrophotometrically (UV-vis spectrophotometer) and colorimetrically (RGB measurement) with the detection limit of 180 and 200mgL -1 , respectively. Linear relationships were also developed for both methods. Also, the response time of the developed colorimetric sensor was around 20s. Both of the colorimetric and spectrophotometric methods showed a reliable performance for determination of ammonia in the real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Oligonucleotide-Gold Nanoparticle Networks for Detection of Cryptosporidium parvum Heat Shock Protein 70 mRNA ▿

PubMed Central

Javier, David J.; Castellanos-Gonzalez, Alejandro; Weigum, Shannon E.; White, A. Clinton; Richards-Kortum, Rebecca

2009-01-01

We report on a novel strategy for the detection of mRNA targets derived from Cryptosporidium parvum oocysts by the use of oligonucleotide-gold nanoparticles. Gold nanoparticles are functionalized with oligonucleotides which are complementary to unique sequences present on the heat shock protein 70 (HSP70) DNA/RNA target. The results indicate that the presence of HPS70 targets of increasing complexity causes the formation of oligonucleotide-gold nanoparticle networks which can be visually monitored via a simple colorimetric readout measured by a total internal reflection imaging setup. Furthermore, the induced expression of HSP70 mRNA in Cryptosporidium parvum oocysts via a simple heat shock process provides nonenzymatic amplification such that the HSP70 mRNA derived from as few as 5 × 103 purified C. parvum oocysts was successfully detected. Taken together, these results support the use of oligonucleotide-gold nanoparticles for the molecular diagnosis of cryptosporidiosis, offering new opportunities for the further development of point-of-care diagnostic assays with low-cost, robust reagents and simple colorimetric detection. PMID:19828740

An Illumination-Adaptive Colorimetric Measurement Using Color Image Sensor

NASA Astrophysics Data System (ADS)

Lee, Sung-Hak; Lee, Jong-Hyub; Sohng, Kyu-Ik

An image sensor for a use of colorimeter is characterized based on the CIE standard colorimetric observer. We use the method of least squares to derive a colorimetric characterization matrix between RGB output signals and CIE XYZ tristimulus values. This paper proposes an adaptive measuring method to obtain the chromaticity of colored scenes and illumination through a 3×3 camera transfer matrix under a certain illuminant. Camera RGB outputs, sensor status values, and photoelectric characteristic are used to obtain the chromaticity. Experimental results show that the proposed method is valid in the measuring performance.

Mobile micro-colorimeter and micro-spectrometer sensor modules as enablers for the replacement of subjective inspections by objective measurements for optically clear colored liquids in-field

NASA Astrophysics Data System (ADS)

Dittrich, Paul-Gerald; Grunert, Fred; Ehehalt, Jörg; Hofmann, Dietrich

2015-03-01

Aim of the paper is to show that the colorimetric characterization of optically clear colored liquids can be performed with different measurement methods and their application specific multichannel spectral sensors. The possible measurement methods are differentiated by the applied types of multichannel spectral sensors and therefore by their spectral resolution, measurement speed, measurement accuracy and measurement costs. The paper describes how different types of multichannel spectral sensors are calibrated with different types of calibration methods and how the measurement values can be used for further colorimetric calculations. The different measurement methods and the different application specific calibration methods will be explained methodically and theoretically. The paper proofs that and how different multichannel spectral sensor modules with different calibration methods can be applied with smartpads for the calculation of measurement results both in laboratory and in field. A given practical example is the application of different multichannel spectral sensors for the colorimetric characterization of petroleum oils and fuels and their colorimetric characterization by the Saybolt color scale.

Functionalized graphene oxide quantum dot-PVA hydrogel: a colorimetric sensor for Fe2+, Co2+ and Cu2+ ions

NASA Astrophysics Data System (ADS)

Baruah, Upama; Chowdhury, Devasish

2016-04-01

Functionalized graphene oxide quantum dots (GOQDs)-poly(vinyl alcohol) (PVA) hybrid hydrogels were prepared using a simple, facile and cost-effective strategy. GOQDs bearing different surface functional groups were introduced as the cross-linking agent into the PVA matrix thereby resulting in gelation. The four different types of hybrid hydrogels were prepared using graphene oxide, reduced graphene oxide, ester functionalized graphene oxide and amine functionalized GOQDs as cross-linking agents. It was observed that the hybrid hydrogel prepared with amine functionalized GOQDs was the most stable. The potential applicability of using this solid sensing platform has been subsequently explored in an easy, simple, effective and sensitive method for optical detection of M2+ (Fe2+, Co2+ and Cu2+) in aqueous media involving colorimetric detection. Amine functionalized GOQDs-PVA hybrid hydrogel when put into the corresponding solution of Fe2+, Co2+ and Cu2+ renders brown, orange and blue coloration respectively of the solution detecting the presence of Fe2+, Co2+ and Cu2+ ions in the solution. The minimum detection limit observed was 1 × 10-7 M using UV-visible spectroscopy. Further, the applicability of the sensing material was also tested for a mixture of co-existing ions in solution to demonstrate the practical applicability of the system. Insight into the probable mechanistic pathway involved in the detection process is also being discussed.

Colorimetric detection of 1,5-anhydroglucitol based on graphene quantum dots and enzyme-catalyzed reaction.

PubMed

Zhou, Zhide; Zhao, Le; Wang, Zhihong; Xue, Wen; Wang, Yunxiao; Huang, Yong; Liang, Jintao; Chen, Jiejing; Li, Guiyin

2018-06-01

Early diagnosis of diabetes yields significant clinical benefits. The serum level of 1,5‑anhydroglucitol (1,5‑AG) has been a new biochemical marker for postprandial hyperglycemia. In this study, a simple colorimetric method for 1,5‑AG detection has been designed based on highly efficient peroxidase mimetic activity of GQDs and enzyme-catalyzed reaction. By the catalytic action of pyranose oxidase (PROD), the 1,5‑AG was oxidized to 1,5‑anhydrofuctose and H 2 O 2 . The GQDs in the presence of H 2 O 2 exhibited highly efficient catalytic activity toward the oxidation of 3, 3', 5, 5'‑tetramethylbenzidine (TMB) to a blue colored product. The influence of relevant experimental variables was optimized. A linear relationship of optical signal with the concentration of 1,5‑AG in the range of 20.0-100.0μg/mL with the regression correlation coefficient of 0.9985 was obtained which could be monitored by colorimetry detection. The limit of detection (LOD) for 1,5‑AG detection was approximately 0.144μg/mL. All in all, the proposed 1,5‑AG detection system based on GQDs and PROD-catalyzed reaction showed better performances with simple operation, low-cost, higher selectivity. Copyright © 2018 Elsevier B.V. All rights reserved.

A new cation-exchange method for accurate field speciation of hexavalent chromium

USGS Publications Warehouse

Ball, J.W.; McCleskey, R. Blaine

2003-01-01

A new method for field speciation of Cr(VI) has been developed to meet present stringent regulatory standards and to overcome the limitations of existing methods. The method consists of passing a water sample through strong acid cation-exchange resin at the field site, where Cr(III) is retained while Cr(VI) passes into the effluent and is preserved for later determination. The method is simple, rapid, portable, and accurate, and makes use of readily available, inexpensive materials. Cr(VI) concentrations are determined later in the laboratory using any elemental analysis instrument sufficiently sensitive to measure the Cr(VI) concentrations of interest. The new method allows measurement of Cr(VI) concentrations as low as 0.05 ??g 1-1, storage of samples for at least several weeks prior to analysis, and use of readily available analytical instrumentation. Cr(VI) can be separated from Cr(III) between pH 2 and 11 at Cr(III)/Cr(VI) concentration ratios as high as 1000. The new method has demonstrated excellent comparability with two commonly used methods, the Hach Company direct colorimetric method and USEPA method 218.6. The new method is superior to the Hach direct colorimetric method owing to its relative sensitivity and simplicity. The new method is superior to USEPA method 218.6 in the presence of Fe(II) concentrations up to 1 mg 1-1 and Fe(III) concentrations up to 10 mg 1-1. Time stability of preserved samples is a significant advantage over the 24-h time constraint specified for USEPA method 218.6.

DETERMINING SERUM BICARBONATE—A Simple Syringe Titrator and Colorimeter

PubMed Central

Boone, Charles W.; Field, John B.

1953-01-01

The use of a tuberculin syringe as a burette has made possible an easy bedside technique for the determination of serum bicarbonate. By combining it with the use of a simple colorimeter, a relatively untrained person can do numerous bicarbonate determinations with a high degree of accuracy. The same technique also lends itself to other colorimetric clinical procedures such as determination of gastric acidity. PMID:13106724

Determining serum bicarbonate; a simple syringe titrator and colorimeter.

PubMed

BOONE, C W; FIELD, J B

1953-12-01

The use of a tuberculin syringe as a burette has made possible an easy bedside technique for the determination of serum bicarbonate. By combining it with the use of a simple colorimeter, a relatively untrained person can do numerous bicarbonate determinations with a high degree of accuracy. The same technique also lends itself to other colorimetric clinical procedures such as determination of gastric acidity.

Design of a colorimetric sensing platform using reflection mode plasmonic colour filters

NASA Astrophysics Data System (ADS)

Mudachathi, Renilkumar; Tanaka, Takuo

2017-08-01

Plasmonic nano structures fabricated using inexpensive and abundant aluminum metal shows intense narrow reflection peaks with strong response to the external stimuli, provides a simple yet powerful detection mechanism that is well suited for the development of low cost and low power sensors, such as colorimetric sensors, which transduces external stimuli or environmental changes in to visible colour changes. Such low cost and disposable sensors have huge demands in the point-of-care and home health care diagnostic applications. We present the design of a colorimetric sensing platform based on reflection mode plasmonic colour filters on both silicon and glass substrate, which demonstrate a sharp colour change for varying ambient refractive index. The sensor is essentially a plasmonic metamaterial in which the aluminum square plate hovering on a PMMA nano pillar in the background of a perforated aluminum reflector forms the unit cell which is arranged periodically in a 2D square lattice. The meta-surface has two distinct absorption peaks in the visible region leaving a strong reflection band, which strongly responds to the ambient refractive index change, provides a means for the realization of low cost colorimetric sensing platform.

Evaluation of micro-colorimetric lipid determination method with samples prepared using sonication and accelerated solvent extraction methods

EPA Science Inventory

Two common laboratory extraction techniques were evaluated for routine use with the micro-colorimetric lipid determination method developed by Van Handel (1985) [E. Van Handel, J. Am. Mosq. Control Assoc. 1(1985) 302] and recently validated for small samples by Inouye and Lotufo ...

Colorimetric characterization of digital cameras with unrestricted capture settings applicable for different illumination circumstances

NASA Astrophysics Data System (ADS)

Fang, Jingyu; Xu, Haisong; Wang, Zhehong; Wu, Xiaomin

2016-05-01

With colorimetric characterization, digital cameras can be used as image-based tristimulus colorimeters for color communication. In order to overcome the restriction of fixed capture settings adopted in the conventional colorimetric characterization procedures, a novel method was proposed considering capture settings. The method calculating colorimetric value of the measured image contains five main steps, including conversion from RGB values to equivalent ones of training settings through factors based on imaging system model so as to build the bridge between different settings, scaling factors involved in preparation steps for transformation mapping to avoid errors resulted from nonlinearity of polynomial mapping for different ranges of illumination levels. The experiment results indicate that the prediction error of the proposed method, which was measured by CIELAB color difference formula, reaches less than 2 CIELAB units under different illumination levels and different correlated color temperatures. This prediction accuracy for different capture settings remains the same level as the conventional method for particular lighting condition.

Basic methods for measuring the reflectance color of iron oxides

NASA Astrophysics Data System (ADS)

Pospisil, Jaroslav; Hrdy, Jan; Hrdy Jan, Jr.

2007-06-01

The main contribution of the present article consists in coherent description and interpretation of the principles of basic measuring methods and colorimeters for color classification and evaluation of light reflecting samples containing iron oxides. The chosen relevant theoretical background is based on the CIE tristimulus colorimetric system (X,Y,Z), the CIE colorimetric system (L*,a*,b*) and the Munsell colorimetric system (H,V,C). As an example of color identification and evaluation, some specific mathematical and graphical relationships between the soil redness rate and the corresponding hematite content are shown.

Tropospheric haze and colors of the clear daytime sky.

PubMed

Lee, Raymond L

2015-02-01

To casual observers, haze's visible effects on clear daytime skies may seem mundane: significant scattering by tropospheric aerosols visibly (1) reduces the luminance contrast of distant objects and (2) desaturates sky blueness. However, few published measurements of hazy-sky spectra and chromaticities exist to compare with these naked-eye observations. Hyperspectral imaging along sky meridians of clear and hazy skies at one inland and two coastal sites shows that they have characteristic colorimetric signatures of scattering and absorption by haze aerosols. In addition, a simple spectral transfer function and a second-order scattering model of skylight reveal the net spectral and colorimetric effects of haze.

A simple analytical procedure to replace HPLC for monitoring treatment concentrations of chloramine-T on fish culture facilities

USGS Publications Warehouse

Dawson, V.K.; Meinertz, J.R.; Schmidt, L.J.; Gingerich, W.H.

2003-01-01

Concentrations of chloramine-T must be monitored during experimental treatments of fish when studying the effectiveness of the drug for controlling bacterial gill disease. A surrogate analytical method for analysis of chloramine-T to replace the existing high-performance liquid chromatography (HPLC) method is described. A surrogate method was needed because the existing HPLC method is expensive, requires a specialist to use, and is not generally available at fish hatcheries. Criteria for selection of a replacement method included ease of use, analysis time, cost, safety, sensitivity, accuracy, and precision. The most promising approach was to use the determination of chlorine concentrations as an indicator of chloramine-T. Of the currently available methods for analysis of chlorine, the DPD (N,N-diethyl-p-phenylenediamine) colorimetric method best fit the established criteria. The surrogate method was evaluated under a variety of water quality conditions. Regression analysis of all DPD colorimetric analyses with the HPLC values produced a linear model (Y=0.9602 X+0.1259) with an r2 value of 0.9960. The average accuracy (percent recovery) of the DPD method relative to the HPLC method for the combined set of water quality data was 101.5%. The surrogate method was also evaluated with chloramine-T solutions that contained various concentrations of fish feed or selected densities of rainbow trout. When samples were analyzed within 2 h, the results of the surrogate method were consistent with those of the HPLC method. When samples with high concentrations of organic material were allowed to age more than 2 h before being analyzed, the DPD method seemed to be susceptible to interference, possibly from the development of other chloramine compounds. However, even after aging samples 6 h, the accuracy of the surrogate DPD method relative to the HPLC method was within the range of 80-120%. Based on the data comparing the two methods, the U.S. Food and Drug Administration has concluded that the DPD colorimetric method is appropriate to use to measure chloramine-T in water during pivotal efficacy trials designed to support the approval of chloramine-T for use in fish culture. ?? 2003 Elsevier Science B.V. All rights reserved.

Sensitive colorimetric assay for uric acid and glucose detection based on multilayer-modified paper with smartphone as signal readout.

PubMed

Wang, Xu; Li, Fang; Cai, Ziqi; Liu, Kaifan; Li, Jing; Zhang, Boyang; He, Jianbo

2018-04-01

In this work, a multilayer-modified paper-based colorimetric sensing platform with improved color uniformity and intensity was developed for the sensitive and selective determination of uric acid and glucose with smartphone as signal readout. In detail, chitosan, different kinds of chromogenic reagents, and horseradish peroxidase (HRP) combined with a specific oxidase, e.g., uricase or glucose oxidase (GOD), were immoblized onto the paper substrate to form a multilayer-modified test paper. Hydrogen peroxide produced by the oxidases (uricase or GOD) reacts with the substrates (uric acid or glucose), and could oxidize the co-immoblized chromogenic reagents to form colored products with HRP as catalyst. A simple strategy by placing the test paper on top of a light-emitting diode lamp was adopted to efficiently prevent influence from the external light. The color images were recorded by the smartphone camera, and then the gray values of the color images were calculated for quantitative analysis. The developed method provided a wide linear response from 0.01 to 1.0 mM for uric acid detection and from 0.02 to 4.0 mM for glucose detection, with a limit of detection (LOD) as low as 0.003 and 0.014 mM, respectively, which was much lower than for previously reported paper-based colorimetric assays. The proposed assays were successfully applied to uric acid and glucose detection in real serum samples. Furthermore, the enhanced analytical performance of the proposed method allowed the non-invasive detection of glucose levels in tear samples, which holds great potential for point-of-care analysis. Graphical abstract ᅟ.

Determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium salts.

PubMed

Tsukatani, Tadayuki; Suenaga, Hikaru; Ishiyama, Munetaka; Ezoe, Takatoshi; Matsumoto, Kiyoshi

2011-07-15

A method for the determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of the tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8)} via 2-methyl-1,4-napthoquinone (NQ) was developed. Measurement conditions were optimized for the microbiological determination of water-soluble vitamins, such as vitamin B(6), biotin, folic acid, niacin, and pantothenic acid, using microorganisms that have a water-soluble vitamin requirement. A linear relationship between absorbance and water-soluble vitamin concentration was obtained. The proposed method was applied to determine the concentration of vitamin B(6) in various foodstuffs. There was good agreement between vitamin B(6) concentrations determined after 24h using the WST-8 colorimetric method and those obtained after 48h using a conventional method. The results suggest that the WST-8 colorimetric assay is a useful method for the rapid determination of water-soluble vitamins in a 96-well microtiter plate. Copyright © 2011 Elsevier Ltd. All rights reserved.

Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy.

PubMed

Agustina, Elsye; Goak, Jeungchoon; Lee, Suntae; Seo, Youngho; Park, Jun-Young; Lee, Naesung

2015-10-01

Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red-orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO4/HNO3 and H2SO4/HNO3 mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.

Fluoride-selective colorimetric sensor based on thiourea binding site and anthraquinone reporter.

PubMed

Wu, Fang-ying; Hu, Mei-hua; Wu, Yu-mei; Tan, Xiao-fang; Zhao, Yong-qiang; Ji, Zhao-jun

2006-11-01

A structurally simple colorimetric sensor, N-4-nitrobenzene-N'-1'-anthraquinone-thiourea (1), for anions was synthesized and characterized by (1)H NMR, ESI mass and IR methods. In acetonitrile, the addition of F(-) changed 1 solution from colorless to yellow. In the presence of other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-), however, the absorption spectrum of 1 was slightly red shifted with no obvious color changes observed. The association constants of anionic complexes followed the order of F(-)>CH(3)CO(2)(-)>H(2)PO(4)(-)>HSO(4)(-)>Cl(-)>Br(-), which was different from the order of anion basicity. AM1 calculation results indicated that the most stable configuration of 1 existed in the Z-E-conformation with a six-membered ring via intramolecular hydrogen bond. This made thiourea moiety of 1 in an unfavorable conformation to bond with oxygen-anionic substrates such as CH(3)CO(2)(-) and H(2)PO(4)(-), thus leading to a high selectivity and sensitivity for the detection of F(-).

Prediction of warmed-over flavour development in cooked chicken by colorimetric sensor array.

PubMed

Kim, Su-Yeon; Li, Jinglei; Lim, Na-Ri; Kang, Bo-Sik; Park, Hyun-Jin

2016-11-15

The aim of this study was to develop a simple and rapid method based on colorimetric sensor array (CSA) for evaluation of warmed-over flavour (WOF) in cooked chicken. All samples were classified according to storage time by CSA coupled with principle component analysis (PCA) or hierarchical cluster analysis (HCA). The CSA data were used to establish prediction models with thiobarbituric acid reactive substances (TBARS), pentanal, hexanal, or heptanal associated with WOF by partial least square regression (PLSR). For the TBARS model, the coefficient of determination (rp(2)) was 0.9997 in the prediction range of 0.28-0.69mg/kg. In each of the models for pentanal, hexanal, and heptanal, all rp(2) were higher than 0.960 in the range of 0.58-2.10mg/kg, 5.50-11.69mg/kg, and 0.09-0.16mg/kg, respectively. These results demonstrate that the CSA was able to predict WOF development and to distinguish between each storage time. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigation of Chemically Treated Test-Strips for Ozone Measurement

NASA Technical Reports Server (NTRS)

Bush, Linda C.

1997-01-01

A colorimetric passive ozone monitoring system is currently in use in the GLOBE project, as well as several other environmental studies, as commercially supplied as Eco-Badge by Vistanomics. This simple, but effective, system consists of papers treated with a chemical preparation, tin(II) diphenylcarbazidel that reacts with ozone to change them from white to purple. The intensity of the purple coloration is dependent on the concentration of ozone. Our previous contributions to that method of analysis involved modest modifications to the chemical substrate employed. The new formulation improved the reproducibility and linearity of the color change of treated papers.

Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases

NASA Astrophysics Data System (ADS)

Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

2014-03-01

Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

Accelerated Colorimetric Micro-assay for Screening Mold Inhibitors

Treesearch

Carol A. Clausen; Vina W. Yang

2014-01-01

Rapid quantitative laboratory test methods are needed to screen potential antifungal agents. Existing laboratory test methods are relatively time consuming, may require specialized test equipment and rely on subjective visual ratings. A quantitative, colorimetric micro-assay has been developed that uses XTT tetrazolium salt to metabolically assess mold spore...

An improved colorimetric method for the determination of proline in the presence of other ninhydrin-positive compounds

PubMed Central

Wren, J. J.; Wiggall, P. H.

1965-01-01

1. The conditions required for sensitive and specific colorimetric determination of proline with acidified ninhydrin were investigated. 2. A method applicable to protein samples was developed. 3. The only compound found to interfere appreciably was a hydroxyproline. PMID:14342233

Multiplexed Paper Analytical Device for Quantification of Metals using Distance-Based Detection

PubMed Central

Cate, David M.; Noblitt, Scott D.; Volckens, John; Henry, Charles S.

2015-01-01

Exposure to metal-containing aerosols has been linked with adverse health outcomes for almost every organ in the human body. Commercially available techniques for quantifying particulate metals are time-intensive, laborious, and expensive; often sample analysis exceeds $100. We report a simple technique, based upon a distance-based detection motif, for quantifying metal concentrations of Ni, Cu, and Fe in airborne particulate matter using microfluidic paper-based analytical devices. Paper substrates are used to create sensors that are self-contained, self-timing, and require only a drop of sample for operation. Unlike other colorimetric approaches in paper microfluidics that rely on optical instrumentation for analysis, with distance-based detection, analyte is quantified visually based on the distance of a colorimetric reaction, similar to reading temperature on a thermometer. To demonstrate the effectiveness of this approach, Ni, Cu, and Fe were measured individually in single-channel devices; detection limits as low as 0.1, 0.1, and 0.05 µg were reported for Ni, Cu, and Fe. Multiplexed analysis of all three metals was achieved with detection limits of 1, 5, and 1 µg for Ni, Cu, and Fe. We also extended the dynamic range for multi-analyte detection by printing concentration gradients of colorimetric reagents using an off the shelf inkjet printer. Analyte selectivity was demonstrated for common interferences. To demonstrate utility of the method, Ni, Cu, and Fe were measured from samples of certified welding fume; levels measured with paper sensors matched known values determined gravimetrically. PMID:26009988

Ultra-sensitive non-aggregation colorimetric sensor for detection of iron based on the signal amplification effect of Fe3+ catalyzing H2O2 oxidize gold nanorods.

PubMed

Liu, Jia-Ming; Wang, Xin-Xing; Jiao, Li; Cui, Ma-Lin; Lin, Li-Ping; Zhang, Li-Hong; Jiang, Shu-Lian

2013-11-15

Fe(3+) can catalyze H2O2 to oxidize along on the longitudinal axis of gold nanorods (AuNRs), which caused the aspect ratio of AuNRs to decrease, longitudinal plasmon absorption band (LPAB) of AuNRs to blueshift (Δλ) and the color of the solution to change obviously. Thus, a rapid response and highly sensitive non-aggregation colorimetric sensor for the determination of Fe(3+) has been developed based on the signal amplification effect of catalyzing H2O2 to oxidize AuNRs. This simple and selective sensor with a wide linear range of 0.20-30.00 μM has been utilized to detect Fe(3+) in blood samples, and the results consisted with those obtained by inductively coupled plasma-mass spectroscopy (ICP-MS). Simultaneously, the mechanism of colorimetric sensor for the detection of Fe(3+) was also discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

A novel colorimetric assay for rapid detection of cysteine and Hg²⁺ based on gold clusters.

PubMed

Wang, Yi-Wei; Tang, Shurong; Yang, Huang-Hao; Song, Hongbo

2016-01-01

Inhibition and recovery of the catalytic activity of bovine serum albumin-capped gold nanoclusters (BSA-AuNCs) is observed for the first time by introduction of cysteine and Hg(2+). The prepared BSA-AuNCs possess highly intrinsic peroxidase-like activity. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine by H2O2 to produce a blue colored product. Based on this phenomenon, a new colorimetric assay for rapid, selective and sensitive detection of cysteine and Hg(2+) in aqueous solution has been demonstrated. The interaction process between target molecule and BSA-AuNCs is very fast, so that the whole test can be completed within ten minutes. Moreover, the fabricated colorimetric sensor is simple and cost-effective, without the need of nucleic acid based recognition element and complicated washing, separation and labeling process, thus holds great promise for routine analysis of cysteine and Hg(2+) in real samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Doped colorimetric assay liposomes

DOEpatents

Charych, Deborah; Stevens, Raymond C.

2001-01-01

The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

Assessment of a colorimetric method for the measurement of low concentrations of peracetic acid and hydrogen peroxide in water.

PubMed

Domínguez-Henao, Laura; Turolla, Andrea; Monticelli, Damiano; Antonelli, Manuela

2018-06-01

The recent growing interest in peracetic acid (PAA) as disinfectant for wastewater treatment demands reliable and readily-available methods for its measurement. In detail, the monitoring of PAA in wastewater treatment plants requires a simple, accurate, rapid and inexpensive measurement procedure. In the present work, a method for analyzing low concentrations of PAA, adapted from the US EPA colorimetric method for total chlorine, is assessed. This method employs N,N-diethyl-p-phenylelnediamine (DPD) in the presence of an excess of iodide in a phosphate buffer system. Pink colored species are produced proportionally to the concentration of PAA in the sample. Considering that PAA is available commercially as an equilibrium solution of PAA and hydrogen peroxide (H 2 O 2 ), a measurement method for H 2 O 2 is also investigated. This method, as the one for the determination of PAA, is also based on the oxidation of iodide to iodine, with the difference that ammonium molybdate Mo(VI) is added to catalyze the oxidation reaction between H 2 O 2 and iodide, quantifying the total peroxides (PAA+ H 2 O 2 ). The two methods are suitable for concentration ranges from about 0.1-1.65 mg L -1 and from about 0.3-3.3 mg L -1 , respectively for PAA and H 2 O 2 . Moreover, the work elucidates some relevant aspects related to the operational conditions, kinetics and the possible interference of H 2 O 2 on PAA measurement. Copyright © 2018 Elsevier B.V. All rights reserved.

Colorimetric characterization models based on colorimetric characteristics evaluation for active matrix organic light emitting diode panels.

PubMed

Gong, Rui; Xu, Haisong; Tong, Qingfen

2012-10-20

The colorimetric characterization of active matrix organic light emitting diode (AMOLED) panels suffers from their poor channel independence. Based on the colorimetric characteristics evaluation of channel independence and chromaticity constancy, an accurate colorimetric characterization method, namely, the polynomial compensation model (PC model) considering channel interactions was proposed for AMOLED panels. In this model, polynomial expressions are employed to calculate the relationship between the prediction errors of XYZ tristimulus values and the digital inputs to compensate the XYZ prediction errors of the conventional piecewise linear interpolation assuming the variable chromaticity coordinates (PLVC) model. The experimental results indicated that the proposed PC model outperformed other typical characterization models for the two tested AMOLED smart-phone displays and for the professional liquid crystal display monitor as well.

A paper-based Colorimetric Indicator Label using Natural Dye for Monitoring Shrimp Spoilage

NASA Astrophysics Data System (ADS)

Listyarini, A.; Sholihah, W.; Imawan, C.

2018-05-01

Shrimp is a type of perishable food. This study developed a simple indicator label using colorimetric method for monitoring shrimp freshness. This indicator label was made from natural dye extract of Ruellia simplex flowers which immobilized on cellulose paper by dip coating method. The indicator labels were used for examining freshness of shrimp. In this experiment, shrimp were stored in sealed bottles that have been labeled using the indicator and stored at 13 °C, 25 °C, and 40 °C for a certain range of time. Color changes of the indicator labels were observed using digital photography after shrimp storage for 0 h, 2 h, 17 h and 24 h. The color changes that occur were quantified and analyzed using the ImageJ program. The color of the indicator label when detecting the fresh shrimp was pink and after the shrimp spoilage began, the color of the label changed to purple and then became yellow when the shrimp is badly spoilage. The color change rates of label indicator increases as the shrimp storage temperature increased. These results indicate that this label indicator can be used as an indicator of the freshness of shrimps and it is not toxic and safe for food.

Colorimetric microdetermination of captopril in pure form and in pharmaceutical formulations

NASA Astrophysics Data System (ADS)

Shama, Sayed Ahmed; El-Sayed Amin, Alla; Omara, Hany

2006-11-01

A simple, rapid, accurate, precise and sensitive colorimetric method for the determination of captopril (CAP) in bulk sample and in dosage forms is described. The method is based on oxidation of the drug by potassium permanganate in acidic medium and determination of the unreacted oxidant by measuring the decrease in absorbance for five different dyes; methylene blue (MB); acid blue 74 (AB), acid red 73 (AR), amaranth dye (AM) and acid orange 7 (AO) at a suitable λmax (660, 610, 510, 520, and 485 nm), respectively. Regression analysis of Beer's plots showed good correlation in the concentration ranges (0.4 12.5, 0.3 10, 0.5 11, 0.4 8.3 and 0.5 9.3 μg ml-1), respectively. The apparent molar absorbtivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.5 12, 0.5 9.6, 0.6 10.5, 0.5 8.0 and 0.7 9.0 μg ml-1, respectively. The validity of the proposed method was tested by analyzing in pure and dosage forms containing CAP whether alone or in combination with hydrochlorothiazide. Statistical analysis of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of CAP in pure form and in pharmaceutical preparations. Also, the stability constant was determined and the free energy change was calculated potentiometrically.

Gold Nanoparticles-based Extraction-Free Colorimetric Assay in Organic Media: An Optical Index for Determination of Total Polyphenols in Fat-Rich Samples.

PubMed

Della Pelle, Flavio; González, María Cristina; Sergi, Manuel; Del Carlo, Michele; Compagnone, Dario; Escarpa, Alberto

2015-07-07

In this work, a rapid and simple gold nanoparticle (AuNPs)-based colorimetric assay meets a new type of synthesis of AuNPs in organic medium requiring no sample extraction. The AuNPs synthesis extraction-free approach strategically involves the use of dimethyl sulfoxide (DMSO) acting as an organic solvent for simultaneous sample analyte solubilization and AuNPs stabilization. Moreover, DMSO works as a cryogenic protector avoiding solidification at the temperatures used to block the synthesis. In addition, the chemical function as AuNPs stabilizers of the sample endogenous fatty acids is also exploited, avoiding the use of common surfactant AuNPs stabilizers, which, in an organic/aqueous medium, rise to the formation of undesirable emulsions. This is controlled by adding a fat analyte free sample (sample blank). The method was exhaustively applied for the determination of total polyphenols in two selected kinds of fat-rich liquid and solid samples with high antioxidant activity and economic impact: olive oil (n = 28) and chocolate (n = 16) samples. Fatty sample absorbance is easily followed by the absorption band of localized surface plasmon resonance (LSPR) at 540 nm and quantitation is refereed to gallic acid equivalents. A rigorous evaluation of the method was performed by comparison with the well and traditionally established Folin-Ciocalteu (FC) method, obtaining an excellent correlation for olive oil samples (R = 0.990, n = 28) and for chocolate samples (R = 0.905, n = 16). Additionally, it was also found that the proposed approach was selective (vs other endogenous sample tocopherols and pigments), fast (15-20 min), cheap and simple (does not require expensive/complex equipment), with a very limited amount of sample (30 μL) needed and a significant lower solvent consumption (250 μL in 500 μL total reaction volume) compared to classical methods.

Simple Colorimetric Sensor for Trinitrotoluene Testing

NASA Astrophysics Data System (ADS)

Samanman, S.; Masoh, N.; Salah, Y.; Srisawat, S.; Wattanayon, R.; Wangsirikul, P.; Phumivanichakit, K.

2017-02-01

A simple operating colorimetric sensor for trinitrotoluene (TNT) determination using a commercial scanner as a captured image was designed. The sensor is based on the chemical reaction between TNT and sodium hydroxide reagent to produce the color change within 96 well plates, which observed finally, recorded using a commercial scanner. The intensity of the color change increased with increase in TNT concentration and could easily quantify the concentration of TNT by digital image analysis using the Image J free software. Under optimum conditions, the sensor provided a linear dynamic range between 0.20 and 1.00 mg mL-1(r = 0.9921) with a limit of detection of 0.10± 0.01 mg mL-1. The relative standard deviation for eight experiments for the sensitivity was 3.8%. When applied for the analysis of TNT in two soil extract samples, the concentrations were found to be non-detectable to 0.26±0.04 mg mL-1. The obtained recovery values (93-95%) were acceptable for soil samples tested.

Measurement of Chlorine Dioxide in Water by DPD Colorimetric Method

NASA Astrophysics Data System (ADS)

Song, Min; Yan, Panping; Yao, Jun

2018-01-01

In order to solve the problems of chlorine dioxide in water by DPD colorimetric method, this paper discusses the effects of the formulation, temperature, color development time and amount of color reagent on the measurement process, improving the on-line instrument for domestic and drinking water in chlorine dioxide measurement precision and accuracy.

Colorimetric micro-assay for accelerated screening of mould inhibitors

Treesearch

Carol A. Clausen; Vina W. Yang

2013-01-01

Since current standard laboratory methods are time-consuming macro-assays that rely on subjective visual ratings of mould growth, rapid and quantitative laboratory methods are needed to screen potential mould inhibitors for use in and on cellulose-based products. A colorimetric micro-assay has been developed that uses XTT tetrazolium salt to enzymatically assess...

Simultaneous pre-concentration and separation on simple paper-based analytical device for protein analysis.

PubMed

Niu, Ji-Cheng; Zhou, Ting; Niu, Li-Li; Xie, Zhen-Sheng; Fang, Fang; Yang, Fu-Quan; Wu, Zhi-Yong

2018-02-01

In this work, fast isoelectric focusing (IEF) was successfully implemented on an open paper fluidic channel for simultaneous concentration and separation of proteins from complex matrix. With this simple device, IEF can be finished in 10 min with a resolution of 0.03 pH units and concentration factor of 10, as estimated by color model proteins by smartphone-based colorimetric detection. Fast detection of albumin from human serum and glycated hemoglobin (HBA1c) from blood cell was demonstrated. In addition, off-line identification of the model proteins from the IEF fractions with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was also shown. This PAD IEF is potentially useful either for point of care test (POCT) or biomarker analysis as a cost-effective sample pretreatment method.

Development of a new colorimetric assay for detection of bisphenol-A in aqueous media using green synthesized silver chloride nanoparticles: experimental and theoretical study.

PubMed

Khalililaghab, Shiva; Momeni, Safieh; Farrokhnia, Maryam; Nabipour, Iraj; Karimi, Sadegh

2017-04-01

In the present study, a cost-effective, green and simple synthesis method was applied for preparation of stable silver chloride nanoparticles (AgCl-NPs). The method was done by forming AgCl-NPs from Ag + ions using aqueous extract of brown algae (Sargassum boveanum) obtained from the Persian Gulf Sea. This extract served as capping agent during the formation of AgCl-NPs. Creation of AgCl-NPs was confirmed by UV-visible spectroscopy, powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy, while the morphology and size analyses were characterized using high-resolution transmission electron microscopy and dynamic light scattering. After optimization of some experimental conditions, particularly pH, a simple and facile system was developed for the naked-eye detection of bisphenol-A. Moreover, a theoretical study of AgCl interaction with bisphenol-A was performed at the density functional level of theory in both gas and solvent phases. Theoretical results showed that electrostatic and van der Waal interactions play important roles in complexation of bisphenol-A with AgCl-NPs, which can lead to aggregation of the as-prepared AgCl-NPs and results in color change from specific yellow to dark purple, where a new aggregation band induced at 542 nm appears. The absorbance at 542 nm was found to be linearly dependent on the bisphenol-A concentration in the range of 1 × 10 -6 -1 × 10 -4  M, with limit of detection of 45 nM. In conclusion, obtained results from the present study can open up an innovative application of the green synthesis of AgCl-NPs using brown algae extract as colorimetric sensors.

Rapid colorimetric sensing of tetracycline antibiotics with in situ growth of gold nanoparticles.

PubMed

Shen, Li; Chen, Jing; Li, Na; He, Pingli; Li, Zhen

2014-08-11

A colorimetric assay utilizing the formation of gold nanoparticles was developed to detect tetracycline antibiotics in fluidic samples. Tetracycline antibiotics showed the capability of directly reducing aurate salts into atomic gold which form gold nanoparticles spontaneously under proper conditions. The resulted gold nanoparticles showed characteristic plasmon absorbance at 526 nm, which can be visualized by naked eyes or with a spectrophotometer. UV-vis absorbance of the resulted gold nanoparticles is correlated directly with the concentrations of tetracycline antibiotics in the solution, allowing for quantitative colorimetric detection of tetracycline antibiotics. Reaction conditions, such as pH, temperature, reaction time, and ionic strength were optimized. Sensitivity of the colorimetric assay can be enhanced by the addition of gold nanoparticle seeds, a LOD as low as 20 ng mL(-1) can be achieved with the help of seed particles. The colorimetric assay showed minimum interference from ethanol, methanol, urea, glucose, and other antibiotics such as sulfonamides, amino glycosides etc. Validity of the method was also evaluated on urine samples spiked with tetracycline antibiotics. The method provides a broad spectrum detection method for rapid and sensitive detection of reductive substances such as tetracycline antibiotics in liquid and biological samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimization of the cydex blue assay: A one-step colorimetric protein assay using cyclodextrins and compatible with detergents and reducers

PubMed Central

2018-01-01

Sodium dodecyl sulfate electrophoresis (SDS) is a protein separation technique widely used, for example, prior to immunoblotting. Samples are usually prepared in a buffer containing both high concentrations of reducers and high concentrations of SDS. This conjunction renders the samples incompatible with common protein assays. By chelating the SDS, cyclodextrins make the use of simple, dye-based colorimetric assays possible. In this paper, we describe the optimization of the assay, focussing on the cyclodextrin/SDS ratio and the use of commercial assay reagents. The adaptation of the assay to a microplate format and using other detergent-containing conventional extraction buffers is also described. PMID:29641569

Development of a simple and low-cost enzymatic methodology for quantitative analysis of carbamates in meat samples of forensic interest.

PubMed

Sabino, Bruno Duarte; Torraca, Tathiana Guilliod; Moura, Claudia Melo; Rozenbaum, Hannah Felicia; de Castro Faria, Mauro Velho

2010-05-01

Foods contaminated with a granulated material similar to Temik (a commercial pesticide formulation containing the carbamate insecticide aldicarb) are often involved in accidental ingestion, suicides, and homicides in Brazil. We developed a simple technique to detect aldicarb. This technique is based on the inhibition of a stable preparation of the enzyme acetylcholinesterase, and it is specially adapted for forensic purposes. It comprises an initial extraction step with the solvent methylene chloride followed by a colorimetric acetylcholinesterase assay. We propose that results of testing contaminated forensic samples be expressed in aldicarb equivalents because, even though all other carbamates are also potent enzyme inhibitors, aldicarb is the contaminant most frequently found in forensic samples. This method is rapid (several samples can be run in a period of 2 h) and low cost. This method also proved to be precise and accurate, detecting concentrations as low as 40 microg/kg of aldicarb in meat samples.

Naked eye detection of infertility based on sperm protamine-induced aggregation of heparin gold nanoparticles.

PubMed

Vidya, Raj; Saji, Alex

2018-05-01

The development of an easy to use, one-pot, environmentally friendly, non-invasive and label-free colorimetric probe for the determination of semen protamines, the biochemical marker of male fertility, using heparin gold nanoparticles (HAuNPs) is presented. The affinity of HAuNPs for protamines was due to the electrostatic interactions between polycationic protamine and polyanionic heparin. The binding of HAuNPs to protamine was characterized by variation in the plasmon absorption spectra followed by a visibly observable colour change of the solution from red to blue. We observed a red shift in the plasmon peak and the method exhibited linearity in the range of 10-70 ng/mL with a detection limit of 5 ng/mL, which is much lower than that reported for colorimetric sensors of protamine. The colour change and the variation in the absorbance of HAuNPs were highly specific for protamines in the presence of different interfering compounds and the method was successfully applied for determining protamine in real samples of semen and serum. Rather than a quantitative estimation, it seems that the method provides a quick screening between a large array of positive and negative samples and, moreover, it maintains the privacy of the user. The method appears to be simple and would be very useful in third-world countries where high-tech diagnostic aids are inaccessible to the majority of the population. Graphical Abstract Heparin gold nanoparticles aided visual detection of infertility.

Colorimetric and fluorescent detection of hydrazine with high sensitivity and excellent selectivity

NASA Astrophysics Data System (ADS)

Shi, Bingjie; Qi, Sujie; Yu, Mingming; Liu, Chunxia; Li, Zhanxian; Wei, Liuhe; Ni, Zhonghai

2018-01-01

It is critical to develop probes for rapid, selective, and sensitive detection of the highly toxic hydrazine in both environmental and biological science. In this work, under mild condition, a novel colorimetric and off-on fluorescent probe was synthesized for rapid recognition of hydrazine with excellent selectivity over other various species including some biological species, metal ions and anions. The limit of quantification (LOQ) value was 1.5 × 10- 4 M-3.2 × 10- 3 M (colorimetric method) and 1.5 × 10- 4 M - 3.2 × 10- 3 M (fluorescent method) with as low as detection limit of 46.2 μM.

Colorimetric detection for paper-based biosensing applications

NASA Astrophysics Data System (ADS)

Brink, C.; Joubert, T.-H.

2016-02-01

Research on affordable point-of-care health diagnostics is rapidly advancing1. Colorimetric biosensor applications are typically qualitative, but recently the focus has been shifted to quantitative measurements2,3. Although numerous qualitative point-of-care (POC) health diagnostic devices are available, the challenge exists of developing a quantitative colorimetric array reader system that complies with the ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, Deliverable to end-users) principles of the World Health Organization4. This paper presents a battery powered 8-bit tonal resolution colorimetric sensor circuit for paper microfluidic assays using low cost photo-detection circuitry and a low-power LED light source. A colorimetric 3×3-pixel array reader was developed for rural environments where resources and personnel are limited. The device sports an ultralow-power E-ink paper display. The colorimetric device includes integrated GPS functionality and EEPROM memory to log measurements with geo-tags for possible analysis of regional trends. The device competes with colour intensity measurement techniques using smartphone cameras, but proves to be a cheaper solution, compensating for the typical performance variations between cameras of different brands of smartphones. Inexpensive methods for quantifying bacterial assays have been shown using desktop scanners, which are not portable, and cameras, which suffer severely from changes in ambient light in different environments. Promising colorimetric detection results have been demonstrated using devices such as video cameras5, digital colour analysers6, flatbed scanners7 or custom portable readers8. The major drawback of most of these methods is the need for specialized instrumentation and for image analysis on a computer.

Comparative analysis for strength serum sodium and potassium in three different methods: Flame photometry, ion-selective electrode (ISE) and colorimetric enzymatic.

PubMed

Garcia, Rafaela Alvim; Vanelli, Chislene Pereira; Pereira Junior, Olavo Dos Santos; Corrêa, José Otávio do Amaral

2018-06-19

Hydroelectrolytic disorders are common in clinical situations and may be harmful to the patient, especially those involving plasma sodium and potassium dosages. Among the possible methods for the dosages are flame photometry, ion-selective electrode (ISE) and colorimetric enzymatic method. We analyzed 175 samples in the three different methods cited from patients attending the laboratory of the University Hospital of the Federal University of Juiz de Fora. The values obtained were statistically treated using SPSS 19.0 software. The present study aims to evaluate the impact of the use of these different methods in the determination of plasma sodium and potassium. The averages obtained for sodium and potassium measurements by flame photometry were similar (P > .05) to the means obtained for the two electrolytes by ISE. The averages obtained by the colorimetric enzymatic method presented statistical difference in relation to ISE, both for sodium and potassium. In the correlation analysis, both flame photometry and colorimetric enzymatic showed a strong correlation with the ISE method for both dosages. At the first time in the same work sodium and potassium were analyzed by three different methods and the results allowed us to conclude that the methods showed a positive and strong correlation, and can be applied in the clinical routine. © 2018 Wiley Periodicals, Inc.

Colorimetric Quantification and in Situ Detection of Collagen

ERIC Educational Resources Information Center

Esteban, Francisco J.; del Moral, Maria L.; Sanchez-Lopez, Ana M.; Blanco, Santos; Jimenez, Ana; Hernandez, Raquel; Pedrosa, Juan A.; Peinado, Maria A.

2005-01-01

A simple multidisciplinary and inexpensive laboratory exercise is proposed, in which the undergraduate student may correlate biochemical and anatomical findings. The entire practical session can be completed in one 2.5-3 hour laboratory period, and consists of the quantification of collagen and total protein content from tissue sections--without…

Synthesis and Analysis of Copper Hydroxy Double Salts

ERIC Educational Resources Information Center

Brigandi, Laura M.; Leber, Phyllis A.; Yoder, Claude H.

2005-01-01

A project involving the synthesis of several naturally occurring copper double salts using simple aqueous conditions is reported. The ions present in the compound are analyzed using colorimetric, gravimetric, and gas-analysis techniques appropriate for the first-year laboratory and from the percent composition, the empirical formula of each…

Redox-iodometry: a new potentiometric method.

PubMed

Gottardi, Waldemar; Pfleiderer, Jörg

2005-07-01

A new iodometric method for quantifying aqueous solutions of iodide-oxidizing and iodine-reducing substances, as well as plain iodine/iodide solutions, is presented. It is based on the redox potential of said solutions after reaction with iodide (or iodine) of known initial concentration. Calibration of the system and calculations of unknown concentrations was performed on the basis of developed algorithms and simple GWBASIC-programs. The method is distinguished by a short analysis time (2-3 min) and a simple instrumentation consisting of pH/mV meter, platinum and reference electrodes. In general the feasible concentration range encompasses 0.1 to 10(-6) mol/L, although it goes down to 10(-8) mol/L (0.001 mg Cl2/L) for oxidants like active chlorine compounds. The calculated imprecision and inaccuracy of the method were found to be 0.4-0.9% and 0.3-0.8%, respectively, resulting in a total error of 0.5-1.2%. Based on the experiments, average imprecisions of 1.0-1.5% at c(Ox)>10(-5) M, 1.5-3% at 10(-5) to 10(-7) M, and 4-7% at <10(-7) M were found. Redox-iodometry is a simple, precise, and time-saving substitute for the more laborious and expensive iodometric titration method, which, like other well-established colorimetric procedures, is clearly outbalanced at low concentrations; this underlines the practical importance of redox-iodometry.

4-Aminothiophenol functionalized gold nanoparticle-based colorimetric sensor for the determination of nitramine energetic materials.

PubMed

Üzer, Ayşem; Can, Ziya; Akın, Ilknur; Erçağ, Erol; Apak, Reşat

2014-01-07

The heterocyclic nitramine compounds, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), are two most important military-purpose high explosives. Differentiation of RDX and HMX with colorimetric methods of determination has not yet been made because of their similar chemical structures. In this study, a sensitive colorimetric method for the determination of RDX and HMX was proposed on the basis of differential kinetics in the hydrolysis of the two compounds (yielding nitrite as a product) followed by their colorimetric determination using 4-aminothiophenol (4-ATP) modified gold nanoparticles (AuNPs) and naphthylethylene diamine (NED) as coupling agent for azo-dye formation, abbreviated as "4-ATP-AuNP+NED" colorimetric method. After alkaline hydrolysis in a 1 M Na2CO3 + 0.04 M NaOH mixture solution at room temperature, only RDX (but not HMX) was hydrolyzed to give a sufficient colorimetric response in neutralized solution, the molar absorptivity (ε) at 565 nm and the limit of detection (LOD) for RDX being (17.6 ± 1.3) × 10(3) L mol(-1) cm(-1) and 0.55 μg mL(-1), respectively. On the other hand, hot water bath (at 60 °C) hydrolysis enabled both nitramines, RDX and HMX, to give substantial colorimetric responses; i.e., ε and LOD for RDX were (32.8 ± 0.5) × 10(3) L mol(-1)cm(-1) and 0.20 μg mL(-1) and for HMX were (37.1 ± 2.8) × 10(3) L mol(-1)cm(-1) and 0.24 μg mL(-1), respectively. Unlike other AuNP-based nitrite sensors in the literature showing absorbance quenching within a relatively narrow concentration range, the developed sensor operated with an absorbance increase over a wide range of nitrite. Synthetic mixtures of (RDX + HMX) gave additive responses, and the proposed method was statistically validated against HPLC using nitramine mixtures.

Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.

PubMed

Corredor, Charlie; Borysiak, Mark D; Wolfer, Jay; Westerhoff, Paul; Posner, Jonathan D

2015-03-17

There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles (NPs) in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation. Here, we investigate a simple and portable colorimetric detection assay that assesses the surface reactivity of NPs, which can be used to detect the presence of NPs, in complex matrices (e.g., environmental waters, serum, urine, and in dissolved organic matter) at as low as part per billion (ppb) or ng/mL concentration levels. Surface redox reactivity is a key emerging property related to potential toxicity of NPs with living cells, and is used in our assays as a key surrogate for the presence of NPs and a first tier analytical strategy toward assessing NP exposures. We detect a wide range of metal (e.g., Ag and Au) and oxide (e.g., CeO2, SiO2, VO2) NPs with a diameter range of 5 to 400 nm and multiple capping agents (tannic acid (TA), polyvinylpyrrolidone (PVP), branched polyethylenimine (BPEI), polyethylene glycol (PEG)). This method is sufficiently sensitive (ppb levels) to measure concentrations typically used in toxicological studies, and uses inexpensive, commercially available reagents.

Development of a solenoid pumped in situ zinc analyzer for environmental monitoring

USGS Publications Warehouse

Chapin, T.P.; Wanty, R.B.

2005-01-01

A battery powered submersible chemical analyzer, the Zn-DigiScan (Zn Digital Submersible Chemical Analyzer), has been developed for near real-time, in situ monitoring of zinc in aquatic systems. Microprocessor controlled solenoid pumps propel sample and carrier through an anion exchange column to separate zinc from interferences, add colorimetric reagents, and propel the reaction complex through a simple photometric detector. The Zn-DigiScan is capable of self-calibration with periodic injections of standards and blanks. The detection limit with this approach was 30 ??g L-1. Precision was 5-10% relative standard deviation (R.S.D.) below 100 ??g L-1, improving to 1% R.S.D. at 1000 ??g L-1. The linear range extended from 30 to 3000 ??g L-1. In situ field results were in agreement with samples analyzed by inductively coupled plasma mass spectrometry (ICPMS). This pump technology is quite versatile and colorimetric methods with complex online manipulations such as column reduction, preconcentration, and dilution can be performed with the DigiScan. However, long-term field deployments in shallow high altitude streams were hampered by air bubble formation in the photometric detector. ?? 2005 Elsevier B.V. All rights reserved.

[Comparative research into sensitivity and specificity of immune-enzyme analysis with chemiluminescence and colorimetric detection for detecting antigens and antibodies to avian influenza viruses and newcastle disease].

PubMed

Vitkova, O N; Kapustina, T P; Mikhailova, V V; Safonov, G A; Vlasova, N N; Belousova, R V

2015-01-01

The goal of this work was to demonstrate the results of the development of the enzyme-linked immunosorbent tests with chemiluminescence detection and colorimetric detection of specific viral antigens and antibodies for identifying the avian influenza and the Newcastle disease viruses: high sensitivity and specificity of the immuno- chemiluminescence assay, which are 10-50 times higher than those of the ELISA colorimetric method. The high effectiveness of the results and the automation of the process of laboratory testing (using a luminometer) allow these methods to be recommended for including in primary screening tests for these infectious diseases.

A novel fluoride ion colorimetric chemosensor based on coumarin.

PubMed

Zhuang, Xiaoqing; Liu, Weimin; Wu, Jiasheng; Zhang, Hongyan; Wang, Pengfei

2011-09-01

A novel visible colorimetric sensor (L1) with high selectivity for fluoride ion based on coumarin has been synthesized by a simple modification of our earlier report. The chemosensor L1 shows an obvious color change from yellow to blue upon addition of fluoride ion with a large red shift of 145 nm in acetonitrile, and without interference of other anions such as Cl-, Br-, I-, NO3-, H2PO4-, HSO4-, and AcO-. The investigation of 1H NMR spectrum titration indicates the proposed mechanism is that F- first establishes a hydrogen bonding interaction with L1, and then the formation of [F-H-F]- induces deprotonation. Copyright © 2011 Elsevier B.V. All rights reserved.

Highly selective "turn-on" fluorescent and colorimetric sensing of fluoride ion using 2-(2-hydroxyphenyl)-2,3-dihydroquinolin-4(1H)-one based on excited-state proton transfer.

PubMed

Kanagaraj, Kuppusamy; Pitchumani, Kasi

2014-01-01

A simple, highly selective and sensitive colorimetric system for the detection of fluoride ion in an aqueous medium has been developed using 2-(2-hydroxyphenyl)-2,3-dihydroquinolin-4(1H)-one. This system allows selective "turn-on" fluorescence detection of fluoride ion, which is found to be dependent upon guest basicity. An excited-state proton transfer is proposed to be the signaling mechanism, which is rationalized by DFT and TD-DFT calculations. The present sensor can also be applied to detect fluoride levels in real water samples. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybrid nanosensor for colorimetric and ultrasensitive detection of nuclease contaminations

NASA Astrophysics Data System (ADS)

Cecere, Paola; Valentini, Paola; Pompa, Pier Paolo

2016-04-01

Nucleases are ubiquitous enzymes that degrade DNA or RNA, thus they can prejudice the good outcome of molecular biology experiments involving nucleic acids. We propose a colorimetric test for the naked-eye detection of nuclease contaminations. The system uses an hybrid nanosensor, based on gold nanoparticles functionalized with DNA probes. Our assay is rapid, instrument-free, simple and low-cost. Moreover, it reaches sensitivity equal or better than those of commercial kits, and presents a lot of advantageous aspects. Therefore, it is very competitive, with a real market potential. This test will be relevant in routine process monitoring in scientific laboratories, and in quality control in clinical laboratories and industrial processes, allowing the simultaneous detection of nucleases with different substrate specificities and large-scale screening.

Discovering the enzyme mimetic activity of metal-organic framework (MOF) for label-free and colorimetric sensing of biomolecules.

PubMed

Wang, Ying; Zhu, Yingjing; Binyam, Atsebeha; Liu, Misha; Wu, Yinan; Li, Fengting

2016-12-15

A label-free sensing strategy based on the enzyme-mimicking activity of MOF was demonstrated for colorimetric detection of biomolecules. Firstly obvious blue color was observed due to the high efficiency of peroxidase-like catalytic activity of Fe-MIL-88A (an ion-based MOF material) toward 3,3',5,5'-tetramethylbenzidine (TMB). Then in the presence of target biomolecule and corresponding aptamer, the mimetic activity of Fe-MIL-88A can be strongly inhibited and used directly to realize the colorimetric detection. On the basis of the interesting findings, we designed a straightforward, label-free and sensitive colorimetric method for biomolecule detection by using the enzyme mimetic property of MOF coupling with molecular recognition element. Compared with the existed publications, our work breaks the routine way by setting up an inorganic-organic MOF-aptamer hybrid platform for colorimetric determination of biomolecules, expanding the targets scope from H2O2 or glucose to biomolecules. As a proof of concept, thrombin and thrombin aptamer was used as a model analyte. The limit of detection of 10nM can be achieved with naked eyes and ultrahigh selectivity of thrombin toward numerous interfering substances with 10-fold concentration was demonstrated significantly. Of note, the method was further applied for the detection of thrombin in human serum samples, showing the results in agreement with those values obtained in an immobilization buffer by the colorimetric method. This inorganic-organic MOF-aptamer sensing strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interests. Copyright © 2016 Elsevier B.V. All rights reserved.

A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

PubMed

Shi, Xinhao; Gu, Wei; Zhang, Cuiling; Zhao, Longyun; Peng, Weidong; Xian, Yuezhong

2015-03-14

In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 μM and the limit of detection (LOD) was evaluated to be 0.05 μM. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry.

Succinic acid functionalized silver nanoparticles (Suc-Ag NPs) for colorimetric sensing of melamine

NASA Astrophysics Data System (ADS)

Rajar, Kausar; Sirajuddin; Balouch, Aamna; Bhanger, M. I.; Shah, Muhammad Tariq; Shaikh, Tayyaba; Siddiqui, Samia

2018-03-01

In this study, a quantitative colorimetric sensing strategy is developed for the rapid, sensitive and selective determination of melamine. The sensing system relies on the application of succinic acid as a selective recognition probe functionalized over Ag NPs. The synthesized Ag NPs were modified with cysteamine to induce positively charged atmosphere which allowed easy and favorable functionalization of succinic acid. The di-carboxyl nature of succinic acid enabled its binding to both cysteamine and melamine. The strong and favorable linkage between succinic acids carbonyl and amine moieties of melamine triggered aggregation of silver NPs producing a significant shift in the measured absorption excitation. This change in the excitation along with the colorimetric response was found linearly proportional to the melamine concentration in the range of 0.1-1.2 μM. The developed sensor system is simple and unlike electrostatic attraction based sensor system utilize selective linkage for the recognition of melamine. In addition to this, the developed optical probe can efficiently be used for the determination of melamine in milk samples.

A colorimetric sensor array for detection of triacetone triperoxide vapor.

PubMed

Lin, Hengwei; Suslick, Kenneth S

2010-11-10

Triacetone triperoxide (TATP), one of the most dangerous primary explosives, has emerged as an explosive of choice for terrorists in recent years. Owing to the lack of UV absorbance, fluorescence, or facile ionization, TATP is extremely difficult to detect directly. Techniques that are able to detect generally require expensive instrumentation, need extensive sample preparation, or cannot detect TATP in the gas phase. Here we report a simple and highly sensitive colorimetric sensor for the detection of TATP vapor with semiquantitative analysis from 50 ppb to 10 ppm. By using a solid acid catalyst to pretreat a gas stream, we have discovered that a colorimetric sensor array of redox sensitive dyes can detect even very low levels of TATP vapor from its acid decomposition products (e.g., H(2)O(2)) with limits of detection (LOD) below 2 ppb (i.e., <0.02% of its saturation vapor pressure). Common potential interferences (e.g., humidity, personal hygiene products, perfume, laundry supplies, volatile organic compounds, etc.) do not generate an array response, and the array can also differentiate TATP from other chemical oxidants (e.g., hydrogen peroxide, bleach, tert-butylhydroperoxide, peracetic acid).

Sunlight Induced Preparation of Functionalized Gold Nanoparticles as Recyclable Colorimetric Dual Sensor for Aluminum and Fluoride in Water.

PubMed

Kumar, Anshu; Bhatt, Madhuri; Vyas, Gaurav; Bhatt, Shreya; Paul, Parimal

2017-05-24

A sunlight induced simple green route has been developed for the synthesis of polyacrylate functionalized gold nanoparticles (PAA-AuNPs), in which poly(acrylic acid) functions as a reducing as well as stabilizing agent. This material has been characterized on the basis of spectroscopic and microscopic studies; it exhibited selective colorimetric detection of Al 3+ in aqueous media, and the Al 3+ induced aggregated PAA-AuNPs exhibited detection of F - with sharp color change and high selectivity and sensitivity out of a large number of metal ions and anions tested. The mechanistic study revealed that, for Al 3+ , the color change is due to a shift of the SPR band because of the Al 3+ induced aggregation of PAA-AuNPs, whereas for F - , the reverse color change (blue to red) with return of the SPR band to its original position is due to dispersion of aggregated PAA-AuNPs, as F - removes Al 3+ from the aggregated species by complex formation. Only concentration-dependent fluoride ion can prevent Al 3+ from aggregating PAA-AuNPs. The method is successfully used for the detection of F - in water collected from various sources by the spiking method, in toothpastes of different brands by the direct method. The solid Al 3+ -PAA-AuNPs were isolated, adsorbed on ZIF@8 (zeolitic imidazolate framework) and on a cotton strip, and applied as solid sensing material for detection of F - in aqueous media.

A SIMPLE COLORIMETRIC ASSAY FOR PHENOTYPING THE MAJOR HUMAN THERMOSTABLE PHENOL SULFOTRANSFERASE (SULT1A1) USING PLATELET CYTOSOLS. (R825280)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Simple telemedicine for developing regions: camera phones and paper-based microfluidic devices for real-time, off-site diagnosis.

PubMed

Martinez, Andres W; Phillips, Scott T; Carrilho, Emanuel; Thomas, Samuel W; Sindi, Hayat; Whitesides, George M

2008-05-15

This article describes a prototype system for quantifying bioassays and for exchanging the results of the assays digitally with physicians located off-site. The system uses paper-based microfluidic devices for running multiple assays simultaneously, camera phones or portable scanners for digitizing the intensity of color associated with each colorimetric assay, and established communications infrastructure for transferring the digital information from the assay site to an off-site laboratory for analysis by a trained medical professional; the diagnosis then can be returned directly to the healthcare provider in the field. The microfluidic devices were fabricated in paper using photolithography and were functionalized with reagents for colorimetric assays. The results of the assays were quantified by comparing the intensities of the color developed in each assay with those of calibration curves. An example of this system quantified clinically relevant concentrations of glucose and protein in artificial urine. The combination of patterned paper, a portable method for obtaining digital images, and a method for exchanging results of the assays with off-site diagnosticians offers new opportunities for inexpensive monitoring of health, especially in situations that require physicians to travel to patients (e.g., in the developing world, in emergency management, and during field operations by the military) to obtain diagnostic information that might be obtained more effectively by less valuable personnel.

Method for hue plane preserving color correction.

PubMed

Mackiewicz, Michal; Andersen, Casper F; Finlayson, Graham

2016-11-01

Hue plane preserving color correction (HPPCC), introduced by Andersen and Hardeberg [Proceedings of the 13th Color and Imaging Conference (CIC) (2005), pp. 141-146], maps device-dependent color values (RGB) to colorimetric color values (XYZ) using a set of linear transforms, realized by white point preserving 3×3 matrices, where each transform is learned and applied in a subregion of color space, defined by two adjacent hue planes. The hue plane delimited subregions of camera RGB values are mapped to corresponding hue plane delimited subregions of estimated colorimetric XYZ values. Hue planes are geometrical half-planes, where each is defined by the neutral axis and a chromatic color in a linear color space. The key advantage of the HPPCC method is that, while offering an estimation accuracy of higher order methods, it maintains the linear colorimetric relations of colors in hue planes. As a significant result, it therefore also renders the colorimetric estimates invariant to exposure and shading of object reflection. In this paper, we present a new flexible and robust version of HPPCC using constrained least squares in the optimization, where the subregions can be chosen freely in number and position in order to optimize the results while constraining transform continuity at the subregion boundaries. The method is compared to a selection of other state-of-the-art characterization methods, and the results show that it outperforms the original HPPCC method.

Field demonstration of on-site analytical methods for TNT and RDX in ground water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craig, H.; Ferguson, G.; Markos, A.

1996-12-31

A field demonstration was conducted to assess the performance of eight commercially-available and emerging colorimetric, immunoassay, and biosensor on-site analytical methods for explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in ground water and leachate at the Umatilla Army Depot Activity, Hermiston, Oregon and US Naval Submarine Base, Bangor, Washington, Superfund sites. Ground water samples were analyzed by each of the on-site methods and results compared to laboratory analysis using high performance liquid chromatography (HPLC) with EPA SW-846 Method 8330. The commercial methods evaluated include the EnSys, Inc., TNT and RDX colorimetric test kits (EPA SW-846 Methods 8515 and 8510) with amore » solid phase extraction (SPE) step, the DTECH/EM Science TNT and RDX immunoassay test kits (EPA SW-846 Methods 4050 and 4051), and the Ohmicron TNT immunoassay test kit. The emerging methods tested include the antibody-based Naval Research Laboratory (NRL) Continuous Flow Immunosensor (CFI) for TNT and RDX, and the Fiber Optic Biosensor (FOB) for TNT. Accuracy of the on-site methods were evaluated using linear regression analysis and relative percent difference (RPD) comparison criteria. Over the range of conditions tested, the colorimetric methods for TNT and RDX showed the highest accuracy of the emerging methods for TNT and RDX. The colorimetric method was selected for routine ground water monitoring at the Umatilla site, and further field testing on the NRL CFI and FOB biosensors will continue at both Superfund sites.« less

Detection of influenza A virus subtypes using a solid-phase PCR microplate chip assay.

PubMed

Sun, Xin-Cheng; Wang, YunLong; Yang, Liping; Zhang, HuiRu

2015-01-01

A rapid and sensitive microplate chip based on solid PCR was developed to identify influenza A subtypes. A simple ultraviolet cross-linking method was used to immobilize DNA probes on pretreated microplates. Solid-phase PCR was proven to be a convenient method for influenza A screening. The sensitivity of the microplate chip was 10(-3) μg/mL for the enzymatic colorimetric method and 10(-4) μg/mL for the fluorescence method. The 10 sets of primers and probes for the microplate chip were highly specific and did not interfere with each other. These results suggest that the microplate chip based on solid PCR can be used to rapidly detect universal influenza A and its subtypes. This platform can also be used to detect other pathogenic microorganisms. Copyright © 2014 Elsevier B.V. All rights reserved.

A Colorimetric and Fluorescent Probe for the Detection of Cu2+ in a Complete Aqueous Solution.

PubMed

Xu, Jing; Wang, Zuokai; Liu, Caiyun; Xu, Zhenghe; Zhu, Baocun; Wang, Ning; Wang, Kun; Wang, Jiangting

2018-01-01

The fluorescent probe has become an important method for the detection of heavy metal ions. In the present work, a new and simple fluorescent probe, Cu-P, for detecting copper ion (Cu 2+ ) was designed and synthesized. The probe has shown high sensitivity and selectivity toward Cu 2+ . The detection limit was 13 nM (based on the 3σ/slope). A significant color change from yellow to pink was observed; thus, the probe Cu-P could serve as a "naked-eye" indicator for Cu 2+ . Furthermore, the proposed probe was used to detect Cu 2+ in real water and soil extract samples, with the result being satisfactory. Therefore, our proposed probe would provide a promising method for the detection of Cu 2+ in the environment.

Quantification of Soluble Sugars and Sugar Alcohols by LC-MS/MS.

PubMed

Feil, Regina; Lunn, John Edward

2018-01-01

Sugars are simple carbohydrates composed primarily of carbon, hydrogen, and oxygen. They play a central role in metabolism as sources of energy and as building blocks for synthesis of structural and nonstructural polymers. Many different techniques have been used to measure sugars, including refractometry, colorimetric and enzymatic assays, gas chromatography, high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy. In this chapter we describe a method that combines an initial separation of sugars by high-performance anion-exchange chromatography (HPAEC) with detection and quantification by tandem mass spectrometry (MS/MS). This combination of techniques provides exquisite specificity, allowing measurement of a diverse range of high- and low-abundance sugars in biological samples. This method can also be used for isotopomer analysis in stable-isotope labeling experiments to measure metabolic fluxes.

L-cysteine protected copper nanoparticles as colorimetric sensor for mercuric ions.

PubMed

Soomro, Razium A; Nafady, Ayman; Sirajuddin; Memon, Najma; Sherazi, Tufail H; Kalwar, Nazar H

2014-12-01

This report demonstrates a novel, simple and efficient protocol for the synthesis of copper nanoparticles in aqueous solution using L-cysteine as capping or protecting agent. UV-visible (UV-vis) spectroscopy was employed to monitor the LSPR band of L-cysteine functionalized copper nanoparticles (Cyst-Cu NPs) based on optimizing various reaction parameters. Fourier Transform Infrared (FTIR) spectroscopy provided information about the surface interaction between L-cysteine and Cu NPs. Transmission Electron Microscopy (TEM) confirmed the formation of fine spherical, uniformly distributed Cyst-Cu NPs with average size of 34 ± 2.1 nm. X-ray diffractometry (XRD) illustrated the formation of pure metallic phase crystalline Cyst-Cu NPs. As prepared Cyst-Cu NPs were tested as colorimetric sensor for determining mercuric (Hg(2+)) ions in an aqueous system. Cyst-Cu NPs demonstrated very sensitive and selective colorimetric detection of Hg(2+) ions in the range of 0.5 × 10(-6)-3.5 × 10(-6) mol L(-1) based on decrease in LSPR intensity as monitored by a UV-vis spectrophotometer. The developed sensor is simple, economic compared to those based on precious metal nanoparticles and sensitive to detect Hg(2+) ions with detection limit down to 4.3 × 10(-8) mol L(-1). The sensor developed in this work has a high potential for rapid and on-site detection of Hg(2+) ions. The sensor was successfully applied for assessment of Hg(2+) ions in real water samples collected from various locations of the Sindh River. Copyright © 2014 Elsevier B.V. All rights reserved.

Multispectral Image Compression for Improvement of Colorimetric and Spectral Reproducibility by Nonlinear Spectral Transform

NASA Astrophysics Data System (ADS)

Yu, Shanshan; Murakami, Yuri; Obi, Takashi; Yamaguchi, Masahiro; Ohyama, Nagaaki

2006-09-01

The article proposes a multispectral image compression scheme using nonlinear spectral transform for better colorimetric and spectral reproducibility. In the method, we show the reduction of colorimetric error under a defined viewing illuminant and also that spectral accuracy can be improved simultaneously using a nonlinear spectral transform called Labplus, which takes into account the nonlinearity of human color vision. Moreover, we show that the addition of diagonal matrices to Labplus can further preserve the spectral accuracy and has a generalized effect of improving the colorimetric accuracy under other viewing illuminants than the defined one. Finally, we discuss the usage of the first-order Markov model to form the analysis vectors for the higher order channels in Labplus to reduce the computational complexity. We implement a multispectral image compression system that integrates Labplus with JPEG2000 for high colorimetric and spectral reproducibility. Experimental results for a 16-band multispectral image show the effectiveness of the proposed scheme.

Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

ERIC Educational Resources Information Center

Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

2012-01-01

A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and…

Modified nondestructive colorimetric method to evaluate the variability of oxygen diffusion rate through wine bottle closures.

PubMed

Brotto, Laura; Battistutta, Franco; Tat, Lara; Comuzzo, Piergiorgio; Zironi, Roberto

2010-03-24

Some modifications to a previous nondestructive colorimetric method that permits evaluation of the oxygen diffusion rate through wine closures were proposed. The method is based on the reaction of indigo carmine solution with oxygen and the tristimulus measurement of the consequent color change. Simplified preparation and measurement procedures were set up, allowing the analysis of a large number of samples simultaneously. The method was applied to the evaluation of the variability within the lot of 20 different types of stoppers (synthetic, produced by molding, and natural cork). The closures were tested at a storage temperature of 26 degrees C. With regard to oxygen permeability, the natural cork stopper showed a low homogeneity within the lot, especially during the first month after bottling, whereas the synthetic closure showed a greater steadiness in the performance. The limits of the colorimetric method were also analyzed, and three possible causes of degradation of the indigo carmine solution were identified: oxygen, light, and heat.

Application of bacteriophages in sensor development.

PubMed

Peltomaa, Riikka; López-Perolio, Irene; Benito-Peña, Elena; Barderas, Rodrigo; Moreno-Bondi, María Cruz

2016-03-01

Bacteriophage-based bioassays are a promising alternative to traditional antibody-based immunoassays. Bacteriophages, shortened to phages, can be easily conjugated or genetically engineered. Phages are robust, ubiquitous in nature, and harmless to humans. Notably, phages do not usually require inoculation and killing of animals; and thus, the production of phages is simple and economical. In recent years, phage-based biosensors have been developed featuring excellent robustness, sensitivity, and selectivity in combination with the ease of integration into transduction devices. This review provides a critical overview of phage-based bioassays and biosensors developed in the last few years using different interrogation methods such as colorimetric, enzymatic, fluorescence, surface plasmon resonance, quartz crystal microbalance, magnetoelastic, Raman, or electrochemical techniques.

Reaction-based Indicator displacement Assay (RIA) for the selective colorimetric and fluorometric detection of peroxynitrite.

PubMed

Sun, Xiaolong; Lacina, Karel; Ramsamy, Elena C; Flower, Stephen E; Fossey, John S; Qian, Xuhong; Anslyn, Eric V; Bull, Steven D; James, Tony D

2015-05-01

Using the self-assembly of aromatic boronic acids with Alizarin Red S (ARS), we developed a new chemosensor for the selective detection of peroxynitrite. Phenylboronic acid (PBA), benzoboroxole (BBA) and 2-( N , N -dimethylaminomethyl)phenylboronic acid (NBA) were employed to bind with ARS to form the complex probes. In particular, the ARS-NBA system with a high binding affinity can preferably react with peroxynitrite over hydrogen peroxide and other ROS/RNS due to the protection of the boron via the solvent-insertion B-N interaction. Our simple system produces a visible colorimetric change and on-off fluorescence response towards peroxynitrite. By coupling a chemical reaction that leads to an indicator displacement, we have developed a new sensing strategy, referred to herein as RIA (Reaction-based Indicator displacement Assay).

Easy design of colorimetric logic gates based on nonnatural base pairing and controlled assembly of gold nanoparticles.

PubMed

Zhang, Li; Wang, Zhong-Xia; Liang, Ru-Ping; Qiu, Jian-Ding

2013-07-16

Utilizing the principles of metal-ion-mediated base pairs (C-Ag-C and T-Hg-T), the pH-sensitive conformational transition of C-rich DNA strand, and the ligand-exchange process triggered by DL-dithiothreitol (DTT), a system of colorimetric logic gates (YES, AND, INHIBIT, and XOR) can be rationally constructed based on the aggregation of the DNA-modified Au NPs. The proposed logic operation system is simple, which consists of only T-/C-rich DNA-modified Au NPs, and it is unnecessary to exquisitely design and alter the DNA sequence for different multiple molecular logic operations. The nonnatural base pairing combined with unique optical properties of Au NPs promises great potential in multiplexed ion sensing, molecular-scale computers, and other computational logic devices.

Naphthaldimine-based simple glucose derivative as a highly selective sensor for colorimetric detection of Cu2+ ion in aqueous media

NASA Astrophysics Data System (ADS)

Dolai, Bholanath; Bhaumik, Atanu; Pramanik, Nabakumar; Ghosh, Kalyan Sundar; Atta, Ananta Kumar

2018-07-01

Naphthaldimine-based glucose derivatives 1 and 3 have been designed, synthesized and characterized. In aqueous media, glucose derivative 1, exhibited high selectivity and sensitivity towards Cu2+ ion in comparison with various cations and anions. In presence of Cu2+, sensor 1 has provided significant naked-eye detectable color change. The formation of 1-Cu2+ complex has been analyzed by UV-vis spectroscopy, 1H NMR titration experiments, mass spectrometry and DFT (density functional theory) calculations. Limit of detection of 1 as a colorimetric sensor for Cu2+ ion is found to be 0.23 μM, much lower than recommended value of World Health Organization (WHO), which makes to Cu2+ sensor 1 more effective and useful.

Implementation of cascade logic gates and majority logic gate on a simple and universal molecular platform.

PubMed

Gao, Jinting; Liu, Yaqing; Lin, Xiaodong; Deng, Jiankang; Yin, Jinjin; Wang, Shuo

2017-10-25

Wiring a series of simple logic gates to process complex data is significantly important and a large challenge for untraditional molecular computing systems. The programmable property of DNA endows its powerful application in molecular computing. In our investigation, it was found that DNA exhibits excellent peroxidase-like activity in a colorimetric system of TMB/H 2 O 2 /Hemin (TMB, 3,3', 5,5'-Tetramethylbenzidine) in the presence of K + and Cu 2+ , which is significantly inhibited by the addition of an antioxidant. According to the modulated catalytic activity of this DNA-based catalyst, three cascade logic gates including AND-OR-INH (INHIBIT), AND-INH and OR-INH were successfully constructed. Interestingly, by only modulating the concentration of Cu 2+ , a majority logic gate with a single-vote veto function was realized following the same threshold value as that of the cascade logic gates. The strategy is quite straightforward and versatile and provides an instructive method for constructing multiple logic gates on a simple platform to implement complex molecular computing.

Low picomolar, instrument-free visual detection of mercury and silver ions using low-cost programmable nanoprobes

PubMed Central

Rana, Muhit; Balcioglu, Mustafa; Robertson, Neil M.; Hizir, Mustafa Salih; Yumak, Sumeyra

2017-01-01

The EPA's recommended maximum allowable level of inorganic mercury in drinking water is 2 ppb (10 nM). To our knowledge, the most sensitive colorimetric mercury sensor reported to date has a limit of detection (LOD) of 800 pM. Here, we report an instrument-free and highly practical colorimetric methodology, which enables detection of as low as 2 ppt (10 pM) of mercury and/or silver ions with the naked eye using a gold nanoprobe. Synthesis of the nanoprobe costs less than $1.42, which is enough to perform 200 tests in a microplate; less than a penny for each test. We have demonstrated the detection of inorganic mercury from water, soil and urine samples. The assay takes about four hours and the color change is observed within minutes after the addition of the last required element of the assay. The nanoprobe is highly programmable which allows for the detection of mercury and/or silver ions separately or simultaneously by changing only a single parameter of the assay. This highly sensitive approach for the visual detection relies on the combination of the signal amplification features of the hybridization chain reaction with the plasmonic properties of the gold nanoparticles. Considering that heavy metal ion contamination of natural resources is a major challenge and routine environmental monitoring is needed, yet time-consuming, this colorimetric approach may be instrumental for on-site heavy metal ion detection. Since the color transition can be measured in a variety of formats including using the naked eye, a simple UV-Vis spectrophotometer, or recording using mobile phone apps for future directions, our cost-efficient assay and method have the potential to be translated into the field. PMID:28451261

Offset-sparsity decomposition for enhancement of color microscopic image of stained specimen in histopathology: further results

NASA Astrophysics Data System (ADS)

Kopriva, Ivica; Popović Hadžija, Marijana; Hadžija, Mirko; Aralica, Gorana

2016-03-01

Recently, novel data-driven offset-sparsity decomposition (OSD) method was proposed by us to increase colorimetric difference between tissue-structures present in the color microscopic image of stained specimen in histopathology. The OSD method performs additive decomposition of vectorized spectral images into image-adapted offset term and sparse term. Thereby, the sparse term represents an enhanced image. The method was tested on images of the histological slides of human liver stained with hematoxylin and eosin, anti-CD34 monoclonal antibody and Sudan III. Herein, we present further results related to increase of colorimetric difference between tissue structures present in the images of human liver specimens with pancreatic carcinoma metastasis stained with Gomori, CK7, CDX2 and LCA, and with colon carcinoma metastasis stained with Gomori, CK20 and PAN CK. Obtained relative increase of colorimetric difference is in the range [19.36%, 103.94%].

Nucleic acid-coupled colorimetric analyte detectors

DOEpatents

Charych, Deborah H.; Jonas, Ulrich

2001-01-01

The present invention relates to methods and compositions for the direct detection of analytes and membrane conformational changes through the detection of color changes in biopolymeric materials. In particular, the present invention provide for the direct colorimetric detection of analytes using nucleic acid ligands at surfaces of polydiacetylene liposomes and related molecular layer systems.

Clinical chemistry measurements with commercially available test slides on a smartphone platform: Colorimetric determination of glucose and urea.

PubMed

Wu, Yuanyuan; Boonloed, Anukul; Sleszynski, Neal; Koesdjojo, Myra; Armstrong, Chadd; Bracha, Shay; Remcho, Vincent T

2015-08-25

Rapidly increasing healthcare costs in economically advantaged countries are currently unsustainable, while in many developing nations, even 50-year-old technologies are too expensive to implement. New and unconventional technologies are being explored as solutions to this problem. In this study, we examined the use of a smartphone as the detection platform for 2 well-developed, relatively inexpensive, commercially available clinical chemistry assays as a model for rapid and inexpensive clinical diagnostic testing. An Apple iPhone 4 camera phone equipped with a color analysis application (ColorAssist) was combined with Vitros® glucose and urea colorimetric assays. Color images of assay slides at various concentrations of glucose or urea were collected with the iPhone 4 and quantitated in three different spectral ranges (red/green/blue or RGB) using the ColorAssist app. When the diffuse reflectance data was converted into absorbance, it was possible to quantitate glucose or blood urea nitrogen (BUN) over their clinically important concentration ranges (30-515mg/dl for glucose or 2-190mg/dl for BUN), with good linearity (R(2)=0.9994 or 0.9996, respectively [n=5]). Data collected using the iPhone 4 and canine serum samples were in agreement with results from the instrumental "gold standard" (Beckman Coulter AU480 Chemistry System) (R(2)=0.9966 and slope=1.0001 for glucose; R(2)=0.9958 and slope=0.9454 for BUN). Glucose determinations of serum samples made using this smartphone method were as accurate as or more accurate than a commercial colorimetric dry slide analyzer (Heska® Element DC Chemistry Analyzer, Loveland, CO) and 2 glucometers: ReliOn® Ultima (Abbott Diabetes Care Inc) and Presto® (AgaMatrix Inc.H). BUN determinations made using the smartphone approach were comparable in accuracy to the Heska instrument. This demonstration shows that smartphones have the potential to be used as simple, effective colorimetric detectors for quantitative diagnostic tests, and may be applicable for both point-of-care applications in the developed world and field deployment in developing nations. Copyright © 2015 Elsevier B.V. All rights reserved.

Azomethine H colorimetric method for determining dissolved boron in water

USGS Publications Warehouse

Spencer, R.R.; Erdmann, D.E.

1979-01-01

An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

Detection of heavy metal by paper-based microfluidics.

PubMed

Lin, Yang; Gritsenko, Dmitry; Feng, Shaolong; Teh, Yi Chen; Lu, Xiaonan; Xu, Jie

2016-09-15

Heavy metal pollution has shown great threat to the environment and public health worldwide. Current methods for the detection of heavy metals require expensive instrumentation and laborious operation, which can only be accomplished in centralized laboratories. Various microfluidic paper-based analytical devices have been developed recently as simple, cheap and disposable alternatives to conventional ones for on-site detection of heavy metals. In this review, we first summarize current development of paper-based analytical devices and discuss the selection of paper substrates, methods of device fabrication, and relevant theories in these devices. We then compare and categorize recent reports on detection of heavy metals using paper-based microfluidic devices on the basis of various detection mechanisms, such as colorimetric, fluorescent, and electrochemical methods. To finalize, the future development and trend in this field are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Bottom-up fabrication of paper-based microchips by blade coating of cellulose microfibers on a patterned surface.

PubMed

Gao, Bingbing; Liu, Hong; Gu, Zhongze

2014-12-23

We report a method for the bottom-up fabrication of paper-based capillary microchips by the blade coating of cellulose microfibers on a patterned surface. The fabrication process is similar to the paper-making process in which an aqueous suspension of cellulose microfibers is used as the starting material and is blade-coated onto a polypropylene substrate patterned using an inkjet printer. After water evaporation, the cellulose microfibers form a porous, hydrophilic, paperlike pattern that wicks aqueous solution by capillary action. This method enables simple, fast, inexpensive fabrication of paper-based capillary channels with both width and height down to about 10 μm. When this method is used, the capillary microfluidic chip for the colorimetric detection of glucose and total protein is fabricated, and the assay requires only 0.30 μL of sample, which is 240 times smaller than for paper devices fabricated using photolithography.

Aptamer-mediated colorimetric method for rapid and sensitive detection of chloramphenicol in food.

PubMed

Yan, Chao; Zhang, Jing; Yao, Li; Xue, Feng; Lu, Jianfeng; Li, Baoguang; Chen, Wei

2018-09-15

We report an aptamer-mediated colorimetric method for sensitive detection of chloramphenicol (CAP). The aptamer of CAP is immobilized by the hybridization with pre-immobilized capture probe in the microtiter plate. The horseradish peroxidase (HRP) is covalently attached to the aptamer by the biotin-streptavidin system for signal production. CAP will preferably bind with aptamer due to the high binding affinity, which attributes to the release of aptamer and HRP and thus, affects the optical signal intensity. Quantitative determination of CAP is successfully achieved in the wide range from 0.001 to 1000 ng/mL with detection limit of 0.0031 ng/mL, which is more sensitive than traditional immunoassays. This method is further validated by measuring the recovery of CAP spiked in two different food matrices (honey and fish). The aptamer-mediated colorimetric method can be a useful protocol for rapid and sensitive screening of CAP, and may be used as an alternative means for traditional immunoassays. Copyright © 2018 Elsevier Ltd. All rights reserved.

Improving reflectance reconstruction from tristimulus values by adaptively combining colorimetric and reflectance similarities

NASA Astrophysics Data System (ADS)

Cao, Bin; Liao, Ningfang; Li, Yasheng; Cheng, Haobo

2017-05-01

The use of spectral reflectance as fundamental color information finds application in diverse fields related to imaging. Many approaches use training sets to train the algorithm used for color classification. In this context, we note that the modification of training sets obviously impacts the accuracy of reflectance reconstruction based on classical reflectance reconstruction methods. Different modifying criteria are not always consistent with each other, since they have different emphases; spectral reflectance similarity focuses on the deviation of reconstructed reflectance, whereas colorimetric similarity emphasizes human perception. We present a method to improve the accuracy of the reconstructed spectral reflectance by adaptively combining colorimetric and spectral reflectance similarities. The different exponential factors of the weighting coefficients were investigated. The spectral reflectance reconstructed by the proposed method exhibits considerable improvements in terms of the root-mean-square error and goodness-of-fit coefficient of the spectral reflectance errors as well as color differences under different illuminants. Our method is applicable to diverse areas such as textiles, printing, art, and other industries.

False positive acetaminophen concentrations in patients with liver injury.

PubMed

Polson, Julie; Wians, Frank H; Orsulak, Paul; Fuller, Dwain; Murray, Natalie G; Koff, Jonathan M; Khan, Adil I; Balko, Jody A; Hynan, Linda S; Lee, William M

2008-05-01

Acetaminophen toxicity is the most common form of acute liver failure in the U.S. After acetaminophen overdoses, quantitation of plasma acetaminophen can aid in predicting severity of injury. However, recent case reports have suggested that acetaminophen concentrations may be falsely increased in the presence of hyperbilirubinemia. We tested sera obtained from 43 patients with acute liver failure, mostly unrelated to acetaminophen, utilizing 6 different acetaminophen quantitation systems to determine the significance of this effect. In 36 of the 43 samples with bilirubin concentrations ranging from 1.0-61.5 mg/dl no acetaminophen was detectable by gas chromatography-mass spectroscopy. These 36 samples were then utilized to test the performance characteristics of 2 immunoassay and 4 enzymatic-colorimetric methods. Three of four colorimetric methods demonstrated 'detectable' values for acetaminophen in from 4 to 27 of the 36 negative samples, low concentration positive values being observed when serum bilirubin concentrations exceeded 10 mg/dl. By contrast, the 2 immunoassay methods (EMIT, FPIA) were virtually unaffected. The false positive values obtained were, in general, proportional to the quantity of bilirubin in the sample. However, prepared samples of normal human serum with added bilirubin showed a dose-response curve for only one of the 4 colorimetric assays. False positive acetaminophen tests may result when enzymatic-colorimetric assays are used, most commonly with bilirubin concentrations >10 mg/dl, leading to potential clinical errors in this setting. Bilirubin (or possibly other substances in acute liver failure sera) appears to affect the reliable measurement of acetaminophen, particularly with enzymatic-colorimetric assays.

Colorimetric molecular diagnosis of the HIV gag gene using DNAzyme and a complementary DNA-extended primer.

PubMed

Kim, Seong U; Batule, Bhagwan S; Mun, Hyoyoung; Byun, Ju-Young; Shim, Won-Bo; Kim, Min-Gon

2018-02-07

We have developed a novel strategy for the colorimetric detection of PCR products by utilizing a target-specific primer modified at the 5'-end with an anti-DNAzyme sequence. A single-stranded DNAzyme sequence folds into a G-quadruplex structure with hemin and shows strong peroxidase activity. When the complementary strand binds to the DNAzyme sequence, it blocks the formation of the G-quadraduplex structure and loses its peroxidase activity. In the presence of the target gene, PCR amplification proceeds, and anti-DNAzyme sequence modified primers present in the reaction mixture form a double strand through primer extension. Therefore, it does not block the DNAzyme sequence. Further, a colorimetric signal is generated by the addition of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and H 2 O 2 at the end of the reaction. We have successfully detected a single copy of the HIV type 1 gag gene in buffer and 10 copies in human serum. The strategy developed could be used to detect DNA and RNA in complex biological samples by simple primer designing that includes DNAzyme and a DNA extended primer.

Colorimetric Nucleic Acid Detection on Paper Microchip Using Loop Mediated Isothermal Amplification and Crystal Violet Dye.

PubMed

Roy, Sharmili; Mohd-Naim, Noor Faizah; Safavieh, Mohammadali; Ahmed, Minhaz Uddin

2017-11-22

Nucleic acid detection is of paramount importance in monitoring of microbial pathogens in food safety and infectious disease diagnostic applications. To address these challenges, a rapid, cost-effective label-free technique for nucleic acid detection with minimal instrumentations is highly desired. Here, we present paper microchip to detect and quantify nucleic acid using colorimetric sensing modality. The extracted DNA from food samples of meat as well as microbial pathogens was amplified utilizing loop-mediated isothermal amplification (LAMP). LAMP amplicon was then detected and quantified on a paper microchip fabricated in a cellulose paper and a small wax chamber utilizing crystal violet dye. The affinity of crystal violet dye toward dsDNA and positive signal were identified by changing the color from colorless to purple. Using this method, detection of Sus scrofa (porcine) and Bacillus subtilis (bacteria) DNA was possible at concentrations as low as 1 pg/μL (3.43 × 10 -1 copies/μL) and 10 pg/μL (2.2 × 10 3 copies/μL), respectively. This strategy can be adapted for detection of other DNA samples, with potential for development of a new breed of simple and inexpensive paper microchip at the point-of-need.

Development of a high-throughput colorimetric Zika virus infection assay.

PubMed

Müller, Janis A; Harms, Mirja; Schubert, Axel; Mayer, Benjamin; Jansen, Stephanie; Herbeuval, Jean-Philippe; Michel, Detlef; Mertens, Thomas; Vapalahti, Olli; Schmidt-Chanasit, Jonas; Münch, Jan

2017-04-01

Zika virus (ZIKV) is an emerging pathogen that causes congenital infections which may result in birth defects, such as microcephaly. Currently, no approved treatment or vaccination is available. ZIKV can be readily detected in cell culture where virally infected cells are normally stained by specific antibodies. As ZIKV regularly causes a cytopathic effect, we were wondering whether this viral property can be used to quantitatively determine viral infectivity. We here describe the use of an 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide-(MTT)-based cell viability assay that allows to determine ZIKV-induced cell death. We show that this colorimetric assay quantifies ZIKV infection over a broad range of viral dilutions in both monkey and human cells. It allows to determine inhibitory activities of antivirals that block ZIKV or to define the neutralizing antibody titers of ZIKV antisera. This MTT-based ZIKV detection assay can be evaluated by naked eye or computational tools, has a broad linear range, does not require large equipment or costly reagents, and thus represents a promising alternative to antibody-based assays, in particular in resource-poor settings. We propose to use this simple, fast, and cheap method for quantification of ZIKV neutralizing antibodies and testing of antiviral compounds.

Colorimetric detection of UV light-induced single-strand DNA breaks using gold nanoparticles.

PubMed

Kim, Joong Hyun; Chung, Chan Ho; Chung, Bong Hyun

2013-02-21

We developed a colorimetric method to specifically detect single-strand DNA breaks using gold nanoparticles. In our assay, broken DNA cannot stabilize gold nanoparticles to prevent salt-induced aggregation as good as intact DNA can, and this effect can be easily observed with the naked eye as a red-to-purple color change.

Lab-in-a-syringe using gold nanoparticles for rapid colorimetric chiral discrimination of enantiomers.

PubMed

Zor, Erhan; Bekar, Nisa

2017-05-15

Nanomaterials with different characteristics are offering many ingenious sensing approaches with interest for simple and disposable paper-based (bio)sensing applications. In this study, the colorimetric discrimination of alanine enantiomers is examined and, more importantly, AuNPs-embedded paper-based lab-in-a-syringe (LIS) device is developed as a sensing strategy. The LIS consists of two cellulose acetate membranes: the conjugate pad capturing the analyte and the detection pad signaling the presence of the captured analyte, both are sandwiched between reusable plastic filter holders connected to a disposable syringe. The principle of LIS assay is based on the enantioselective interaction occurring between the inherently chiral AuNPs and enantiomers in the first filter holder, which results in aggregation of AuNPs to give a distinct colour change from red to purple in solution and finally the aggregated AuNPs is kept on the detection pad through vertical-flow operation. AuNPs show an enantioselective recognition response toward L-Alanine and limit of detection (LOD) value is determined as 0.77mM. In addition, we demonstrate the efficiency of the LIS device for detecting L-Alanine in human serum. The proposed LIS assay has some advantages such as useful for naked-eye observation, disposable, not time-consuming, inexpensive, no need of advanced instruments, easy to prepare and easy to handle. In the field, the approach which is the first demonstration of applicability of LIS device to show simple colorimetric enantioselective sensing of chiral species with a fast readout in less than 5min is truly new and may have broad interest in enantiosensing of various chiral molecules. Copyright © 2016 Elsevier B.V. All rights reserved.

The Synthesis and Characterization of Rouaite, a Copper Hydroxy Nitrate: An Integrated First-Year Laboratory Project

ERIC Educational Resources Information Center

Bushong, Elizabeth J.; Yoder, Claude H.

2009-01-01

The synthesis and analysis of a copper hydroxy nitrate provides an exposure to a simple ionic synthesis, qualitative analysis of copper and nitrate, two gravimetric analyses (copper and nitrate), one volumetric analysis (hydroxide), and a colorimetric analysis (copper). The results allow the student to determine the identity of the double salt and…

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2+ in ~100% aqueous media and application to real samples.

PubMed

Sun, Tao; Niu, Qingfen; Li, Tianduo; Guo, Zongrang; Liu, Haixia

2018-01-05

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu 2+ was developed. Sensor ADA showed high selectivity and sensitivity toward Cu 2+ in ~100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu 2+ recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu 2+ in drinking water set by U.S. Environmental Protection Agency (~20μM) and the World Health Organization (~30μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu 2+ with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field. Copyright © 2017 Elsevier B.V. All rights reserved.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2 + in 100% aqueous media and application to real samples

NASA Astrophysics Data System (ADS)

Sun, Tao; Niu, Qingfen; Li, Tianduo; Guo, Zongrang; Liu, Haixia

2018-01-01

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu2 + was developed. Sensor ADA showed high selectivity and sensitivity toward Cu2 + in 100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480 nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu2 + recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8 nM, which is much lower than the allowable level of Cu2 + in drinking water set by U.S. Environmental Protection Agency ( 20 μM) and the World Health Organization ( 30 μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu2 + with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.

A rapid molecular diagnosis of cutaneous leishmaniasis by colorimetric malachite green-loop-mediated isothermal amplification (LAMP) combined with an FTA card as a direct sampling tool.

PubMed

Nzelu, Chukwunonso O; Cáceres, Abraham G; Guerrero-Quincho, Silvia; Tineo-Villafuerte, Edwin; Rodriquez-Delfin, Luis; Mimori, Tatsuyuki; Uezato, Hiroshi; Katakura, Ken; Gomez, Eduardo A; Guevara, Angel G; Hashiguchi, Yoshihisa; Kato, Hirotomo

2016-01-01

Leishmaniasis remains one of the world's most neglected diseases, and early detection of the infectious agent, especially in developing countries, will require a simple and rapid test. In this study, we established a quick, one-step, single-tube, highly sensitive loop-mediated isothermal amplification (LAMP) assay for rapid detection of Leishmania DNA from tissue materials spotted on an FTA card. An FTA-LAMP with pre-added malachite green was performed at 64°C for 60min using a heating block and/or water bath and DNA amplification was detected immediately after incubation. The LAMP assay had high detection sensitivity down to a level of 0.01 parasites per μl. The field- and clinic-applicability of the colorimetric FTA-LAMP assay was demonstrated with 122 clinical samples collected from patients suspected of having cutaneous leishmaniasis in Peru, from which 71 positives were detected. The LAMP assay in combination with an FTA card described here is rapid and sensitive, as well as simple to perform, and has great potential usefulness for diagnosis and surveillance of leishmaniasis in endemic areas. Copyright © 2015 Elsevier B.V. All rights reserved.

Method for estimating effects of unknown correlations in spectral irradiance data on uncertainties of spectrally integrated colorimetric quantities

NASA Astrophysics Data System (ADS)

Kärhä, Petri; Vaskuri, Anna; Mäntynen, Henrik; Mikkonen, Nikke; Ikonen, Erkki

2017-08-01

Spectral irradiance data are often used to calculate colorimetric properties, such as color coordinates and color temperatures of light sources by integration. The spectral data may contain unknown correlations that should be accounted for in the uncertainty estimation. We propose a new method for estimating uncertainties in such cases. The method goes through all possible scenarios of deviations using Monte Carlo analysis. Varying spectral error functions are produced by combining spectral base functions, and the distorted spectra are used to calculate the colorimetric quantities. Standard deviations of the colorimetric quantities at different scenarios give uncertainties assuming no correlations, uncertainties assuming full correlation, and uncertainties for an unfavorable case of unknown correlations, which turn out to be a significant source of uncertainty. With 1% standard uncertainty in spectral irradiance, the expanded uncertainty of the correlated color temperature of a source corresponding to the CIE Standard Illuminant A may reach as high as 37.2 K in unfavorable conditions, when calculations assuming full correlation give zero uncertainty, and calculations assuming no correlations yield the expanded uncertainties of 5.6 K and 12.1 K, with wavelength steps of 1 nm and 5 nm used in spectral integrations, respectively. We also show that there is an absolute limit of 60.2 K in the error of the correlated color temperature for Standard Illuminant A when assuming 1% standard uncertainty in the spectral irradiance. A comparison of our uncorrelated uncertainties with those obtained using analytical methods by other research groups shows good agreement. We re-estimated the uncertainties for the colorimetric properties of our 1 kW photometric standard lamps using the new method. The revised uncertainty of color temperature is a factor of 2.5 higher than the uncertainty assuming no correlations.

"Dip-and-read" paper-based analytical devices using distance-based detection with color screening.

PubMed

Yamada, Kentaro; Citterio, Daniel; Henry, Charles S

2018-05-15

An improved paper-based analytical device (PAD) using color screening to enhance device performance is described. Current detection methods for PADs relying on the distance-based signalling motif can be slow due to the assay time being limited by capillary flow rates that wick fluid through the detection zone. For traditional distance-based detection motifs, analysis can take up to 45 min for a channel length of 5 cm. By using a color screening method, quantification with a distance-based PAD can be achieved in minutes through a "dip-and-read" approach. A colorimetric indicator line deposited onto a paper substrate using inkjet-printing undergoes a concentration-dependent colorimetric response for a given analyte. This color intensity-based response has been converted to a distance-based signal by overlaying a color filter with a continuous color intensity gradient matching the color of the developed indicator line. As a proof-of-concept, Ni quantification in welding fume was performed as a model assay. The results of multiple independent user testing gave mean absolute percentage error and average relative standard deviations of 10.5% and 11.2% respectively, which were an improvement over analysis based on simple visual color comparison with a read guide (12.2%, 14.9%). In addition to the analytical performance comparison, an interference study and a shelf life investigation were performed to further demonstrate practical utility. The developed system demonstrates an alternative detection approach for distance-based PADs enabling fast (∼10 min), quantitative, and straightforward assays.

Battery operated preconcentration-assisted lateral flow assay.

PubMed

Kim, Cheonjung; Yoo, Yong Kyoung; Han, Sung Il; Lee, Junwoo; Lee, Dohwan; Lee, Kyungjae; Hwang, Kyo Seon; Lee, Kyu Hyoung; Chung, Seok; Lee, Jeong Hoon

2017-07-11

Paper-based analytical devices (e.g. lateral flow assays) are highly advantageous as portable diagnostic systems owing to their low costs and ease of use. Because of their low sensitivity and detection limits for biomolecules, these devices have several limitations in applications for real-field diagnosis. Here, we demonstrate a paper-based preconcentration enhanced lateral flow assay using a commercial β-hCG-based test. Utilizing a simple 9 V battery operation with a low power consumption of approximately 81 μW, we acquire a 25-fold preconcentration factor, demonstrating a clear sensitivity enhancement in the colorimetric lateral flow assay; consequently, clear colors are observed in a rapid kit test line, which cannot be monitored without preconcentration. This device can also facilitate a semi-quantitative platform using the saturation value and/or color intensity in both paper-based colorimetric assays and smartphone-based diagnostics.

Spectrophotometric determination of ammonia levels in tobacco fillers of and sidestream smoke from different cigarette brands in Japan.

PubMed

Inaba, Yohei; Uchiyama, Shigehisa; Kunugita, Naoki

2018-04-27

The ammonia contained in tobacco fillers and mainstream and sidestream cigarette smoke accelerates nicotine dependence in cigarette smokers. Ammonia has been included in the non-exhaustive priority list of 39 tobacco components and emissions of cigarette published by the World Health Organization (WHO) Study Group on Tobacco Product Regulation. The development of a simple ammonia detection method will contribute to the establishment of tobacco product regulation under tobacco control policies and allow surveys to be conducted, even by laboratories with small research budgets. We developed a simple colorimetric method based on the salicylate-chlorine reaction and absorption spectrometry with two reagents (sodium nitroprusside and sodium dichloroisocyanurate). To compare this method to conventional ion chromatography, we analyzed the ammonia levels in tobacco fillers extracted from 35 Japanese commercially marketed cigarette brands manufactured by four tobacco companies (Japan Tobacco (JT) Inc., British American Tobacco (BAT), Philip Morris Japan, and Natural American Spirit). We also analyzed the ammonia levels in the sidestream smoke from cigarettes of the brands that were found to contain high or low tobacco filler ammonia levels. The ammonia levels in the reference cigarette (3R4F) measured by our method and ion chromatography were similar and comparable to previously reported levels. The ammonia levels in tobacco fillers extracted from 35 cigarette brands ranged from 0.25 to 1.58 mg/g. The mean ammonia level of JT cigarette brands was significantly higher (0.83 ± 0.28 mg/g) than that of Natural American Spirit cigarette brands (0.30 ± 0.08 mg/g) and lower than those in the other two cigarette brands (1.11 ± 0.19 mg/g for BAT and 1.24 ± 0.15 mg/g for Philip Morris) (p < 0.001 by Bonferroni test). The ammonia levels in the sidestream smoke of CABIN, Marlboro Black Menthol, American Spirit Light, and Seven Stars were 5.89 ± 0.28, 5.23 ± 0.12, 6.92 ± 0.56, and 4.14 ± 0.19 mg/cigarette, respectively. The ammonia levels were higher in sidestream smoke than in tobacco filler. Our simple colorimetric could be used to analyze ammonia in tobacco fillers and sidestream smoke. There were significant differences between the ammonia levels of the 35 commercially marketed cigarette brands in Japan manufactured by four tobacco manufacturers. Over 90% of the ammonia in sidestream smoke was in gaseous phase.

A New Colorimetric Assay of Tabletop Sweeteners Using a Modified Biuret Reagent: An Analytical Chemistry Experiment for the Undergraduate Curriculum

ERIC Educational Resources Information Center

Fenk, Christopher J.; Kaufman, Nathan; Gerbig, Donald G., Jr.

2007-01-01

A new, fast and effective colorimetric analysis of the artificial sweetener aspartame is presented for application in undergraduate laboratory courses. This new method incorporates the use of a modified biuret reagent for selective detection and analysis of aspartame in aqueous solutions. The modified reagent is less caustic than the traditional…

Application of Colorimetric Solid Phase Extraction (C-SPE) to Monitoring Nickel(II) and Lead(II) in Spacecraft Water Supplies

NASA Technical Reports Server (NTRS)

Diaz, Neil C.; Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.; Rutz, Jeff; Mudgett, Paul; Schultz, John

2004-01-01

Archived water samples collected on the International Space Station (ISS) and returned to Earth for analysis have, in a few instances, contained trace levels of heavy metals. Building on our previous advances using Colorimetric Solid Phase Extraction (C-SPE) as a biocide monitoring technique, we are devising methods for the low level monitoring of nickel(II), lead(II) and other heavy metals. C-SPE is a sorption-spectrophotometric platform based on the extraction of analytes onto a membrane impregnated with a colorimetric reagent that are then quantified on the surface of the membrane using a diffuse reflectance spectrophotometer. Along these lines, we have determined nickel(II) via complexation with dimethylglyoxime (DMG) and begun to examine the analysis of lead(II) by its reaction with 2,5- dimercapto-1,3,4-thiadiazole (DMTD) and 4-(2- pyridylazo)-resorcinol (PAR). These developments are also extending a new variant of C-SPE in which immobilized reagents are being incorporated into this methodology in order to optimize sample reaction conditions and to introduce the colorimetric reagent. This paper describes the status of our development of these two new methods.

Colorimetric and fluorimetric detection of Hg2 + and Cr3 + by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells

NASA Astrophysics Data System (ADS)

Vallu, Rama Krishna; Velugula, Krishna; Doshi, Sejal; Chinta, Jugun Prakash

2018-01-01

Colorimetric and fluorimetric detection of toxic metal ions such as Hg2 + and Cr3 + has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg2 + or Cr3 + were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg2 +, Cr3 + and Fe3 + among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg2 + and Cr3 + by the change in color of the solution to pink and reddish pink with Fe3 +. The detailed mechanism involved in the detection of Hg2 + was deduced by 1H NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg2 + and Cr3 + in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg2 + and Cr3 +, which are known for their toxic influence on bacterial cells.

A Rapid Colorimetric Method Reveals Fraudulent Substitutions in Sea Urchin Roe Marketed in Sardinia (Italy).

PubMed

Meloni, Domenico; Spina, Antonio; Satta, Gianluca; Chessa, Vittorio

2016-06-25

In recent years, besides the consumption of fresh sea urchin specimens, the demand of minimally-processed roe has grown considerably. This product has made frequent consumption in restaurants possible and frauds are becoming widespread with the partial replacement of sea urchin roe with surrogates that are similar in colour. One of the main factors that determines the quality of the roe is its colour and small differences in colour scale cannot be easily discerned by the consumers. In this study we have applied a rapid colorimetric method for reveal the fraudulent partial substitution of semi-solid sea urchin roe with liquid egg yolk. Objective assessment of whiteness (L*), redness (a*), yellowness (b*), hue (h*), and chroma (C*) was carried out with a digital spectrophotometer using the CIE L*a*b* colour measurement system. The colorimetric method highlighted statistically significant differences among sea urchin roe and liquid egg yolk that could be easily discerned quantitatively.

Enhanced Sensitivity to Detection Nanomolar Level of Cu2 + Compared to Spectrophotometry Method by Functionalized Gold Nanoparticles: Design of Sensor Assisted by Exploiting First-order Data with Chemometrics

NASA Astrophysics Data System (ADS)

Rasouli, Zolaikha; Ghavami, Raouf

2018-02-01

A simple, sensitive and efficient colorimetric assay platform for the determination of Cu2 + was proposed with the aim of developing sensitive detection based on the aggregation of AuNPs in presence of a histamine H2-receptor antagonist (famotidine, FAM) as recognition site. This study is the first to demonstrate that the molar extinction coefficients of the complexes formed by FAM and Cu2 + are very low (by analyzing the chemometrics methods on the first order data arising from different metal to ligand ratio method), leading to the undesirable sensitivity of FAM-based assays. To resolve the problem of low sensitivity, the colorimetry method based on the Cu2 +-induced aggregation of AuNPs functionalized with FAM was introduced. This procedure is accompanied by a color change from bright red to blue which can be observed with the naked eyes. Detection sensitivity obtained by the developed method increased about 100 fold compared with the spectrophotometry method. This sensor exhibited a good linear relation between the absorbance ratios at 670 to 520 nm (A670/520) and the concentration in the range 2-110 nM with LOD = 0.76 nM. The satisfactory analytical performance of the proposed sensor facilitates the development of simple and affordable UV-Vis chemosensors for environmental applications.

Distinction of Gram-positive and -negative bacteria using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium salts with a selection medium.

PubMed

Tsukatani, Tadayuki; Suenaga, Hikaru; Higuchi, Tomoko; Shiga, Masanobu; Noguchi, Katsuya; Matsumoto, Kiyoshi

2011-01-01

Bacteria are fundamentally divided into two groups: Gram-positive and Gram-negative. Although the Gram stain and other techniques can be used to differentiate these groups, some issues exist with traditional approaches. In this study, we developed a method for differentiating Gram-positive and -negative bacteria using a colorimetric microbial viability assay based on the reduction of the tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt} (WST-8) via 2-methyl-1,4-napthoquinone with a selection medium. We optimized the composition of the selection medium to allow the growth of Gram-negative bacteria while inhibiting the growth of Gram-positive bacteria. When the colorimetric viability assay was carried out in a selection medium containing 0.5µg/ml crystal violet, 5.0 µg/ml daptomycin, and 5.0µg/ml vancomycin, the reduction in WST-8 by Gram-positive bacteria was inhibited. On the other hand, Gram-negative bacteria produced WST-8-formazan in the selection medium. The proposed method was also applied to determine the Gram staining characteristics of bacteria isolated from various foodstuffs. There was good agreement between the results obtained using the present method and those obtained using a conventional staining method. These results suggest that the WST-8 colorimetric assay with selection medium is a useful technique for accurately differentiating Gram-positive and -negative bacteria.

Sensor Systems for Biological Agent Attacks: Protecting Buildings and Military Bases

DTIC Science & Technology

2004-01-01

simple aerosol detectors, to those that identify an agent based on its genetic, structural, or chemical properties , to so- called "functional...Cytometry, 122 Target Binding That Changes Detectable Properties of Smart Sensor Surfaces, 124 Colorimetric Detection, 124 Fluorescence Detection, 125 One...microscopy. In addition to particles directly derived from living organisms, other particles in air may also share properties with the bioaerosols

Colorimetric Detection of Multidrug-Resistant or Extensively Drug-Resistant Tuberculosis by Use of Malachite Green Indicator Dye▿

PubMed Central

Farnia, Parissa; Masjedi, Mohammad Reza; Mohammadi, Foroozan; Tabarsei, Payam; Farnia, Poopak; Mohammadzadeh, Ali Reza; Baghei, Parvaneh; Varahram, Mohammad; Hoffner, Sven; Velayati, Ali Akbar

2008-01-01

The malachite green microtube (MGMT) susceptibility assay was performed directly on sputum specimens (n = 80) and indirectly on Mycobacterium tuberculosis clinical isolates (n = 60). The technique is based on the malachite green dye, which changes color in response to M. tuberculosis growth. The MGMT assay is simple and rapid and does not require expensive instruments. PMID:18094133

An imaging-based photometric and colorimetric measurement method for characterizing OLED panels for lighting applications

NASA Astrophysics Data System (ADS)

Zhu, Yiting; Narendran, Nadarajah; Tan, Jianchuan; Mou, Xi

2014-09-01

The organic light-emitting diode (OLED) has demonstrated its novelty in displays and certain lighting applications. Similar to white light-emitting diode (LED) technology, it also holds the promise of saving energy. Even though the luminous efficacy values of OLED products have been steadily growing, their longevity is still not well understood. Furthermore, currently there is no industry standard for photometric and colorimetric testing, short and long term, of OLEDs. Each OLED manufacturer tests its OLED panels under different electrical and thermal conditions using different measurement methods. In this study, an imaging-based photometric and colorimetric measurement method for OLED panels was investigated. Unlike an LED that can be considered as a point source, the OLED is a large form area source. Therefore, for an area source to satisfy lighting application needs, it is important that it maintains uniform light level and color properties across the emitting surface of the panel over a long period. This study intended to develop a measurement procedure that can be used to test long-term photometric and colorimetric properties of OLED panels. The objective was to better understand how test parameters such as drive current or luminance and temperature affect the degradation rate. In addition, this study investigated whether data interpolation could allow for determination of degradation and lifetime, L70, at application conditions based on the degradation rates measured at different operating conditions.

Click chemistry-mediated cyclic cleavage of metal ion-dependent DNAzymes for amplified and colorimetric detection of human serum copper (II).

PubMed

Li, Daxiu; Xie, Jiaqing; Zhou, Wenjiao; Jiang, Bingying; Yuan, Ruo; Xiang, Yun

2017-11-01

The determination of the level of Cu 2+ plays important roles in disease diagnosis and environmental monitoring. By coupling Cu + -catalyzed click chemistry and metal ion-dependent DNAzyme cyclic amplification, we have developed a convenient and sensitive colorimetric sensing method for the detection of Cu 2+ in human serums. The target Cu 2+ can be reduced by ascorbate to form Cu + , which catalyzes the azide-alkyne cycloaddition between the azide- and alkyne-modified DNAs to form Mg 2+ -dependent DNAzymes. Subsequently, the Mg 2+ ions catalyze the cleavage of the hairpin DNA substrate sequences of the DNAzymes and trigger cyclic generation of a large number of free G-quadruplex sequences, which bind hemin to form the G-quadruplex/hemin artificial peroxidase to cause significant color transition of the sensing solution for sensitive colorimetric detection of Cu 2+ . This method shows a dynamic range of 5 to 500 nM and a detection limit of 2 nM for Cu 2+ detection. Besides, the level of Cu 2+ in human serums can also be determined by using this sensing approach. With the advantages of simplicity and high sensitivity, such sensing method thus holds great potential for on-site determination of Cu 2+ in different samples. Graphical abstract Sensitive colorimetric detection of copper (II) by coupling click chemistry with metal ion-dependentDNAzymes.

Convert a low-cost sensor to a colorimeter using an improved regression method

NASA Astrophysics Data System (ADS)

Wu, Yifeng

2008-01-01

Closed loop color calibration is a process to maintain consistent color reproduction for color printers. To perform closed loop color calibration, a pre-designed color target should be printed, and automatically measured by a color measuring instrument. A low cost sensor has been embedded to the printer to perform the color measurement. A series of sensor calibration and color conversion methods have been developed. The purpose is to get accurate colorimetric measurement from the data measured by the low cost sensor. In order to get high accuracy colorimetric measurement, we need carefully calibrate the sensor, and minimize all possible errors during the color conversion. After comparing several classical color conversion methods, a regression based color conversion method has been selected. The regression is a powerful method to estimate the color conversion functions. But the main difficulty to use this method is to find an appropriate function to describe the relationship between the input and the output data. In this paper, we propose to use 1D pre-linearization tables to improve the linearity between the input sensor measuring data and the output colorimetric data. Using this method, we can increase the accuracy of the regression method, so as to improve the accuracy of the color conversion.

A plasmonic colorimetric strategy for visual miRNA detection based on hybridization chain reaction

NASA Astrophysics Data System (ADS)

Miao, Jie; Wang, Jingsheng; Guo, Jinyang; Gao, Huiguang; Han, Kun; Jiang, Chengmin; Miao, Peng

2016-08-01

In this work, a novel colorimetric strategy for miRNA analysis is proposed based on hybridization chain reaction (HCR)-mediated localized surface plasmon resonance (LSPR) variation of silver nanoparticles (AgNPs). miRNA in the sample to be tested is able to release HCR initiator from a solid interface to AgNPs colloid system by toehold exchange-mediated strand displacement, which then triggers the consumption of fuel strands with single-stranded tails for HCR. The final produced long nicked double-stranded DNA loses the ability to protect AgNPs from salt-induced aggregation. The stability variation of the colloid system can then be monitored by recording corresponding UV-vis spectrum and initial miRNA level is thus determined. This sensing system involves only four DNA strands which is quite simple. The practical utility is confirmed to be excellent by employing different biological samples.

Fluoride-responsive gelator and colorimetric sensor based on simple and easy-to-prepare cyano-substituted amide.

PubMed

Zhang, Yuping; Jiang, Shimei

2012-09-14

A new and easy-to-prepare gelator based on cyano-substituted amide (BPNIA) was designed and synthesized. BPNIA could form thermoreversible gel in DMSO-H(2)O (v/v, 9 : 1) and ultrasound-stimulated gel in DMSO. FT-IR, UV-vis and XRD spectra indicated that the gelator molecules self-assemble into a fibrous network resulting from the cooperation of intermolecular hydrogen bonding, π-π stacking and cyano interactions. BPNIA can act as a highly selective colorimetric sensor for fluoride in DMSO, overcoming the interference of H(2)PO(4)(-), AcO(-) and other halide anions. The deprotonation of the NH groups is responsible for the dramatic color change from colorless to yellow. Interestingly, the organogel of BPNIA could allow a two channel fluoride response by proton controlled reversible sol-gel transition and color changes.

Spectrophotometric determination of L-cysteine by using polyvinylpyrrolidone-stabilized silver nanoparticles in the presence of barium ions.

PubMed

Bamdad, Farzad; Khorram, Fateme; Samet, Maryam; Bamdad, Kourosh; Sangi, Mohammad Reza; Allahbakhshi, Fateme

2016-05-15

In this article a simple and selective colorimetric probe for cysteine determination using silver nano particles (AgNPS) is described. The determination process was based upon the surface plasmon resonance properties of polyvinylpyrrolidone-stabilized AgNPS. Interaction of AgNPS with cysteine molecules in the presence of barium ions induced a red shift in the surface plasmon resonance (SPR) maximum of AgNPs, as a result of nanoparticle aggregation. Consequently, yellow color of AgNP solution was changed to pink. The linear range for the determination of cysteine was 3.2-8.2 μM (R=0.9965) with a limit of detection equal to 2.8 μM (3σ). The proposed method was successfully applied to the determination of cysteine in human plasma samples. Acceptable recovery results of the spiked samples confirmed the validity of the proposed method. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectrophotometric determination of L-cysteine by using polyvinylpyrrolidone-stabilized silver nanoparticles in the presence of barium ions

NASA Astrophysics Data System (ADS)

Bamdad, Farzad; Khorram, Fateme; Samet, Maryam; Bamdad, Kourosh; Sangi, Mohammad Reza; Allahbakhshi, Fateme

2016-05-01

In this article a simple and selective colorimetric probe for cysteine determination using silver nano particles (AgNPS) is described. The determination process was based upon the surface plasmon resonance properties of polyvinylpyrrolidone-stabilized AgNPS. Interaction of AgNPS with cysteine molecules in the presence of barium ions induced a red shift in the surface plasmon resonance (SPR) maximum of AgNPs, as a result of nanoparticle aggregation. Consequently, yellow color of AgNP solution was changed to pink. The linear range for the determination of cysteine was 3.2-8.2 μM (R = 0.9965) with a limit of detection equal to 2.8 μM (3σ). The proposed method was successfully applied to the determination of cysteine in human plasma samples. Acceptable recovery results of the spiked samples confirmed the validity of the proposed method.

Determination of small and large amounts of fluorine in rocks

USGS Publications Warehouse

Grimaldi, F.S.; Ingram, B.; Cuttitta, F.

1955-01-01

Gelatinous silica and aluminum ions retard the distillation of fluorine in the Willard and Winter distillation method. A generally applicable, simple method for the determination of fluorine in rocks containing aluminum or silicon or both as major constituents was desired. In the procedure developed, the sample is fused with a mixture of sodium carbonate and zinc oxide, leached with water, and filtered. The residue is granular and retains nearly all of the silica. The fluorine in the filtrate is distilled directly from a perchloric acid-phosphoric acid mixture. Phosphoric acid permits the quantitative distillation of fluorine in the presence of much aluminum at the usual distillation temperature and without the collection of large volumes of distillate. The fluorine is determined either by microtitration with thorium nitrate or colorimetrically with thoron. The procedure is rapid and has yielded excellent results on silicate rocks and on samples from the aluminum phosphate (leached) zone of the Florida phosphate deposits.

Chromatic biosensor for detection of phosphinothricin acetyltransferase by use of polydiacetylene vesicles encapsulated within automatically generated immunohydrogel beads.

PubMed

Jung, Sung-Ho; Jang, Huisoo; Lim, Min-Cheol; Kim, Jae-Hwan; Shin, Kong-Sik; Kim, Sun Min; Kim, Hae-Yeong; Kim, Young-Rok; Jeon, Tae-Joon

2015-02-17

We developed a simple and sensitive colorimetric biosensor in the form of microparticles by using polydiacetylene (PDA) vesicles encapsulated within a hydrogel matrix for the detection of phosphinothricin acetyltransferase (PAT) protein, which is one of the most important marker proteins in genetically modified (GM) crops. Although PDA is commonly used as a sensing material due to its unique colorimetric properties, existing PDA biosensors are ineffective due to their low sensitivity as well as their lack of robustness. To overcome these disadvantages, we devised immunohydrogel beads made of anti-PAT-conjugated PDA vesicles embedded at high density within a poly(ethylene glycol) diacrylate (PEG-DA) hydrogel matrix. In addition, the construction of immunohydrogel beads was automated by use of a microfluidic device. In the immunoreaction, the sensitivity of antibody-conjugated PDA vesicles was significantly amplified, as monitored by the unaided eye. The limit of detection for target molecules reached as low as 20 nM, which is sufficiently low enough to detect target materials in GM organisms. Collectively, the results show that immunohydrogel beads constitute a promising colorimetric sensing platform for onsite testing in a number of fields, such as the food and medical industries, as well as warfare situations.

A MODIFIED LOW COST COLOURIMETRIC METHOD FOR PARACETAMOL (ACETAMINOPHEN) MEASUREMENT IN PLASMA

PubMed Central

Shihana, Fathima; Dissanayake, Dhammika Menike; Dargan, Paul Ivor; Dawson, Andrew Hamilton

2011-01-01

Background Despite a significant increase in the number of patients with paracetamol poisoning in the developing world, plasma paracetamol assays are not widely available. The purpose of this study was to assess a low cost modified colorimetric paracetamol assay that has the potential to be performed in small laboratories with restricted resources. Methods The paracetamol assay used in this study was based on the Glynn and Kendal colorimetric method with a few modifications in order to decrease the production of nitrous gas and thereby reduce infrastructure costs. Preliminary validation studies were performed using spiked aqueous samples with known concentrations of paracetamol. Subsequently, the results from the colorimetric method for 114 stored clinical samples from patients with paracetamol poisoning were compared with those from the current gold-standard high-performance liquid chromatography (HPLC) method. A prospective survey, assessing the clinical use of the paracetamol assay, was performed on all patients with paracetamol poisoning attending the Peradeniya General Hospital, Sri Lanka over a ten-month period. Results The recovery study showed an excellent correlation (r2 >0.998) for paracetamol concentrations from 25- 400 mg/l. The final yellow colour was stable for at least 10 minutes at room temperature. There was also excellent correlation with the HPLC method (r2=0.9758). In the clinical cohort study, use of the antidote N-acetylcysteine was avoided in over a third of patients who had a plasma paracetamol concentration measured. The cost of consumables used per assay was $0.50 (US). Conclusions This colorimetric paracetamol assay is reliable and accurate and can be performed rapidly, easily and economically. Use of this assay in resource poor clinical settings has the potential to have a significant clinical and economic impact on the management of paracetamol poisoning. PMID:20095813

Achromatic-chromatic colorimetric sensors for on-off type detection of analytes.

PubMed

Heo, Jun Hyuk; Cho, Hui Hun; Lee, Jin Woong; Lee, Jung Heon

2014-12-21

We report the development of achromatic colorimetric sensors; sensors changing their colors from achromatic black to other chromatic colors. An achromatic colorimetric sensor was prepared by mixing a general colorimetric indicator, whose color changes between chromatic colors, and a complementary colored dye with no reaction to the targeted analyte. As the color of an achromatic colorimetric sensor changes from black to a chromatic color, the color change could be much easily recognized than general colorimetric sensors with naked eyes. More importantly, the achromatic colorimetric sensors enable on-off type recognition of the presence of analytes, which have not been achieved from most colorimetric sensors. In addition, the color changes from some achromatic colorimetric sensors (achromatic Eriochrome Black T and achromatic Benedict's solution) could be recognized with naked eyes at much lower concentration ranges than normal chromatic colorimetric sensors. These results provide new opportunities in the use of colorimetric sensors for diverse applications, such as harsh industrial, environmental, and biological detection.

Analysis of phytochemical profile of Terminalia arjuna bark extract with antioxidative and antimicrobial properties

PubMed Central

Mandal, Shreya; Patra, Arpita; Samanta, Animesh; Roy, Suchismita; Mandal, Arpita; Mahapatra, Tapasi Das; Pradhan, Shrabani; Das, Koushik; Nandi, Dilip Kumar

2013-01-01

Objective To investigate phytochemical screening, antimicrobial activity and qualitative thin layer chromatographic separation of flavonoid components, antioxidant activity and total flavonoid compound of Terminalia arjuna. Methods For phytochemical screening, some common and available standard tests were done. Antimicrobial bioassay was done through agar well diffusion method. Detection of antioxidant activity and flavonoid compounds were done through thin layer chromatography. Total antioxidant activity was measured by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) in colorimetric method. Aluminum chloride colorimetric method was used for total flavonoid determination. Results Phytochemical screening showed the active compounds presence in high concentration, such as phytosterol, lactones, flavonoids, phenolic compounds and tannins and glycosides. The antimicrobial activity of extract showed that greater inhibition zone against Gram negative bacteria than Gram positive bacteria. This methanolic extract showed a promising antioxidant activity, as absorption of DPPH redicles decreased in DPPH free radical scavenging assay. Flavonoids components having antioxidant property present in the methanol extract at a level of 199.00 mg quercetin equivalent/g of dried methanol extract in colorimetric method. Conclusions The Terminalia arjuna bark extract revealed the presence of bio-active constituents which are known to exhibit medicinal as well as physiological activities. PMID:24093787

Color digital halftoning taking colorimetric color reproduction into account

NASA Astrophysics Data System (ADS)

Haneishi, Hideaki; Suzuki, Toshiaki; Shimoyama, Nobukatsu; Miyake, Yoichi

1996-01-01

Taking colorimetric color reproduction into account, the conventional error diffusion method is modified for color digital half-toning. Assuming that the input to a bilevel color printer is given in CIE-XYZ tristimulus values or CIE-LAB values instead of the more conventional RGB or YMC values, two modified versions based on vector operation in (1) the XYZ color space and (2) the LAB color space were tested. Experimental results show that the modified methods, especially the method using the LAB color space, resulted in better color reproduction performance than the conventional methods. Spatial artifacts that appear in the modified methods are presented and analyzed. It is also shown that the modified method (2) with a thresholding technique achieves a good spatial image quality.

Construction of mathematical model for measuring material concentration by colorimetric method

NASA Astrophysics Data System (ADS)

Liu, Bing; Gao, Lingceng; Yu, Kairong; Tan, Xianghua

2018-06-01

This paper use the method of multiple linear regression to discuss the data of C problem of mathematical modeling in 2017. First, we have established a regression model for the concentration of 5 substances. But only the regression model of the substance concentration of urea in milk can pass through the significance test. The regression model established by the second sets of data can pass the significance test. But this model exists serious multicollinearity. We have improved the model by principal component analysis. The improved model is used to control the system so that it is possible to measure the concentration of material by direct colorimetric method.

Spectral data compression using weighted principal component analysis with consideration of human visual system and light sources

NASA Astrophysics Data System (ADS)

Cao, Qian; Wan, Xiaoxia; Li, Junfeng; Liu, Qiang; Liang, Jingxing; Li, Chan

2016-10-01

This paper proposed two weight functions based on principal component analysis (PCA) to reserve more colorimetric information in spectral data compression process. One weight function consisted of the CIE XYZ color-matching functions representing the characteristic of the human visual system, while another was made up of the CIE XYZ color-matching functions of human visual system and relative spectral power distribution of the CIE standard illuminant D65. The improvement obtained from the proposed two methods were tested to compress and reconstruct the reflectance spectra of 1600 glossy Munsell color chips and 1950 Natural Color System color chips as well as six multispectral images. The performance was evaluated by the mean values of color difference under the CIE 1931 standard colorimetric observer and the CIE standard illuminant D65 and A. The mean values of root mean square errors between the original and reconstructed spectra were also calculated. The experimental results show that the proposed two methods significantly outperform the standard PCA and another two weighted PCA in the aspects of colorimetric reconstruction accuracy with very slight degradation in spectral reconstruction accuracy. In addition, weight functions with the CIE standard illuminant D65 can improve the colorimetric reconstruction accuracy compared to weight functions without the CIE standard illuminant D65.

Spectroscopic detection of metals ions using a novel selective sensor

NASA Astrophysics Data System (ADS)

Peralta-Domínguez, D.; Ramos-Ortiz, G.; Maldonado, J. L.; Rodriguez, M.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Santillan, R.; Farfan, N.

2011-09-01

Colorimetric chemosensors are simple, economical and practical optical approach for detecting toxic metal ions (Hg2+, Pb2+, Ni2+, etc.) in the environment. In this work, we present a simple but highly specific organic compound 4-chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for divalent metal ions in H2O. The mechanism of the interaction between L1 and various metal-ions has been established by UV-vis absorption and emission spectroscopic experiments that indicate favorable coordination of metal ions with L1 in different solvents. Experimental results indicate that the shape of the electronic transition band of L1 (receptor compound) changed after the interaction with divalent metal-ions, such as Hg2+, Pb2+, Mn2+, Co2+, Cu2+, and Ni2+ in aqueous solution. We found that L1 have a considerable selectivity for Ni2+ ions, even in presence of other metals ions when mixtures of DMSO/H2O as are used as solvents. L1, which has been targeted for sensing transition metal ions, exhibits binding-induced color changes from yellow to pink observed even by the naked eye in presence of Ni2+ ions.

Novel colorimetric assay for paraquat detection on-silica bead using negatively charged silver nanoparticles.

PubMed

Siangproh, Weena; Somboonsuk, Thachkorn; Chailapakul, Orawan; Songsrirote, Kriangsak

2017-11-01

A simple, rapid, sensitive, and economical method based on colorimetry for the determination of paraquat, a widely used herbicide, was developed. Citrate-coated silver nanoparticles (AgNPs) were synthesized as the colorimetric probe. The mechanism of the assay is related to the aggregation of negatively charged AgNPs as induced by positively-charged paraquat resulting from coulombic attraction which causes the color to change from a deep greenish yellow to pale yellow in accordance with the concentrations of paraquat. Silica gel was exploited as the paraquat adsorbent for purification and pre-concentration prior to the direct determination with negatively charged AgNPs without the requirement of the elution step. The validity of the proposed approach was evaluated by spiking standard paraquat in water and plant samples. Recoveries of paraquat in water samples were 93.6% and 95.4% for groundwater and canal water, respectively, while those in plant samples were 89.5% and 86.6% for Chinese cabbage and green apple, respectively,after using the optimized extraction procedure. The absorbance of AgNPs at 400nm was linearly related to the concentration of paraquat over the range of 0.05-50mgL -1 , with detection limits of 0.05mgL -1 for water samples, and 0.10mgL -1 for plant samples by naked eye determination. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of magnetic nanoparticle based calorimetric assay for the detection of bovine mastitis in cow milk.

PubMed

Chinnappan, Raja; Al Attas, Sana; Kaman, Wendy E; Bikker, Floris J; Zourob, Mohammed

2017-04-15

Mastitis in dairy cattle is an inflammatory reaction of the udder tissue. Mastitis increases plasmin levels, leading to an increased proteolysis of milk proteins such as casein, resulting in a significant decrease in milk quality and related dairy products. Due to its key-role in mastitis, we used plasmin proteolytic activity as a biomarker for the detection of mastitis in bovine mastitic milk. Inspired by earlier studies on protease activity using mastitic milk samples, we developed a simple colorimetric assay to distinguish mastitic milk from milk derived from healthy animals. The plasmin substrate coupled to magnetic nanoparticles form a black self-assembled monolayer on a gold sensor surface. In the presence of increased levels of plasmin, the substrate is cleaved and the peptide fragment attached to the magnetic beads, will be attracted by the magnet which is present under the sensor strips revealing the golden surface. We found the area of the golden color surface proportional to plasmin activity. The sensitivity of this method was determined to be 1 ng/ml of plasmin in vitro. Next, we tested the biosensor using mastitis positive milk of which infection is confirmed by bacterial cultures. This newly developed colorimetric biosensor has high potential in applications for the diagnosis of mastitis with potential spin offs to health, food and environmental sectors. Copyright © 2017 Elsevier Inc. All rights reserved.

A new microtitre plate screening method for evaluating the viability of aerobic respiring bacteria in high surface biofilms.

PubMed

Pérez, L M; Alvarez, B L; Codony, F; Fittipaldi, M; Adrados, B; Peñuela, G; Morató, J

2010-09-01

It is difficult to determine the effects of bactericidal compounds against bacteria in a biofilm because classical procedures for determining cell viability require several working days, multiple complicated steps and are frequently only applicable to cells in suspension. We attempt to develop a compact, inexpensive and versatile system to measure directly the extent of biofilm formation from water systems and to determine the viability of respiring bacteria in high surface biofilms. It has been reported that the reduction of tetrazolium sodium salts, such as XTT (sodium 3,3'-[1-[(phenylamino)carbonyl]-3,4-tetrazolium]Bis(4-methoxy)-6-nitro)benzene sulfonic acid hydrate), during active bacterial metabolism can be incorporated into a colorimetric method for quantifying cell viability. XTT is reduced to a soluble formazan compound during bacterial aerobic metabolism such that the amount of formazan generated is proportional to the bacterial biomass. We show here, for the first time, that this colorimetric approach can be used to determine the metabolic activity of adherent aerobic bacteria in a biofilm as a measure of cell viability. This technique has been used to estimate viability and proliferation of bacteria in suspension, but this is the first application to microbial communities in a real undisturbed biofilm. This simple new system can be used to evaluate the complex biofilm community without separating the bacteria from their support. Thus, the results obtained by this practice may be more representative of the circumstances in a natural system, opening the possibility to multiple potential applications.

Recyclable colorimetric sensor of Cr3 + and Pb2 + ions simultaneously using a zwitterionic amino acid modified gold nanoparticles

NASA Astrophysics Data System (ADS)

Sang, Fuming; Li, Xin; Zhang, Zhizhou; Liu, Jia; Chen, Guofu

2018-03-01

In this work, a rapid, simple and sensitive colorimetric sensor for simultaneous (or respective) detection of Cr3 + and Pb2 + using tyrosine functionalized gold nanoparticles (AuNPsTyr) has been developed. Tyrosine, a natural and zwitterionic amino acid, could be as a reducing and capping agent to synthesise AuNPs and allow for the simultaneous and selective detection of Cr3 + and Pb2 +. Upon the addition of Cr3 + or Pb2 + (a combination of them), the color of AuNPsTyr solution changes from red to blue grey and the characteristic surface plasmon resonance (SPR) band is red-shifted to 580 nm due to the aggregation of AuNPs. Interestingly, the aggregated AuNPsTyr can be regnerated and recycled by removing Pb2 + and Cr3 +. Even after 3 rounds, AuNPsTyr show almost the same A580 nm / A520 nm value for the assays of Pb2 + and Cr3 +, indicating the good recyclability of the colorimetric sensor. The responding time (within 1 min) and sensitivity of the colorimetric sensor are largely improved after the addition of 0.1 M NaCl. Moreover, the AuNPsTyr aggregated by Cr3 + or Pb2 + (a combination of them) show excellent selectivity compared to other metal ions (Cr3 +, Pb2 +, Fe2 +,Cu2 +,Zn2 +,Cr6 +,Ni2 +,Co2 +,Hg2 +,Mn2 +,Mg2 +,Ca2 +,Cd2 +). More importantly, the developed sensor manifests good stability at room temperature for 3 months, which has been successfully used to determine Cr3 + and Pb2 + in the real water samples with a high sensitivity.

A New Enzyme-linked Sorbent Assay (ELSA) to Quantify Syncytiotrophoblast Extracellular Vesicles in Biological Fluids.

PubMed

Göhner, Claudia; Weber, Maja; Tannetta, Dionne S; Groten, Tanja; Plösch, Torsten; Faas, Marijke M; Scherjon, Sicco A; Schleußner, Ekkehard; Markert, Udo R; Fitzgerald, Justine S

2015-06-01

The pregnancy-associated disease preeclampsia is related to the release of syncytiotrophoblast extracellular vesicles (STBEV) by the placenta. To improve functional research on STBEV, reliable and specific methods are needed to quantify them. However, only a few quantification methods are available and accepted, though imperfect. For this purpose, we aimed to provide an enzyme-linked sorbent assay (ELSA) to quantify STBEV in fluid samples based on their microvesicle characteristics and placental origin. Ex vivo placenta perfusion provided standards and samples for the STBEV quantification. STBEV were captured by binding of extracellular phosphatidylserine to immobilized annexin V. The membranous human placental alkaline phosphatase on the STBEV surface catalyzed a colorimetric detection reaction. The described ELSA is a rapid and simple method to quantify STBEV in diverse liquid samples, such as blood or perfusion suspension. The reliability of the ELSA was proven by comparison with nanoparticle tracking analysis. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

A Surface Plasmon Resonance-Based Method for Detection and Determination of Cannabinoids Using Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Amjadi, M.; Sodouri, T.

2014-05-01

In this work, a simple colorimetric method based on the formation of silver nanoparticles (Ag NPs) was developed for the determination of cannabinoids including Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiol (CBD) and cannabinol (CBN). These compounds in a basic solution at 80°C reduce [Ag(NH3)2]+ to form Ag NPs. The produced NPs were characterized by transmission electron microscopy and UV-Vis absorption spectroscopy. The brown-yellow color of the solution that results from the localized surface plasmon resonance of Ag NPs can be observed by the bare eye. The calibration graph obtained by plotting the absorbance at 410 nm versus the concentration of each analyte was linear in the range of 0.1-5.0 μg/ml for all tested cannabinoids. The limits of detection were 0.065, 0.077, and 0.052 μg/ml for Δ9-THC, CBN and CBD, respectively. The developed method was applied to the determination of total cannabinoids in hashish.

Colorimetric DNAzyme Biosensor for Convenience Detection of Enterotoxin B Harboring Staphylococcus aureus from Food Samples.

PubMed

Mondal, Bhairab; N, Bhavanashri; Ramlal, Shylaja; Kingston, Joseph

2018-02-14

In the present study, a colorimetric DNAzymes biosensor strategy was devised in combination with immunomagnetic separation for rapid and easy detection of enterotoxin B harboring Staphylococcus aureus from food and clinical samples. The method employs immunocapture of S. aureus and amplification of seb gene by DNAzyme complementary sequence integrated forward primer and with specific reverse primer. The DNAzyme sequence integrated dsDNA PCR products when treated with hemin and TMB (3,3',5,5'-tetramethylbenzidine) in the presence of H 2 O 2 produce colorimetric signal. A linear relationship of optical signal with the initial template of seb was obtained which could be monitored by visually or spectrophotrometrically for qualitative and quantitative detection. The limit of detection for the assay was approximately 10 2 CFU/mL of seb gene harboring target. This method is convenient compared to gel based and ELISA systems. Further, spiking studies and analysis on natural samples emphasized the robustness and applicability of developed method. Altogether, the established assay could be a reliable alternative, low-cost, viable detection tool for the routine investigation of seb from food and clinical sources.

Indigo Carmine-Cu complex probe exhibiting dual colorimetric/fluorimetric sensing for selective determination of mono hydrogen phosphate ion and its logic behavior

NASA Astrophysics Data System (ADS)

Tavallali, Hossein; Deilamy-Rad, Gohar; Moaddeli, Ali; Asghari, Khadijeh

2017-08-01

A new selective probe based on copper complex of Indigo Carmine (IC-Cu2) for colorimetric, naked-eye, and fluorimetric recognition of mono hydrogen phosphate (MHP) ion in H2O/DMSO (4:1 v/v, 1.0 mmol L- 1 HEPES buffer solution pH 7.5) was developed. Detection limit of HPO42 - determination, achieved by fluorimetric and 3lorimetric method, are 0.071 and 1.46 μmol L- 1, respectively. Potential, therefore is clearly available in IC-Cu2 complex to detect HPO42 - in micromolar range via dual visible color change and fluorescence response. Present method shows high selectivity toward HPO42 - over other phosphate species and other anions and was successfully utilized for analysis of P2O5 content of a fertilizer sample. The results obtained by proposed chemosensor presented good agreement with those obtained the colorimetric reference method. INHIBIT and IMPLICATION logic gates operating at molecular level have been achieved using Cu2 + and HPO42 - as chemical inputs and UV-Vis absorbance signal as output.

Simple flow injection colorimetric system for determination of paraquat in natural water.

PubMed

Chuntib, Prakit; Jakmunee, Jaroon

2015-11-01

A simple and low cost flow injection colorimetric system has been developed for determination of paraquat in natural water. The developed method is based on the reduction of paraquat by using sodium dithionite as a reducing agent in an alkaline medium to produce a blue free radical ion that can be detected by a simple light emitting diode-light dependent resistor (LED-LDR) colorimeter. The standard or sample solution was injected via a set of 3-way solenoid valves into a water carrier stream and flowed to merge with reagent to generate a colored product which is proportional to the concentration of paraquat ion in the solution. Under the optimum condition of the system, i.e., mixing coil length 30 cm, flow rate 2.0 mL min(-1), sample volume 100 μL, concentrations of dithionite 0.1% (w/v) and sodium hydroxide 0.06 mol L(-1), a linear calibration graph in the range of 0.2-10.0 mg L(-1) with a correlation coefficient of 0.9996, and a limit of detection of 0.15 mg L(-1) were achieved. Relative standard deviation for 9 replicate injections of 1 mg L(-1) paraquat is 3.7%. A sample throughput of 40 injections h(-1) was achieved. The limit of detection can be improved by off-line preconcentration of paraquat employing a column packed with Dowex 50WX8-100 (H) cation exchange resin and eluted with 10% (w/v) ammonium chloride in ammonium buffer solution pH 10. The eluting solution was then injected into the FI system for paraquat determination. The proposed system did not suffer from interferences of some possible ions in natural water and other herbicides. Recoveries obtained by spiking 0.5 and 5.0 mg L(-1) paraquat standard into water samples were in the range of 104-110% and 101-105%, respectively. The developed system can be conveniently applied for screening of paraquat contaminated in natural water. Copyright © 2015 Elsevier B.V. All rights reserved.

Gold nanorods for in-drop colorimetric determination of thiomersal after photochemical decomposition.

PubMed

Martín-Alonso, Manuel; Pena-Pereira, Francisco; Lavilla, Isela; Bendicho, Carlos

2018-03-13

This work reports on the implementation of gold nanorods (AuNRs) in headspace solvent microextraction for colorimetric determination of volatile analyte derivatives in a single drop. The exposure of AuNRs to both H 2 Se and elemental mercury (Hg 0 ) results in a shift of the longitudinal plasmonic band, unlike a number of volatiles. Accordingly, a method is reported for the determination of Hg 0 with potential applicability to the determination of thiomersal (sodium ethylmercurithiosalicylate). It is based on the photochemical decomposition of thiomersal into Hg(II) and subsequent exposure of AuNRs-containing microdrop to in situ generated Hg 0 . Colorimetric analysis of the enriched drop was carried out without dilution by means of a cuvetteless microvolume UV-vis spectrometer. Under optimal conditions, the limit of detection was 0.5 ng mL -1 (as Hg). The repeatability, expressed as relative standard deviation, was 8.4% (for n = 10). AuNRs exposed to increasing concentrations of the analyte were characterized by means of transmission electron microscopy and UV-vis spectrophotometry to ascertain the mechanism of detection. The method was finally applied to the determination of thiomersal in various pharmaceutical samples and showed quantitative recoveries. Graphical abstract Schematic illustration of a miniaturized colorimetric method based on the use of a microdrop of gold nanorods (AuNRs) for thiomersal determination in pharmaceuticals. It is based on the photochemical decomposition of thiomersal and subsequent Hg 0 generation with in-drop amalgamation.

Reverse phase protein microarrays: fluorometric and colorimetric detection.

PubMed

Gallagher, Rosa I; Silvestri, Alessandra; Petricoin, Emanuel F; Liotta, Lance A; Espina, Virginia

2011-01-01

The Reverse Phase Protein Microarray (RPMA) is an array platform used to quantitate proteins and their posttranslationally modified forms. RPMAs are applicable for profiling key cellular signaling pathways and protein networks, allowing direct comparison of the activation state of proteins from multiple samples within the same array. The RPMA format consists of proteins immobilized directly on a nitrocellulose substratum. The analyte is subsequently probed with a primary antibody and a series of reagents for signal amplification and detection. Due to the diversity, low concentration, and large dynamic range of protein analytes, RPMAs require stringent signal amplification methods, high quality image acquisition, and software capable of precisely analyzing spot intensities on an array. Microarray detection strategies can be either fluorescent or colorimetric. The choice of a detection system depends on (a) the expected analyte concentration, (b) type of microarray imaging system, and (c) type of sample. The focus of this chapter is to describe RPMA detection and imaging using fluorescent and colorimetric (diaminobenzidine (DAB)) methods.

Fluorescent detection of (-)-epicatechin in microsamples from cacao seeds and cocoa products: Comparison with Folin-Ciocalteu method.

PubMed

Ramirez-Sanchez, Israel; Maya, Lisandro; Ceballos, Guillermo; Villarreal, Francisco

2010-12-01

Polyphenolic compounds of the flavanoid family are abundantly present in cacao seed and its cocoa products. Results from studies using cocoa products indicate beneficial effects of flavanols on cardiovascular endpoints. Evidence indicates that (-)-epicatechin is the main cacao flavanol associated with cardiovascular effects, so the accurate quantification of its content in cacao seeds or cocoa products is important. Common methods for the quantification of phenolic content in cocoa products are based on the reaction of phenols with colorimetric reagents such as the Folin-Ciocalteu (FC) In this study, we compared the FC method of phenolic determinations using 2 different standards (gallic acid and (-)-epicatechin) to construct calibration curves. We compare these results with those obtained from a simple fluorometric method (Ex(280)/Em(320) nm) used to determine catechin/(-)-epicatechin content in samples of cacao seeds and cocoa products. Values obtained from the FC method determination of polyphenols yield an overestimation of phenol (flavonoid) content when gallic acid is used as standard. Moreover, the epicatechin is a more reliable standard because of its abundance in cacao seeds and cocoa products. The use of fluorometric spectra yields a simple and highly quantitative means for a more precise and rapid quantification of cacao catechins. Fluorometric values are essentially in agreement with those reported using more cumbersome methods. In conclusion, the use of fluorescence emission spectra is a quick, practical and suitable means to quantifying catechins in cacao seeds and cocoa products.

Automated, colorimetric methods for determination of nitrate plus nitrite, nitrite, ammonium and orthophosphate ions in natural water samples

USGS Publications Warehouse

Antweiler, Ronald C.; Patton, Charles J.; Taylor, Howard E.

1996-01-01

The apparatus and methods used for the automatic, colorimetric determinations of dissolved nutrients (nitrate plus nitrite, nitrite, ammonium and orthophosphate) in natural waters are described. These techniques allow for the determination of nitrate plus nitrite for the concentration range 0.02 to 8 mg/L (milligrams per liter) as N (nitrogen); for nitrite, the range is 0.002 to 1.0 mg/L as N; for ammonium, the range is 0.006 to 2.0 mg/L as N; and for orthophosphate, the range is 0.002 to 1.0 mg/L as P (phosphorus). Data are presented that demonstrate the accuracy, precision and quality control of the methods.

An Improved Method for Determination of Cyanide Content in Bitter Almond Oil.

PubMed

Chen, Jia; Liu, Lei; Li, Mengjun; Yu, Xiuzhu; Zhang, Rui

2018-01-01

An improved colorimetric method for determination of cyanide content in bitter almond oil was developed. The optimal determination parameters were as follows: volume ratio of hydrochloric acid to bitter almond oil (v/v), 1.5:1; holding time for hydrolysis, 120 min; and volume ratio of distillation solution to bitter almond oil (v/v), 8:1. Analytical results showed that the relative standard deviations (SDs) of determinations were less than 10%, which satisfies the test requirements. The results of high-performance liquid chromatography and measurements exhibited a significant correlation (R = 0.9888, SD = 0.2015). Therefore, the improved colorimetric method can be used to determine cyanide content in bitter almond oil.

Development of DNAzyme-based PCR signal cascade amplification for visual detection of Listeria monocytogenes in food.

PubMed

Liu, Zhanmin; Yao, Chenhui; Yang, Cuiyun; Wang, Yanming; Wan, Sibao; Huang, Junyi

2018-05-16

Listeria monocytogenes is an important foodborne pathogen, and it can cause severe diseases. Rapid detection of L. monocytogenes is crucial to control this pathogen. A simple and robust strategy based on the cascade of PCR and G-quadruplex DNAzyme catalyzed reaction was used to detect L. monocytogenes. In the presence of hemin and the aptamer formed during PCR, the catalytic horseradish peroxidase-mimicking G-quadruplex DNAzymes allow the colorimetric responses of target DNA from L. monocytogenes. This assay can detect genomic DNA of L. monocytogenes specifically with as low as 50 pg/reaction with the naked eye. Through 20 pork samples assay, visual detection assay had the same results as conventional detection methods, and had a good performance. This is a powerful demonstration of the ability of G-quadruplex DNAzyme to be used for PCR-based assay with significant advantages of high sensitivity, low cost and simple manipulation over existing approaches and offers the opportunity for application in pathogen detection. Copyright © 2018 Elsevier Inc. All rights reserved.

G-Quadruplex-based DNAzyme for colorimetric detection of cocaine: using magnetic nanoparticles as the separation and amplification element.

PubMed

Du, Yan; Li, Bingling; Guo, Shaojun; Zhou, Zhixue; Zhou, Ming; Wang, Erkang; Dong, Shaojun

2011-02-07

The appearance of the aptamer provides good recognition elements for small molecules, especially for drugs. In this work, by combining the advantages of magnetic nanoparticles (MNPs) with colorimetric drug detection using hemin-G-quadruplex complex as the sensing element, we report a simple and sensitive DNAzyme-based colorimetric sensor for cocaine detection in a 3,3,5,5-tetramethylbenzidine sulfate (TMB)-H(2)O(2) reaction system. The whole experimental processes are simplified. Cocaine aptamer fragments, SH-C2, are covalently labeled onto the amine-functionalized MNPs. When the target cocaine and another cocaine aptamer fragments (C1) grafted with G-riched strand AG4 (i.e. C1-AG4) are present simultaneously, the C2 layer on MNPs hybridizes partly with C1-AG4 to bind the cocaine. The C1-AG4 can be combinded with hemin to form DNAzyme which can effectively catalyze the H(2)O(2)-mediated oxidation of TMB, giving rise to a change in solution color. Importantly, using MNPs as the separation and amplification elements could effectively reduce the background signal and the interference from the real samples. A linear response from 0.1 μM to 20 μM is obtained for cocaine and a detection limit of 50 nM is achieved, which provides high sensitivity and selectivity to detect cocaine.

Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline

NASA Astrophysics Data System (ADS)

He, Yi; Peng, Rufang

2014-11-01

In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (˜25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 μg for colorimetric detection and from 10 ng to 1.0 μg for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

Colorimetric detection of genetically modified organisms based on exonuclease III-assisted target recycling and hemin/G-quadruplex DNAzyme amplification.

PubMed

Zhang, Decai; Wang, Weijia; Dong, Qian; Huang, Yunxiu; Wen, Dongmei; Mu, Yuejing; Yuan, Yong

2017-12-21

An isothermal colorimetric method is described for amplified detection of the CaMV 35S promoter sequence in genetically modified organism (GMO). It is based on (a) target DNA-triggered unlabeled molecular beacon (UMB) termini binding, and (b) exonuclease III (Exo III)-assisted target recycling, and (c) hemin/G-quadruplex (DNAzyme) based signal amplification. The specific binding of target to the G-quadruplex sequence-locked UMB triggers the digestion of Exo III. This, in turn, releases an active G-quadruplex segment and target DNA for successive hybridization and cleavage. The Exo III impellent recycling of targets produces numerous G-quadruplex sequences. These further associate with hemin to form DNAzymes and hence will catalyze H 2 O 2 -mediated oxidation of the chromogenic enzyme substrate ABTS 2- causing the formation of a green colored product. This finding enables a sensitive colorimetric determination of GMO DNA (at an analytical wavelength of 420 nm) at concentrations as low as 0.23 nM. By taking advantage of isothermal incubation, this method does not require sophisticated equipment or complicated syntheses. Analyses can be performed within 90 min. The method also discriminates single base mismatches. In our perception, it has a wide scope in that it may be applied to the detection of many other GMOs. Graphical abstract An isothermal and sensitive colorimetric method is described for amplified detection of CaMV 35S promoter sequence in genetically modified organism (GMO). It is based on target DNA-triggered molecular beacon (UMB) termini-binding and exonuclease III assisted target recycling, and on hemin/G-quadruplex (DNAzyme) signal amplification.

Visual detection of telomerase activity with a tunable dynamic range by using a gold nanoparticle probe-based hybridization protection strategy

NASA Astrophysics Data System (ADS)

Wang, Jiasi; Wu, Li; Ren, Jinsong; Qu, Xiaogang

2014-01-01

We developed a novel telomere complementary (TC) oligonucleotide modified AuNP probe (TC-AuNPs) for colorimetric analysis of telomerase activity. The mechanism of this method is that the telomerase reaction products (TRP), which can hybridize with the TC-AuNPs, are able to protect the AuNPs from the aggregation induced by salt. It is demonstrated that the colorimetric method enabled the analysis of the telomerase activity in 1000 HeLa cells with the naked eye, and down to 100 HeLa cells with the aid of UV-Vis spectroscopy. This strategy is not only convenient and sensitive, but also has a tunable dynamic range. The platform is also applicable for the initial screening of a telomerase inhibitor to discover new anticancer drugs.We developed a novel telomere complementary (TC) oligonucleotide modified AuNP probe (TC-AuNPs) for colorimetric analysis of telomerase activity. The mechanism of this method is that the telomerase reaction products (TRP), which can hybridize with the TC-AuNPs, are able to protect the AuNPs from the aggregation induced by salt. It is demonstrated that the colorimetric method enabled the analysis of the telomerase activity in 1000 HeLa cells with the naked eye, and down to 100 HeLa cells with the aid of UV-Vis spectroscopy. This strategy is not only convenient and sensitive, but also has a tunable dynamic range. The platform is also applicable for the initial screening of a telomerase inhibitor to discover new anticancer drugs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05185d

Effect of black point on accuracy of LCD displays colorimetric characterization

NASA Astrophysics Data System (ADS)

Li, Tong; Xie, Kai; He, Nannan; Ye, Yushan

2018-03-01

Black point is the point at which RGB's single channel digital drive value is 0. Due to the problem of light leakage of liquid-crystal displays (LCDs), black point's luminance value is not 0, this phenomenon bring some errors to colorimetric characterization of LCDs, especially low luminance value driving greater sampling effect. This paper describes the characteristic accuracy of polynomial model method and the effect of black point on accuracy, the color difference accuracy is given. When considering the black point in the characteristics equation, the maximum color difference is 3.246, the maximum color difference than without considering the black points reduced by 2.36. The experimental results show that the accuracy of LCDs colorimetric characterization can be improved, if the effect of black point is eliminated properly.

Colorimetric determination of Al(III) based on the aggregation of gold nanoparticles functionalized with novel 4-benzoyl pyrazolone derivative

NASA Astrophysics Data System (ADS)

Abubaker, Mariam; Ngah, Che Wan Zanariah Che Wan; Ahmad, Musa; Kuswandi, Bambang

2018-06-01

A sensitive and selective colorimetric method has been developed for detection of Al3+ ion using 4-benzoyl pyrazolone-functionalized gold nanoparticles (BMPBP-AuNPs) as novel colorimetric probes. The BMPBP-AuNPs were characterized by UV-visible spectrometry and transmission electron microscopy (TEM). It was found that the addition of the Al3+ ions led to a rapid aggregation of the BMPBP-AuNPs, which changed the color of the mixture from red to blue. Furthermore, there was a shift in the characteristic surface plasmon resonance (SPR) peak from 524 to 650 nm of BMPBP-AuNPs, which confirmed that a good linear relation (R2 = 0.9935) was present between the absorption ratio of 524 and 650 nm. Also, the assay detected the Al3+ ion concentrations in the linear range 0-12 ppm with the detection limit is 0.05 ppm. Finally, the synthesized BMPBP-AuNPs were successfully used as a colorimetric sensor for the selective and sensitive detection of the Al3+ ions in water samples.

Augmented Reality for Real-Time Detection and Interpretation of Colorimetric Signals Generated by Paper-Based Biosensors.

PubMed

Russell, Steven M; Doménech-Sánchez, Antonio; de la Rica, Roberto

2017-06-23

Colorimetric tests are becoming increasingly popular in point-of-need analyses due to the possibility of detecting the signal with the naked eye, which eliminates the utilization of bulky and costly instruments only available in laboratories. However, colorimetric tests may be interpreted incorrectly by nonspecialists due to disparities in color perception or a lack of training. Here we solve this issue with a method that not only detects colorimetric signals but also interprets them so that the test outcome is understandable for anyone. It consists of an augmented reality (AR) app that uses a camera to detect the colored signals generated by a nanoparticle-based immunoassay, and that yields a warning symbol or message when the concentration of analyte is higher than a certain threshold. The proposed method detected the model analyte mouse IgG with a limit of detection of 0.3 μg mL -1 , which was comparable to the limit of detection afforded by classical densitometry performed with a nonportable device. When adapted to the detection of E. coli, the app always yielded a "hazard" warning symbol when the concentration of E. coli in the sample was above the infective dose (10 6 cfu mL -1 or higher). The proposed method could help nonspecialists make a decision about drinking from a potentially contaminated water source by yielding an unambiguous message that is easily understood by anyone. The widespread availability of smartphones along with the inexpensive paper test that requires no enzymes to generate the signal makes the proposed assay promising for analyses in remote locations and developing countries.

Pitfalls in the detection of cholesterol in Huntington's disease models.

PubMed

Marullo, Manuela; Valenza, Marta; Leoni, Valerio; Caccia, Claudio; Scarlatti, Chiara; De Mario, Agnese; Zuccato, Chiara; Di Donato, Stefano; Carafoli, Ernesto; Cattaneo, Elena

2012-10-11

Background Abnormalities in brain cholesterol homeostasis have been reported in Huntington's disease (HD), an adult-onset neurodegenerative disorder caused by an expansion in the number of CAG repeats in the huntingtin (HTT) gene. However, the results have been contradictory with respect to whether cholesterol levels increase or decrease in HD models. Biochemical and mass spectrometry methods show reduced levels of cholesterol precursors and cholesterol in HD cells and in the brains of several HD animal models. Abnormal brain cholesterol homeostasis was also inferred from studies in HD patients. In contrast, colorimetric and enzymatic methods indicate cholesterol accumulation in HD cells and tissues. Here we used several methods to investigate cholesterol levels in cultured cells in the presence or absence of mutant HTT protein. Results Colorimetric and enzymatic methods with low sensitivity gave variable results, whereas results from a sensitive analytical method, gas chromatography-mass spectrometry, were more reliable. Sample preparation, high cell density and cell clonality also influenced the detection of intracellular cholesterol. Conclusions Detection of cholesterol in HD samples by colorimetric and enzymatic assays should be supplemented by detection using more sensitive analytical methods. Care must be taken to prepare the sample appropriately. By evaluating lathosterol levels using isotopic dilution mass spectrometry, we confirmed reduced cholesterol biosynthesis in knock-in cells expressing the polyQ mutation in a constitutive or inducible manner. *Correspondence should be addressed to Elena Cattaneo: elena.cattaneo@unimi.it.

Simple, fast, and low-cost camera-based water content measurement with colorimetric fluorescent indicator

NASA Astrophysics Data System (ADS)

Song, Seok-Jeong; Kim, Tae-Il; Kim, Youngmi; Nam, Hyoungsik

2018-05-01

Recently, a simple, sensitive, and low-cost fluorescent indicator has been proposed to determine water contents in organic solvents, drugs, and foodstuffs. The change of water content leads to the change of the indicator's fluorescence color under the ultra-violet (UV) light. Whereas the water content values could be estimated from the spectrum obtained by a bulky and expensive spectrometer in the previous research, this paper demonstrates a simple and low-cost camera-based water content measurement scheme with the same fluorescent water indicator. Water content is calculated over the range of 0-30% by quadratic polynomial regression models with color information extracted from the captured images of samples. Especially, several color spaces such as RGB, xyY, L∗a∗b∗, u‧v‧, HSV, and YCBCR have been investigated to establish the optimal color information features over both linear and nonlinear RGB data given by a camera before and after gamma correction. In the end, a 2nd order polynomial regression model along with HSV in a linear domain achieves the minimum mean square error of 1.06% for a 3-fold cross validation method. Additionally, the resultant water content estimation model is implemented and evaluated in an off-the-shelf Android-based smartphone.

Utility of NBD-Cl for the spectrophotometric determination of some skeletal muscle relaxant and antihistaminic drugs

NASA Astrophysics Data System (ADS)

Saleh, Hanaa M.; EL-Henawee, Magda M.; Ragab, Gamal H.; El-Hay, Soad S. Abd

2007-08-01

A simple, accurate, precise and sensitive colorimetric method for the determination of some skeletal muscle relaxant drugs, namely orphenadrine citrate ( I), baclofen ( II), antihistaminic drugs as acrivastine ( III) and fexofenadine hydrochloride ( IV) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) in non-aqueous medium. The orange color products were measured at 472, 465, 475 and 469 nm for drugs I, II, III and IV, respectively. The optimization of various experimental conditions was described. Beer's Law was obeyed in the range (2.5-17.5), (5-70), (2.5-25) and (10-50) μg/ml for drugs I, II, III and IV, respectively. The molar absorptivity ( ɛ), sandell sensitivity, detection (LOD) and quantitation limits (LOQ) are calculated. The procedure was favorably applied for determination of certain pharmaceutical dosage forms containing the studied drugs. The obtained results were compared with the official and reported methods. There were no significant differences between proposed, reported and the official methods.

Determination of Lead in Urine by Atomic Absorption Spectrophotometry1

PubMed Central

Selander, Stig; Cramé, Kim

1968-01-01

A method for the determination of lead in urine by means of atomic absorption spectrophotometry (AAS) is described. A combination of wet ashing and extraction with ammonium pyrrolidine dithiocarbamate into isobutylmethylketone was used. The sensitivity was about 0·02 μg./ml. for 1% absorption, and the detection limit was about 0·02 μg./ml. with an instrumental setting convenient for routine analyses of urines. Using the scale expansion technique, the detection limit was below 0·01 μg./ml., but it was found easier to determine urinary lead concentrations below 0·05 μg./ml. by concentrating the lead in the organic solvent by increasing the volume of urine or decreasing that of the solvent. The method was applied to fresh urines, stored urines, and to urines, obtained during treatment with chelating agents, of patients with lead poisoning. Urines with added inorganic lead were not used. The results agreed well with those obtained with a colorimetric dithizone extraction method (r = 0·989). The AAS method is somewhat more simple and allows the determination of smaller lead concentrations. PMID:5647975

Using instrumental (CIE and reflectance) measures to predict consumers' acceptance of beef colour.

PubMed

Holman, Benjamin W B; van de Ven, Remy J; Mao, Yanwei; Coombs, Cassius E O; Hopkins, David L

2017-05-01

We aimed to establish colorimetric thresholds based upon the capacity for instrumental measures to predict consumer satisfaction with beef colour. A web-based survey was used to distribute standardised photographs of beef M. longissimus lumborum with known colorimetrics (L*, a*, b*, hue, chroma, ratio of reflectance at 630nm and 580nm, and estimated deoxymyoglobin, oxymyoglobin and metmyoglobin concentrations) for scrutiny. Consumer demographics and perceived importance of colour to beef value were also evaluated. It was found that a* provided the most simple and robust prediction of beef colour acceptability. Beef colour was considered acceptable (with 95% acceptance) when a* values were equal to or above 14.5. Demographic effects on this threshold were negligible, but consumer nationality and gender did contribute to variation in the relative importance of colour to beef value. These results provide future beef colour studies with context to interpret objective colour measures in terms of consumer acceptance and market appeal. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Smartphone-Based VOC Sensor Using Colorimetric Polydiacetylenes.

PubMed

Park, Dong-Hoon; Heo, Jung-Moo; Jeong, Woomin; Yoo, Young Hyuk; Park, Bum Jun; Kim, Jong-Man

2018-02-07

Owing to a unique colorimetric (typically blue-to-red) feature upon environmental stimulation, polydiacetylenes (PDAs) have been actively employed in chemosensor systems. We developed a highly accurate and simple volatile organic compound (VOC) sensor system that can be operated using a conventional smartphone. The procedure begins with forming an array of four different PDAs on conventional paper using inkjet printing of four corresponding diacetylenes followed by photopolymerization. A database of color changes (i.e., red and hue values) is then constructed on the basis of different solvatochromic responses of the 4 PDAs to 11 organic solvents. Exposure of the PDA array to an unknown solvent promotes color changes, which are imaged using a smartphone camera and analyzed using the app. A comparison of the color changes to the database promoted by the 11 solvents enables the smartphone app to identify the unknown solvent with 100% accuracy. Additionally, it was demonstrated that the PDA array sensor was sufficiently sensitive to accurately detect the 11 VOC gases.

Array-based disease diagnostics using lipid/polydiacetylene vesicles encapsulated in a sol-gel matrix.

PubMed

Kolusheva, S; Yossef, R; Kugel, A; Katz, M; Volinsky, R; Welt, M; Hadad, U; Drory, V; Kliger, M; Rubin, E; Porgador, A; Jelinek, R

2012-07-17

We demonstrate a novel array-based diagnostic platform comprising lipid/polydiacetylene (PDA) vesicles embedded within a transparent silica-gel matrix. The diagnostic scheme is based upon the unique chromatic properties of PDA, which undergoes blue-red transformations induced by interactions with amphiphilic or membrane-active analytes. We show that constructing a gel matrix array hosting PDA vesicles with different lipid compositions and applying to blood plasma obtained from healthy individuals and from patients suffering from disease, respectively, allow distinguishing among the disease conditions through application of a simple machine-learning algorithm, using the colorimetric response of the lipid/PDA/gel matrix as the input. Importantly, the new colorimetric diagnostic approach does not require a priori knowledge on the exact metabolite compositions of the blood plasma, since the concept relies only on identifying statistically significant changes in overall disease-induced chromatic response. The chromatic lipid/PDA/gel array-based "fingerprinting" concept is generic, easy to apply, and could be implemented for varied diagnostic and screening applications.

Colorimetric detection of glucose based on ficin with peroxidase-like activity

NASA Astrophysics Data System (ADS)

Pang, Yanjiao; Huang, Zili; Yang, Yufang; Long, Yijuan; Zheng, Huzhi

2018-01-01

In this work, we developed a colorimetric biosensing system for glucose detection by coupling the peroxidase-like of ficin and the glucose oxidase (GOx). GOx can catalyze the oxidation of glucose to produce H2O2, then, ficin catalyzes the oxidation of peroxidase substrate 3,3‧,5,5‧-tetramethylbenzidine (TMB) by H2O2 to produce a blue color reaction. The present sensing system showed a linear response toward glucose detection over range of 2.0-100 μM with a detection limit of 0.5 μM. This system is simple, low cost, highly sensitive and selective for glucose detection, and was also applied to measuring glucose in human serum. Furthermore, in order to expand the application of ficin in biological sensing, we immobilized ficin onto the SiO2@Fe3O4 NPs, which exhibited the merits of recycling as well as allowing the repeated detection of glucose. Thus it may provide great potential applications in biomedicine, biotechnology and environmental chemistry.

A Method for Selecting Structure-switching Aptamers Applied to a Colorimetric Gold Nanoparticle Assay

PubMed Central

Martin, Jennifer A.; Smith, Joshua E.; Warren, Mercedes; Chávez, Jorge L.; Hagen, Joshua A.; Kelley-Loughnane, Nancy

2015-01-01

Small molecules provide rich targets for biosensing applications due to their physiological implications as biomarkers of various aspects of human health and performance. Nucleic acid aptamers have been increasingly applied as recognition elements on biosensor platforms, but selecting aptamers toward small molecule targets requires special design considerations. This work describes modification and critical steps of a method designed to select structure-switching aptamers to small molecule targets. Binding sequences from a DNA library hybridized to complementary DNA capture probes on magnetic beads are separated from nonbinders via a target-induced change in conformation. This method is advantageous because sequences binding the support matrix (beads) will not be further amplified, and it does not require immobilization of the target molecule. However, the melting temperature of the capture probe and library is kept at or slightly above RT, such that sequences that dehybridize based on thermodynamics will also be present in the supernatant solution. This effectively limits the partitioning efficiency (ability to separate target binding sequences from nonbinders), and therefore many selection rounds will be required to remove background sequences. The reported method differs from previous structure-switching aptamer selections due to implementation of negative selection steps, simplified enrichment monitoring, and extension of the length of the capture probe following selection enrichment to provide enhanced stringency. The selected structure-switching aptamers are advantageous in a gold nanoparticle assay platform that reports the presence of a target molecule by the conformational change of the aptamer. The gold nanoparticle assay was applied because it provides a simple, rapid colorimetric readout that is beneficial in a clinical or deployed environment. Design and optimization considerations are presented for the assay as proof-of-principle work in buffer to provide a foundation for further extension of the work toward small molecule biosensing in physiological fluids. PMID:25870978

An enzyme-free catalytic DNA circuit for amplified detection of aflatoxin B1 using gold nanoparticles as colorimetric indicators

NASA Astrophysics Data System (ADS)

Chen, Junhua; Wen, Junlin; Zhuang, Li; Zhou, Shungui

2016-05-01

An enzyme-free biosensor for the amplified detection of aflatoxin B1 has been constructed based on a catalytic DNA circuit. Three biotinylated hairpin DNA probes (H1, H2, and H3) were designed as the assembly components to construct the sensing system (triplex H1-H2-H3 product). Cascaded signal amplification capability was obtained through toehold-mediated strand displacement reactions to open the hairpins and recycle the trigger DNA. By the use of streptavidin-functionalized gold nanoparticles as the signal indicators, the colorimetric readout can be observed by the naked eye. In the presence of a target, the individual nanoparticles (red) aggregate into a cross-linked network of nanoparticles (blue) via biotin-streptavidin coupling. The colorimetric assay is ultrasensitive, enabling the visual detection of trace levels of aflatoxin B1 (AFB1) as low as 10 pM without instrumentation. The calculated limit of detection (LOD) is 2 pM in terms of 3 times standard deviation over the blank response. The sensor is robust and works even when challenged with complex sample matrices such as rice samples. Our sensing platform is simple and convenient in operation, requiring only the mixing of several solutions at room temperature to achieve visible and intuitive results, and holds great promise for the point-of-use monitoring of AFB1 in environmental and food samples.An enzyme-free biosensor for the amplified detection of aflatoxin B1 has been constructed based on a catalytic DNA circuit. Three biotinylated hairpin DNA probes (H1, H2, and H3) were designed as the assembly components to construct the sensing system (triplex H1-H2-H3 product). Cascaded signal amplification capability was obtained through toehold-mediated strand displacement reactions to open the hairpins and recycle the trigger DNA. By the use of streptavidin-functionalized gold nanoparticles as the signal indicators, the colorimetric readout can be observed by the naked eye. In the presence of a target, the individual nanoparticles (red) aggregate into a cross-linked network of nanoparticles (blue) via biotin-streptavidin coupling. The colorimetric assay is ultrasensitive, enabling the visual detection of trace levels of aflatoxin B1 (AFB1) as low as 10 pM without instrumentation. The calculated limit of detection (LOD) is 2 pM in terms of 3 times standard deviation over the blank response. The sensor is robust and works even when challenged with complex sample matrices such as rice samples. Our sensing platform is simple and convenient in operation, requiring only the mixing of several solutions at room temperature to achieve visible and intuitive results, and holds great promise for the point-of-use monitoring of AFB1 in environmental and food samples. Electronic supplementary information (ESI) available: Experimental details and additional data. See DOI: 10.1039/c6nr01381c

Analysis of phytochemical profile of Terminalia arjuna bark extract with antioxidative and antimicrobial properties.

PubMed

Mandal, Shreya; Patra, Arpita; Samanta, Animesh; Roy, Suchismita; Mandal, Arpita; Mahapatra, Tapasi Das; Pradhan, Shrabani; Das, Koushik; Nandi, Dilip Kumar

2013-12-01

To investigate phytochemical screening, antimicrobial activity and qualitative thin layer chromatographic separation of flavonoid components, antioxidant activity and total flavonoid compound of Terminalia arjuna. For phytochemical screening, some common and available standard tests were done. Antimicrobial bioassay was done through agar well diffusion method. Detection of antioxidant activity and flavonoid compounds were done through thin layer chromatography. Total antioxidant activity was measured by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) in colorimetric method. Aluminum chloride colorimetric method was used for total flavonoid determination. Phytochemical screening showed the active compounds presence in high concentration, such as phytosterol, lactones, flavonoids, phenolic compounds and tannins and glycosides. The antimicrobial activity of extract showed that greater inhibition zone against Gram negative bacteria than Gram positive bacteria. This methanolic extract showed a promising antioxidant activity, as absorption of DPPH redicles decreased in DPPH free radical scavenging assay. Flavonoids components having antioxidant property present in the methanol extract at a level of 199.00 mg quercetin equivalent/g of dried methanol extract in colorimetric method. The Terminalia arjuna bark extract revealed the presence of bio-active constituents which are known to exhibit medicinal as well as physiological activities. Copyright © 2013 Asian Pacific Tropical Biomedical Magazine. Published by Elsevier B.V. All rights reserved.

[Research on the designing method of a special shade guide for tooth whitening].

PubMed

Xu, Yingxin

2015-10-01

To investigate a method of designing an accurate and scientific shade guide, especially used for judging the effect of tooth whitening, by analyzing the colorimetric values of discolored teeth statistically. One hundred thirty-six pictures of patients who had been receiving the Beyond cold light whitening treatment from February 2009 to July 2014 were analyzed, including 25 tetracycline teeth, 61 mottled-enamel teeth, and 50 yellow teeth. The colorimetric values of discolored teeth were measured. The L* values of shade tabs were calculated by hierarchical clustering of those of discolored teeth. The a* and b* values of shade tabs were the mean of those observed for discolored teeth. Accordingly, different shade guides were designed for each type of discolored teeth, and the effects were evaluated. A statistically significant difference in colorimetric values was found among the three types of discolored teeth. Compared with the Vitapan Classical shade guide, the shade guides designed through the present method were more scientific and accurate in judging the effect of tooth whitening. Moreover, the arrangement of shade tabs was more logical, and the color difference between shade tabs and discolored teeth was smaller. The proposed designing method is theoretically feasible, although its clinical effect has yet to be proven.

Colorimetric and atomic absorption spectrometric determination of mucolytic drug ambroxol through ion-pair formation with iron and thiocyanate.

PubMed

Levent, Abdulkadir; Sentürk, Zühre

2010-09-01

Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which extractable chloroform. The red-coloured complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe(3+) and SCN(-), shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) - 5.7x10(-5) M (1.7-23.6 µg mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 µg mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 µg mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.

Direct detection of hyaluronidase in urine using cationic gold nanoparticles: a potential diagnostic test for bladder cancer.

PubMed

Nossier, Ahmed Ibrahim; Eissa, Sanaa; Ismail, Manal Fouad; Hamdy, Mohamed Ahmed; Azzazy, Hassan Mohamed El-Said

2014-04-15

Hyaluronidase (HAase) was reported as a urinary marker of bladder cancer. In this study, a simple colorimetric gold nanoparticle (AuNP) assay was developed for rapid and sensitive detection of urinary HAase activity. Charge interaction between polyanionic hyaluronic acid (HA) and cationic AuNPs stabilized with cetyl trimethyl ammonium bromide (CTAB) led to formation of gold aggregates and a red to blue color shift. HAase digests HA into small fragments preventing the aggregation of cationic AuNPs. The nonspecific aggregation of AuNPs in urine samples was overcome by pre-treatment of samples with the polycationic chitosan that was able to agglomerate all negatively charged interfering moieties before performing the assay. The developed AuNP assay was compared with zymography for qualitative detection of urinary HAase activity in 40 bladder carcinoma patients, 11 benign bladder lesions patients and 15 normal individuals, the assay sensitivity was 82.5% vs. 65% for zymography, while the specificity for both assays was 96.1%. The absorption ratio, A530/A620 of the reacted AuNP solution was used to quantify the HAase activity. The best cut off value was 93.5 μU/ng protein, at which the sensitivity was 90% and the specificity was 80.8%.The developed colorimetric AuNP HAase assay is simple, inexpensive, and can aid noninvasive diagnosis of bladder cancer. © 2013 Elsevier B.V. All rights reserved.

Colorimetric susceptibility testing for Aspergillus fumigatus: comparison of menadione-augmented 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and Alamar blue tests.

PubMed Central

Jahn, B; Stüben, A; Bhakdi, S

1996-01-01

Two colorimetric methods that use Alamar Blue or 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) for assaying the in vitro activities of antifungal agents have been described. We report that both tests performed similarly when the antifungal activity of amphotericin B against Candida albicans was determined. However, only the MTT test generated interpretable data when Aspergillus fumigatus was used. PMID:8818910

A smartphone colorimetric reader integrated with an ambient light sensor and a 3D printed attachment for on-site detection of zearalenone.

PubMed

Chen, Yuan; Fu, Qiangqiang; Li, Dagang; Xie, Jun; Ke, Dongxu; Song, Qifang; Tang, Yong; Wang, Hong

2017-11-01

Smartphone biosensors could be cost-effective, portable instruments to be used for the readout of liquid colorimetric assays. However, current reported smartphone colorimetric readers have relied on photos of liquid assays captured using a camera, and then analyzed using software programs. This approach results in a relatively low accuracy and low generality. In this work, we reported a novel smartphone colorimetric reader that has been integrated with an ambient light sensor and a 3D printed attachment for the readout of liquid colorimetric assays. The portable and low-cost ($0.15) reader utilized a simplified electronic and light path design. Furthermore, our reported smartphone colorimetric reader can be compatible with different smartphones. As a proof of principle, the utility of this device was demonstrated using it in conjunction with an enzyme-linked immunosorbent assay to detect zearalenone. Results were consistent with those obtained using a professional microplate reader. The developed smartphone colorimetric reader was capable of providing scalable, cost-effective, and accurate results for liquid colorimetric assays that related to clinical diagnoses, environment pollution, and food testing. Graphical abstract A novel smartphone colorimetric reader that has been integrated with an ambient light sensor and a 3D printed attachment for the readout of liquid colorimetric assays.

A colorimetric method for the molecular weight determination of polyethylene glycol using gold nanoparticles

PubMed Central

2013-01-01

A gold nanoparticle (AuNP)-based colorimetric method was developed for the molecular weight (MW) determination of polyethylene glycol (PEG), a commonly used hydrophilic polymer. Addition of a salt solution to PEG-coated AuNP solutions helps in screening the electrostatic repulsion between nanoparticles and generating a color change of the solutions from wine red to blue in 10 min in accordance with the MW of PEG, which illustrates the different stability degrees (SDs) of the AuNPs. The SDs are calculated by the absorbance ratios of the stable to the aggregated AuNPs in the solution. The root mean square end-to-end length (〈h2〉1/2) of PEG molecules shows a linear fit to the SDs of the PEG-coated AuNPs in a range of 1.938 ± 0.156 to 10.151 ± 0.176 nm. According to the Derjaguin-Landau-Verwey-Overbeek theory, the reason for this linear relationship is that the thickness of the PEG adlayer is roughly equivalent to the 〈h2〉1/2 of the PEG molecules in solution, which determines the SDs of the AuNPs. Subsequently, the MW of the PEG can be obtained from its 〈h2〉1/2 using a mathematical relationship between 〈h2〉1/2 and MW of PEG molecule. Applying this approach, we determined the 〈h2〉1/2 and the MW of four PEG samples according to their absorbance values from the ordinary ultraviolet–visible spectrophotometric measurements. Therefore, the MW of PEG can be distinguished straightforwardly by visual inspection and determined by spectrophotometry. This novel approach is simple, rapid, and sensitive. PMID:24359120

An improved method for LCD displays colorimetric characterization

NASA Astrophysics Data System (ADS)

Li, Tong; Xie, Kai; Wang, Qiaojie; He, Nannan; Ye, Yushan

2018-03-01

The colorimetric characterization of the display can achieve the purpose of precisely controlling the color of the monitor. This paper describes an improved method for estimating the gamma value of liquid-crystal displays (LCDs) without using a measurement device was described by Xiao et al. It relies on observer's luminance matching by presenting eight half-tone patterns with luminance from 1/9 to 8/9 of the maximum value of each color channel. Since the previous method lacked partial low frequency information, we partially replaced the half-tone patterns. A large number of experiments show that the color difference is reduced from 3.726 to 2.835, and our half-tone pattern can better estimate the visual gamma value of LCDs.

Enzyme-free colorimetric detection systems based on the DNA strand displacement competition reaction

NASA Astrophysics Data System (ADS)

Zhang, Z.; Birkedal, V.; Gothelf, K. V.

2016-05-01

The strand displacement competition assay is based on the dynamic equilibrium of the competitive hybridization of two oligonucleotides (A and B) to a third oligonucleotide (S). In the presence of an analyte that binds to a specific affinity-moiety conjugated to strand B, the equilibrium shifts, which can be detected by a shift in the fluorescence resonance energy transfer signal between dyes attached to the DNA strands. In the present study we have integrated an ATP aptamer in the strand B and demonstrated the optical detection of ATP. Furthermore we explore a new readout method using a split G-quadruplex DNAzyme for colorimetric readout of the detection of streptavidin by the naked eye. Finally, we integrate the whole G-quadruplex DNAzyme system in a single DNA strand and show that it is applicable to colorimetric detection.

The Disassembly of a Core-Satellite Nanoassembled Substrate for Colorimetric Biomolecular Detection

PubMed Central

Waldeisen, John R.; Wang, Tim; Ross, Benjamin M.; Lee, Luke P.

2012-01-01

The disassembly of a core-satellite nanostructured substrate is presented as a colorimetric biosensor observable under dark field illumination. The fabrication method described herein utilizes thiol-mediated adsorption and streptavidin-biotin binding to self-assemble core-satellite nanostructures with a sacrificial linking peptide. Biosensing functionality is demonstrated with the protease trypsin and the optical properties of the nanoassemblies are characterized. A figure of merit is presented to determine the optimal core and satellite size for visual detection. Nanoassemblies with 50 nm cores and 30 nm or 50 nm satellites are superior as these structures achieve an orange to green color shift greater than 70 nm that is easily discernible by naked eye. This colorimetric substrate may prove to be a favorable alternative to liquid-based colloidal sensors and a useful visual readout mechanism for microfluidic diagnostic assays. PMID:21667984

Colour change evaluation on UV radiation exposure for Păun-Repedea calcareous geomaterial

NASA Astrophysics Data System (ADS)

Pelin, V.; Sandu, I.; Munteanu, M.; Iurcovschi, C. T.; Gurlui, S.; Sandu, AV; Vasilache, V.; Brȃnzilă, M.; Sandu, I. G.

2016-06-01

When talking about the preservation treatments that can be applied to natural stones used in different constructions, the surface hydrophobization plays an important part, especially when referring to porous surfaces like the calcareous oolithic stones specific to Repedea area, Iasi County, Romania. The present paper presents a method that evaluates the hydrophobization efficiency of two types of pellicles, involving UV artificial ageing and colorimetric analysis of the treated surfaces. The evaluation was done through continuous colorimetric monitoring and by comparing the evolution of the chromatic modifications of the two treated surfaces with the original colorimetric values and with the witness area, which was exposed to UV radiations under the same conditions, but left chemical untreated. The techniques used during this experiment were: CIE L*a*b* colorimetry, OM, SEM-EDX, UV radiation exposure and Spectrum Irradiance Measurement.

Disulfide-induced self-assembled targets: A novel strategy for the label free colorimetric detection of DNAs/RNAs via unmodified gold nanoparticles

NASA Astrophysics Data System (ADS)

Shokri, Ehsan; Hosseini, Morteza; Davari, Mehdi D.; Ganjali, Mohammad R.; Peppelenbosch, Maikel P.; Rezaee, Farhad

2017-04-01

A modified non-cross-linking gold-nanoparticles (Au-NPs) aggregation strategy has been developed for the label free colorimetric detection of DNAs/RNAs based on self-assembling target species in the presence of thiolated probes. Two complementary thiol- modified probes, each of which specifically binds at one half of the target introduced SH groups at both ends of dsDNA. Continuous disulfide bond formation at 3‧ and 5‧ terminals of targets leads to the self-assembly of dsDNAs into the sulfur- rich and flexible products with different lengths. These products have a high affinity for the surface of Au-NPs and efficiently protect the surface from salt induced aggregation. To evaluate the assay efficacy, a small part of the citrus tristeza virus (CTV) genome was targeted, leading to a detection limit of about 5 × 10-9 mol.L-1 over a linear ranged from 20 × 10-9 to 10 × 10-7 mol.L-1. This approach also exhibits good reproducibility and recovery levels in the presence of plant total RNA or human plasma total circulating RNA extracts. Self-assembled targets can be then sensitively distinguished from non-assembled or mismatched targets after gel electrophoresis. The disulfide reaction method and integrating self-assembled DNAs/RNAs targets with bare AuNPs as a sensitive indicator provide us a powerful and simple visual detection tool for a wide range of applications.

Use of a Smartphone as a Colorimetric Analyzer in Paper-based Devices for Sensitive and Selective Determination of Mercury in Water Samples.

PubMed

Jarujamrus, Purim; Meelapsom, Rattapol; Pencharee, Somkid; Obma, Apinya; Amatatongchai, Maliwan; Ditcharoen, Nadh; Chairam, Sanoe; Tamuang, Suparb

2018-01-01

A smartphone application, called CAnal, was developed as a colorimetric analyzer in paper-based devices for sensitive and selective determination of mercury(II) in water samples. Measurement on the double layer of a microfluidic paper-based analytical device (μPAD) fabricated by alkyl ketene dimer (AKD)-inkjet printing technique with special design doped with unmodified silver nanoparticles (AgNPs) onto the detection zones was performed by monitoring the gray intensity in the blue channel of AgNPs, which disintegrated when exposed to mercury(II) on μPAD. Under the optimized conditions, the developed approach showed high sensitivity, low limit of detection (0.003 mg L -1 , 3SD blank/slope of the calibration curve), small sample volume uptake (two times of 2 μL), and short analysis time. The linearity range of this technique ranged from 0.01 to 10 mg L -1 (r 2 = 0.993). Furthermore, practical analysis of various water samples was also demonstrated to have acceptable performance that was in agreement with the data from cold vapor atomic absorption spectrophotometry (CV-AAS), a conventional method. The proposed technique allows for a rapid, simple (instant report of the final mercury(II) concentration in water samples via smartphone display), sensitive, selective, and on-site analysis with high sample throughput (48 samples h -1 , n = 3) of trace mercury(II) in water samples, which is suitable for end users who are unskilled in analyzing mercury(II) in water samples.

L-arginine modified magnetic nanoparticles: green synthesis and characterization

NASA Astrophysics Data System (ADS)

Bagherpour, A. R.; Kashanian, F.; Seyyed Ebrahimi, S. A.; Habibi-Rezaei, M.

2018-02-01

In recent years, there has been considerable interest in Arg which is a unique, nontoxic, and biocompatible biomolecule since it can be utilized as an agent for the functionalization and subsequent stabilization of MNPs against oxidation and aggregation, during or after a synthesis procedure. Our studies demonstrate that Arg has great impacts on MNPs with the decreasing size of the particle. Also, saturation magnetization and electrostatic interactions of RMNPs have a direct impact on biological molecules such as proteins and nucleic acids. By controlling the concentration of Arg, it is possible to accurately control the above-mentioned characteristics, which are useful tools for applications such as connecting to antibodies, catalysis, drug loading, and modification of MNP stability. In the current study, three RMNPs with different Arg densities, i.e. 0.42, 1.62, and 2.29 μg per mg were successfully synthesized through a simple co-precipitation method (named p 0.5, p 1, and p 1.5, respectively) and verified by colorimetric determination. Also, the as-synthesized RMNP powders were characterized by XRD, SEM/EDAX, FTIR, VSM, and zeta potential analysis. The presence of a magnetic core was proved by XRD, FTIR, and EDAX. Colorimetric analysis showed the existence of Arg in the synthesized samples. According to the zeta potential and VSM results, increasing the cap of Arg on the MNP surface leads to an increase in the surface charge and decrease in the magnetization of the RMNPs, respectively.

Uricase-free on-demand colorimetric biosensing of uric acid enabled by integrated CoP nanosheet arrays as a monolithic peroxidase mimic.

PubMed

He, Yanfang; Qi, Fei; Niu, Xiangheng; Zhang, Wenchi; Zhang, Xifeng; Pan, Jianming

2018-08-27

In clinical diagnosis, monitoring of uric acid (UA) is generally realized by combining uricase with natural peroxidase. The use of bio-enzymes, however, shadows some highlights of these methods due to their vulnerable activities against environments. Herein, we report a novel biosensor for the natural enzyme-free colorimetric detection of UA by using CoP nanosheet arrays grown on Ni foam (NF) as a monolithic peroxidase mimic. The integrated nanozyme can be put into and taken out from reaction systems conveniently with only tweezers, making it possible for on-demand analysis. As demonstrated, the obtained CoP/NF exhibits outstanding peroxidase-like activity to trigger the oxidation reaction of colorless 3,3'5,5'-tetramethylbenzidine (TMB) to a blue product (TMBox) mediated by H 2 O 2 . It is found that the blue TMBox can be reduced to colorless TMB again by UA selectively, thus the presence of UA in solutions will suppress the color reaction of TMB. Based on this principle, an uricase-free biosensor is developed for the photometric determination of UA, providing a wide detection range of 1-200 μM and a limit of detection down to 1.0 μM. In addition, the fabricated biosensor can be applied for measuring UA in clinical samples with merits of simple operation and good reliability, exhibiting its great promise in clinical diagnosis. Copyright © 2018 Elsevier B.V. All rights reserved.

Triple-helix molecular switch-based aptasensors and DNA sensors.

PubMed

Bagheri, Elnaz; Abnous, Khalil; Alibolandi, Mona; Ramezani, Mohammad; Taghdisi, Seyed Mohammad

2018-07-15

Utilization of traditional analytical techniques is limited because they are generally time-consuming and require high consumption of reagents, complicated sample preparation and expensive equipment. Therefore, it is of great interest to achieve sensitive, rapid and simple detection methods. It is believed that nucleic acids assays, especially aptamers, are very important in modern life sciences for target detection and biological analysis. Aptamers and DNA-based sensors have been widely used for the design of various sensors owing to their unique features. In recent years, triple-helix molecular switch (THMS)-based aptasensors and DNA sensors have been broadly utilized for the detection and analysis of different targets. The THMS relies on the formation of DNA triplex via Watson-Crick and Hoogsteen base pairings under optimal conditions. This review focuses on recent progresses in the development and applications of electrochemical, colorimetric, fluorescence and SERS aptasensors and DNA sensors, which are based on THMS. Also, the advantages and drawbacks of these methods are discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Paper-based Platform for Urinary Creatinine Detection.

PubMed

Sittiwong, Jarinya; Unob, Fuangfa

2016-01-01

A new paper platform was developed for the colorimetric detection of creatinine. The filter paper was coated with 3-propylsulfonic acid trimethoxysilane and used as the platform. Creatinine in a cationic form was extracted onto the paper via an ion-exchange mechanism and detected through the Jaffé reaction, resulting in a yellow-orange color complex. The color change on the paper could be observed visually, and the quantitative detection of creatinine was achieved through monitoring the color intensity change. The color intensity of creatinine complexes on the paper platform as a function of the creatinine concentration provided a linear range for creatinine detection in the range of 10 - 60 mg L(-1) and a detection limit of 4.2 mg L(-1). The accuracy of the proposed paper-based method was comparable to the conventional standard Jaffé method. This paper platform could be applied for simple and rapid detection of creatinine in human urine samples with a low consumption of reagent.

A hyperspectral imaging system for the evaluation of the human iris spectral reflectance

NASA Astrophysics Data System (ADS)

Di Cecilia, Luca; Marazzi, Francesco; Rovati, Luigi

2017-02-01

According to previous studies, the measurement of the human iris pigmentation can be exploited to detect certain eye pathological conditions in their early stage. In this paper, we propose an instrument and a method to perform hyperspectral quantitative measurements of the iris spectral reflectance. The system is based on a simple imaging setup, which includes a monochrome camera mounted on a standard ophthalmic microscope movement controller, a monochromator, and a flashing LED-based slit lamp. To assure quantitative measurements, the system is properly calibrated against a NIST reflectance standard. Iris reflectance images can be obtained in the spectral range 495-795 nm with a resolution of 25 nm. Each image consists of 1280 x 1024 pixels having a spatial resolution of 18 μm. Reflectance spectra can be calculated both from discrete areas of the iris and as the average of the whole iris surface. Preliminary results suggest that hyperspectral imaging of the iris can provide much more morphological and spectral information with respect to conventional qualitative colorimetric methods.

Poly(acrylic acid)-templated silver nanoclusters as a platform for dual fluorometric turn-on and colorimetric detection of mercury (II) ions.

PubMed

Tao, Yu; Lin, Youhui; Huang, Zhenzhen; Ren, Jinsong; Qu, Xiaogang

2012-01-15

An easy prepared fluorescence turn-on and colorimetric dual channel probe was developed for rapid assay of Hg(2+) ions with high sensitivity and selectivity by using poly(acrylic acid)-templated silver nanoclusters (PAA-AgNCs). The PAA-AgNCs exhibited weak fluorescence, while upon the addition of Hg(2+) ions, AgNCs gives a dramatic increase in fluorescence as a result of the changes of the AgNCs states. The detection limit was estimated to be 2 nM, which is much lower than the Hg(2+) detection requirement for drinking water of U.S. Environmental Protection Agency, and the turn-on sensing mode offers additional advantage to efficiently reduce background noise. Also, a colorimetric assay of Hg(2+) ions can be realized due to the observed absorbance changes of the AgNCs. More importantly, the method was successfully applied to the determination of Hg(2+) ions in real water samples, which suggests our proposed method has a great potential of application in environmental monitoring. Copyright © 2011 Elsevier B.V. All rights reserved.

Improving colorimetric assays through protein enzyme-assisted gold nanoparticle amplification.

PubMed

Xie, Xiaoji; Xu, Wei; Liu, Xiaogang

2012-09-18

The discovery of the DNA-mediated assembly of gold nanoparticles was a great moment in the history of science; this understanding and chemical control enabled the rational design of functional nanomaterials as novel probes in biodetection. In contrast with conventional probes such as organic dyes, gold nanoparticles exhibit high photostability and unique size-dependent optical properties. Because of their high extinction coefficients and strong distance dependent optical properties, these nanoparticles have emerged over the past decade as a promising platform for rapid, highly sensitive colorimetric assays that allow for the visual detection of low concentrations of metal ions, small molecules, and biomacromolecules. These discoveries have deepened our knowledge of biological phenomena and facilitated the development of many new diagnostic and therapeutic tools. Despite these many advances and continued research efforts, current nanoparticle-based colorimetric detection systems still suffer from several drawbacks, such as limited sensitivity and selectivity. This Account describes the recent development of colorimetric assays based on protein enzyme-assisted gold nanoparticle amplification. The benefits of such detection systems include significantly improved detection sensitivity and selectivity. First, we discuss the general design of enzyme-modified nanoparticle systems in colorimetric assays. We show that a quantitative understanding of the unique properties of different enzymes is paramount for effective biological assays. We then examine the assays for nucleic acid detection based on different types of enzymes, including endonucleases, ligases, and polymerases. For each of these assays, we identify the underlying principles that contribute to the enhanced detection capability of nanoparticle systems and illustrate them with selected examples. Furthermore, we demonstrate that the combination of gold nanoparticles and specific enzymes can probe enzyme dynamics and function with high specificity, offering substantial advantages in both sensitivity and specificity over conventional detection methods. The screening of nuclease, methyltransferase, protease, and kinase activities can be colorimetrically performed in a straightforward manner. Finally, we discuss examples of colorimetric assays for metal ions and small molecules that constitute important advances toward visual monitoring of enzyme catalytic functions and gene expression. Although these enzyme-assisted assay methods hold great promise for myriad applications in biomedicine and bioimaging, the application of the described techniques in vivo faces formidable challenges. In addition, researchers do not fully understand the interactions of gold nanoparticles with enzyme molecules. This understanding will require the development of new techniques to probe enzyme substrate dynamics at the particle interface with higher spatial resolution and chemical specificity.

Ultrasensitive colorimetric immunoassay for hCG detection based on dual catalysis of Au@Pt core-shell nanoparticle functionalized by horseradish peroxidase

NASA Astrophysics Data System (ADS)

Wang, Weiguo; Zou, Yake; Yan, Jinwu; Liu, Jing; Chen, Huixiong; Li, Shan; Zhang, Lei

2018-03-01

In this paper, an ultrasensitive colorimetric biosensor for human chorionic gonadotrophin (hCG) detection was designed from bottom-up method based on the dual catalysis of the horseradish peroxidase (HRP) and Au@Pt nanoparticles (NPs) relative to H2O2-TEM system. HRP and monoclonal mouse anti-hCG antibody (β-submit, mAb1) were co-immobilized onto the Au@Pt NP surface to improve catalytic efficiency and specificity, which formed a dual functionalized Au@Pt-HRP probe with the mean size of 42.8 nm (D50). The colorimetric immunoassay was developed for the hCG detection, and the Au@Pt-HRP probe featured a higher sensitivity in the concentration range of 0.4-12.8 IU L- 1 with a low limit of detection (LOD) of 0.1 IU L- 1 compared with the LODs of 0.8 IU L- 1 for BA-ELISA and of 2.0 IU L- 1 for Au@Pt, which indicated that the Au@Pt-HRP probe possessed higher catalytic efficiency with 2.8-fold increase over Au@Pt and 33.8-fold increase over HRP. Also, the Au@Pt-HRP probe exhibited good precision and reproducibility, high specificity and acceptable accuracy with CV being less than 15%. The dual functionalized Au@Pt-HRP probe as a type of signal amplified method was firstly applied in the colorimetric immunoassay for the hCG detection.

Optical and Electrochemical Aptasensors for Sensitive Detection of Streptomycin in Blood Serum and Milk.

PubMed

Ramezani, Mohammad; Abnous, Khalil; Taghdisi, Seyed Mohammad

2017-01-01

Detection and quantitation of antibiotic residues in blood serum and foodstuffs are in great demand. We have developed aptasensors for detection of streptomycin using electrochemical and optical methods. In the first method, an electrochemical aptasensor was developed for sensitive and selective detection of streptomycin, based on combination of exonuclease I (Exo I), complementary strand of aptamer (CS), arch shaped structure of aptamer (Apt)-CS conjugate, and gold electrode. The designed electrochemical aptasensor exhibited high selectivity toward streptomycin with a limit of detection (LOD) as low as 11.4 nM. Moreover, the developed electrochemical aptasensor was successfully used to detect streptomycin in milk and serum with LODs of 14.1 and 15.3 nM, respectively. In the second method, fluorescence quenching and colorimetric aptasensors were designed for detection of streptomycin based on aqueous gold nanoparticles (AuNPs) and double-stranded DNA (dsDNA). In the absence of streptomycin, aptamer/FAM-labeled complementary strand dsDNA is stable, resulting in the aggregation of AuNPs by salt bridge and an obvious color change from red to blue and strong emission of fluorescence. The colorimetric and fluorescence quenching aptasensors showed excellent selectivity toward streptomycin with limit of detections as low as 73.1 and 47.6 nM, respectively. The presented aptasensors were successfully used to detect streptomycin in milk and serum. For serum, LODs were determined to be 58.2 and 102.4 nM for fluorescence quenching and colorimetric aptasensors, respectively. For milk, LODs were calculated to be 56.2 and 108.7 nM for fluorescence quenching and colorimetric aptasensors, respectively.

Dual-responsive immunosensor that combines colorimetric recognition and electrochemical response for ultrasensitive detection of cancer biomarkers.

PubMed

Hong, Wooyoung; Lee, Sooyeon; Cho, Youngnam

2016-12-15

We developed a nanoroughened, biotin-doped polypyrrole immunosensor for the detection of tumor markers through dual-signal (electrochemical and colorimetric) channels, electrochemical and colorimetric, that demonstrates remarkable analytical performance. A rapid, one-step electric field-mediated method was employed to fabricate the immunosensor with nanoscale roughness by simply modulating the applied electrical potential. We demonstrated the successful detection of three tumor markers (CA125, CEA, and PSA) via the double enzymatic signal amplifications in the presence of a target antigen, ultimately leading to desired diagnostic accuracy and reliability. The addition of multiple horseradish peroxidase (HRP)- and antibody-labeled nanoparticles greatly amplified the signal and simplified the measurement of cancer biomarker proteins by sequentially magnifying electrochemical and colorimetric signals in a single platform. The two parallel assays performed using the proposed immunosensor have yielded highly consistent and reproducible results. Additionally, for the analysis of plasma samples in a clinical setting, the values obtained with our immunosensor were validated by correlating the results with those of a standard radioimmunoassay (RIA), which obtained very similar clinically valid responses. Copyright © 2016 Elsevier B.V. All rights reserved.

CHEMICAL METHODS FOR THE DETERMINATION OF BORON IN REACTOR MATERIALS. PART I. ION-EXCHANGE SEPARATION OF BORON FROM COKES, PITCHES AND GRAPHITES AND ITS COLORIMETRIC DETERMINATION BY THE CURCUMIN-TRI-CHLORACETIC ACID METHOD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desai, H.B.; Desai, S.R.; Nadkarni, M.N.

1961-01-01

A procedure has been standardized for the determination of boron in cokes, pitches, and graphites. The method consists of fixing the boron present in the sample as calcium borate, ion-exchange separation of boric acid from the associated cations, and the colorimetric determination of boron using the curcumin-trichloracetic acid method. Sulfur which is usually present in pitches and cokes is expected to be oxidized to sulfate during the fixation of boron and hence its effect on the colorimetry has been studied. Application of the procedure to the determination of 0.50 and 1.00 microgram amounts of boron, has given coefficients of variationmore » of l0.0 and 6.7% respectively. (auth)« less

Evaluation of a colorimetric reagent strip assay for urine specific gravity.

PubMed

Kirschbaum, B B

1983-06-01

N-Multistix SG provides a convenient colorimetric assay for the determination of the specific gravity (sp. gr.) of freshly voided urine. When compared with results obtained by standard hydrometry, the colorimetric assay sp. gr. was observed to decrease by as much as 0.010 units as urine pH increased from 5 to 7. Moderate levels of proteinuria that did not alter hydrometer readings effectively raised the colorimetric sp. gr. by 0.005-0.010 units. The colorimetric assay was almost completely insensitive to clinically encountered concentrations of glucose and urea but responded appropriately to monovalent salts. The magnitude of these observed discrepancies places serious limitations on the value of the colorimetric sp. gr. measurement.

Pitfalls in the detection of cholesterol in Huntington’s disease models

PubMed Central

Marullo, Manuela; Valenza, Marta; Leoni, Valerio; Caccia, Claudio; Scarlatti, Chiara; De Mario, Agnese; Zuccato, Chiara; Di Donato, Stefano; Carafoli, Ernesto; Cattaneo, Elena

2012-01-01

Background Abnormalities in brain cholesterol homeostasis have been reported in Huntington’s disease (HD), an adult-onset neurodegenerative disorder caused by an expansion in the number of CAG repeats in the huntingtin (HTT) gene. However, the results have been contradictory with respect to whether cholesterol levels increase or decrease in HD models. Biochemical and mass spectrometry methods show reduced levels of cholesterol precursors and cholesterol in HD cells and in the brains of several HD animal models. Abnormal brain cholesterol homeostasis was also inferred from studies in HD patients. In contrast, colorimetric and enzymatic methods indicate cholesterol accumulation in HD cells and tissues. Here we used several methods to investigate cholesterol levels in cultured cells in the presence or absence of mutant HTT protein. Results Colorimetric and enzymatic methods with low sensitivity gave variable results, whereas results from a sensitive analytical method, gas chromatography-mass spectrometry, were more reliable. Sample preparation, high cell density and cell clonality also influenced the detection of intracellular cholesterol. Conclusions Detection of cholesterol in HD samples by colorimetric and enzymatic assays should be supplemented by detection using more sensitive analytical methods. Care must be taken to prepare the sample appropriately. By evaluating lathosterol levels using isotopic dilution mass spectrometry, we confirmed reduced cholesterol biosynthesis in knock-in cells expressing the polyQ mutation in a constitutive or inducible manner. *Correspondence should be addressed to Elena Cattaneo: elena.cattaneo@unimi.it PMID:23145355

Colorimetric protein determination in microalgae (Chlorophyta): association of milling and SDS treatment for total protein extraction.

PubMed

Mota, Maria Fernanda S; Souza, Marcella F; Bon, Elba P S; Rodrigues, Marcoaurelio A; Freitas, Suely Pereira

2018-05-24

The use of colorimetric methods for protein quantification in microalgae is hindered by their elevated amounts of membrane-embedded intracellular proteins. In this work, the protein content of three species of microalgae was determined by the Lowry method after the cells were dried, ball-milled, and treated with the detergent sodium dodecyl sulfate (SDS). Results demonstrated that the association of milling and SDS treatment resulted in a 3- to 7-fold increase in protein quantification. Milling promoted microalgal disaggregation and cell wall disruption enabling access of the SDS detergent to the microalgal intracellular membrane proteins and their efficient solubilization and quantification. © 2018 Phycological Society of America.

Removal of interfering nucleotides from brain extracts containing substance p. Effect of drugs on brain concentrations of substance p

PubMed Central

Laszlo, I.

1963-01-01

Several methods for removing interfering nucleotides, adenosine-5'-monophosphate and adenosine 5'-triphosphate from brain extracts have been studied. An enzymic method, using adenylic acid deaminase, has been found suitable. This deaminates adenosine monophosphate to 5'-inosinic acid, an inactive compound which does not influence the estimations of substance P. Owing to the adenosine triphosphatase content of the enzyme extract, adenosine triphosphate was also inactivated. For the estimation of adenosine monophosphate-deaminase activity, a simple colorimetric method is described which measures the ammonia liberated from adenosine monophosphate. Substance P in mouse brain extracts was estimated after treatment of the animals with various drugs, and after the enzymic removal of interfering nucleotides from the brain extracts. The drugs had no effect on the substance P content of mouse brain. The effect of drugs on the contractions of the guinea-pig ileum induced by substance P was also investigated, and the effect of drugs on the estimations of substance P in brain extracts is discussed. PMID:14066136

Plasmon-Based Colorimetric Nanosensors for Ultrasensitive Molecular Diagnostics.

PubMed

Tang, Longhua; Li, Jinghong

2017-07-28

Colorimetric detection of target analytes with high specificity and sensitivity is of fundamental importance to clinical and personalized point-of-care diagnostics. Because of their extraordinary optical properties, plasmonic nanomaterials have been introduced into colorimetric sensing systems, which provide significantly improved sensitivity in various biosensing applications. Here we review the recent progress on these plasmonic nanoparticles-based colorimetric nanosensors for ultrasensitive molecular diagnostics. According to their different colorimetric signal generation mechanisms, these plasmonic nanosensors are classified into two categories: (1) interparticle distance-dependent colorimetric assay based on target-induced forming cross-linking assembly/aggregate of plasmonic nanoparticles; and (2) size/morphology-dependent colorimetric assay by target-controlled growth/etching of the plasmonic nanoparticles. The sensing fundamentals and cutting-edge applications will be provided for each of them, particularly focusing on signal generation and/or amplification mechanisms that realize ultrasensitive molecular detection. Finally, we also discuss the challenge and give our future perspective in this emerging field.

Bio-inspired colorimetric film based on hygroscopic coloration of longhorn beetles (Tmesisternus isabellae)

PubMed Central

Seo, Han-bok; Lee, Seung-Yop

2017-01-01

Structure-dependent colour is caused by the interaction of light with photonic crystal structures rather than pigments. The elytra of longhorn beetles Tmesisternus isabellae appear to be iridescent green in a dry state and turn to red when exposed to humidity. Based on the hygroscopic colouration of the longhorn beetle, we have developed centimeter-scale colorimetric opal films using a novel self-assembly method. The micro-channel assisted assembly technique adopts both natural evaporation and rotational forced drying, enhancing the surface binding of silica particles and the packing density by reducing the lattice constant and structural defects. The fabricated large-scale photonic film changes its structural colour from green to red when exposed to water vapour, similarly to the colorimetric feature of the longhorn beetle. The humidity-dependent colour change of the opal film is shown to be reversible and durable over five-hundred cycles of wetting and drying. PMID:28322307

Bio-inspired colorimetric film based on hygroscopic coloration of longhorn beetles (Tmesisternus isabellae)

NASA Astrophysics Data System (ADS)

Seo, Han-Bok; Lee, Seung-Yop

2017-03-01

Structure-dependent colour is caused by the interaction of light with photonic crystal structures rather than pigments. The elytra of longhorn beetles Tmesisternus isabellae appear to be iridescent green in a dry state and turn to red when exposed to humidity. Based on the hygroscopic colouration of the longhorn beetle, we have developed centimeter-scale colorimetric opal films using a novel self-assembly method. The micro-channel assisted assembly technique adopts both natural evaporation and rotational forced drying, enhancing the surface binding of silica particles and the packing density by reducing the lattice constant and structural defects. The fabricated large-scale photonic film changes its structural colour from green to red when exposed to water vapour, similarly to the colorimetric feature of the longhorn beetle. The humidity-dependent colour change of the opal film is shown to be reversible and durable over five-hundred cycles of wetting and drying.

GAMMA AND X-RAY DOSIMETER AND DOSIMETRIC METHOD

DOEpatents

Taplin, G.V.; Douglas, C.H.; Sigoloff, S.C.

1958-08-19

An improvement in colorimetric gamma and x-ray dosimeter systems and a self-contained. hand carried dostmeter of the afore-mentioned type ts described. A novel point of the invention ltes in the addition of specific quantities of certain normalizing agents to the two phase chlorinated hydro-carbon-aqueous dyc colortmetric dosimeter to eliminate the after reaction and thereby extend the utility of such systein. The structure of the two phase colorimetric dosimeter tubes and the carrying case for the tubes of the portable dosimeter are unique features.

A rapid, straightforward, and print house compatible mass fabrication method for integrating 3D paper-based microfluidics.

PubMed

Xiao, Liangpin; Liu, Xianming; Zhong, Runtao; Zhang, Kaiqing; Zhang, Xiaodi; Zhou, Xiaomian; Lin, Bingcheng; Du, Yuguang

2013-11-01

Three-dimensional (3D) paper-based microfluidics, which is featured with high performance and speedy determination, promise to carry out multistep sample pretreatment and orderly chemical reaction, which have been used for medical diagnosis, cell culture, environment determination, and so on with broad market prospect. However, there are some drawbacks in the existing fabrication methods for 3D paper-based microfluidics, such as, cumbersome and time-consuming device assembly; expensive and difficult process for manufacture; contamination caused by organic reagents from their fabrication process. Here, we present a simple printing-bookbinding method for mass fabricating 3D paper-based microfluidics. This approach involves two main steps: (i) wax-printing, (ii) bookbinding. We tested the delivery capability, diffusion rate, homogeneity and demonstrated the applicability of the device to chemical analysis by nitrite colorimetric assays. The described method is rapid (<30 s), cheap, easy to manipulate, and compatible with the flat stitching method that is common in a print house, making itself an ideal scheme for large-scale production of 3D paper-based microfluidics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of Colorimetric Methods Using Nicotinamide for Rapid Detection of Pyrazinamide Resistance in Mycobacterium tuberculosis▿

PubMed Central

Mirabal, Niuris C.; Yzquierdo, Sergio L.; Lemus, Dihadenys; Madruga, Mariela; Milián, Yoslaine; Echemendía, Miguel; Takiff, Howard; Martin, Anandi; Van der Stuyf, Patrick; Palomino, Juan Carlos; Montoro, Ernesto

2010-01-01

The direct detection of pyrazinamide resistance in Mycobacterium tuberculosis is sufficiently difficult that many laboratories do not attempt it. Most pyrazinamide resistance is caused by mutations that inactivate the pyrazinamidase enzyme needed to convert the prodrug pyrazinamide to its active form. We evaluated two newer and simpler methods to assess pyrazinamidase activity, the nitrate reductase and malachite green microtube assays, using nicotinamide in place of pyrazinamide. A total of 102 strains were tested by these methods and the results compared with those obtained by the classic Wayne assay. Mutations in the pncA gene were identified by sequencing the pncA genes from all isolates in which pyrazinamide resistance was detected by any of the three methods. Both the nitrate reductase and malachite green microtube assays showed sensitivities of 93.75% and specificities of 97.67%. Mutations in the pncA gene were found in 14 of 16 strains that were pyrazinamide resistant and in 1 of 4 strains that were sensitive by the Wayne assay. Both of these simple methods, used with nicotinamide, are promising and inexpensive alternatives for the rapid detection of pyrazinamide resistance in limited-resource countries. PMID:20554826

Considerations for point-of-care diagnostics: evaluation of acridine orange staining and postprocessing methods for a three-part leukocyte differential test

NASA Astrophysics Data System (ADS)

Powless, Amy J.; Conley, Roxanna J.; Freeman, Karan A.; Muldoon, Timothy J.

2017-03-01

There exists a broad range of techniques that can be used to classify and count white blood cells in a point-of-care (POC) three-part leukocyte differential test. Improvements in lenses, light sources, and cameras for image-based POC systems have renewed interest in acridine orange (AO) as a contrast agent, whereby subpopulations of leukocytes can be differentiated by colorimetric analysis of AO fluorescence emission. We evaluated the effect on test accuracy using different AO staining and postprocessing methods in the context of an image-based POC colorimetric cell classification scheme. Thirty blood specimens were measured for percent cell counts using our POC system and a conventional hematology analyzer for comparison. Controlling the AO concentration used during whole-blood staining, the incubation time with AO, and the colorimetric ratios among the three population of leukocytes yielded a percent deviation of 0.706%, -1.534%, and -0.645% for the lymphocytes, monocytes, and granulocytes, respectively. Overall, we demonstrated that a redshift in AO fluorescence was observed at elevated AO concentrations, which lead to reproducible inaccuracy of cell counts. This study demonstrates there is a need for a strict control of the AO staining and postprocessing methods to improve test accuracy in these POC systems.

Spectrophotometric determination of some anti-tussive and anti-spasmodic drugs through ion-pair complex formation with thiocyanate and cobalt(II) or molybdenum(V)

NASA Astrophysics Data System (ADS)

El-Shiekh, Ragaa; Zahran, Faten; El-Fetouh Gouda, Ayman Abou

2007-04-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of anti-tussive drugs, e.g., dextromethorphan hydrobromide (DEX) and pipazethate hydrochloride (PiCl) and anti-spasmodic drugs, e.g., drotaverine hydrochloride (DvCl) and trimebutine maleate (TM) in bulk and in their pharmaceutical formulations. The proposed methods depend upon the reaction of cobalt(II)-thiocyanate (method A) and molybdenum(V)-thiocyanate ions (method B) with the cited drugs to form stable ion-pair complexes which extractable with an n-butnol-dichloromethane solvent mixture (3.5:6.5) and methylene chloride for methods A and B, respectively. The blue and orange red color complexes are determined either colorimetrically at λmax 625 nm (using method A) and 467 or 470 nm for (DEX and PiCl) or (DvCl and TM), respectively (using method B). The concentration range is 20-400 and 2.5-50 μg mL -1 for methods A and B, respectively. The proposed method was successfully applied for the determination of the studied drugs in pure and in pharmaceutical formulations applying the standard additions technique and the results obtained in good agreement well with those obtained by the official method.

A simple colorimetric chemosensor bearing a carboxylic acid group with high selectivity for CN-

NASA Astrophysics Data System (ADS)

Park, Gyeong Jin; Choi, Ye Won; Lee, Dongkuk; Kim, Cheal

2014-11-01

A new simple ‘naked eye' chemosensor 1 (sodium (E)-2-((2-(3-hydroxy-2-naphthoyl)hydrazono)methyl)benzoate) has been synthesized for detection of CN- in a mixture of DMF/H2O (9:1). The sensor 1 comprises of a naphthoic hydrazide as efficient hydrogen bonding donor group and a benzoic acid as the moiety with the water solubility. The receptor 1 showed high selectivity toward cyanide ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to yellow for CN- over other anions. Therefore, receptor 1 could be useful for cyanide detection in aqueous environment, displaying a high distinguishable selectivity from hydrogen bonded anions and being clearly visible to the naked eye.

Novel colorimetric method overcoming phosphorus interference during trace arsenic analysis in soil solution.

PubMed

Makris, Konstantinos C; Punamiya, Pravin; Sarkar, Dibyendu; Datta, Rupali

2008-02-01

A sensitive (method detection limit, 2.0 microg As L(-1)) colorimetric determination of trace As(v) and As(iii) concentrations in the presence of soluble phosphorus (P) concentrations in soil/water extracts is presented. The proposed method modifies the malachite green method (MG) originally developed for P in soil and water. Our method relies upon the finding that As(iii) and As(v) do not develop the green color during P analysis using the MG method. When an optimum concentration of ascorbic acid (AA) is added to a sample containing up to 15 times P > As (microM) concentrations, the final sample absorbance due to P will be equal to that of As(v) molecules. The soluble As concentration can then be quantified by the concentration difference between the mixed oxyanion (As + P) absorbance (proposed method) and the MG method absorbance that measures only P. Our method is miniaturized using a 96-well microplate UV-VIS reader that utilizes minute reagent and sample volumes (120 and 200 microL sample(-1), respectively), thus, minimizing waste and offering flexibility in the field. Our method was tested in a suite of As-contaminated soils that successfully measured both As and P in soil water extracts and total digests. Mean% As recoveries ranged between 84 and 117%, corroborating data obtained with high-resolution inductively-coupled plasma mass-spectrometry. The performance of the proposed colorimetric As method was unaffected by the presence of Cu, Zn, Pb, Ni, Fe, Al, Si, and Cr in both neutral and highly-acidic (ca. pH 2) soil extracts. Data from this study provide the proof of concept towards creating a field-deployable, portable As kit.

Programming function into mechanical forms by directed assembly of silk bulk materials

PubMed Central

Patel, Nereus; Duggan, Thomas; Perotto, Giovanni; Shirman, Elijah; Li, Chunmei; Kaplan, David L.; Omenetto, Fiorenzo G.

2017-01-01

We report simple, water-based fabrication methods based on protein self-assembly to generate 3D silk fibroin bulk materials that can be easily hybridized with water-soluble molecules to obtain multiple solid formats with predesigned functions. Controlling self-assembly leads to robust, machinable formats that exhibit thermoplastic behavior consenting material reshaping at the nanoscale, microscale, and macroscale. We illustrate the versatility of the approach by realizing demonstrator devices where large silk monoliths can be generated, polished, and reshaped into functional mechanical components that can be nanopatterned, embed optical function, heated on demand in response to infrared light, or can visualize mechanical failure through colorimetric chemistries embedded in the assembled (bulk) protein matrix. Finally, we show an enzyme-loaded solid mechanical part, illustrating the ability to incorporate biological function within the bulk material with possible utility for sustained release in robust, programmably shapeable mechanical formats. PMID:28028213

A simple and sensitive immunoassay for the determination of human chorionic gonadotropin by graphene-based chemiluminescence resonance energy transfer.

PubMed

Lei, Jiuqian; Jing, Tao; Zhou, Tingting; Zhou, Yusun; Wu, Wei; Mei, Surong; Zhou, Yikai

2014-04-15

In this study, we report a strategy of chemiluminescence resonance energy transfer (CRET) using graphene as an efficient long-range energy acceptor. Magnetic nanoparticles were also used in CRET for simple magnetic separation and immobilization of horseradish peroxidase (HRP)-labeled anti-HCG antibody. In the design of CRET system, the sandwich-type immunocomplex was formed between human chorionic gonadotropin (HCG, antigen) and two different antibodies bridged the magnetic nanoparticles and graphene (acceptors), which led to the occurrence of CRET from chemiluminescence light source to graphene. After optimizing the experimental conditions, the quenching of chemiluminescence signal depended linearly on the concentration of HCG in the range of 0.1 mIU mL(-1)-10 mIU mL(-1) and the detection limit was 0.06 mIU mL(-1). The proposed method was successfully applied for the determination of HCG levels in saliva and serum samples, and the results were in good agreement with the plate ELISA with colorimetric detection. It could also be developed for detection of other antigen-antibody immune complexes by using the corresponding antigens and respective antibodies. © 2013 Published by Elsevier B.V.

Biomarker detection for disease diagnosis using cost-effective microfluidic platforms.

PubMed

Sanjay, Sharma T; Fu, Guanglei; Dou, Maowei; Xu, Feng; Liu, Rutao; Qi, Hao; Li, XiuJun

2015-11-07

Early and timely detection of disease biomarkers can prevent the spread of infectious diseases, and drastically decrease the death rate of people suffering from different diseases such as cancer and infectious diseases. Because conventional diagnostic methods have limited application in low-resource settings due to the use of bulky and expensive instrumentation, simple and low-cost point-of-care diagnostic devices for timely and early biomarker diagnosis is the need of the hour, especially in rural areas and developing nations. The microfluidics technology possesses remarkable features for simple, low-cost, and rapid disease diagnosis. There have been significant advances in the development of microfluidic platforms for biomarker detection of diseases. This article reviews recent advances in biomarker detection using cost-effective microfluidic devices for disease diagnosis, with the emphasis on infectious disease and cancer diagnosis in low-resource settings. This review first introduces different microfluidic platforms (e.g. polymer and paper-based microfluidics) used for disease diagnosis, with a brief description of their common fabrication techniques. Then, it highlights various detection strategies for disease biomarker detection using microfluidic platforms, including colorimetric, fluorescence, chemiluminescence, electrochemiluminescence (ECL), and electrochemical detection. Finally, it discusses the current limitations of microfluidic devices for disease biomarker detection and future prospects.

Evaluating an alternative method for rapid urinary creatinine determination

EPA Science Inventory

Creatinine (CR) is an endogenously-produced chemical routinely assayed in urine specimens to assess kidney function, sample dilution. The industry-standard method for CR determination, known as the kinetic Jaffe (KJ) method, relies on an exponential rate of a colorimetric change,...

Biochip Which Examines Hepatic Function by Employing Colorimetric Method

NASA Astrophysics Data System (ADS)

Oki, Akio; Ogawa, Hiroki; Takamura, Yuzuru; Horiike, Yasuhiro

2003-03-01

A biochip that is able to quickly analyze hepatic function from the bedside or at home was investigated. The chip essentially consisted of two chips, one that mixed the substrate buffer solution with serums using a centrifugal method and a chip that measured the amounts of γ-glutamyltranspeptidase (γ-GTP), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in the serums employing a colorimetric method. The chip should be inexpensive and disposable. Therefore the mixing and measurement channels were fabricated by molding their reverse patterns onto a poly (ethylene terephthalate) (PET) plate. Furthermore, a hydrophobic treatment was performed on the inner wall of the measurement channel to efficiently propagate the light efficiently in the channel. Subsequently, calibration curves were obtained for γ-GTP, GOT and GPT activity levels based on an endpoint method for the γ-GTP and a rate assay for GOT and GPT.

Colorimetric sensor for cysteine in human urine based on novel gold nanoparticles.

PubMed

Zhang, Yan; Jiang, Jingjing; Li, Min; Gao, Pengfei; Zhou, Ying; Zhang, Guomei; Shuang, Shaomin; Dong, Chuan

2016-12-01

Herein, a novel, high sensitive, and specific colorimetric sensor for cysteine (Cys) based on pectinase protected gold nanoparticles (P@AuNPs) has been demonstrated for the first time. The P@AuNPs were synthesized by "MW-assisted heat method" and were characterized by UV-vis, TEM, FT-IR and zeta potential techniques. Cys could cause the aggregation of P@AuNPs due to formation of the strong covalent Au-S bond and electrostatic binding. As the Cys concentration increased, the color of the solutions gradually changed from wine-red to blue as well as the large absorption band shifted from 523 to 650nm upon P@AuNPs aggregation. In addition, various experimental parameters such as pH, the amount of P@AuNPs and incubation time were investigated for the optimum sensing conditions. The concentration of Cys could be determined by monitoring with the naked eye or a UV-vis spectrometer. The proposed colorimetric sensor showed an extreme selectivity toward the determination of Cys in the presence of 20-fold all other different interferents. Under optimum conditions, this method exhibited two good linear ranges from 4.85×10 -9 to 3.02×10 -4 M (R 2 =0.996) and 3.25×10 -3 to 1.03×10 -2 M (R 2 =0.999), with a low detection limit of 4.6×10 -9 M. Moreover, this colorimetric sensor was successfully applied to the detection of Cys in human urine samples, demonstrating its great value for practical application in biological systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of a novel colorimetric sensor based on alginate beads for monitoring rainbow trout spoilage.

PubMed

Majdinasab, Marjan; Hosseini, Seyed Mohammad Hashem; Sepidname, Marziyeh; Negahdarifar, Manizheh; Li, Peiwu

2018-05-01

Alginate is a non-toxic, renewable, and linear copolymer obtained from the brown algae Laminaria digitata that can be easily shaped into beads. Its good gel forming properties have made it useful for entrapping food and pharmaceutical ingredients. In this study, alginate beads were used in a novel application as a colorimetric sensor in food intelligent packaging. Colorimetric sensor was developed through entrapping red cabbage extract as a pH indicator in alginate beads. The pH indicator beads were used in rainbow trout packaging for monitoring fillets spoilage. Color change of beads during fish storage was measured using the CIELab method. The alginate bead colorimetric sensor is validated by measuring total volatile basic nitrogen (TVB-N) levels and microbial populations in fish samples. Moreover, peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were evaluated during storage. Results indicated that increasing the bacterial population during storage and production of proteolytic enzymes resulted in protein degradation, accumulation of volatile amine compounds, increase in the pH and finally color change of alginate beads. The values of TVB-N, pH, PV and TBARS increased with time of storage. The results of TVB-N and microbial growth were in accordance with color change of beads and CIELab data. Therefore, the proposed system enjoys a high sensitivity to pH variations and is capable of monitoring the spoilage of fish or other protein-rich products through its wide range of color changes. The alginate beads containing the red cabbage extract can, thus, be used as a low-cost colorimetric sensor for intelligent packaging applications.

Improved detection of chemical substances from colorimetric sensor data using probabilistic machine learning

NASA Astrophysics Data System (ADS)

Mølgaard, Lasse L.; Buus, Ole T.; Larsen, Jan; Babamoradi, Hamid; Thygesen, Ida L.; Laustsen, Milan; Munk, Jens Kristian; Dossi, Eleftheria; O'Keeffe, Caroline; Lässig, Lina; Tatlow, Sol; Sandström, Lars; Jakobsen, Mogens H.

2017-05-01

We present a data-driven machine learning approach to detect drug- and explosives-precursors using colorimetric sensor technology for air-sampling. The sensing technology has been developed in the context of the CRIM-TRACK project. At present a fully- integrated portable prototype for air sampling with disposable sensing chips and automated data acquisition has been developed. The prototype allows for fast, user-friendly sampling, which has made it possible to produce large datasets of colorimetric data for different target analytes in laboratory and simulated real-world application scenarios. To make use of the highly multi-variate data produced from the colorimetric chip a number of machine learning techniques are employed to provide reliable classification of target analytes from confounders found in the air streams. We demonstrate that a data-driven machine learning method using dimensionality reduction in combination with a probabilistic classifier makes it possible to produce informative features and a high detection rate of analytes. Furthermore, the probabilistic machine learning approach provides a means of automatically identifying unreliable measurements that could produce false predictions. The robustness of the colorimetric sensor has been evaluated in a series of experiments focusing on the amphetamine pre-cursor phenylacetone as well as the improvised explosives pre-cursor hydrogen peroxide. The analysis demonstrates that the system is able to detect analytes in clean air and mixed with substances that occur naturally in real-world sampling scenarios. The technology under development in CRIM-TRACK has the potential as an effective tool to control trafficking of illegal drugs, explosive detection, or in other law enforcement applications.

Discrimination of complex mixtures by a colorimetric sensor array: coffee aromas.

PubMed

Suslick, Benjamin A; Feng, Liang; Suslick, Kenneth S

2010-03-01

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 degrees C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures.

Discrimination of Complex Mixtures by a Colorimetric Sensor Array: Coffee Aromas

PubMed Central

Suslick, Benjamin A.; Feng, Liang; Suslick, Kenneth S.

2010-01-01

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 °C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures. PMID:20143838

Facial skin color measurement based on camera colorimetric characterization

NASA Astrophysics Data System (ADS)

Yang, Boquan; Zhou, Changhe; Wang, Shaoqing; Fan, Xin; Li, Chao

2016-10-01

The objective measurement of facial skin color and its variance is of great significance as much information can be obtained from it. In this paper, we developed a new skin color measurement procedure which includes following parts: first, a new skin tone color checker made of pantone Skin Tone Color Checker was designed for camera colorimetric characterization; second, the chromaticity of light source was estimated via a new scene illumination estimation method considering several previous algorithms; third, chromatic adaption was used to convert the input facial image into output facial image which appears taken under canonical light; finally the validity and accuracy of our method was verified by comparing the results obtained by our procedure with these by spectrophotometer.

Rapid screening method for male DNA by using the loop-mediated isothermal amplification assay.

PubMed

Kitamura, Masashi; Kubo, Seiji; Tanaka, Jin; Adachi, Tatsushi

2017-08-12

Screening for male-derived biological material from collected samples plays an important role in criminal investigations, especially those involving sexual assaults. We have developed a loop-mediated isothermal amplification (LAMP) assay targeting multi-repeat sequences of the Y chromosome for detecting male DNA. Successful amplification occurred with 0.5 ng of male DNA under isothermal conditions of 61 to 67 °C, but no amplification occurred with up to 10 ng of female DNA. Under the optimized conditions, the LAMP reaction initiated amplification within 10 min and amplified for 20 min. The LAMP reaction was sensitive at levels as low as 1-pg male DNA, and a quantitative LAMP assay could be developed because of the strong correlation between the reaction time and the amount of template DNA in the range of 10 pg to 10 ng. Furthermore, to apply the LAMP assay to on-site screening for male-derived samples, we evaluated a protocol using a simple DNA extraction method and a colorimetric intercalating dye that allows detection of the LAMP reaction by evaluating the change in color of the solution. Using this protocol, samples of male-derived blood and saliva stains were processed in approximately 30 min from DNA extraction to detection. Because our protocol does not require much hands-on time or special equipment, this LAMP assay promises to become a rapid and simple screening method for male-derived samples in forensic investigations.

A simple and inexpensive thermal optic nanosensor formed by triblock copolymer and polydiacetylene mixture.

PubMed

Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Hespanhol, Maria do Carmo; Rezende, Jaqueline de Paula; Pires, Ana Clarissa Dos Santos; Ortega, Paulo Fernando Ribeiro; da Silva, Luis Henrique Mendes

2018-02-15

Polydiacetylene (PDA) vesicles have been applied as optical sensors in different areas, although there are difficulties in controlling their responses. In this study, we prepared nanoblends of PDA with triblock copolymers (TC) as a better sensor system for detecting temperature change. The influences of diacetylene (DA) monomer, and the TC chemical structure and concentration on the colorimetric response (CR) were examined. The TC/PDA nanoblend was remarkably more sensitive to temperature change, than classical vesicles. A higher L64 concentration of 12.0% (w/w) reduced the chromatic transition temperature (T tr ) to as low as 24°C. When using different TCs, the T tr values can be ordered as L35

Colorimetric Sensor Array for White Wine Tasting.

PubMed

Chung, Soo; Park, Tu San; Park, Soo Hyun; Kim, Joon Yong; Park, Seongmin; Son, Daesik; Bae, Young Min; Cho, Seong In

2015-07-24

A colorimetric sensor array was developed to characterize and quantify the taste of white wines. A charge-coupled device (CCD) camera captured images of the sensor array from 23 different white wine samples, and the change in the R, G, B color components from the control were analyzed by principal component analysis. Additionally, high performance liquid chromatography (HPLC) was used to analyze the chemical components of each wine sample responsible for its taste. A two-dimensional score plot was created with 23 data points. It revealed clusters created from the same type of grape, and trends of sweetness, sourness, and astringency were mapped. An artificial neural network model was developed to predict the degree of sweetness, sourness, and astringency of the white wines. The coefficients of determination (R2) for the HPLC results and the sweetness, sourness, and astringency were 0.96, 0.95, and 0.83, respectively. This research could provide a simple and low-cost but sensitive taste prediction system, and, by helping consumer selection, will be able to have a positive effect on the wine industry.

Colorimetric Sensor Array for White Wine Tasting

PubMed Central

Chung, Soo; Park, Tu San; Park, Soo Hyun; Kim, Joon Yong; Park, Seongmin; Son, Daesik; Bae, Young Min; Cho, Seong In

2015-01-01

A colorimetric sensor array was developed to characterize and quantify the taste of white wines. A charge-coupled device (CCD) camera captured images of the sensor array from 23 different white wine samples, and the change in the R, G, B color components from the control were analyzed by principal component analysis. Additionally, high performance liquid chromatography (HPLC) was used to analyze the chemical components of each wine sample responsible for its taste. A two-dimensional score plot was created with 23 data points. It revealed clusters created from the same type of grape, and trends of sweetness, sourness, and astringency were mapped. An artificial neural network model was developed to predict the degree of sweetness, sourness, and astringency of the white wines. The coefficients of determination (R2) for the HPLC results and the sweetness, sourness, and astringency were 0.96, 0.95, and 0.83, respectively. This research could provide a simple and low-cost but sensitive taste prediction system, and, by helping consumer selection, will be able to have a positive effect on the wine industry. PMID:26213946

A colorimetric sensor array of porous pigments.

PubMed

Lim, Sung H; Kemling, Jonathan W; Feng, Liang; Suslick, Kenneth S

2009-12-01

The development of a low-cost, simple colorimetric sensor array capable of the detection and identification of toxic gases is reported. This technology uses a disposable printed array of porous pigments in which metalloporphyrins and chemically-responsive dyes are immobilized in a porous matrix of organically modified siloxanes (ormosils) and printed on a porous membrane. The printing of the ormosil into the membrane is highly uniform and does not lessen the porosity of the membrane, as shown by scanning electron microscopy. When exposed to an analyte, these pigments undergo reactions that result in well-defined color changes due to strong chemical interactions: ligation to metal ions, Lewis or Brønsted acid-base interactions, hydrogen bonding, etc. Striking visual identification of 3 toxic gases has been shown at the IDLH (immediately dangerous to life and health) concentration, at the PEL (permissible exposure level), and at a level well below the PEL. Identification and quantification of analytes were achieved using the color change profiles, which were readily distinguishable in a hierarchical clustering analysis (HCA) dendrogram, with no misclassifications in 50 trials.

A colorimetric sensor array of porous pigments

PubMed Central

Lim, Sung H.; Kemling, Jonathan W.; Feng, Liang

2010-01-01

The development of a low-cost, simple colorimetric sensor array capable of detection and identification of toxic gases is reported. This technology uses a disposable printed array of porous pigments in which metalloporphyrins and chemically responsive dyes are immobilized in a porous matrix of organically modified siloxanes (ormosils) and printed on a porous membrane. The printing of the ormosil into the membrane is highly uniform and does not lessen the porosity of the membrane, as shown by scanning electron microscopy. When exposed to an analyte, these pigments undergo reactions that result in well-defined color changes due to strong chemical interactions: ligation to metal ions, Lewis or Bronsted acid-base interactions, hydrogen bonding, etc. Striking visual identification of 3 toxic gases has been shown at the IDLH (immediately dangerous to life and health), at the PEL (permissible exposure level), and at a level well below the PEL. Identification and quantification of analytes were achieved using the color change profiles, which were readily distinguishable in a hierarchical clustering analysis (HCA) dendrogram, with no misclassifications in 50 trials. PMID:19918616

Colorimetric sensing of anions in water using ratiometric indicator-displacement assay.

PubMed

Feng, Liang; Li, Hui; Li, Xiao; Chen, Liang; Shen, Zheng; Guan, Yafeng

2012-09-19

The analysis of anions in water presents a difficult challenge due to their low charge-to-radius ratio, and the ability to discriminate among similar anions often remains problematic. The use of a 3×6 ratiometric indicator-displacement assay (RIDA) array for the colorimetric detection and identification of ten anions in water is reported. The sensor array consists of different combinations of colorimetric indicators and metal cations. The colorimetric indicators chelate with metal cations, forming the color changes. Upon the addition of anions, anions compete with the indicator ligands according to solubility product constants (K(sp)). The indicator-metal chelate compound changes color back dramatically when the competition of anions wins. The color changes of the RIDA array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis and hierarchical clustering analysis. No confusion or errors in classification by hierarchical clustering analysis were observed in 44 trials. The limit of detection was calculated approximately, and most limits of detections of anions are well below μM level using our RIDA array. The pH effect, temperature influence, interfering anions were also investigated, and the RIDA array shows the feasibility of real sample testing. Copyright © 2012 Elsevier B.V. All rights reserved.

Tuning the chromaticity of the emission color of the copolymers containing Eu(III), Tb(III), Be(II) ions based on colorimetric principle

NASA Astrophysics Data System (ADS)

Zhang, Aiqin; Yang, Yamin; Zhai, Guangmei; Jia, Husheng; Xu, Bingshe

2016-02-01

In this work, a method of tuning the chromaticity of the emission color of the copolymers containing Eu(III), Tb(III), Be(II) ions based on colorimetric principle was proposed. The technological route from coordination to copolymerization was employed to obtain the white light macromolecular phosphor. The three primary color monomers have been synthesized and their Commission Internationale de L'Eclairage (CIE) coordinates are respectively (0.540, 0.314), (0.231, 0.463), and (0.161, 0.054). The molar feed ratios of the three primary color monomers were calculated from the CIE coordinates based on colorimetric principle. Serial copolymers have been synthesized by free radical copolymerization of the three primary color monomers and methyl methacrylate. The quantum efficiency of the copolymers was higher than that of the complex monomers. The complexes were directly boned to the polymer chain, in which the energy transfer was reduced significantly compared to the doped-polymers. The experimental values of copolymers' CIE coordinates were located in the white light region in good agreement with theoretical values. The results indicate that the chromaticity of the emission color of the copolymers containing Eu(III), Tb(III), Be(II) ions could be tuned by theoretical calculation based on colorimetric principle.

Versatile fabrication of paper-based microfluidic devices with high chemical resistance using scholar glue and magnetic masks.

PubMed

Cardoso, Thiago M G; de Souza, Fabrício R; Garcia, Paulo T; Rabelo, Denilson; Henry, Charles S; Coltro, Wendell K T

2017-06-29

Simple methods have been developed for fabricating microfluidic paper-based analytical devices (μPADs) but few of these devices can be used with organic solvents and/or aqueous solutions containing surfactants. This study describes a simple fabrication strategy for μPADs that uses readily available scholar glue to create the hydrophobic flow barriers that are resistant to surfactants and organic solvents. Microfluidic structures were defined by magnetic masks designed with either neodymium magnets or magnetic sheets to define the patter, and structures were created by spraying an aqueous solution of glue on the paper surface. The glue-coated paper was then exposed to UV/Vis light for cross-linking to maximize chemical resistance. Examples of microzone arrays and microfluidic devices are demonstrated. μPADs fabricated with scholar glue retained their barriers when used with surfactants, organic solvents, and strong/weak acids and bases unlike common wax-printed barriers. Paper microzones and microfluidic devices were successfully used for colorimetric assays of clinically relevant analytes commonly detected in urinalysis to demonstrate the low background of the barrier material and generally applicability to sensing. The proposed fabrication method is attractive for both its ability to be used with diverse chemistries and the low cost and simplicity of the materials and process. Copyright © 2017 Elsevier B.V. All rights reserved.

Formaldehyde concentrations in household air of asthma patients determined using colorimetric detector tubes

PubMed Central

Dannemiller, Karen C.; Murphy, Johnna S.; Dixon, Sherry L.; Pennell, Kelly G.; Suuberg, Eric M.; Jacobs, David E.; Sandel, Megan

2013-01-01

Formaldehyde is a colorless, pungent gas commonly found in homes that is a respiratory irritant, sensitizer, carcinogen and asthma trigger. Typical household sources include plywood and particleboard, cleaners, cosmetics, pesticides, and others. Development of a fast and simple measurement technique could facilitate continued research on this important chemical. The goal of this research is to apply an inexpensive short-term measurement method to find correlations between formaldehyde sources and concentration, and formaldehyde concentration and asthma control. Formaldehyde was measured using 30-minute grab samples in length-of-stain detector tubes in homes (n=70) of asthmatics in the Boston, MA area. Clinical status and potential formaldehyde sources were determined. The geometric mean formaldehyde level was 35.1 ppb and ranged from 5–132 ppb. Based on one-way ANOVA, t-tests, and linear regression, predictors of log-transformed formaldehyde concentration included absolute humidity, season, and the presence of decorative laminates, fiberglass, or permanent press fabrics (p<0.05), as well as temperature and household cleaner use (p<0.10). The geometric mean formaldehyde concentration was 57% higher in homes of children with very poorly controlled asthma compared to homes of other asthmatic children (p=0.078). This study provides a simple method for measuring household formaldehyde and suggests that exposure is related to poorly controlled asthma. PMID:23278296

Seeing diabetes: visual detection of glucose based on the intrinsic peroxidase-like activity of MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Lin, Tianran; Zhong, Liangshuang; Guo, Liangqia; Fu, Fengfu; Chen, Guonan

2014-09-01

Molybdenum disulfide (MoS2) has attracted increasing research interest recently due to its unique physical, optical and electrical properties, correlated with its 2D ultrathin atomic-layered structure. Until now, however, great efforts have focused on its applications such as lithium ion batteries, transistors, and hydrogen evolution reactions. Herein, for the first time, MoS2 nanosheets are discovered to possess an intrinsic peroxidase-like activity and can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a color reaction. The catalytic activity follows the typical Michaelis-Menten kinetics and is dependent on temperature, pH, H2O2 concentration, and reaction time. Based on this finding, a highly sensitive and selective colorimetric method for H2O2 and glucose detection is developed and applied to detect glucose in serum samples. Moreover, a simple, inexpensive, instrument-free and portable test kit for the visual detection of glucose in normal and diabetic serum samples is constructed by utilizing agarose hydrogel as a visual detection platform.Molybdenum disulfide (MoS2) has attracted increasing research interest recently due to its unique physical, optical and electrical properties, correlated with its 2D ultrathin atomic-layered structure. Until now, however, great efforts have focused on its applications such as lithium ion batteries, transistors, and hydrogen evolution reactions. Herein, for the first time, MoS2 nanosheets are discovered to possess an intrinsic peroxidase-like activity and can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a color reaction. The catalytic activity follows the typical Michaelis-Menten kinetics and is dependent on temperature, pH, H2O2 concentration, and reaction time. Based on this finding, a highly sensitive and selective colorimetric method for H2O2 and glucose detection is developed and applied to detect glucose in serum samples. Moreover, a simple, inexpensive, instrument-free and portable test kit for the visual detection of glucose in normal and diabetic serum samples is constructed by utilizing agarose hydrogel as a visual detection platform. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03393k

Green synthesized nickel nanoparticles for targeted detection and killing of S. typhimurium.

PubMed

Jeyaraj Pandian, Chitra; Palanivel, Rameshthangam; Balasundaram, Usha

2017-09-01

Simple and sensitive colorimetric immunosensor based on peroxidase mimetic activity and photothermal effect of nickel oxide nanoparticle (NiOGs) has been developed to detect and kill food borne pathogen Salmonella typhimurium. NiOGs showed superior peroxidase mimetic activity for oxidation of peroxidase substrate 3, 3', 5, 5'-tetramethylbenzidine (TMB). Oxidation of TMB by NiOGs followed Michaelis-Menten kinetics with K m and V max values of 0.25mM and 2.64×10 -8 M/s respectively. NiOGs was coated with citric acid (CA-NiOGs) followed by conjugation with antibody (anti-S. typhimurium) (Ab-CA-NiOGs) that effectively captured S. typhimurium. Colorimetric detection of S. typhimurium by Ab-CA-NiOGs showed a linear relationship between pathogen concentration (1×10 1 to 1×10 6 cfu/mL) and color signal (652nm) with limit of detection (LOD) of 10cfu/mL. The proposed method showed no cross reactivity against other pathogens. Recovery of S. typhimurium in milk and juice samples was found to be 95 to 100% and 92 to 99% respectively. NiOGs exposed to laser irradiation showed dose dependent increase in temperature and singlet oxygen within 5min. Bacteria bound to Ab-CA-NiOGs after laser irradiation, induced membrane damage and reduced bacterial viability to 6%. The bifunctional peroxidase-mimetic activity and photothermal effect of NiOGs can be exploited in selective sensing and killing of target pathogens respectively in food products. Copyright © 2017 Elsevier B.V. All rights reserved.

EPA Method 3135.2I: Cyanide, Total and Amenable in Aqueous and Solid Samples Automated Colorimetric With Manual Digestion

EPA Pesticide Factsheets

This method describes procedures for preparation and analysis of solid, water and wipe samples for detection and measurement of cyanide amendable to chlorination using acid digestion and spectrophotometry.

Plasmonic colorimetric sensors based on etching and growth of noble metal nanoparticles: Strategies and applications.

PubMed

Zhang, Zhiyang; Wang, Han; Chen, Zhaopeng; Wang, Xiaoyan; Choo, Jaebum; Chen, Lingxin

2018-08-30

Plasmonic colorimetric sensors have emerged as a powerful tool in chemical and biological sensing applications due to the localized surface plasmon resonance (LSPR) extinction in the visible range. Among the plasmonic sensors, the most famous sensing mode is the "aggregation" plasmonic colorimetric sensor which is based on plasmon coupling due to nanoparticle aggregation. Herein, this review focuses on the newly-developing plasmonic colorimetric sensing mode - the etching or the growth of metal nanoparticles induces plasmon changes, namely, "non-aggregation" plasmonic colorimetric sensor. This type of sensors has attracted increasing interest because of their exciting properties of high sensitivity, multi-color changes, and applicability to make a test strip. Of particular interest, the test strip by immobilization of nanoparticles on the substrate can avoid the influence of nanoparticle auto-aggregation and increase the simplicity in storage and use. Although there are many excellent reviews available that describe the advance of plasmonic sensors, limited attention has been paid to the plasmonic colorimetric sensors based on etching or growth of metal nanoparticles. This review highlights recent progress on strategies and application of "non-aggregation" plasmonic colorimetric sensors. We also provide some personal insights into current challenges associated with "non-aggregation" plasmonic colorimetric sensors and propose future research directions. Copyright © 2018 Elsevier B.V. All rights reserved.

A Colorimetric and Fluorescent Chemosensor of Fe3+ Based on an Asymmetrical Squarylium Dye

NASA Astrophysics Data System (ADS)

Lu, Min; Wang, Yue; Li, Ying; Li, Zhongyu; Xu, Song; Yao, Chao

2018-05-01

A novel asymmetrical squarylium-dye-based dual signaling probe was synthesized and found to exhibit colorimetric and fluorescent properties on selective binding towards Fe3+ in ethanol/water (4:1, v/v) solution. The binding constant was determined to be 7.69 × 102 M-1, and the detection limit of SQ was 9.158 × 10-6 M. Most importantly, the 1:2 stoichiometry of the host-guest complexation was confirmed by Job's method. Moreover, the high sensing ability of the receptor towards Fe3+ was also investigated by the electrochemical technique.

Exploration of Nanoparticle-Mediated Photothermal Effect of TMB-H2O2 Colorimetric System and Its Application in a Visual Quantitative Photothermal Immunoassay.

PubMed

Fu, Guanglei; Sanjay, Sharma T; Zhou, Wan; Brekken, Rolf A; Kirken, Robert A; Li, XiuJun

2018-05-01

The exploration of new physical and chemical properties of materials and their innovative application in different fields are of great importance to advance analytical chemistry, material science, and other important fields. Herein, we, for the first time, discovered the photothermal effect of an iron oxide nanoparticles (NPs)-mediated TMB (3,3',5,5'-tetramethylbenzidine)-H 2 O 2 colorimetric system, and applied it toward the development of a new NP-mediated photothermal immunoassay platform for visual quantitative biomolecule detection using a thermometer as the signal reader. Using a sandwich-type proof-of-concept immunoassay, we found that the charge transfer complex of the iron oxide NPs-mediated one-electron oxidation product of TMB (oxidized TMB) exhibited not only color changes, but also a strong near-infrared (NIR) laser-driven photothermal effect. Hence, oxidized TMB was explored as a new sensitive photothermal probe to convert the immunoassay signal into heat through the near-infrared laser-driven photothermal effect, enabling simple photothermal immunoassay using a thermometer. Based on the new iron oxide NPs-mediated TMB-H 2 O 2 photothermal immunoassay platform, prostate-specific antigen (PSA) as a model biomarker can be detected at a concentration as low as 1.0 ng·mL -1 in normal human serum. The discovered photothermal effect of the colorimetric system and the developed new photothermal immunoassay platform open up a new horizon for affordable detection of disease biomarkers and have great potential for other important material and biomedical applications of interest.

Selective chromo-fluorogenic detection of DFP (a Sarin and Soman mimic) and DCNP (a Tabun mimic) with a unique probe based on a boron dipyrromethene (BODIPY) dye.

PubMed

Barba-Bon, Andrea; Costero, Ana M; Gil, Salvador; Martínez-Máñez, Ramón; Sancenón, Félix

2014-11-21

A novel colorimetric probe (P4) for the selective differential detection of DFP (a Sarin and Soman mimic) and DCNP (a Tabun mimic) was prepared. Probe P4 contains three reactive sites; i.e. (i) a nucleophilic phenol group able to undergo phosphorylation with nerve gases, (ii) a carbonyl group as a reactive site for cyanide; and (iii) a triisopropylsilyl (TIPS) protecting group that is known to react with fluoride. The reaction of P4 with DCNP in acetonitrile resulted in both the phosphorylation of the phenoxy group and the release of cyanide, which was able to react with the carbonyl group of P4 to produce a colour modulation from pink to orange. In contrast, phosphorylation of P4 with DFP in acetonitrile released fluoride that hydrolysed the TIPS group in P4 to yield a colour change from pink to blue. Probe P4 was able to discriminate between DFP and DCNP with remarkable sensitivity; limits of detection of 0.36 and 0.40 ppm for DCNP and DFP, respectively, were calculated. Besides, no interference from other organophosphorous derivatives or with presence of acid was observed. The sensing behaviour of P4 was also retained when incorporated into silica gel plates or onto polyethylene oxide membranes, which allowed the development of simple test strips for the colorimetric detection of DCNP and DFP in the vapour phase. P4 is the first probe capable of colorimetrically differentiating between a Tabun mimic (DCNP) and a Sarin and Soman mimic (DFP).

Simplified Quantitative Assay System for Measuring Activities of Drugs against Intracellular Legionella pneumophila

PubMed Central

Higa, Futoshi; Kusano, Nobuchika; Tateyama, Masao; Shinzato, Takashi; Arakaki, Noriko; Kawakami, Kazuyoshi; Saito, Atsushi

1998-01-01

We developed a new simple assay for the quantitation of the activities of drugs against intracellular Legionella pneumophila. The cells of a murine macrophage-like cell line (J774.1 cells) allowed the intracellular growth and replication of the bacteria, which ultimately resulted in cell death. The infected J774.1 cell monolayers in 96-well microplates were first treated with antibiotics and were further cultured for 72 h. The number of viable J774.1 cells in each well was quantified by a colorimetric assay with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and an enzyme-linked immunosorbent assay reader. The number of growing bacteria in each well was also determined by counting the numbers of CFU on buffered charcoal yeast extract-α agar plates. Viable J774.1 cell counts, determined by the colorimetric assay, were inversely proportional to the number of intracellular replicating bacteria. The minimum extracellular concentrations (MIECs) of 24 antibiotics causing inhibition of intracellular growth of L. pneumophila were determined by the colorimetric assay system. The MIECs of beta-lactams and aminoglycosides were markedly higher than the MICs in buffered yeast extract-α broth. The MIECs of macrolides, fluoroquinolones, rifampin, and minocycline were similar to the respective MICs. According to their intracellular activities, clarithromycin and sparfloxacin were the most potent among the macrolides or fluoroquinolones tested in this study. Our results indicated that the MTT assay system allows comparative and quantitative evaluations of the intracellular activities of antibiotics and efficient processing of a large number of samples. PMID:9574712

Miniaturized Sample Preparation and Rapid Detection of Arsenite in Contaminated Soil Using a Smartphone.

PubMed

Siddiqui, Mohd Farhan; Kim, Soocheol; Jeon, Hyoil; Kim, Taeho; Joo, Chulmin; Park, Seungkyung

2018-03-04

Conventional methods for analyzing heavy metal contamination in soil and water generally require laboratory equipped instruments, complex procedures, skilled personnel and a significant amount of time. With the advancement in computing and multitasking performances, smartphone-based sensors potentially allow the transition of the laboratory-based analytical processes to field applicable, simple methods. In the present work, we demonstrate the novel miniaturized setup for simultaneous sample preparation and smartphone-based optical sensing of arsenic As(III) in the contaminated soil. Colorimetric detection protocol utilizing aptamers, gold nanoparticles and NaCl have been optimized and tested on the PDMS-chip to obtain the high sensitivity with the limit of detection of 0.71 ppm (in the sample) and a correlation coefficient of 0.98. The performance of the device is further demonstrated through the comparative analysis of arsenic-spiked soil samples with standard laboratory method, and a good agreement with a correlation coefficient of 0.9917 and the average difference of 0.37 ppm, are experimentally achieved. With the android application on the device to run the experiment, the whole process from sample preparation to detection is completed within 3 hours without the necessity of skilled personnel. The approximate cost of setup is estimated around 1 USD, weight 55 g. Therefore, the presented method offers the simple, rapid, portable and cost-effective means for onsite sensing of arsenic in soil. Combined with the geometric information inside the smartphones, the system will allow the monitoring of the contamination status of soils in a nation-wide manner.

Modulated growth of nanoparticles. Application for sensing nerve gases.

PubMed

Virel, Ana; Saa, Laura; Pavlov, Valeri

2009-01-01

Hydrolysis of acetylthiocholine mediated by acetylcholine esterase yields the thiol-bearing compound thiocholine. At trace concentrations, thiocholine modulates the growth of Au-Ag nanoparticles on seeding gold nanoparticles in the presence of ascorbic acid. Inhibition of the enzyme by 1,5-bis(4-allyldimethylammoniumphenyl)pentan-3-one dibromide (BW284c51) or by diethyl p-nitrophenyl phosphate (paraoxon) produces lower yields of thiocholine, promoting the catalytic growth of Au-Ag nanoparticles. Here, we describe the development of a simple and sensitive colorimetric assay for the detection of AChE inhibitors.

A colorimetric assay of 1-aminocyclopropane-1-carboxylate (ACC) based on ninhydrin reaction for rapid screening of bacteria containing ACC deaminase.

PubMed

Li, Z; Chang, S; Lin, L; Li, Y; An, Q

2011-08-01

1-Aminocyclopropane-1-carboxylate (ACC) deaminase activity is an efficient marker for bacteria to promote plant growth by lowering ethylene levels in plants. We aim to develop a method for rapidly screening bacteria containing ACC deaminase, based on a colorimetric ninhydrin assay of ACC. A reliable colorimetric ninhydrin assay was developed to quantify ACC using heat-resistant polypropylene chimney-top 96-well PCR plates, having the wells evenly heated in boiling water, preventing accidental contamination from boiling water and limiting evaporation. With this method to measure bacterial consumption of ACC, 44 ACC-utilizing bacterial isolates were rapidly screened out from 311 bacterial isolates that were able to grow on minimal media containing ACC as the sole nitrogen source. The 44 ACC-utilizing bacterial isolates showed ACC deaminase activities and belonged to the genus Burkholderia, Pseudomonas or Herbaspirillum. Determination of bacterial ACC consumption by the PCR-plate ninhydrin-ACC assay is a rapid and efficient method for screening bacteria containing ACC deaminase from a large number of bacterial isolates. The PCR-plate ninhydrin-ACC assay extends the utility of the ninhydrin reaction and enables a rapid screening of bacteria containing ACC deaminase from large numbers of bacterial isolates. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

Colorimetric determination of glutathione by using a nanohybrid composed of manganese dioxide and carbon dots.

PubMed

Wang, Qian; Pang, Hongchang; Dong, Yongqiang; Chi, Yuwu; Fu, Fengfu

2018-05-10

A kind of single-layer carbon based dots (CDs) with abundant carboxyl functional groups was hybridized with manganese dioxide (MnO 2 ). The resulting nanohybrid is stable and can be well dispersed in water. MnO 2 is capable of oxidizing the substrate 3,3'5,5'-tetramethylbenzidine (TMB) to form a blue product whose absorption (peaking at 655 nm) fades in the presence of glutathione (GSH). A sensitive and selective colorimetric GSH assay was worked out that has a linear response in the 10 to 0.1 µM GSH concentration range, with a 0.095 μM detection limit. The method was applied to the determination of GSH in spiked fetal calf serum where it gave excellent recoveries. Graphical abstract Schematic of the preparation of a nanohybrid composed of manganese dioxide and carbon based dots (MnO 2 /CDs). They can be used for the colorimetric detection of glutathione (GSH) based on the color change of 3,3'5,5'-tetramethylbenzidine (TMB).

Spectral gamuts and spectral gamut mapping

NASA Astrophysics Data System (ADS)

Rosen, Mitchell R.; Derhak, Maxim W.

2006-01-01

All imaging devices have two gamuts: the stimulus gamut and the response gamut. The response gamut of a print engine is typically described in CIE colorimetry units, a system derived to quantify human color response. More fundamental than colorimetric gamuts are spectral gamuts, based on radiance, reflectance or transmittance units. Spectral gamuts depend on the physics of light or on how materials interact with light and do not involve the human's photoreceptor integration or brain processing. Methods for visualizing a spectral gamut raise challenges as do considerations of how to utilize such a data-set for producing superior color reproductions. Recent work has described a transformation of spectra reduced to 6-dimensions called LabPQR. LabPQR was designed as a hybrid space with three explicit colorimetric axes and three additional spectral reconstruction axes. In this paper spectral gamuts are discussed making use of LabPQR. Also, spectral gamut mapping is considered in light of the colorimetric-spectral duality of the LabPQR space.

Enhanced Colorimetric Immunoassay Accompanying with Enzyme Cascade Amplification Strategy for Ultrasensitive Detection of Low-Abundance Protein

PubMed Central

Gao, Zhuangqiang; Hou, Li; Xu, Mingdi; Tang, Dianping

2014-01-01

Methods based on enzyme labels have been developed for colorimetric immunoassays, but most involve poor sensitivity and are unsuitable for routine use. Herein, we design an enhanced colorimetric immunoassay for prostate-specific antigen (PSA) coupling with an enzyme-cascade-amplification strategy (ECAS-CIA). In the presence of target PSA, the labeled alkaline phosphatase on secondary antibody catalyzes the formation of palladium nanostructures, which catalyze 3,3′,5,5′-tetramethylbenzidine-H2O2 system to produce the colored products, thus resulting in the signal cascade amplification. Results indicated that the ECAS-CIA presents good responses toward PSA, and allows detection of PSA at a concentration as low as 0.05 ng mL−1. Intra- and inter-assay coefficients of variation are below 9.5% and 10.7%, respectively. Additionally, the methodology is validated for analysis of clinical serum specimens with consistent results obtained by PSA ELISA kit. Importantly, the ECAS-CIA opens a new horizon for protein diagnostics and biosecurity. PMID:24509941

A new colorimetric DPPH• scavenging activity method with no need for a spectrophotometer applied on synthetic and natural antioxidants and medicinal herbs.

PubMed

Akar, Zeynep; Küçük, Murat; Doğan, Hacer

2017-12-01

2,2-Diphenyl-1-picrylhydrazyl (DPPH • ) radical scavenging, the most commonly used antioxidant method with more than seventeen thousand articles cited, is very practical; however, as with most assays, it has the major disadvantage of dependence on a spectrophotometer. To overcome this drawback, the colorimetric determination of the antioxidant activity using a scanner and freely available Image J software was developed. In this new method, the mixtures of solutions of DPPH • and standard antioxidants or extracts of common medicinal herbs were dropped onto TLC plates, after an incubation period. The spot images were evaluated with Image J software to determine CSC 50 values, the sample concentrations providing 50% colour reduction, which were very similar with the SC 50 values obtained with spectrophotometric method. The advantages of the new method are the use of lower amounts of reagents and solvents, no need for costly spectrophotometers, and thus significantly lowered costs, and convenient implementation in any environment and situation.

Comparing different methods for fast screening of microbiological quality of beach sand aimed at rapid-response remediation.

PubMed

Testolin, Renan C; Almeida, Tito C M; Polette, Marcus; Branco, Joaquim O; Fischer, Larissa L; Niero, Guilherme; Poyer-Radetski, Gabriel; Silva, Valéria C; Somensi, Cleder A; Corrêa, Albertina X R; Corrêa, Rogério; Rörig, Leonardo R; Itokazu, Ana Gabriela; Férard, Jean-François; Cotelle, Sylvie; Radetski, Claudemir M

2017-05-15

There is scientific evidence that beach sands are a significant contributor to the pathogen load to which visitors are exposed. To develop beach quality guidelines all beach zones must be included in microbiological evaluations, but monitoring methods for beach sand quality are relatively longstanding, expensive, laborious and require moderate laboratory infrastructure. This paper aimed to evaluate the microorganism activity in different beach zones applying and comparing a classical method of membrane filtration (MF) with two colorimetric screening methods based on fluorescein (FDA) and tetrazolium (TTC) salt biotransformation to evaluate a new rapid and low-cost method for beach sand microbiological contamination assessments. The colorimetric results can help beach managers to evaluate rapidly and at low cost the microbiological quality of different beach zones in order to decide whether remedial actions need to be adopted to prevent exposure of the public to microbes due to beach sand and/or water contamination. Copyright © 2017. Published by Elsevier Ltd.

Reconstruction of reflectance data using an interpolation technique.

PubMed

Abed, Farhad Moghareh; Amirshahi, Seyed Hossein; Abed, Mohammad Reza Moghareh

2009-03-01

A linear interpolation method is applied for reconstruction of reflectance spectra of Munsell as well as ColorChecker SG color chips from the corresponding colorimetric values under a given set of viewing conditions. Hence, different types of lookup tables (LUTs) have been created to connect the colorimetric and spectrophotometeric data as the source and destination spaces in this approach. To optimize the algorithm, different color spaces and light sources have been used to build different types of LUTs. The effects of applied color datasets as well as employed color spaces are investigated. Results of recovery are evaluated by the mean and the maximum color difference values under other sets of standard light sources. The mean and the maximum values of root mean square (RMS) error between the reconstructed and the actual spectra are also calculated. Since the speed of reflectance reconstruction is a key point in the LUT algorithm, the processing time spent for interpolation of spectral data has also been measured for each model. Finally, the performance of the suggested interpolation technique is compared with that of the common principal component analysis method. According to the results, using the CIEXYZ tristimulus values as a source space shows priority over the CIELAB color space. Besides, the colorimetric position of a desired sample is a key point that indicates the success of the approach. In fact, because of the nature of the interpolation technique, the colorimetric position of the desired samples should be located inside the color gamut of available samples in the dataset. The resultant spectra that have been reconstructed by this technique show considerable improvement in terms of RMS error between the actual and the reconstructed reflectance spectra as well as CIELAB color differences under the other light source in comparison with those obtained from the standard PCA technique.

Determination of pyrophosphate and sulfate using polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles.

PubMed

Terenteva, E A; Apyari, V V; Dmitrienko, S G; Garshev, A V; Volkov, P A; Zolotov, Yu A

2018-04-01

Positively charged polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles (PHMG-AgNPs) were prepared and applied as a colorimetric probe for single-step determination of pyrophosphate and sulfate. The approach is based on the nanoparticles aggregation leading to change in their absorption spectra and color of the solution. Due to both electrostatic and steric stabilization these nanoparticles show decreased sensitivity relatively to many common anions, which allows for simple and rapid direct single-step determination of pyrophosphate and sulfate. Effects of different factors (time of interaction, pH, concentrations of anions and the nanoparticles) on aggregation of PHMG-AgNPs and analytical performance of the procedure were investigated. The method allows for the determination of pyrophosphate and sulfate in the range of 0.16-2μgmL -1 and 20-80μgmL -1 with RSD of 2-5%, respectively. The analysis can be performed using either spectrophotometry or naked-eye detection. Practical application of the method was shown by the example of pyrophosphate determination in baking powder sample. Copyright © 2017 Elsevier B.V. All rights reserved.

Phosphorus Determination by Derivative Activation Analysis: A Multifaceted Radiochemical Application.

ERIC Educational Resources Information Center

Kleppinger, E. W.; And Others

1984-01-01

Although determination of phosphorus is important in biology, physiology, and environmental science, traditional gravimetric and colorimetric methods are cumbersome and lack the requisite sensitivity. Therefore, a derivative activation analysis method is suggested. Background information, procedures, and results are provided. (JN)

Colorimetric consideration of transparencies for a typical LACIE scene

NASA Technical Reports Server (NTRS)

Juday, R. D. (Principal Investigator)

1979-01-01

The production film converter used to produce LACIE imagery is described as well as schemes designed to provide the analyst with operational film products. Two of these products are discussed from the standpoint of color theory. Colorimetric terminology is defined and the mathematical calculations are given. Topics covered include (1) history of product 1 and 3 algorithm development; (2) colorimetric assumptions for product 1 and 3 algorithms; (3) qualitative results from a colorimetric analysis of a typical LACIE scene; and (4) image-to-image color stability.

Highly selective fluorescent and colorimetric chemosensor for detection of Hg2 + ion in aqueous media

NASA Astrophysics Data System (ADS)

Zareh Jonaghani, Mohammad; Zali-Boeini, Hassan

2017-05-01

A highly efficient and selective fluorescent and colorimetric chemosensor based on naphthothiazole skeleton was synthesized and its colorimetric and fluorescent properties were investigated. The sensor displays a rapid and highly selective colorimetric and fluorescence response toward Hg2 + without interference with other metal ions in CH3CN/H2O mixture (50/50, v/v). The detection limit for the fluorescent chemosensor S1 toward Hg2 + was 3.42 × 10- 8 M.

Colorimetric sensing of selenocystine using gold nanoparticles.

PubMed

Liu, Liyang; Wang, Xia; Yang, Juan; Bai, Yan

2017-10-15

We present a highly selective and sensitive colorimetric method for the detection of selenocystine (SeCys) coexisting with other amino acids, especially cysteine (Cys) using the gold nanoparticles (AuNPs). Firstly, Cys was oxidized to cystine (Cys-Cys) by dissolved oxygen under Cu 2+ catalysis in the pre-reaction, which eliminated the interference of Cys in the SeCys sensing process. Then SeCys induced the rapid aggregation of AuNPs through Au-Se bond and complex formation of Cu 2+ -SeCys in the colorimetric reaction, in which the color change of AuNPs from red to blue or purple with the naked eye detection or with a UV-vis spectrophotometric determination. The concentration of SeCys was quantified by the value at 670 nm from the second-derivative SPR absorbance spectrum. The linear range was from 2 μM to 14 μM with correlation coefficient of 0.999 and a detection limit (LOD) was 0.14 μM. Moreover, the colorimetric response of AuNPs exhibited remarkable specificity to SeCys coexisting with 18 amino acids in a simulation sample, in which the total concentration of Cys and Cys-Cys was less than 15 μM and the each concentration of other 16 common amino acids was 10 μM. Copyright © 2017 Elsevier Inc. All rights reserved.

The effect of carbonated beverages on colorimetric end-tidal CO(2) determination

PubMed

Qureshi; Park; Sturmann; Hsu

2000-10-01

Esophageal intubation is a significant complication of attempted airway control. Colorimetric end-tidal CO(2) monitors are highly sensitive and specific for detecting the presence of CO(2). There are reports of false-positive end-tidal CO(2) readings from esophageal intubations in patients who had ingested carbonated beverages. OBJECTIVE: To determine whether carbonated gastric contents can affect colorimetric end-tidal CO(2) readings. METHODS: End-tidal CO(2) was measured in sacrificed piglets at measured time intervals after instillation of 5-, 10-, 15-, and 20-mL aliquots of Diet Coke were placed into the stomach via a 28-French orogastric tube followed by esophageal intubation. The stomach was completely evacuated prior to each instillation and rechecked for baseline CO(2). RESULTS: Compiled data from three piglets (20-30 kg). Piglets were not ventilated or moved and determinations were measured at 20 degrees while supine. All data collected within 2 hours postmortem (table 24-1). CONCLUSIONS: The colorimetric end-tidal CO(2) turned "yellow" and did not change to blue with extended insufflations. The CO(2) of a small quantity of carbonated beverage in the stomach could be "blown off" by multiple insufflations. We conclude that esophageal intubation in the setting of recent ingestion of a carbonated beverage may result in a false-positive end-tidal CO(2) determination.

Efficacy of a lead based paint XRF analyzer and a commercially available colorimetric lead test kit as qualitative field tools for determining presence of lead in religious powders.

PubMed

Shah, Manthan P; Shendell, Derek G; Meng, Qingyu; Ohman-Strickland, Pamela; Halperin, William

2018-04-23

The performances of a portable X-Ray Fluorescence (XRF) lead paint analyzer (RMD LPA-1, Protec Instrument Corp., Waltham, MA) and a commercially available colorimetric lead test kit (First Alert Lead Test Kit, eAccess Solutions, Inc., Palatine, IL) were evaluated for use by local or state health departments as potential cost-effective rapid analysis or "spot test" field techniques for tentative identification of lead content in sindoor powders. For both field-sampling methods, sensitivity, specificity and predictive values varied widely for samples containing <300,000 μg/g lead. For samples containing ≥300,000 μg/g lead, the aforementioned metrics were 100% (however, the CIs had a wide range). In addition, both field sampling methods showed clear, consistent positive readings only for samples containing ≥300,000 μg/g lead. Even samples with lead content as high as 5,110 μg/g were not positively identified by either field analysis technique. The results of this study suggest the XRF analyzer and colorimetric lead test kit cannot be used as a rapid field test for sindoor by health department inspectors.

Determination of dasatinib in the tablet dosage form by ultra high performance liquid chromatography, capillary zone electrophoresis, and sequential injection analysis.

PubMed

Gonzalez, Aroa Garcia; Taraba, Lukáš; Hraníček, Jakub; Kozlík, Petr; Coufal, Pavel

2017-01-01

Dasatinib is a novel oral prescription drug proposed for treating adult patients with chronic myeloid leukemia. Three analytical methods, namely ultra high performance liquid chromatography, capillary zone electrophoresis, and sequential injection analysis, were developed, validated, and compared for determination of the drug in the tablet dosage form. The total analysis time of optimized ultra high performance liquid chromatography and capillary zone electrophoresis methods was 2.0 and 2.2 min, respectively. Direct ultraviolet detection with detection wavelength of 322 nm was employed in both cases. The optimized sequential injection analysis method was based on spectrophotometric detection of dasatinib after a simple colorimetric reaction with folin ciocalteau reagent forming a blue-colored complex with an absorbance maximum at 745 nm. The total analysis time was 2.5 min. The ultra high performance liquid chromatography method provided the lowest detection and quantitation limits and the most precise and accurate results. All three newly developed methods were demonstrated to be specific, linear, sensitive, precise, and accurate, providing results satisfactorily meeting the requirements of the pharmaceutical industry, and can be employed for the routine determination of the active pharmaceutical ingredient in the tablet dosage form. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improvement of the uric acid determination by the carbonate method for serum and urine

PubMed Central

Eichhorn, F.; Zelmanowski, S.; Lew, E.; Rutenberg, A.; Fanias, B.

1961-01-01

An improved colorimetric procedure for determining uric acid by the carbonate method in serum and urine is described, using a 20% sodium carbonate solution with urea. Reliable results are also obtained in high concentrations of uric acid. PMID:13726059

Method 365.5 Determination of Orthophosphate in Estuarine and Coastal Waters by Automated Colorimetric Analysis

EPA Science Inventory

This method provides a procedure for the determination of low-level orthophosphate concentrations normally found in estuarine and/or coastal waters. It is based upon the method of Murphy and Riley1 adapted for automated segmented flow analysis2 in which the two reagent solutions ...

Development of a field method for measuring manganese in welding fume.

PubMed

Dale Marcy, A; Drake, Pamela L

2007-11-01

Workers who perform routine welding tasks are potentially exposed to fume that may contain manganese. Manganese may cause respiratory problems and is implicated in causing the occurrence of Parkinson-like symptoms. In this study, a field colorimetric method for extracting and measuring manganese in welding fume was developed. The method uses ultrasonic extraction with an acidic hydrogen peroxide solution to extract welding fume collected on polyvinyl chloride filters. Commercially available pre-packaged reagents are used to produce a colored solution, created by a reaction of manganese(ii) with 1-(2-pyridylazo)-2-naphthol. Absorbance measurements are then made using a portable spectrophotometer. The method detection limit and limit of quantification (LOQ) were 5.2 microg filter(-1) and 17 microg filter(-1), respectively, with a dynamic range up to 400 microg filter(-1). When the results are above the LOQ for the colorimetric method, the manganese masses are equivalent to those measured by the International Organization for Standardization Method 15202-2, which employs a strong acid digestion and analysis using inductively coupled plasma-optical emission spectrometry.

Rapid detection of aflatoxigenic Aspergillus sp. in herbal specimens by a simple, bendable, paper-based lab-on-a-chip.

PubMed

Chaumpluk, Piyasak; Plubcharoensook, Pattra; Prasongsuk, Sehanat

2016-06-01

Postharvest herbal product contamination with mycotoxins and mycotoxin-producing fungi represents a potentially carcinogenic hazard. Aspergillus flavus is a major cause of this issue. Available mold detection methods are PCR-based and rely heavily on laboratories; thus, they are unsuitable for on-site monitoring. In this study, a bendable, paper-based lab-on-a-chip platform was developed to rapidly detect toxigenic Aspergillus spp. DNA. The 3.0-4.0 cm(2) chip is fabricated using Whatman™ filter paper, fishing line and a simple plastic lamination process and has nucleic acid amplification and signal detection components. The Aspergillus assay specifically amplifies the aflatoxin biosynthesis gene, aflR, using loop-mediated isothermal amplification (LAMP); hybridization between target DNA and probes on blue silvernanoplates (AgNPls) yields colorimetric results. Positive results are indicated by the detection pad appearing blue due to dispersed blue AgNPls; negative results are indicated by the detection pad appearing colorless or pale yellow due to probe/target DNA hybridization and AgNPls aggregation. Assay completion requires less than 40 min, has a limit of detection (LOD) of 100 aflR copies, and has high specificity (94.47%)and sensitivity (100%). Contamination was identified in 14 of 32 herbal samples tested (43.75%). This work demonstrates the fabrication of a simple, low-cost, paper-based lab-on-a-chip platform suitable for rapid-detection applications. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of thiaminase activity in fish using the radiometric and 4-nitrothiophenol colorimetric methods

USGS Publications Warehouse

Honeyfield, D.C.; Hanes, J.W.; Brown, L.; Kraft, C.E.; Begley, T.P.

2010-01-01

Thiaminase induced thiamine deficiency occurs in fish, humans, livestock and wild animals. A non-radioactive thiaminase assay was described in 2007, but a direct comparison with the radioactive 14C-thiamine method which has been in use for more than 30years has not been reported. The objective was to measure thiaminase activity in forage fish (alewife Alosa pseudoharengus, rainbow smelt Osmerus mordax, and slimy sculpin Cottus cognatus) consumed by predators that manifest thiamine deficiency using both methods. Modifications were made to the colorimetric assay to improve repeatability. Modification included a change in assay pH, enhanced sample clean-up, constant assay temperature (37??C), increase in the concentration of 4-nitrothiophenol (4NTP) and use of a spectrophotometer fitted with a 0.2cm cell. A strong relationship between the two assays was found for 51 alewife (R2=0.85), 36 smelt (R2=0.87) and 20 sculpin (R2=0.82). Thiaminase activity in the colorimetric assay was about 1000 times higher than activity measured by the radioactive method. Application of the assay to fish species from which no thiaminase activity has previously been reported resulted in no 4NTP thiaminase activity being found in bloater Coregonus hoyi, lake trout Salvelinus namaycusch, steelhead trout Oncorhynchus mykiss or Chinook salmon Oncorhynchus tshawytscha. In species previously reported to contain thiaminase, 4NTP thiaminase activity was measured in bacteria Paenibacillus thiaminolyticus, gizzard shad Dorosoma cepedianum, bracken fern Pteridium aquilinum, quagga mussel Dreissena bugensis and zebra mussels D. polymorpha. ?? 2010.

Fully 3D printed integrated reactor array for point-of-care molecular diagnostics.

PubMed

Kadimisetty, Karteek; Song, Jinzhao; Doto, Aoife M; Hwang, Young; Peng, Jing; Mauk, Michael G; Bushman, Frederic D; Gross, Robert; Jarvis, Joseph N; Liu, Changchun

2018-06-30

Molecular diagnostics that involve nucleic acid amplification tests (NAATs) are crucial for prevention and treatment of infectious diseases. In this study, we developed a simple, inexpensive, disposable, fully 3D printed microfluidic reactor array that is capable of carrying out extraction, concentration and isothermal amplification of nucleic acids in variety of body fluids. The method allows rapid molecular diagnostic tests for infectious diseases at point of care. A simple leak-proof polymerization strategy was developed to integrate flow-through nucleic acid isolation membranes into microfluidic devices, yielding a multifunctional diagnostic platform. Static coating technology was adopted to improve the biocompatibility of our 3D printed device. We demonstrated the suitability of our device for both end-point colorimetric qualitative detection and real-time fluorescence quantitative detection. We applied our diagnostic device to detection of Plasmodium falciparum in plasma samples and Neisseria meningitides in cerebrospinal fluid (CSF) samples by loop-mediated, isothermal amplification (LAMP) within 50 min. The detection limits were 100 fg for P. falciparum and 50 colony-forming unit (CFU) for N. meningitidis per reaction, which are comparable to that of benchtop instruments. This rapid and inexpensive 3D printed device has great potential for point-of-care molecular diagnosis of infectious disease in resource-limited settings. Copyright © 2018 Elsevier B.V. All rights reserved.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations.

PubMed

Hassan, Wafaa S; El-Henawee, Magda M; Gouda, Ayman A

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at lambda(max) 470nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70microgmL(-1) for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Hassan, Wafaa S.; El-Henawee, Magda M.; Gouda, Ayman A.

2008-01-01

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at λmax 470 nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426 nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70 μg mL -1 for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

A signal-amplified electrochemical DNA biosensor incorporated with a colorimetric internal control for Vibrio cholerae detection using shelf-ready reagents.

PubMed

Low, Kim-Fatt; Zain, Zainiharyati Mohd; Yean, Chan Yean

2017-01-15

A novel enzyme/nanoparticle-based DNA biosensing platform with dual colorimetric/electrochemical approach has been developed for the sequence-specific detection of the bacterium Vibrio cholerae, the causative agent of acute diarrheal disease in cholera. This assay platform exploits the use of shelf-stable and ready-to-use (shelf-ready) reagents to greatly simplify the bioanalysis procedures, allowing the assay platform to be more amenable to point-of-care applications. To assure maximum diagnosis reliability, an internal control (IC) capable of providing instant validation of results was incorporated into the assay. The microbial target, single-stranded DNA amplified with asymmetric PCR, was quantitatively detected via electrochemical stripping analysis of gold nanoparticle-loaded latex microspheres as a signal-amplified hybridization tag, while the incorporated IC was analyzed using a simplified horseradish peroxidase enzyme-based colorimetric scheme by simple visual observation of enzymatic color development. The platform showed excellent diagnostic sensitivity and specificity (100%) when challenged with 145 clinical isolate-spiked fecal specimens. The limits of detection were 0.5ng/ml of genomic DNA and 10 colony-forming units (CFU)/ml of bacterial cells with dynamic ranges of 0-100ng/ml (R 2 =0.992) and log 10 (1-10 4 CFU/ml) (R 2 =0.9918), respectively. An accelerated stability test revealed that the assay reagents were stable at temperatures of 4-37°C, with an estimated ambient shelf life of 200 days. The versatility of the biosensing platform makes it easily adaptable for quantitative detection of other microbial pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

Colorimetric Aptasensor Using Unmodified Gold Nanoparticles for Homogeneous Multiplex Detection

PubMed Central

Niu, Shucao; Lv, Zhenzhen; Liu, Jinchuan; Bai, Wenhui; Yang, Shuming; Chen, Ailiang

2014-01-01

Colorimetric aptasensors using unmodified gold nanoparticles (AuNPs) have attracted much attention because of their low cost, simplicity, and practicality, and they have been developed for various targets in the past several years. However, previous research has focused on developing single-target assays. Here, we report the development of a homogeneous multiplex aptasensor by using more than one class of aptamers to stabilize AuNPs. Using sulfadimethoxine (SDM), kanamycin (KAN) and adenosine (ADE) as example targets, a KAN aptamer (750 nM), an SDM aptamer (250 nM) and an ADE aptamer (500 nM) were mixed at a 1∶1∶1 volume ratio and adsorbed directly onto the surface of unmodified AuNPs by electrostatic interaction. Upon the addition of any of the three targets, the conformation of the corresponding aptamer changed from a random coil structure to a rigid folded structure, which could not adsorb and stabilize AuNPs. The AuNPs aggregated in a specific reaction buffer (20 mM Tris-HCl containing 20 mM NaCl and 5 mM KCl), which led to a color change from red to purple/blue. These results demonstrate that the multiplex colorimetric aptasensor detected three targets simultaneously while maintaining the same sensitivity as a single-target aptasensor for each individual target. The multiplex aptasensor could be extended to other aptamers for various molecular detection events. Due to its simple design, easy operation, fast response, cost effectiveness and lack of need for sophisticated instrumentation, the proposed strategy provides a powerful tool to examine large numbers of samples to screen for a small number of potentially positive samples containing more than one analyte, which can be further validated using sophisticated instruments. PMID:25279730

Spectrophotometric, colorimetric and visually detection of Pseudomonas aeruginosa ETA gene based gold nanoparticles DNA probe and endonuclease enzyme

NASA Astrophysics Data System (ADS)

Amini, Bahram; Kamali, Mehdi; Salouti, Mojtaba; Yaghmaei, Parichehreh

2018-06-01

Colorimetric DNA detection is preferred over other methods for clinical molecular diagnosis because it does not require expensive equipment. In the present study, the colorimetric method based on gold nanoparticles (GNPs) and endonuclease enzyme was used for the detection of P. aeruginosa ETA gene. Firstly, the primers and probe for P. aeruginosa exotoxin A (ETA) gene were designed and checked for specificity by the PCR method. Then, GNPs were synthesized using the citrate reduction method and conjugated with the prepared probe to develop the new nano-biosensor. Next, the extracted target DNA of the bacteria was added to GNP-probe complex to check its efficacy for P. aeruginosa ETA gene diagnosis. A decrease in absorbance was seen when GNP-probe-target DNA cleaved into the small fragments of BamHI endonuclease due to the weakened electrostatic interaction between GNPs and the shortened DNA. The right shift of the absorbance peak from 530 to 562 nm occurred after adding the endonuclease. It was measured using a UV-VIS absorption spectroscopy that indicates the existence of the P. aeruginosa ETA gene. Sensitivity was determined in the presence of different concentrations of target DNA of P. aeruginosa. The results obtained from the optimized conditions showed that the absorbance value has linear correlation with concentration of target DNA (R: 0.9850) in the range of 10-50 ng mL-1 with the limit detection of 9.899 ng mL-1. Thus, the specificity of the new method for detection of P. aeruginosa was established in comparison with other bacteria. Additionally, the designed assay was quantitatively applied to detect the P. aeruginosa ETA gene from 103 to 108 CFU mL-1 in real samples with a detection limit of 320 CFU mL-1.

A novel alendronate functionalized nanoprobe for simple colorimetric detection of cancer-associated hypercalcemia.

PubMed

Sahu, Abhishek; Hwang, Youngmin; Vilos, Cristian; Lim, Jong-Min; Kim, Sunghyun; Choi, Won Il; Tae, Giyoong

2018-05-22

The calcium (Ca2+) ion concentration in the blood serum is tightly regulated, and any abnormalities in the level of serum calcium ions are associated with many potentially dangerous diseases. Thus, monitoring of the Ca2+ ion concentration in the blood serum is of fundamental importance. Gold nanoparticle (GNP)-based colorimetric biosensors have enormous potential in clinical diagnostic applications due to their simplicity, versatility, and unique optical properties. In this study, we have developed an alendronate functionalized gold nanoparticle (GNP-ALD) system for the measurement of Ca2+ ion concentration in biological samples. The GNP-ALD system showed higher sensitivity towards the Ca2+ ion compared to adenosine diphosphate (ADP) or adenosine triphosphate (ATP). The strong interaction between the Ca2+ ion and ALD at the GNP/solution interface resulted in significant aggregation of the ALD conjugated GNPs, and induced a color change of the solution from red to blue, which could be visually observed with the naked eye. The interaction between the Ca2+ ion and GNP-ALD was characterized by UV-visible spectroscopy, transmission electron microscopy (TEM) imaging, and dynamic light scattering (DLS) analysis. Under the optimized conditions, the lower limit of Ca2+ ion detection using this method was found to be 25 μM and a linear response range from 25 μM to 300 μM Ca2+ ions was obtained with excellent discrimination against other metal ions. The GNP-ALD nanoprobe could successfully determine the ionized Ca2+ concentration in various serum samples and the results were validated using a commercial calcium assay kit. Moreover, as a practical application, we demonstrated the utility of this nanoprobe for the detection of cancer-associated hypercalcemia in a mouse model.

A selectively rhodamine-based colorimetric probe for detecting copper(II) ion.

PubMed

Zhang, Jiangang; Zhang, Li; Wei, Yanli; Chao, Jianbing; Shuang, Shaomin; Cai, Zongwei; Dong, Chuan

2014-11-11

A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2×10(4) L mol(-1). Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667-240 μmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis. Copyright © 2014 Elsevier B.V. All rights reserved.

A highly selective colorimetric and ratiometric fluorescent probe for instantaneous sensing of Hg2+ in water, soil and seafood and its application on test strips.

PubMed

Lan, Linxin; Niu, Qingfen; Li, Tianduo

2018-09-06

A new simple and efficient oligothiophene-based colorimetric and ratiometric fluorescent probe has been developed for highly sensitive and fast detection of Hg 2+ in water, soil and seafood. The probe 5-(1,3-dithiolan-2-yl)-2,2':5',2″-terthiophene 3 TS can selectively detect Hg 2+ via the Hg 2+ -promoted deprotection reaction of thioacetals, which caused a remarkable color change from colorless to yellow and a strong fluorescence enhancement with emission color varying from blue to yellow, enabling naked-eye detection of Hg 2+ . The probe shows high sensitivity with the detection limit down to 1.03 × 10 -8  M. Visual color changes of 3 TS were observed on filter paper and TLC testing strips when they were impregnated on testing strips and immersed in Hg 2+ solution. Moreover, the probe 3 TS has been successfully used to rapidly detect trace amounts of hazardous Hg 2+ ions in tap, distilled, river and lake water, cropland soil, fish, shrimp and kelp samples with acceptable results and good recoveries. Copyright © 2018 Elsevier B.V. All rights reserved.

A Soft, Wearable Microfluidic Device for the Capture, Storage, and Colorimetric Sensing of Sweat

PubMed Central

Koh, Ahyeon; Kang, Daeshik; Xue, Yeguang; Lee, Seungmin; Pielak, Rafal M.; Kim, Jeonghyun; Hwang, Taehwan; Min, Seunghwan; Banks, Anthony; Bastien, Philippe; Manco, Megan C.; Wang, Liang; Ammann, Kaitlyn R.; Jang, Kyung-In; Won, Phillip; Han, Seungyong; Ghaffari, Roozbeh; Paik, Ungyu; Slepian, Marvin J.; Balooch, Guive; Huang, Yonggang; Rogers, John A.

2017-01-01

Capabilities in health monitoring via capture and quantitative chemical analysis of sweat could complement, or potentially obviate the need for, approaches based on sporadic assessment of blood samples. Established sweat monitoring technologies use simple fabric swatches and are limited to basic analysis in controlled laboratory or hospital settings. We present a collection of materials and device designs for soft, flexible and stretchable microfluidic systems, including embodiments that integrate wireless communication electronics, which can intimately and robustly bond to the surface of skin without chemical and mechanical irritation. This integration defines access points for a small set of sweat glands such that perspiration spontaneously initiates routing of sweat through a microfluidic network and set of reservoirs. Embedded chemical analyses respond in colorimetric fashion to markers such as chloride and hydronium ions, glucose and lactate. Wireless interfaces to digital image capture hardware serve as a means for quantitation. Human studies demonstrated the functionality of this microfluidic device during fitness cycling in a controlled environment and during long-distance bicycle racing in arid, outdoor conditions. The results include quantitative values for sweat rate, total sweat loss, pH and concentration of both chloride and lactate. PMID:27881826

Enhancing the peroxidase-like activity of ficin via heme binding and colorimetric detection for uric acid.

PubMed

Pan, Yadi; Yang, Yufang; Pang, Yanjiao; Shi, Ying; Long, Yijuan; Zheng, Huzhi

2018-08-01

Ficin, a classical sulfhydryl protease, was found to possess intrinsic peroxidase-like activity. In this paper, we have put forward a novel strategy to improving the peroxidase-like activity of ficin through binding heme. Heme-ficin complexes were successfully obtained by simple one-step syntheticism. The results demonstrated that the catalytic activity and efficiency of heme-ficin complexes were about 1.7 times and 3 times higher than those of native ficin, respectively. Taking advantages of the high peroxidase-like activity, the heme-ficin complexes were used for colorimetric determination of uric acid with a low detection limit of 0.25 μM. Based on the excellent selectivity and sensitivity, we detected the concentration of uric acid in human serum successfully. On the basis of these findings, the heme-ficin complexes are promising for wide applications in various fields. Thus we not only optimized the peroxidase-like activity of the ficin, but also established a new strategy for development of artificial enzyme mimics by mimicking the architecture of the active site in horseradish peroxidase. Copyright © 2018 Elsevier B.V. All rights reserved.

Smartphone Based Platform for Colorimetric Sensing of Dyes

NASA Astrophysics Data System (ADS)

Dutta, Sibasish; Nath, Pabitra

We demonstrate the working of a smartphone based optical sensor for measuring absorption band of coloured dyes. By integration of simple laboratory optical components with the camera unit of the smartphone we have converted it into a visible spectrometer with a pixel resolution of 0.345 nm/pixel. Light from a broadband optical source is allowed to transmit through a specific dye solution. The transmitted light signal is captured by the camera of the smartphone. The present sensor is inexpensive, portable and light weight making it an ideal handy sensor suitable for different on-field sensing.

Quantitation of proteins using a dye-metal-based colorimetric protein assay.

PubMed

Antharavally, Babu S; Mallia, Krishna A; Rangaraj, Priya; Haney, Paul; Bell, Peter A

2009-02-15

We describe a dye-metal (polyhydroxybenzenesulfonephthalein-type dye and a transition metal) complex-based total protein determination method. The binding of the complex to protein causes a shift in the absorption maximum of the dye-metal complex from 450 to 660 nm. The dye-metal complex has a reddish brown color that changes to green on binding to protein. The color produced from this reaction is stable and increases in a proportional manner over a broad range of protein concentrations. The new Pierce 660 nm Protein Assay is very reproducible, rapid, and more linear compared with the Coomassie dye-based Bradford assay. The assay reagent is room temperature stable, and the assay is a simple and convenient mix-and-read format. The assay has a moderate protein-to-protein variation and is compatible with most detergents, reducing agents, and other commonly used reagents. This is an added advantage for researchers needing to determine protein concentrations in samples containing both detergents and reducing agents.

384 hanging drop arrays give excellent Z-factors and allow versatile formation of co-culture spheroids.

PubMed

Hsiao, Amy Y; Tung, Yi-Chung; Qu, Xianggui; Patel, Lalit R; Pienta, Kenneth J; Takayama, Shuichi

2012-05-01

We previously reported the development of a simple, user-friendly, and versatile 384 hanging drop array plate for 3D spheroid culture and the importance of utilizing 3D cellular models in anti-cancer drug sensitivity testing. The 384 hanging drop array plate allows for high-throughput capabilities and offers significant improvements over existing 3D spheroid culture methods. To allow for practical 3D cell-based high-throughput screening and enable broader use of the plate, we characterize the robustness of the 384 hanging drop array plate in terms of assay performance and demonstrate the versatility of the plate. We find that the 384 hanging drop array plate performance is robust in fluorescence- and colorimetric-based assays through Z-factor calculations. Finally, we demonstrate different plate capabilities and applications, including: spheroid transfer and retrieval for Janus spheroid formation, sequential addition of cells for concentric layer patterning of different cell types, and culture of a wide variety of cell types. Copyright © 2011 Wiley Periodicals, Inc.

384 Hanging Drop Arrays Give Excellent Z-factors and Allow Versatile Formation of Co-culture Spheroids

PubMed Central

Hsiao, Amy Y.; Tung, Yi-Chung; Qu, Xianggui; Patel, Lalit R.; Pienta, Kenneth J.; Takayama, Shuichi

2012-01-01

We previously reported the development of a simple, user-friendly, and versatile 384 hanging drop array plate for 3D spheroid culture and the importance of utilizing 3D cellular models in anti-cancer drug sensitivity testing. The 384 hanging drop array plate allows for high-throughput capabilities and offers significant improvements over existing 3D spheroid culture methods. To allow for practical 3D cell-based high-throughput screening and enable broader use of the plate, we characterize the robustness of the 384 hanging drop array plate in terms of assay performance and demonstrate the versatility of the plate. We find that the 384 hanging drop array plate performance is robust in fluorescence- and colorimetric-based assays through z-factor calculations. Finally, we demonstrate different plate capabilities and applications, including: spheroid transfer and retrieval for Janus spheroid formation, sequential addition of cells for concentric layer patterning of different cell types, and culture of a wide variety of cell types. PMID:22161651

Isolation and quantification of Quillaja saponaria Molina saponins and lipids in iscom-matrix and iscoms.

PubMed

Behboudi, S; Morein, B; Rönnberg, B

1995-12-01

In the iscom, multiple copies of antigen are attached by hydrophobic interaction to a matrix which is built up by Quillaja triterpenoid saponins and lipids. Thus, the iscom presents antigen in multimeric form in a small particle with a built-in adjuvant resulting in a highly immunogenic antigen formulation. We have designed a chloroform-methanol-water extraction procedure to isolate the triterpenoid saponins and lipids incorporated into iscom-matrix and iscoms. The triterpenoids in the triterpenoid phase were quantitated using orcinol sulfuric acid detecting their carbohydrate chains and by HPLC. The cholesterol and phosphatidylcholine in the lipid phase were quantitated by HPLC and a commercial colorimetric method for the cholesterol. The quantitative methods showed an almost total separation and recovery of triterpenoids and lipids in their respective phases, while protein was detected in all phases after extraction. The protein content was determined by the method of Lowry and by amino acid analysis. Amino acid analysis was shown to be the reliable method of the two to quantitate proteins in iscoms. In conclusion, simple, reproducible and efficient procedures have been designed to isolate and quantitate the triterpenoids and lipids added for preparation of iscom-matrix and iscoms. The procedures described should also be useful to adequately define constituents in prospective vaccines.

A biodegradable colorimetric film for rapid low-cost field determination of formaldehyde contamination by digital image colorimetry.

PubMed

Wongniramaikul, Worawit; Limsakul, Wadcharawadee; Choodum, Aree

2018-05-30

A biodegradable colorimetric film was fabricated on the lid of portable tube for in-tube formaldehyde detection. Based on the entrapment of colorimetric reagents within a thin film of tapioca starch, the yellow reaction product was observed with formaldehyde. Intensity of the blue channel from the digital image of yellow product showed a linear relationship in the range of 0-25 mg L -1 with low detection limit of 0.7 ± 0.1 mg L -1 . Inter-day precision of 0.61-3.10%RSD were obtained with less than 4.2% relative error from control samples. The developed method was applied for various food samples in Phuket and formaldehyde concentration range was non-detectable to 1.413 mg kg -1 . The quantified concentrations of formaldehyde in fish and squid samples provided relative errors of -7.7% and +10.8% compared to spectrophotometry. This low cost sensor (∼0.04 USD/test) with digital image colorimetry was thus an effective alternative for formaldehyde detection in food sample. Copyright © 2018 Elsevier Ltd. All rights reserved.

Detection and differentiation of Campylobacter jejuni and Campylobacter coli in broiler chicken samples using a PCR/DNA probe membrane based colorimetric detection assay.

PubMed

O'Sullivan, N A; Fallon, R; Carroll, C; Smith, T; Maher, M

2000-02-01

Campylobacter enteritis in humans has been linked to consumption of poultry meat. Surveys show that 30-100% of poultry harbour Campylobacter as normal flora of the digestive tract which indicates a need to identify prevalent organism types in flocks and trace their epidemiology. In this study we describe a Campylobacter genus specific polymerase chain reaction (PCR) assay, amplifying the 16 S-23 S rRNA intergenic spacer region with an internal Campylobacter genus specific DNA probe and species specific probes for Campylobacter jejuni and Campylobacter coli designed for confirmation of the amplified PCR products by Southern blot and colorimetric reverse hybridization assays. The specificity of this assay was established by testing a range of food pathogens. Broiler chicken samples were tested following presumptive positive identification by the Malthus System V analyser (Malthus Instruments, UK). The combined PCR and colorimetric reverse hybridization assay is easy to perform and faster than conventional methods for confirmation and identification of Campylobacter species. Copyright 2000 Academic Press.

Naked eye screening of 11 phenolic compounds and colorimetric determination using polydiacetylene vesicles with α-cyclodextrin

NASA Astrophysics Data System (ADS)

Anekthirakun, Pimpimon; Sukwattanasinitt, Mongkol; Tuntulani, Thawatchai; Imyim, Apichat

2013-07-01

The colorimetric response (CR) of poly(10,12-pentacosadiynoic acid) vesicles (PPCDA) induced by α-cyclodextrin (α-CD) in an aqueous solution has been studied. Various parameters affecting the CR, such as response time and concentration were investigated. The blue color of 0.01 mM PPCDA solution became pinkish red with the addition of α-CD at the concentration higher than 3 mM. The inhibition of the color transition from blue to red was investigated using 11 phenolic compounds. The color transition could be inhibited and observed by naked eye in the presence of 4 phenolic compounds, i.e. 4-nitrophenol (4-NP) and 4-bromophenol (4-BP) and 4-chlorophenol (4-CP) and 3-nitrophenol (3-NP). A colorimetric method for the determination of these compounds was validated and applied for surface water analysis. The linear range from the plot of CR against phenolic compounds concentration was in the order of 0.5-2.0 mM with R2 more than 0.99. The recoveries were 90-95% with good precision (1-4%RSD, n = 10).

A colorimetric method for the determination of carboxyhaemoglobin over a wide range of concentrations

PubMed Central

Trinder, P.; Harper, F. E.

1962-01-01

A colorimetric technique for the determination of carboxyhaemoglobin in blood is described. Carbon monoxide released from blood in a standard Conway unit reacts with palladous chloride/arsenomolybdate solution to produce a blue colour. Using 0·5 to 2 ml. of blood, the method will estimate carboxyhaemoglobin accurately at levels from 0·1% to 100% of total haemoglobin and in the presence of other abnormal pigments. A number of methods are available for the determination of carboxyhaemoglobin; none is accurate below a concentration of 1·5 g. carboxyhaemoglobin per 100 ml. but for most clinical purposes this is not important. For forensic purposes and occasionally in clinical use, an accurate determination of carboxyhaemoglobin below 750 mg. per 100 ml. may be required and no really satisfactory method is at present available. Some time ago when it was important to know whether a person who was found dead in a burning house had died before or after the fire had started, we became interested in developing a method which would determine accurately carboxyhaemoglobin at levels of 750 mg. per 100 ml. PMID:13922505

Automated method for study of drug metabolism

NASA Technical Reports Server (NTRS)

Furner, R. L.; Feller, D. D.

1973-01-01

Commercially available equipment can be modified to provide automated system for assaying drug metabolism by continuous flow-through. System includes steps and devices for mixing drug with enzyme and cofactor in the presence of pure oxygen, dialyzing resulting metabolite against buffer, and determining amount of metabolite by colorimetric method.

REDUCTION OF NITRATE THROUGH THE USE OF NITRATE REDUCTASE FOR THE SMARTCHEM AUTOANALYZER

EPA Science Inventory

The standard method for the determination of nitrate in drinking water, USEPA Method 353.2 “Determination of Nitrate-Nitrite by Automated Colorimetry,” employs cadmium as the reductant for the conversion of nitrate to nitrite. The nitrite is then analyzed colorimetrically by way ...

Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

DOEpatents

Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

2002-11-26

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Sol-gel matrices for direct colorimetric detection of analytes

DOEpatents

Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

2000-01-01

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Highly selective and sensitive colorimetric determination of Cr3 + ion by 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol functionalized Au nanoparticles

NASA Astrophysics Data System (ADS)

Shahrivari, Shima; Faridbod, Farnoush; Ganjali, Mohammad Reza

2018-02-01

In this work, a rapid, selective naked eyes colorimetric chemical probe for the detection of Cr3 + was developed based on functionalization of gold nanoparticles. For this purpose, surface of Au NPs was functionalized using 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (AMTT). Through colorimetric studies, it was found that in the presence of Cr3 + ions, AMTT-Au NPs instantly aggregated and resulted in a color change of the solution from red to blue. The color change of AMTT-Au NPs due to the aggregation induced by Cr3 + can be seen with even naked eyes and also by UV-Vis spectroscopy with a detection limit of 1.8 μM and 0.1 μM, respectively. AMTT-Au NPs showed excellent selectivity toward Cr3 + compared to other cations tested, including K+, Na+, Cs+, Fe3 +, Ni2 +, Cu2 +, Co2 +, Zn2 +, Ba2 +, Ca2 +, Mg2 +, Cd2 +, Pb2 +, Hg2 + ions and especially all trivalent lanthanide ions. The absorbance ratio (A650/A525) was linear toward Cr3 + concentrations in the range of 0.6-6.1 μM (R2 = 0.996). The best response was achieved over a pH range of 3-5. Furthermore, the proposed colorimetric method based on AMTT-Au NPs was successfully used for Cr3 + ion detection in plasma sample and some water samples.

Colorimetric carbon dioxide detector to determine accidental tracheal feeding tube placement.

PubMed

Howes, Daniel W; Shelley, Eric S; Pickett, William

2005-04-01

To determine the accuracy of colorimetric CO2 detection compared to the reference standard two-step radiological confirmation of feeding tube position. A prospective study was conducted with patients presenting to a 21-bed medical-surgical intensive care unit. An adapter was developed using an endotracheal tube adapter to connect a colorimetric CO2 detector to a feeding tube in an airtight manner. In part I of the study a feeding tube connected to the colorimeter was inserted into the endotracheal tubes of ten ventilated patients to test the device's ability to detect tracheal placement. In part II patients undergoing feeding tube insertion had tube position confirmed with the colorimeter as well as the reference standard two-step x-ray. In phase I the colorimeter correctly identified tracheal placement in all ten patients. In phase II 93/100 procedures ultimately were eligible; the colorimeter had a sensitivity of 0.88 (95% confidence interval: 0.65-1.00) and specificity of 0.99 (0.97-1.00). The device missed one of the eight tracheal placements. Agreement between the colorimeter and two-step x-ray interpretations was excellent (Kappa 0.86; standard error 0.10). We describe a novel, convenient method to confirm esophageal feeding tube placement. The device is easily assembled and inexpensive, but should not be reused. Colorimetric determination of tracheal feeding tube placement with this device has excellent agreement with the reference standard two-step radiological technique.

A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu2 + in aqueous solution

NASA Astrophysics Data System (ADS)

Hu, Yang; Zhang, Jing; Lv, Yuan-Zheng; Huang, Xiao-Huan; Hu, Sheng-li

2016-03-01

A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu2 +. The optical feature of 1 for Cu2 + was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu2 +, the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu2 + complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu2 + with high sensitivity.

Improvement of fish freshness determination method by the application of amorphous freeze-dried enzymes.

PubMed

Srirangsan, Paveena; Hamada-Sato, Naoko; Kawai, Kiyoshi; Watanabe, Manabu; Suzuki, Toru

2010-12-08

Alkaline phosphatase (ALP), nucleoside phosphorylase (NP), and xanthine oxidase (XOD) were used in a colorimetric method for evaluation of fish freshness based on the Ki value. Two enzyme mixtures, NP-XOD and ALP-NP-XOD, were prepared with a color developing agent, and stabilities of the enzymes were improved by freeze-drying with glass-forming additives, i.e., sucrose and sucrose-gelatin. As a result, a linear relationship was obtained between the Ki values determined by the developed colorimetric method and a conventional high-performance liquid chromatography with a high correlation coefficient of 0.997. All enzyme samples containing the additive(s) were amorphous, and higher enzymes activities were maintained compared to those freeze-dried without an additive. Sucrose-gelatin/enzyme mixtures showed higher glass transition temperature; consequently, the enzymes were better stabilized than the sucrose/enzyme formulations. Using the sucrose-gelatin/enzyme mixture, Ki values of fish meat could be accurately determined even after 6-month storage of the dried enzymes at 40 °C.

Selective spectrophotometric determination of TNT using a dicyclohexylamine-based colorimetric sensor.

PubMed

Erçağ, Erol; Uzer, Ayşem; Apak, Reşat

2009-05-15

Because of the extremely heterogeneous distribution of explosives in contaminated soils, on-site colorimetric methods are efficient tools to assess the nature and extent of contamination. To meet the need for rapid and low-cost chemical sensing of explosive traces or residues in soil and post-blast debris, a colorimetric absorption-based sensor for trinitrotoluene (TNT) determination has been developed. The charge-transfer (CT) reagent (dicyclohexylamine, DCHA) is entrapped in a polyvinylchloride (PVC) polymer matrix plasticised with dioctylphtalate (DOP), and moulded into a transparent sensor membrane sliced into test strips capable of sensing TNT showing an absorption maximum at 530 nm when placed in a 1-mm spectrophotometer cell. The sensor gave a linear absorption response to 5-50 mg L(-1) TNT solutions in 30% aqueous acetone with limit of detection (LOD): 3 mg L(-1). The sensor is only affected by tetryl, but not by RDX, pentaerythritoltetranitrate (PETN), dinitrotoluene (DNT), and picric acid. The proposed method was statistically validated for TNT assay against high performance liquid chromatography (HPLC) using a standard sample of Comp B. The developed sensor was relatively resistant to air and water, was of low-cost and high specificity, gave a rapid and reproducible response, and was suitable for field use of TNT determination in both dry and humid soil and groundwater with a portable colorimeter.

Colorimetric test-systems for creatinine detection based on composite molecularly imprinted polymer membranes.

PubMed

Sergeyeva, T A; Gorbach, L A; Piletska, E V; Piletsky, S A; Brovko, O O; Honcharova, L A; Lutsyk, O D; Sergeeva, L M; Zinchenko, O A; El'skaya, A V

2013-04-03

An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N'-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25-2.5mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost. Copyright © 2013 Elsevier B.V. All rights reserved.

Selective sensing of submicromolar iron(III) with 3,3‧,5,5‧-tetramethylbenzidine as a chromogenic probe

NASA Astrophysics Data System (ADS)

Zhang, Lufeng; Du, Jianxiu

2016-04-01

The development of highly selective and sensitive method for iron(III) detection is of great importance both from human health as well as environmental point of view. We herein reported a simple, selective and sensitive colorimetric method for the detection of Fe(III) at submicromolar level with 3,3,‧5,5‧-tetramethylbenzidine (TMB) as a chromogenic probe. It was observed that Fe(III) could directly oxidize TMB to form a blue solution without adding any extra oxidants. The reaction has a stoichiometric ratio of 1:1 (Fe(III)/TMB) as determined by a molar ratio method. The resultant color change can be perceived by the naked eye or monitored the absorbance change at 652 nm. The method allowed the measurement of Fe(III) in the range 1.0 × 10- 7-1.5 × 10- 4 mol L- 1 with a detection limit of 5.5 × 10- 8 mol L- 1. The relative standard deviation was 0.9% for eleven replicate measurements of 2.5 × 10- 5 mol L- 1 Fe(III) solution. The chemistry showed high selectivity for Fe(III) in contrast to other common cation ions. The practically of the method was evaluated by the determination of Fe in milk samples; good consistency was obtained between the results of this method and atomic absorption spectrophotometry as indicated by statistical analysis.

Portable and low-cost colorimetric office paper-based device for phenacetin detection in seized cocaine samples.

PubMed

da Silva, Gabriela O; de Araujo, William R; Paixão, Thiago R L C

2018-01-01

An office paper-based colorimetric device is proposed as a portable, rapid, and low-cost sensor for forensic applications aiming to detect phenacetin used as adulterant in illicit seized materials such as cocaine. The proposed method uses white office paper as the substrate and wax printing technology to fabricate the detection zones. Based on the optimum conditions, a linear analytical curve was obtained for phenacetin concentrations ranging from 0 to 64.52µgmL ‒1 , and the straight line was in accordance with the following equation: (Magenta percentage color) = 1.19 + 0.458 (C Phe /µgmL ‒1 ), R 2 = 0.990. The limit of detection was calculated as 3.5µgmL ‒1 (3σ/slope). The accuracy of the proposed method was evaluated using real seized cocaine samples and the spike-recovery procedure. Copyright © 2017 Elsevier B.V. All rights reserved.

Colorimetric analysis of pigmented skin lesions: a pilot study with the Visi-Chroma VC-100 device.

PubMed

Vereecken, P; Mommaerts, M; Duez, C; Petein, M; Laporte, M; Hubinon, J-L; Heenen, M

2006-01-01

Definition of the colour of pigmented skin lesions (PSLs) with the naked eye remains subjective and may be influenced by lighting. This problem underlines the usefulness of instrumental assessments such as epiluminescence microscopy and colorimetric devices. We describe here a new method of colour analysis of PSLs with the Visi-Chroma VC-100 device, which illuminates the surface of the skin with white light-emitting diodes (LEDs) and analyses the reflected light by a red-green-blue (RGB) charge-coupled device (CCD) colour camera. Twenty-one PSLs to be excised for cosmetic or medical reasons were analysed by this device with clinicopathological correlation. This method is feasible and might be useful to assess the colour of PSLs and allow comparisons for changes over time. Further studies are needed to determine the usefulness of this device in clinical practice.

A Sensitive Microplate Assay for Lipase Activity Measurement Using Olive Oil Emulsion Substrate: Modification of the Copper Soap Colorimetric Method.

PubMed

Mustafa, Ahmad; Karmali, Amin; Abdelmoez, Wael

2016-01-01

The present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.

Method 366.0 Determination of Dissolved Silicate in Estuarine and Coastal Watersby Gas Segmented Continuous Flow Colorimetric Analysis

EPA Science Inventory

This method provides a procedure for the determination of dissolved silicate concentration in estuarine and coastal waters. The dissolved silicate is mainly in the form of silicic acid, H SiO , in estuarine and 4 4 coastal waters. All soluble silicate, including colloidal silici...

Use of DCPIP in a Colorimetric Method to Investigate Electron Transport in Crude Heart Mitochondrial Extracts.

ERIC Educational Resources Information Center

Myers, Alan

1990-01-01

A method of obtaining a crude mitochondrial extract from sheep and beef heart is described. The respiratory substrates succinate and malate are examined as well as the inhibitory effect of malonate. An interface with a microcomputer for plotting colorimeter results is discussed. (Author/CW)

A comparison of two colorimetric assays, based upon Lowry and Bradford techniques, to estimate total protein in soil extracts.

PubMed

Redmile-Gordon, M A; Armenise, E; White, R P; Hirsch, P R; Goulding, K W T

2013-12-01

Soil extracts usually contain large quantities of dissolved humified organic material, typically reflected by high polyphenolic content. Since polyphenols seriously confound quantification of extracted protein, minimising this interference is important to ensure measurements are representative. Although the Bradford colorimetric assay is used routinely in soil science for rapid quantification protein in soil-extracts, it has several limitations. We therefore investigated an alternative colorimetric technique based on the Lowry assay (frequently used to measure protein and humic substances as distinct pools in microbial biofilms). The accuracies of both the Bradford assay and a modified Lowry microplate method were compared in factorial combination. Protein was quantified in soil-extracts (extracted with citrate), including standard additions of model protein (BSA) and polyphenol (Sigma H1675-2). Using the Lowry microplate assay described, no interfering effects of citrate were detected even with concentrations up to 5 times greater than are typically used to extract soil protein. Moreover, the Bradford assay was found to be highly susceptible to two simultaneous and confounding artefacts: 1) the colour development due to added protein was greatly inhibited by polyphenol concentration, and 2) substantial colour development was caused directly by the polyphenol addition. In contrast, the Lowry method enabled distinction between colour development from protein and non-protein origin, providing a more accurate quantitative analysis. These results suggest that the modified-Lowry method is a more suitable measure of extract protein (defined by standard equivalents) because it is less confounded by the high polyphenolic content which is so typical of soil extracts.

Comparison of colorimetry and electrothermal atomic absorption spectroscopy for the quantification of non-transferrin bound iron in human sera.

PubMed

Jittangprasert, Piyada; Wilairat, Prapin; Pootrakul, Pensri

2004-12-01

This paper describes a comparison of two analytical techniques, one employing bathophenanthrolinedisulfonate (BPT), a most commonly-used reagent for Fe (II) determination, as chromogen and an electrothermal atomic absorption spectroscopy (ETAAS) for the quantification of non-transferrin bound iron (NTBI) in sera from thalassemic patients. Nitrilotriacetic acid (NTA) was employed as the ligand for binding iron from low molecular weight iron complexes present in the serum but without removing iron from the transferrin protein. After ultrafiltration the Fe (III)-NTA complex was then quantified by both methods. Kinetic study of the rate of the Fe (II)-BPT complex formation for various excess amounts of NTA ligand was also carried out. The kinetic data show that a minimum time duration (> 60 minutes) is necessary for complete complex formation when large excess of NTA is used. Calibration curves given by colorimetric and ETAAS methods were linear over the range of 0.15-20 microM iron (III). The colorimetric and ETAAS methods exhibited detection limit (3sigma) of 0.13 and 0.14 microM, respectively. The NTBI concentrations from 55 thalassemic serum samples measured employing BPT as chromogen were statistically compared with the results determined by ETAAS. No significant disagreement at 95% confidence level was observed. It is, therefore, possible to select any one of these two techniques for determination of NTBI in serum samples of thalassemic patients. However, the colorimetric procedure requires a longer analysis time because of a slow rate of exchange of NTA ligand with BPT, leading to the slow rate of formation of the colored complex.

Toward Quantifying the Aesthetic Outcomes of Breast Cancer Treatment: Comparison of Clinical Photography and Colorimetry

PubMed Central

Kim, Min Soon; Rodney, William N.; Cooper, Tara; Kite, Chris; Reece, Gregory P.; Markey, Mia K.

2011-01-01

Rationale, aims and objectives Scarring is a significant cause of dissatisfaction for women who undergo breast surgery. Scar tissue may be clinically distinguished from normal skin by aberrant color, rough surface texture, increased thickness (hypertrophy), and firmness. Colorimeters or spectrophotometers can be used to quantitatively assess scar color, but they require direct patient interaction and can cost thousands of dollars By comparison, digital photography is already in widespread use to document clinical outcomes and requires less patient interaction. Thus, assessment of scar coloration by digital photography is an attractive alternative. The goal of this study was to compare color measurements obtained by digital photography and colorimetry. Method Agreement between photographic and colorimetric measurements of color were evaluated. Experimental conditions were controlled by performing measurements on artificial scars created by a makeup artist. The colorimetric measurements of the artificial scars were compared to those reported in the literature for real scars in order to confirm the validity of this approach. We assessed the agreement between the colorimetric and photographic measurements of color using a hypothesis test for equivalence, the intra-class correlation coefficient (ICC), and the Bland-Altman method. Results Overall, good agreement was obtained for three parameters (L*a*b*) measured by colorimetry and photography from the results of three statistical analyses. Conclusion Color measurements obtained by digital photography were equivalent to those obtained using colorimetry. Thus, digital photography is a reliable, cost-effective measurement method of skin color and should be further investigated for quantitative analysis of surgical outcomes. PMID:19239578

[A study of biomechanical method for urine test based on color difference estimation].

PubMed

Wang, Chunhong; Zhou, Yue; Zhao, Hongxia; Zhou, Fengkun

2008-02-01

The biochemical analysis of urine is an important inspection and diagnosis method in hospitals. The conventional method of urine analysis covers mainly colorimetric visual appraisement and automation detection, in which the colorimetric visual appraisement technique has been superseded basically, and the automation detection method is adopted in hospital; moreover, the price of urine biochemical analyzer on market is around twenty thousand RMB yuan (Y), which is hard to enter into ordinary families. It is known that computer vision system is not subject to the physiological and psychological influence of person, its appraisement standard is objective and steady. Therefore, according to the color theory, we have established a computer vision system, which can carry through collection, management, display, and appraisement of color difference between the color of standard threshold value and the color of urine test paper after reaction with urine liquid, and then the level of an illness can be judged accurately. In this paper, we introduce the Urine Test Biochemical Analysis method, which is new and can be popularized in families. Experimental result shows that this test method is easy-to-use and cost-effective. It can realize the monitoring of a whole course and can find extensive applications.

A Paper-Based Analytical Device Based on Combination of Thin Film Microextraction and Reflection Scanometry for Sensitive Colorimetric Determination of Ni(II) in Aqueous Matrix.

PubMed

Allafchian, Ali Reza; Farajmand, Bahman; Koupaei, Amin Javaheri

2018-04-01

In this research, the thin film microextraction method was applied for the extraction of Ni(II) ion from aqueous matrixes. Chemically modified cellulosic filter paper with phosphorus was used as a thin film extractor. After extraction, the thin film was treated with a solution of dimethylglyoxime. The colored film was captured by flatbed scanner and the absorbance of the images was extracted by some suitable software. Under the optimum conditions and at the pH 7.0, with the sample volume of 100 mL, the stirring rate of 800 rpm, and the extraction time of 50 min, the calibration curve was obtained in the range of 0.05-5 mg/L Ni(II) (R 2  = 0.989). Limit and relative standard deviation were achieved to be 18 µg/L and less than 6.7%, respectively. Relative recoveries were obtained in the range of 87%-105%. Finally, the proposed method was found to be simple and cost-effective, with adequate analytical performance for the rapid detection of Ni(II) in river and wastewater samples.

Pesticide analysis using nanoceria-coated paper-based devices as a detection platform.

PubMed

Nouanthavong, Souksanh; Nacapricha, Duangjai; Henry, Charles S; Sameenoi, Yupaporn

2016-03-07

We report the first use of a paper-based device coated with nanoceria as a simple, low-cost and rapid detection platform for the analysis of organophosphate (OP) pesticides using an enzyme inhibition assay with acetylcholinesterase (AChE) and choline oxidase (ChOX). In the presence of acetylcholine, AChE and ChOX catalyze the formation of H2O2, which is detected colorimetrically by a nanoceria-coated device resulting in the formation of a yellow color. After incubation with OP pesticides, the AChE activity was inhibited, producing less H2O2, and a reduction in the yellow intensity. The assay is able to analyze OP pesticides without the use of sophisticated instruments and gives detection limits of 18 ng mL(-1) and 5.3 ng mL(-1) for methyl-paraoxon and chlorpyrifos-oxon, respectively. The developed method was successfully applied to detect methyl-paraoxon in spiked vegetables (cabbage) and a dried seafood product (dried green mussel), obtaining ∼95% recovery values for both sample types. The spiked samples were also analyzed using LC-MS/MS as a comparison to the developed method and similar values were obtained, indicating that the developed method gives accurate results and is suitable for OP analysis in real samples.

Simple and Rapid Quantitative Determination of Thiol-Containing Toxicants Using Silver Nanoparticles as an Affinity Probe

NASA Astrophysics Data System (ADS)

Sharma, A.; Tapadia, K.

2017-01-01

A rapid and low-cost nano-drop spectrophotometric method using citrate-modified silver nanoparticles (Ag NPs) for the determination of thiol-containing toxicants was developed. The introduction of thioglycolic acid (TGA) and thiourea (TU) reduced the overall surface charge of Ag NPs, resulting in aggregation of Ag NPs, and a colorimetric response that was individually correlated with the concentration of TGA and TU. Under optimum experimental conditions, the maximum molar absorptivity values for TGA and TU were 1.04 × 105 and 2.13 × 105 L × mol-1 × cm-1, respectively, at λmax of 415 nm. The linear range used was 0.5-2.5 mg/L for TGA, and 0.3-1.5 mg/L for TU. The detection limits (3S) and % relative standard deviation (RSD) for the method were found to be 3 ppb, 2 ppb, and ±1.13%, ±0.96% for TGA and TU, respectively. This new chromogenic method provided a facile and sensitive scheme for the determination of TGA and TU, and could be applied for the determination of thiol-containing biomolecules. This scheme was tested for the analysis of real samples such as urine, blood, and environmental samples.

Zero- and two-dimensional hybrid carbon phosphors for high colorimetric purity white light-emission.

PubMed

Ding, Yamei; Chang, Qing; Xiu, Fei; Chen, Yingying; Liu, Zhengdong; Ban, Chaoyi; Cheng, Shuai; Liu, Juqing; Huang, Wei

2018-03-01

Carbon nanomaterials are promising phosphors for white light emission. A facile single-step synthesis method has been developed to prepare zero- and two-dimensional hybrid carbon phosphors for the first time. Zero-dimensional carbon dots (C-dots) emit bright blue luminescence under 365 nm UV light and two-dimensional nanoplates improve the dispersity and film forming ability of C-dots. As a proof-of-concept application, the as-prepared hybrid carbon phosphors emit bright white luminescence in the solid state, and the phosphor-coated blue LEDs exhibit high colorimetric purity white light-emission with a color coordinate of (0.3308, 0.3312), potentially enabling the successful application of white emitting phosphors in the LED field.

Colorimetric assay for urinary track infection disease diagnostic on flexible substrate

NASA Astrophysics Data System (ADS)

Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Zourob, Mohammed

2012-10-01

We are presenting cassette as a novel point of care diagnostic device. This device is easy to use, low cost to prepare, high throughput and can analyze several samples at the same time. We first, demonstrate the preparation method of the device. Then, fabrication of the flexible substrate has been presented. The device has been used for detection of the real sample of E.coli bacteria following by colorimetric detection. We have shown that we could detect 30 cfu/ml bacteria and 100 fg/μl of Staphylococous aureus DNA in 1 hr using LAMP amplification technique. This device will be helpful in hospitals and doctor's office for analysis of several patients' samples at the same time.

A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu(2+) in aqueous solution.

PubMed

Hu, Yang; Zhang, Jing; Lv, Yuan-Zheng; Huang, Xiao-Huan; Hu, Sheng-Li

2016-03-15

A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu(2+). The optical feature of 1 for Cu(2+) was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu(2+), the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu(2+) complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu(2+) with high sensitivity. Copyright © 2015 Elsevier B.V. All rights reserved.

Rapid Diagnosis of Tuberculosis from Analysis of Urine Volatile Organic Compounds

PubMed Central

Lim, Sung H.; Martino, Raymond; Anikst, Victoria; Xu, Zeyu; Mix, Samantha; Benjamin, Robert; Schub, Herbert; Eiden, Michael; Rhodes, Paul A.; Banaei, Niaz

2017-01-01

The World Health Organization has called for simple, sensitive, and non-sputum diagnostics for tuberculosis. We report development of a urine tuberculosis test using a colorimetric sensor array (CSA). The sensor comprised of 73 different indicators captures high-dimensional, spatiotemporal signatures of volatile chemicals emitted by human urine samples. The sensor responses to 63 urine samples collected from 22 tuberculosis cases and 41 symptomatic controls were measured under five different urine test conditions. Basified testing condition yielded the best accuracy with 85.5% sensitivity and 79.5% specificity. The CSA urine assay offers desired features needed for tuberculosis diagnosis in endemic settings. PMID:29057329

Multiplexed Colorimetric Solid-Phase Extraction

NASA Technical Reports Server (NTRS)

Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.

2009-01-01

Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (C-SPE) an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In CSPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a handheld diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes. In extending C-SPE to a multiplexed format, a filter holder that incorporates discrete analysis channels and a jig that facilitates the concurrent operation of multiple sample syringes have been designed, enabling the simultaneous determination of multiple analytes. Separate, single analyte membranes, placed in a readout cartridge create unique, analyte-specific addresses at the exit of each channel. Following sample exposure, the diffuse reflectance spectrum of each address is collected serially and the Kubelka-Munk function is used to quantify each water quality parameter via calibration curves. In a demonstration, MC-SPE was used to measure the pH of a sample and quantitate Ag(I) and Ni(II).

Development, optimization and validation of a rapid colorimetric microplate bioassay for neomycin sulfate in pharmaceutical drug products.

PubMed

Francisco, Fabiane Lacerda; Saviano, Alessandro Morais; Pinto, Terezinha de Jesus Andreoli; Lourenço, Felipe Rebello

2014-08-01

Microbiological assays have been used to evaluate antimicrobial activity since the discovery of the first antibiotics. Despite their limitations, microbiological assays are widely employed to determine antibiotic potency of pharmaceutical dosage forms, since they provide a measure of biological activity. The aim of this work is to develop, optimize and validate a rapid colorimetric microplate bioassay for the potency of neomycin in pharmaceutical drug products. Factorial and response surface methodologies were used in the development and optimization of the choice of microorganism, culture medium composition, amount of inoculum, triphenyltetrazolium chloride (TTC) concentration and neomycin concentration. The optimized bioassay method was validated by the assessment of linearity (range 3.0 to 5.0μg/mL, r=0.998 and 0.994 for standard and sample curves, respectively), precision (relative standard deviation (RSD) of 2.8% and 4.0 for repeatability and intermediate precision, respectively), accuracy (mean recovery=100.2%) and robustness. Statistical analysis showed equivalency between agar diffusion microbiological assay and rapid colorimetric microplate bioassay. In addition, microplate bioassay had advantages concerning the sensitivity of response, time of incubation, and amount of culture medium and solutions required. Copyright © 2014 Elsevier B.V. All rights reserved.

Biothiols induced colour change of silver nanoparticles: A colorimetric sensing strategy

NASA Astrophysics Data System (ADS)

Thomas, Ambily; Sivasankaran, Unni; Kumar, Krishnapillai Girish

2018-01-01

A sensor for the detection and determination of bio-thiols (glutathione (GSH) and cysteamine (Cyste)) has been developed by integrating the distinguished distance related optical characteristics of silver nanoparticles with the simplicity of colorimetric technique. In presence of these analytes, shift in surface plasmon resonance (SPR) absorption of silver nanoparticles (AgNPs) with change in its colour was observed. Yellow coloured AgNPs solution becomes colourless in presence of GSH and changes to red in presence of Cyste. FTIR, TEM and DLS studies were used to confirm the mechanism. The difference in absorption of AgNPs in the absence and presence of GSH was found to vary linearly in the range 1.00 × 10- 5 M to 5.00 × 10- 7 M concentration range with limit of detection at 3.68 × 10- 7 M. The method can also be applied to quantify Cyste in the range 1.10 × 10- 6 M to 5.00 × 10- 8 M with limit of detection at 1.80 × 10- 8 M. The utility of the proposed colorimetric assay is validated by determination of GSH and Cyste in artificial blood serum.

A soft, wearable microfluidic device for the capture, storage, and colorimetric sensing of sweat.

PubMed

Koh, Ahyeon; Kang, Daeshik; Xue, Yeguang; Lee, Seungmin; Pielak, Rafal M; Kim, Jeonghyun; Hwang, Taehwan; Min, Seunghwan; Banks, Anthony; Bastien, Philippe; Manco, Megan C; Wang, Liang; Ammann, Kaitlyn R; Jang, Kyung-In; Won, Phillip; Han, Seungyong; Ghaffari, Roozbeh; Paik, Ungyu; Slepian, Marvin J; Balooch, Guive; Huang, Yonggang; Rogers, John A

2016-11-23

Capabilities in health monitoring enabled by capture and quantitative chemical analysis of sweat could complement, or potentially obviate the need for, approaches based on sporadic assessment of blood samples. Established sweat monitoring technologies use simple fabric swatches and are limited to basic analysis in controlled laboratory or hospital settings. We present a collection of materials and device designs for soft, flexible, and stretchable microfluidic systems, including embodiments that integrate wireless communication electronics, which can intimately and robustly bond to the surface of the skin without chemical and mechanical irritation. This integration defines access points for a small set of sweat glands such that perspiration spontaneously initiates routing of sweat through a microfluidic network and set of reservoirs. Embedded chemical analyses respond in colorimetric fashion to markers such as chloride and hydronium ions, glucose, and lactate. Wireless interfaces to digital image capture hardware serve as a means for quantitation. Human studies demonstrated the functionality of this microfluidic device during fitness cycling in a controlled environment and during long-distance bicycle racing in arid, outdoor conditions. The results include quantitative values for sweat rate, total sweat loss, pH, and concentration of chloride and lactate. Copyright © 2016, American Association for the Advancement of Science.

DNA-mediated inhibition of peroxidase-like activities on platinum nanoparticles for simple and rapid colorimetric detection of nucleic acids.

PubMed

Chen, Weiwei; Fang, Xueen; Li, Hua; Cao, Hongmei; Kong, Jilie

2017-08-15

In this research, we found that the peroxidase-like activities of noncovalent DNA-Pt hybrid nanoparticles could be obviously blocked, when Pt nanoparticles (PtNPs) were synthesized in situ using DNA as a template. Moreover, this self-assembled synthetic process was very convenient and rapid (within few mintues), and the inhibition mediated by DNA was also very effective. First, by the paper-based analytical device (PAD) we found the catalytic activities of DNA-Pt hybrid nanoparticles exhibited a linear response to the concentration of DNA in the range from 0.0075 to 0.25µM. Then, with the magnetic bead isolated system and target DNA-induced hybridization chain reaction (HCR), we realized the specific target DNA analysis with a low detection of 0.228nM, and demonstrated its effectivity in distinguishing the target DNA from other interferences. To our knowledge, this is the first report that used the nanoassembly between DNA and PtNPs for colorimetric detection of nucleic acids, which was based on DNA-mediated inhibition of catalytic activities of platinum nanoparticles. The results may be useful for understanding the interactions between DNA and metal nanoparticles, and for development of other convenient and effective analytical strategies. Copyright © 2017. Published by Elsevier B.V.

Selection of DNA aptamers against Human Cardiac Troponin I for colorimetric sensor based dot blot application.

PubMed

Dorraj, Ghamar Soltan; Rassaee, Mohammad Javad; Latifi, Ali Mohammad; Pishgoo, Bahram; Tavallaei, Mahmood

2015-08-20

Troponin T and I are ideal markers which are highly sensitive and specific for myocardial injury and have shown better efficacy than earlier markers. Since aptamers are ssDNA or RNA that bind to a wide variety of target molecules, the purpose of this research was to select an aptamer from a 79bp single-stranded DNA (ssDNA) random library that was used to bind the Human Cardiac Troponin I from a synthetic nucleic acids library by systematic evolution of ligands exponential enrichment (Selex) based on several selection and amplification steps. Human Cardiac Troponin I protein was coated onto the surface of streptavidin magnetic beads to extract specific aptamer from a large and diverse random ssDNA initial oligonucleotide library. As a result, several aptamers were selected and further examined for binding affinity and specificity. Finally TnIApt 23 showed beast affinity in nanomolar range (2.69nM) toward the target protein. A simple and rapid colorimetric detection assay for Human Cardiac Troponin I using the novel and specific aptamer-AuNPs conjugates based on dot blot assay was developed. The detection limit for this protein using aptamer-AuNPs-based assay was found to be 5ng/ml. Copyright © 2015 Elsevier B.V. All rights reserved.

Fluorescent and colorimetric ion probes based on conjugated oligopyrroles.

PubMed

Ding, Yubin; Tang, Yunyu; Zhu, Weihong; Xie, Yongshu

2015-03-07

Metal ions and anions play important roles in many industrial and biochemical processes, and thus it is highly desired to detect them in the relevant systems. Small organic molecule based sensors for selective and sensitive detection of target ions show the advantages of low cost, high sensitivity and convenient implementation. In this area, pyrrole has incomparable advantages. It can be easily incorporated into linear and macrocyclic conjugated structures such as dipyrrins, porphyrins, and N-confused porphyrins, which may utilize the imino N and amino NH moieties for binding metal ions and anions, respectively. In this tutorial review, we focus on representative examples to describe the design, syntheses, sensing mechanisms, and applications of the conjugated oligopyrroles. These compounds could be used as colorimetric or fluorescent ion probes, with the advantages of vivid colour and fluorescence changes, easy structural modification and functionalization, and tunable emission wavelengths. Compared with normal porphyrins, simple di- and tripyrrins, as well as some porphyrinoids are more suitable for designing fluorescence "turn-on" metal probes, because they may exhibit flexible confirmations, and metal coordination will improve the rigidity, resulting in vivid fluorescence enhancement. It is noteworthy that the oligopyrrolic moieties may simultaneously act as the binding unit as well as the reporting moiety, which simplifies the design and syntheses of the probes.

76 FR 37796 - Notice of Availability of Government-Owned Inventions; Available for Licensing

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-28

... Aircraft Division, Business and Partnership Office, Office of Research and Technology Applications... October 26, 2010 U.S. Patent Application No. 7,839,304 B2: Method and System for Alerting Aircrew to... Application No. 12/868,772: Colorimetric Method for Detection of Biodiesel in Fuel, Navy Case No. PAX37, filed...

Determination of Total Sulfur, Sulfate, Sulfite, Thiosulfate, and Sulfolipids in Plants.

PubMed

Kurmanbayeva, Assylay; Brychkova, Galina; Bekturova, Aizat; Khozin, Inna; Standing, Dominic; Yarmolinsky, Dmitry; Sagi, Moshe

2017-01-01

In response to oxidative stress the biosynthesis of the ROS scavenger, glutathione is induced. This requires the induction of the sulfate reduction pathway for an adequate supply of cysteine, the precursor for glutathione. Cysteine also acts as the sulfur donor for the sulfuration of the molybdenum cofactor, crucial for the last step of ABA biosynthesis. Sulfate and sulfite are, respectively, the precursor and intermediate for cysteine biosynthesis and there is evidence for stress-induced sulfate uptake and further downstream, enhanced sulfite generation by 5'-phosphosulfate (APS) reductase (APR, EC 1.8.99.2) activity. Sulfite reductase (SiR, E.C.1.8.7.1) protects the chloroplast against toxic levels of sulfite by reducing it to sulfide. In case of sulfite accumulation as a result of air pollution or stress-induced premature senescence, such as in extended darkness, sulfite can be oxidized to sulfate by sulfite oxidase. Additionally sulfite can be catalyzed to thiosulfate by sulfurtransferases or to UDP-sulfoquinovose by SQD1, being the first step toward sulfolipid biosynthesis.Determination of total sulfur in plants can be accomplished using many techniques such as ICP-AES, high-frequency induction furnace, high performance ion chromatography, sulfur combustion analysis, and colorimetric titration. Here we describe a total sulfur detection method in plants by elemental analyzer (EA). The used EA method is simple, sensitive, and accurate, and can be applied for the determination of total S content in plants.Sulfate anions in the soil are the main source of sulfur, required for normal growth and development, of plants. Plants take up sulfate ions from the soil, which are then reduced and incorporated into organic matter. Plant sulfate content can be determined by ion chromatography with carbonate eluents.Sulfite is an intermediate in the reductive assimilation of sulfate to the essential amino acids cysteine and methionine, and is cytotoxic above a certain threshold if not rapidly metabolized and can wreak havoc at the cellular and whole plant levels. Plant sulfite content affects carbon and nitrogen homeostasis Therefore, methods capable of determining sulfite levels in plants are of major importance. Here we present two robust laboratory protocols which can be used for sulfite detection in plants.Thiosulfate is an essential sulfur intermediate less toxic than sulfite which is accumulating in plants in response to sulfite accumulation. The complexity of thiosulfate detection is linked to its chemical properties. Here we present a rapid, sensitive, and accurate colorimetric method based on the enzymatic conversion of thiosulfate to thiocyanate.The plant sulfolipid sulfoquinovosyldiacylglycerol (SQDG) accounts for a large fraction of organic sulfur in the biosphere. Aside from sulfur amino acids, SQDG represents a considerable sink for sulfate in plants and is the only sulfur-containing anionic glycerolipid that is found in the photosynthetic membranes of plastids. We present the separation of sulfolipids from other fatty acids in two simple ways: by one- and two-dimensional thin-layer chromatography.

A paper/polymer hybrid microfluidic microplate for rapid quantitative detection of multiple disease biomarkers.

PubMed

Sanjay, Sharma T; Dou, Maowei; Sun, Jianjun; Li, XiuJun

2016-07-26

Enzyme linked immunosorbent assay (ELISA) is one of the most widely used laboratory disease diagnosis methods. However, performing ELISA in low-resource settings is limited by long incubation time, large volumes of precious reagents, and well-equipped laboratories. Herein, we developed a simple, miniaturized paper/PMMA (poly(methyl methacrylate)) hybrid microfluidic microplate for low-cost, high throughput, and point-of-care (POC) infectious disease diagnosis. The novel use of porous paper in flow-through microwells facilitates rapid antibody/antigen immobilization and efficient washing, avoiding complicated surface modifications. The top reagent delivery channels can simply transfer reagents to multiple microwells thus avoiding repeated manual pipetting and costly robots. Results of colorimetric ELISA can be observed within an hour by the naked eye. Quantitative analysis was achieved by calculating the brightness of images scanned by an office scanner. Immunoglobulin G (IgG) and Hepatitis B surface Antigen (HBsAg) were quantitatively analyzed with good reliability in human serum samples. Without using any specialized equipment, the limits of detection of 1.6 ng/mL for IgG and 1.3 ng/mL for HBsAg were achieved, which were comparable to commercial ELISA kits using specialized equipment. We envisage that this simple POC hybrid microplate can have broad applications in various bioassays, especially in resource-limited settings.

A paper/polymer hybrid microfluidic microplate for rapid quantitative detection of multiple disease biomarkers

PubMed Central

Sanjay, Sharma T.; Dou, Maowei; Sun, Jianjun; Li, XiuJun

2016-01-01

Enzyme linked immunosorbent assay (ELISA) is one of the most widely used laboratory disease diagnosis methods. However, performing ELISA in low-resource settings is limited by long incubation time, large volumes of precious reagents, and well-equipped laboratories. Herein, we developed a simple, miniaturized paper/PMMA (poly(methyl methacrylate)) hybrid microfluidic microplate for low-cost, high throughput, and point-of-care (POC) infectious disease diagnosis. The novel use of porous paper in flow-through microwells facilitates rapid antibody/antigen immobilization and efficient washing, avoiding complicated surface modifications. The top reagent delivery channels can simply transfer reagents to multiple microwells thus avoiding repeated manual pipetting and costly robots. Results of colorimetric ELISA can be observed within an hour by the naked eye. Quantitative analysis was achieved by calculating the brightness of images scanned by an office scanner. Immunoglobulin G (IgG) and Hepatitis B surface Antigen (HBsAg) were quantitatively analyzed with good reliability in human serum samples. Without using any specialized equipment, the limits of detection of 1.6 ng/mL for IgG and 1.3 ng/mL for HBsAg were achieved, which were comparable to commercial ELISA kits using specialized equipment. We envisage that this simple POC hybrid microplate can have broad applications in various bioassays, especially in resource-limited settings. PMID:27456979

A paper/polymer hybrid microfluidic microplate for rapid quantitative detection of multiple disease biomarkers

NASA Astrophysics Data System (ADS)

Sanjay, Sharma T.; Dou, Maowei; Sun, Jianjun; Li, Xiujun

2016-07-01

Enzyme linked immunosorbent assay (ELISA) is one of the most widely used laboratory disease diagnosis methods. However, performing ELISA in low-resource settings is limited by long incubation time, large volumes of precious reagents, and well-equipped laboratories. Herein, we developed a simple, miniaturized paper/PMMA (poly(methyl methacrylate)) hybrid microfluidic microplate for low-cost, high throughput, and point-of-care (POC) infectious disease diagnosis. The novel use of porous paper in flow-through microwells facilitates rapid antibody/antigen immobilization and efficient washing, avoiding complicated surface modifications. The top reagent delivery channels can simply transfer reagents to multiple microwells thus avoiding repeated manual pipetting and costly robots. Results of colorimetric ELISA can be observed within an hour by the naked eye. Quantitative analysis was achieved by calculating the brightness of images scanned by an office scanner. Immunoglobulin G (IgG) and Hepatitis B surface Antigen (HBsAg) were quantitatively analyzed with good reliability in human serum samples. Without using any specialized equipment, the limits of detection of 1.6 ng/mL for IgG and 1.3 ng/mL for HBsAg were achieved, which were comparable to commercial ELISA kits using specialized equipment. We envisage that this simple POC hybrid microplate can have broad applications in various bioassays, especially in resource-limited settings.

The Colour Test for drug susceptibility testing of Mycobacterium tuberculosis strains.

PubMed

Toit, K; Mitchell, S; Balabanova, Y; Evans, C A; Kummik, T; Nikolayevskyy, V; Drobniewski, F

2012-08-01

Tartu, Estonia. To assess the performance and feasibility of the introduction of the thin-layer agar MDR/XDR-TB Colour Test (Colour Test) as a non-commercial method of drug susceptibility testing (DST). The Colour Test combines the thin-layer agar technique with a simple colour-coded quadrant format, selective medium to reduce contamination and colorimetric indication of bacterial growth to simplify interpretation. DST patterns for isoniazid (INH), rifampicin (RMP) and ciprofloxacin (CFX) were determined using the Colour Test for 201 archived Mycobacterium tuberculosis isolates. Susceptibilities were compared to blinded DST results obtained routinely using the BACTEC™ Mycobacteria Growth Indicator Tube™ (MGIT) 960 to assess performance characteristics. In all, 98% of the isolates produced interpretable results. The average time to positivity was 13 days, and all results were interpretable. The Colour Test detected drug resistance with 98% sensitivity for INH, RMP and CFX and 99% for multidrug-resistant tuberculosis. Specificities were respectively 100% (95%CI 82-100), 88% (95%CI 69-97) and 91% (95%CI 83-96) and 90% (95%CI 74-98). Agreement between the Colour Test and BACTEC MGIT 960 were respectively 98%, 96%, 94% and 97%. The Colour Test could be an economical, accurate and simple technique for testing tuberculosis strains for drug resistance. As it requires little specialist equipment, it may be particularly useful in resource-constrained settings with growing drug resistance rates.

Mentha-Stabilized Silver Nanoparticles for High-Performance Colorimetric Detection of Al(III) in Aqueous Systems.

PubMed

Sharma, Rekha; Dhillon, Ankita; Kumar, Dinesh

2018-03-26

The present paper reports a facile and selective colorimetric method for the detection of potential environmental and health hazardous metal ions using green synthesized silver nanoparticles (AgNPs). Here the organic functional groups present in the plant extract (Mentha arvensis) are used as reductants and stabilizers in the synthesis of AgNPs. They also provide a suitable binding site to the (Al(III)) analyte in the detection mechanism. The leaf extract of Mentha arvensis was used to synthesize AgNPs at room-temperature and at 80 °C. The AgNPs synthesized at 80 °C exhibit excellent selective colorimetric detection of Al(III). The as-synthesized AgNPs have been characterized, and the synthesis, stabilization of NPs and detection mechanism has also been illustrated by using UV-vis, XPS, FTIR, TEM, EDX, SEM, AAS, and TGA analytical tools and techniques. The selectivity of detection probe was supported by the reaction between probe and metal ions followed first-order kinetics having the highest value of the regression coefficient (R 2  = 0.99) for Al(III) and the analysis of thermodynamic parameters. The prepared sensor showed a lower limit of detection (LOD) of 1 nM (S/N = 3.2) in real water samples. The proposed method can be successfully utilized for the detection of Al(III) from both drinking and real water samples at the nanomolar level.

Towards quantifying the aesthetic outcomes of breast cancer treatment: comparison of clinical photography and colorimetry.

PubMed

Kim, Min Soon; Rodney, William N; Cooper, Tara; Kite, Chris; Reece, Gregory P; Markey, Mia K

2009-02-01

Scarring is a significant cause of dissatisfaction for women who undergo breast surgery. Scar tissue may be clinically distinguished from normal skin by aberrant colour, rough surface texture, increased thickness (hypertrophy) and firmness. Colorimeters or spectrophotometers can be used to quantitatively assess scar colour, but they require direct patient interaction and can cost thousands of dollars. By comparison, digital photography is already in widespread use to document clinical outcomes and requires less patient interaction. Thus, assessment of scar coloration by digital photography is an attractive alternative. The goal of this study was to compare colour measurements obtained by digital photography and colorimetry. Agreements between photographic and colorimetric measurements of colour were evaluated. Experimental conditions were controlled by performing measurements on artificial scars created by a make-up artist. The colorimetric measurements of the artificial scars were compared with those reported in the literature for real scars in order to confirm the validity of this approach. We assessed the agreement between the colorimetric and photographic measurements of colour using a hypothesis test for equivalence, the intraclass correlation coefficient and the Bland-Altman method. Overall, good agreement was obtained for three parameters (L*a*b*) measured by colorimetry and photography from the results of three statistical analyses. Colour measurements obtained by digital photography were equivalent to those obtained using colorimetry. Thus, digital photography is a reliable, cost-effective measurement method of skin colour and should be further investigated for quantitative analysis of surgical outcomes.

Colorimetric and Fluorescent Dual Mode Sensing of Alcoholic Strength in Spirit Samples with Stimuli-Responsive Infinite Coordination Polymers.

PubMed

Deng, Jingjing; Ma, Wenjie; Yu, Ping; Mao, Lanqun

2015-07-07

This study demonstrates a new strategy for colorimetric and fluorescent dual mode sensing of alcoholic strength (AS) in spirit samples based on stimuli-responsive infinite coordination polymers (ICPs). The ICP supramolecular network is prepared with 1,4-bis(imidazol-1-ylmethyl)benzene (bix) as the ligand and Zn(2+) as the central metal ion in ethanol, in which rhodamine B (RhB) is encapsulated through self-adaptive chemistry. In pure ethanol solvent, the as-formed RhB/Zn(bix) is well dispersed and quite stable. However, the addition of water into the ethanol dispersion of RhB/Zn(bix) destroys Zn(bix) network structure, resulting in the release of RhB from ICP into the solvent. As a consequence, the solvent displays the color of released RhB and, at the meantime, turns on the fluorescence of RhB, which constitutes a new mechanism for colorimetric and fluorescent dual mode sensing of AS in commercial spirit samples. With the method developed here, we could distinguish the AS of different commercial spirit samples by the naked eye within a wide linear range from 20 to 100% vol and by monitoring the increase of fluorescent intensity of the released RhB. This study not only offers a new method for on-spot visible detection of AS in commercial spirit samples, but also provides a strategy for designing dual mode sensing mechanisms for different analytical purposes based on novel stimuli-responsive materials.

Sensitive detection of microRNAs based on the conversion of colorimetric assay into electrochemical analysis with duplex-specific nuclease-assisted signal amplification

PubMed Central

Xia, Ning; Liu, Ke; Zhou, Yingying; Li, Yuanyuan; Yi, Xinyao

2017-01-01

miRNAs have emerged as new biomarkers for the detection of a wide variety of cancers. By employing duplex-specific nuclease for signal amplification and gold nanoparticles (AuNPs) as the carriers of detection probes, a novel electrochemical assay of miRNAs was performed. The method is based on conversion of the well-known colorimetric assay into electrochemical analysis with enhanced sensitivity. DNA capture probes immobilized on the electrode surface and ferrocene (Fc)-labeled DNA detection probes (denoted “Fc-DNA-Fc”) presented in the solution induced the assembly of positively charged AuNPs on the electrode surface through the electrostatic interaction. As a result, a large number of Fc-DNA-Fc molecules were attached on the electrode surface, thus amplifying the electrochemical signal. When duplex-specific nuclease was added to recycle the process of miRNA-initiated digestion of the immobilized DNA probes, Fc-DNA-Fc-induced assembly of AuNPs on the electrode surface could not occur. This resulted in a significant fall in the oxidation current of Fc. The current was found to be inversely proportional to the concentration of miRNAs in the range of 0–25 fM, and a detection limit of 0.1 fM was achieved. Moreover, this work presents a new method for converting colorimetric assays into sensitive electrochemical analyses, and thus would be valuable for design of novel chemical/biosensors. PMID:28761341

The effects of colorimetric detection of heavy metal ions based on Au nanoparticles (NPs): size and shape—a case of Co2+

NASA Astrophysics Data System (ADS)

Leng, Yumin; He, Junbao; Li, Bo; Xing, Xiaojing; Guo, Yongming; Ye, Liqun; Lu, Zhiwen

2017-09-01

The different sized and shaped Au NPs have intrigued considerable attention, because they possess different surface plasma resonance (SPR) absorption bands and thus result in many colorimetric Au NP-based detection applications. In this article, four different sized and shaped Au NPs of nanodots/rods were prepared and characterized. The as-prepared Au NPs were modified by the negatively charged anions of [SCH2CO2]2- to investigate both the size and shape effects of modified Au NPs on colorimetric detection of Co2+ and the corresponding SPR absorption properties. The different-shaped Au NPs possess different SPR absorption properties. The Au nanorods appeared to be colorimetric sensitive for Co2+ sensing.

Spectrophotometric, colorimetric and visually detection of Pseudomonas aeruginosa ETA gene based gold nanoparticles DNA probe and endonuclease enzyme.

PubMed

Amini, Bahram; Kamali, Mehdi; Salouti, Mojtaba; Yaghmaei, Parichehreh

2018-06-15

Colorimetric DNA detection is preferred over other methods for clinical molecular diagnosis because it does not require expensive equipment. In the present study, the colorimetric method based on gold nanoparticles (GNPs) and endonuclease enzyme was used for the detection of P. aeruginosa ETA gene. Firstly, the primers and probe for P. aeruginosa exotoxin A (ETA) gene were designed and checked for specificity by the PCR method. Then, GNPs were synthesized using the citrate reduction method and conjugated with the prepared probe to develop the new nano-biosensor. Next, the extracted target DNA of the bacteria was added to GNP-probe complex to check its efficacy for P. aeruginosa ETA gene diagnosis. A decrease in absorbance was seen when GNP-probe-target DNA cleaved into the small fragments of BamHI endonuclease due to the weakened electrostatic interaction between GNPs and the shortened DNA. The right shift of the absorbance peak from 530 to 562nm occurred after adding the endonuclease. It was measured using a UV-VIS absorption spectroscopy that indicates the existence of the P. aeruginosa ETA gene. Sensitivity was determined in the presence of different concentrations of target DNA of P. aeruginosa. The results obtained from the optimized conditions showed that the absorbance value has linear correlation with concentration of target DNA (R: 0.9850) in the range of 10-50ngmL -1 with the limit detection of 9.899ngmL -1 . Thus, the specificity of the new method for detection of P. aeruginosa was established in comparison with other bacteria. Additionally, the designed assay was quantitatively applied to detect the P. aeruginosa ETA gene from 10 3 to 10 8 CFUmL -1 in real samples with a detection limit of 320CFUmL -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

Headspace-Sampling Paper-Based Analytical Device for Colorimetric/Surface-Enhanced Raman Scattering Dual Sensing of Sulfur Dioxide in Wine.

PubMed

Li, Dan; Duan, Huazhen; Ma, Yadan; Deng, Wei

2018-05-01

This study demonstrates a novel strategy for colorimetric/surface-enhanced Raman scattering (SERS) dual-mode sensing of sulfur dioxide (SO 2 ) by coupling headspace sampling (HS) with paper-based analytical device (PAD). The smart and multifunctional PAD is fabricated with a vacuum filtration method in which 4-mercaptopyridine (Mpy)-modified gold nanorods (GNRs)-reduced graphene oxide (rGO) hybrids (rGO/MPy-GNRs), anhydrous methanol, and starch-iodine complex are immobilized into cellulose-based filter papers. The resultant PAD exhibits a deep-blue color with a strong absorption peak at 600 nm due to the formation of an intermolecular charge-transfer complex between starch and iodine. However, the addition of SO 2 induces the Karl Fischer reaction, resulting in the decrease of color and increase of SERS signals. Therefore, the PAD can be used not only as a naked-eye indicator of SO 2 changed from blue to colorless but also as a highly sensitive SERS substrates because of the SO 2 -triggered conversion of Mpy to pyridine methyl sulfate on the GNRs. A distinguishable change in the color was observed at a SO 2 concentration of 5 μM by the naked eye, and a detection limit as low as 1.45 μM was obtained by virtue of UV-vis spectroscopy. The PAD-based SERS method is effective over a wide range of concentrations (1 μM to 2000 μM) for SO 2 , and the detection limit for SO 2 is found to be 1 μM. The HS-PAD based colorimetric/SERS method is applied for the determination of SO 2 in wine, and the detection results match well with those obtained from the traditional Monier-Williams method. This study not only offers a new method for on-site monitoring of SO 2 but also provides a new strategy for designing of paper-based sensing platform for a wide range of field-test applications.

A comparative study of three cytotoxicity test methods for nanomaterials using sodium lauryl sulfate.

PubMed

Kwon, Jae-Sung; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2014-10-01

The biocompatibility evaluation of nanomaterials is essential for their medical diagnostic and therapeutic usage, where a cytotoxicity test is the simplest form of biocompatibility evaluation. Three methods have been commonly used in previous studies for the cytotoxicity testing of nanomaterials: trypan blue exclusion, colorimetric assay using water soluble tetrazolium (WST), and imaging under a microscope following calcein AM/ethidium homodimer-1 staining. However, there has yet to be a study to compare each method. Therefore, in this study three methods were compared using the standard reference material of sodium lauryl sulfate (SLS). Each method of the cytotoxicity test was carried out using mouse fibroblasts of L-929 exposed to different concentrations of SLS. Compared to the gold standard trypan blue exclusion test, both colorimetric assay using water soluble tetrazolium (WST) and imaging under microscope with calcein AM/ethidium homodimer-1 staining showed results that were not statistically different. Also, each method exhibited various advantages and disadvantages, which included the need of equipment, time taken for the experiment, and provision of additional information such as cell morphology. Therefore, this study concludes that all three methods of cytotoxicity testing may be valid, though careful consideration will be needed when selecting tests with regard to time, finances, and the amount of information required by the researcher(s).

Colorimetric Method of Loop-Mediated Isothermal Amplification with the Pre-Addition of Calcein for Detecting Flavobacterium columnare and its Assessment in Tilapia Farms.

PubMed

Suebsing, Rungkarn; Kampeera, Jantana; Sirithammajak, Sarawut; Withyachumnarnkul, Boonsirm; Turner, Warren; Kiatpathomchai, Wansika

2015-03-01

Flavobacterium columnare, the causative agent of columnaris disease in fish, affects many economically important freshwater fish species. A colorimetric method of loop-mediated isothermal amplification with the pre-addition of calcein (LAMP-calcein) was developed and used to detect the presence of F. columnare in farmed tilapia (Nile Tilapia Oreochromis niloticus and red tilapia [Nile Tilapia × Mozambique Tilapia O. mossambicus]) and rearing water. The detection method, based on a change in color from orange to green, could be performed within 45 min at 63°C. The method was highly specific, as it had no cross-detections with 14 other bacterial species, including other fish pathogens and two Flavobacterium species. The method has a minimum detection limit of 2.2 × 10(2) F. columnare CFU; thus, it is about 10 times more sensitive than conventional PCR. With this method, F. columnare was detected in gonad, gill, and blood samples from apparently healthy tilapia broodstock as well as in samples of fertilized eggs, newly hatched fry, and rearing water. The bacteria isolated from the blood were further characterized biochemically and found to be phenotypically identical to F. columnare. The amplified products from the LAMP-calcein method had 97% homology with the DNA sequence of F. columnare.

Colorimetric determination of DNase I activity with a DNA-methyl green substrate.

PubMed

Sinicropi, D; Baker, D L; Prince, W S; Shiffer, K; Shak, S

1994-11-01

A simple, high throughput, and precise assay was developed for quantification of deoxyribonuclease I (DNase; IUB 3.1.21.1) activity. The method was adapted from the procedure devised by Kurnick which employs a substrate comprised of highly polymerized native DNA complexed with methyl green. Hydrolysis of the DNA produced unbound methyl green and a decrease in the absorbance of the solution at 620 nm. By adjusting the time and temperature of the reaction, the assay permits quantification of DNase activity over a wide concentration range (0.4 to 8900 ng/ml). Samples and standards were added to the substrate in microtiter plates and were incubated for 1-24 h at 25-37 degrees C to achieve the desired assay range. The DNase activity of the samples was interpolated from a standard curve generated with Pulmozyme recombinant human deoxyribonuclease I (rhDNase). Interassay precision was less than 12% CV and recovery was within 100 +/- 11%. Activity determination by the DNA-methyl green method correlated well with that determined by the widely used "hyperchromicity" method originated by Kunitz, which is based on the increase in absorbance at 260 nm upon hydrolysis of DNA. The DNA-methyl green assay was simpler and more versatile than the hyperchromicity method and was used to characterize the activity of rhDNase and DNase isolated from human urine.

Comparison of hydroxy naphthoquinone from North Qinglongyi with different storage times

NASA Astrophysics Data System (ADS)

Xin, G. S.; Ji, Y. B.; Wei, C.

2017-12-01

Objective: To determine the appropriate solvent for the extraction of hydroxy naphthoquinone, and to establish a method for the determination of the content of hydroxy naphthoquinone in the North Qinglongyi, and compare the changes of the content of hydroxy naphthoquinone in North Qinglongyi with different storage times. Methods: According to the nature of hydroxy naphthoquinone in alkaline solution will be discolored, so this experiment for Juglone as the standard reagent, 5% KOH solution as a developer, and the absorbance was measured by UV-spectrophotometry at the wavelength of 515 nm. The content of hydroxy naphthoquinone in North Qinglongyi was determined by colorimetric method, and the contents of hydroxy naphthoquinone in North Qinglongyi of different storage times were compared. Results: The optimum extraction solvent was ethyl acetate. The recoveries were 97.73%±1.11% and the RSD was 1.14% (n = 6). The contents of hydroxy naphthoquinone in the North Qinglunyi were 0.0141%, 0.0104% and 0.0073%, respectively, for one year, two years and three years. The content of hydroxy naphthoquinone decreased with the storage time prolonged. Conclusion This experimental method was stability, high recovery rate, simple and reliable. According to the results of this experiment, we can see that the storage time of North Qinglunyi should not be too long. Should try to choose this year’s North Qinglunyi for experimental research.

A sensitive colorimetric method for the determination of nitrite in water supplies, meat and dairy products using ionic liquid-modified methyl red as a colour reagent.

PubMed

Zhang, Haijuan; Qi, Shengda; Dong, Yalei; Chen, Xiaojiao; Xu, Yinyin; Ma, Yanhua; Chen, Xingguo

2014-05-15

This paper describes a colorimetric approach to determine trace amounts of nitrite in water supplies, meat and dairy products using 1-butyl-3-methylimidazolium-modified methyl red ([BMIM]MR) as a colour reagent. The technique capitalises on the catalytic effect of nitrite on the oxidative degradation of [BMIM]MR by potassium bromate in acidic media. The absorbances were proportional to nitrite concentrations in the range of 8.70×10(-2) to 4.17 μM with a detection limit of 1.64×10(-2) μM. Compared with the method using methyl red as a colour reagent, 60 times improvement of sensitivity was obtained. Activation energy and the apparent rate constant for the catalytic reaction are 61.11 kJ mol(-1) and 1.18×10(4) s(-1), respectively. The proposed method was successfully applied for the analysis of nitrite in Yellow River water, chicken, and milk with recoveries ranging from 96% to 105%. Copyright © 2013 Elsevier Ltd. All rights reserved.

Indirect Determination of Pentaerythritol Tetranitrate (PETN) with a gold nanoparticles-based colorimetric sensor.

PubMed

Üzer, Ayşem; Yalçın, Uğur; Can, Ziya; Erçağ, Erol; Apak, Reşat

2017-12-01

Pentaerythritol tetranitrate (PETN) is the nitrate ester of pentaerythritol, used as an energetic and filling material for military and civilian purposes and rarely for terrorist actions. As there is no reliable nano-colorimetric method for PETN assay, we developed an indirect method based on the determination of nitrite, obtained by reduction of nitrate derived from the alkaline hydrolysis of PETN with H 2 O 2 . We colorimetrically determined the final product, nitrite, by both conventional Griess reaction and a recently developed gold nanoparticle-4-aminothiophenol-N-(1-naphthyl)-ethylenediamine (AuNP-4-ATP+NED) method. Nitramines (RDX and HMX), if present, could be degraded by alkaline hydrolysis, without affecting PETN. The analytical performance characteristics of the developed assays as molar absorptivity (ε), limits of detection (LOD) and quantification (LOQ) were: ɛ=1.06×10 5 L mol -1 cm -1 , LOD=0.03mgL -1 and LOQ=0.11mgL -1 for indirect Griess method; ɛ=1.9×10 4 Lmol -1 cm -1 ; LOD=0.12mgL -1 and LOQ=0.4mgL -1 for AuNP-4-ATP+NED method. Both methods were applied to a 1:1 (w/w) mixture of PETN and TNT (corresponding to the composition of military explosive 'Pentolite'). In order to eliminate the interference from TNT, the Meisenheimer anion of TNT formed in alkaline medium was retained on a strongly basic anion exchange resin column. As PETN had a very low solubility in water, common soil ions could be eliminated by prewashing the sample with water, or in acetone-water mixtures, Ca 2+ , K + , Cl - , SO 4 2- , and NO 3 - could be tolerated at equal (1:1) mass ratios. Soil nitrates and nitrites, at a mass ratio of 50:1, could be separated from PETN with the aid of their insolubilities in acetone and of their retention affinity toward a strongly basic anion-exchange resin. The developed method was statistically validated against a reference GC-MS method. Copyright © 2017 Elsevier B.V. All rights reserved.

Colorimetric end-tidal CO2 detector for verification of endotracheal tube placement in out-of-hospital cardiac arrest.

PubMed

Hayden, S R; Sciammarella, J; Viccellio, P; Thode, H; Delagi, R

1995-06-01

To evaluate the ability of a disposable, colorimetric end-tidal CO2 detector to verify proper endotracheal (ET) tube placement in out-of-hospital cardiac arrest, and to correlate semiquantitative CO2 measurements with the rate of return of spontaneous circulation (ROSC). Prospective, observational study using a convenience sample of intubated out-of-hospital cardiac arrest patients. A disposable, colorimetric end-tidal CO2 detector was attached to the ET tube after intubation. In the absence of a colorimetric change, the paramedics reassessed the tube placement and could reintubate the patient. Tube placement was verified at the hospital. Paramedics were instructed to contact the base station and report the colorimetric change upon hospital arrival. ROSC was defined as restoration of a self-sustaining pulse until hospital arrival. Between December 1990 and May 1993, ET tubes were placed in 566 victims of out-of-hospital cardiac arrest. 541 of the 566 intubations (95.6%) were associated with a color change. In one case with a color change and out-of-hospital clinical evidence of proper tube placement, the tube was determined to be in the esophagus at the hospital. Correct placement of the remaining 565 of 566 (99.8%) tubes was verified. Of the 566 patients who had a colorimetric change, 91 (16%) had ROSC vs one of 25 (4%) patients who did not have a color change. In one subgroup (n = 179), the degree of color change was highly associated with ROSC (p = 0.004). A disposable, colorimetric end-tidal CO2 detector appears reliable in verifying proper ET tube placement in victims of out-of-hospital cardiac arrest. The degree of color change correlates with the probability of ROSC.

Gold nanoparticles mediated colorimetric assay for HIV-Tat protein detection

NASA Astrophysics Data System (ADS)

Hashwan, Saeed S. Ba; Ruslinda, A. Rahim; Fatin, M. F.; Gopinath, Subash C. B.; Thivina, V.; Tony, V. C. S.; Arshad, M. K. Md.; Hashim, U.

2016-07-01

Gold-nanoparticle (AuNP) based colorimetric assays have been formulated for different biomolecular interactions. With this assay the probe such as antibody immobilized on the Au surface and in the presence of appropriate binding partner (antigen), will interact with each other on the Au surface. By following this strategy, herein we formulated a detection system with two anti-HIV-Tat antibodies, Mono (McAb) - and polyclonal (PcAb) by immobilizing them independently with different AuNPs. Under this condition, these two antibodies are under dispersed condition, and in the presence of HIV-Tat antigen, these molecules will be connected and forms the aggregation of AuNPs. This strategy yield rapid results, can be monitored by the spectral changes in UV-Vis spectrophotometry. Experiments were performed with two different methods using two anti-HIV-Tats monoclonal and one Polyclonal antibody against the antigen HIV-Tat. Between these methods conjugation of HIV-Tat and McAb on the AuNP followed by addition of PcAb yielded better results.

Pyrazolone as a recognition site: Rhodamine 6G-based fluorescent probe for the selective recognition of Fe3+ in acetonitrile-aqueous solution.

PubMed

Parihar, Sanjay; Boricha, Vinod P; Jadeja, R N

2015-03-01

Two novel Rhodamine-pyrazolone-based colorimetric off-on fluorescent chemosensors for Fe(3+) ions were designed and synthesized using pyrazolone as the recognition moiety and Rhodamine 6G as the signalling moiety. The photophysical properties and Fe(3+) -binding properties of sensors L(1) and L(2) in acetonitrile-aqueous solution were also investigated. Both sensors successfully exhibit a remarkably 'turn-on' response, toward Fe(3+) , which was attributed to 1: 2 complex formation between Fe(3+) and L(1) /L(2) . The fluorescent and colorimetric response to Fe(3+) can be detected by the naked eye, which provides a facile method for the visual detection of Fe(3+) . Copyright © 2014 John Wiley & Sons, Ltd.

EDTA analysis on the Roche MODULAR analyser.

PubMed

Davidson, D F

2007-05-01

Patient specimens can be subject to subtle interference from cross contamination by liquid-based, potassium-containing EDTA anticoagulant, leading to misinterpretation of results. A rapid method for EDTA analysis to detect such contamination is described. An in-house EDTA assay on the Roche MODULAR analyser was assessed for accuracy and precision by comparison with an adjusted calcium difference measurement (atomic absorption and o-cresolphthalein complexone colorimetry). EDTA method versus adjusted calcium difference showed: slope = 1.038 (95% confidence interval [CI] 0.949-1.131); intercept = 0.073 (95% CI 0.018-0.132) mmol/L; r = 0.914; n = 94. However, inter-assay precision of the calcium difference method was estimated to be poorer (coefficient of variation 24.8% versus 3.4% for the automated colorimetric method at an EDTA concentration of 0.25 mmol/L). Unequivocal contamination was observed at an EDTA concentration of > or =0.2 mmol/L. The automated method showed positive interference from haemolysis and negative interference from oxalate. The method was unaffected by lipaemia (triglycerides <20 mmol/L), icterus (bilirubin <500 micromol/L), glucose (<100 mmol/L), iron (<100 micromol/L), and citrate, phosphate or fluoride (all <2.5 mmol/L). The automated colorimetric assay described is an accurate, precise and rapid (3 min) means of detecting EDTA contamination of unhaemolysed biochemistry specimens.

Sulfuric acid/hydrogen peroxide digestion and colorimetric a collaborative study.

PubMed

Christians, D K; Aspelund, T G; Brayton, S V; Roberts, L L

1991-01-01

Seven laboratories participated in a collaborative study of a method for determination of phosphorus in meat and meat products. Samples are digested in sulfuric acid and hydrogen peroxide; digestion is complete in approximately 10 min. Phosphorus is determined by colorimetric analysis of a dilute aliquot of the sample digest. The collaborators analyzed 3 sets of blind duplicate samples from each of 6 classes of meat (U.S. Department of Agriculture classifications): smoked ham, water-added ham, canned ham, pork sausage, cooked sausage, and hamburger. The calibration curve was linear over the range of standard solutions prepared (phosphorus levels from 0.05 to 1.00%); levels in the collaborative study samples ranged from 0.10 to 0.30%. Standard deviations for repeatability (sr) and reproducibility (SR) ranged from 0.004 to 0.012 and 0.007 to 0.014, respectively. Corresponding relative standard deviations (RSDr and RSDR, respectively) ranged from 1.70 to 7.28% and 3.50 to 9.87%. Six laboratories analyzed samples by both the proposed method and AOAC method 24.016 (14th Ed.). One laboratory reported results by the proposed method only. Statistical evaluations indicated no significant difference between the 2 methods. The method has been adopted official first action by AOAC.

A digital image method of spot tests for determination of copper in sugar cane spirits

NASA Astrophysics Data System (ADS)

Pessoa, Kenia Dias; Suarez, Willian Toito; dos Reis, Marina Ferreira; de Oliveira Krambeck Franco, Mathews; Moreira, Renata Pereira Lopes; dos Santos, Vagner Bezerra

2017-10-01

In this work the development and validation of analytical methodology for determination of copper in sugarcane spirit samples is carried out. The digital image based (DIB) method was applied along with spot test from the colorimetric reaction employing the RGB color model. For the determination of copper concentration, it was used the cuprizone - a bidentate organic reagent - which forms with copper a blue chelate in an alkaline medium. A linear calibration curve over the concentration range from 0.75 to 5.00 mg L- 1 (r2 = 0.9988) was obtained and limits of detection and quantification of 0.078 mg L- 1 and 0.26 mg L- 1 were acquired, respectively. For the accuracy studies, recovery percentages ranged from 98 to 104% were obtained. The comparison of cooper concentration results in sugar cane spirits using the DIB method and Flame Atomic Absorption Spectrometry as reference method showed no significant differences between both methods, which were performed using the paired t-test in 95% of confidence level. Thus, the spot test method associated with DIB allows the use of devices as digital cameras and smartphones to evaluate colorimetric reaction with low waste generation, practicality, quickness, accuracy, precision, high portability and low-cost.

MATRIX DISCRIMINANT ANALYSIS WITH APPLICATION TO COLORIMETRIC SENSOR ARRAY DATA

PubMed Central

Suslick, Kenneth S.

2014-01-01

With the rapid development of nano-technology, a “colorimetric sensor array” (CSA) which is referred to as an optical electronic nose has been developed for the identification of toxicants. Unlike traditional sensors which rely on a single chemical interaction, CSA can measure multiple chemical interactions by using chemo-responsive dyes. The color changes of the chemo-responsive dyes are recorded before and after exposure to toxicants and serve as a template for classification. The color changes are digitalized in the form of a matrix with rows representing dye effects and columns representing the spectrum of colors. Thus, matrix-classification methods are highly desirable. In this article, we develop a novel classification method, matrix discriminant analysis (MDA), which is a generalization of linear discriminant analysis (LDA) for the data in matrix form. By incorporating the intrinsic matrix-structure of the data in discriminant analysis, the proposed method can improve CSA’s sensitivity and more importantly, specificity. A penalized MDA method, PMDA, is also introduced to further incorporate sparsity structure in discriminant function. Numerical studies suggest that the proposed MDA and PMDA methods outperform LDA and other competing discriminant methods for matrix predictors. The asymptotic consistency of MDA is also established. R code and data are available online as supplementary material. PMID:26783371

Two Methods of Determining Total Phenolic Content of Foods and Juices in a General, Organic, and Biological (GOB) Chemistry Lab

ERIC Educational Resources Information Center

Shaver, Lee Alan; Leung, Sam H.; Puderbaugh, Amy; Angel, Stephen A.

2011-01-01

The determination of total phenolics in foods and fruit juices was used successfully as a laboratory experiment in our undergraduate general, organic, and biological (GOB) chemistry course. Two different colorimetric methods were used over three years and comparative student results indicate that a ferrous ammonium sulfate (FAS) indicator…

A new colorimetric method to quantify β-1,3-1,6-glucans in comparison with total β-1,3-glucans in edible mushrooms.

PubMed

Nitschke, Jörg; Modick, Hendrik; Busch, Ekkehard; von Rekowski, Reimund Wantoch; Altenbach, Hans-Josef; Mölleken, Helga

2011-07-15

Mushroom β-glucans are known for their activity as biological response modifiers and anticarcinogenic agents. β-1,3-1,6 Branched glucans with a triple helix tertiary structure are recognised as the most potent ones. In the present work, a colorimetric method for β-1,3-1,6-glucan quantification based on the dye Congo red is introduced. This method is specific for β-glucans with a triple helix. The β-1,3-1,6-glucan content of mycelia and fruiting bodies from various mushrooms was determined and compared with the total β-1,3-glucan content, measured by a fluorimetric method. The results show equal amounts of β-1,3-1,6- and total β-1,3-glucans in the analysed species but obvious differences between mycelia and fruiting bodies. On the average, 3% of mycelia and 8% of fruiting body dry mass consist of β-1,3-1,6-glucans. The average percentage of β-1,3-1,6-glucans in the total β-1,3-glucan content differs between mycelia (46%) and fruiting bodies (87%). Copyright © 2011 Elsevier Ltd. All rights reserved.

G-quadruplex DNA biosensor for sensitive visible detection of genetically modified food.

PubMed

Jiang, Xiaohua; Zhang, Huimin; Wu, Jun; Yang, Xiang; Shao, Jingwei; Lu, Yujing; Qiu, Bin; Lin, Zhenyu; Chen, Guonan

2014-10-01

In this paper, a novel label-free G-quadruplex DNAzyme sensor has been proposed for colorimetric identification of GMO using CaMV 35S promoter sequence as the target. The binary probes can fold into G-quadruplex structure in the presence of DNA-T (Target DNA) and then combine with hemin to form a DNAzyme resembling horseradish peroxidase. The detection system consists of two G-rich probes with 2:2 split mode by using the absorbance and color of ABTS(2-) as signal reporter. Upon the addition of a target sequence, two probes both hybridize with target and then their G-rich sequences combine to form a G-quadruplex DNAzyme, and the DNAzyme can catalyze the reaction of ABTS(2-) with H2O2. Then the linear range is from 0.05 to 0.5 μM while detection limit is 5nM. These results demonstrate that the proposed G-quadruplex DNAzyme method could be used as a simple, sensitive and cost-effective approach for assays of GMO. Copyright © 2014 Elsevier B.V. All rights reserved.

Antioxidant capacity index based on gold nanoparticles formation. Application to extra virgin olive oil samples.

PubMed

Della Pelle, Flavio; Vilela, Diana; González, María Cristina; Lo Sterzo, Claudio; Compagnone, Darío; Del Carlo, Michele; Escarpa, Alberto

2015-07-01

A simple gold nanoparticles (AuNPs) based colorimetric assay for the antioxidant activity determination has been developed. The AuNP formation is mediated by extra virgin olive oil (EVOO's) endogenous polyphenols; the reaction is described by a sigmoidal curve. The ratio KAuNPs/Xc(50) (slope of the linear part of the sigmoid/concentration at half value of the absorbance) was found to be the optimal parameter to report the antioxidant capacity with respect to the single KAuNPs or Xc(50) values. The obtained data demonstrated that the compounds with ortho-diphenols functionality are most active in reducing gold (III) to gold (0). Thus, intermediate activity was found for gallic acid, while tyrosol (mono-phenols) had a significant lower activity than the others antioxidant compounds (at least one order of magnitude). In the analysis of olive oil samples, a significant correlation among classical methods used to determine antioxidant activity and the proposed parameter was found with R values in the 0.96-0.97 range. Copyright © 2015 Elsevier Ltd. All rights reserved.

Allen Brain Atlas: an integrated spatio-temporal portal for exploring the central nervous system

PubMed Central

Sunkin, Susan M.; Ng, Lydia; Lau, Chris; Dolbeare, Tim; Gilbert, Terri L.; Thompson, Carol L.; Hawrylycz, Michael; Dang, Chinh

2013-01-01

The Allen Brain Atlas (http://www.brain-map.org) provides a unique online public resource integrating extensive gene expression data, connectivity data and neuroanatomical information with powerful search and viewing tools for the adult and developing brain in mouse, human and non-human primate. Here, we review the resources available at the Allen Brain Atlas, describing each product and data type [such as in situ hybridization (ISH) and supporting histology, microarray, RNA sequencing, reference atlases, projection mapping and magnetic resonance imaging]. In addition, standardized and unique features in the web applications are described that enable users to search and mine the various data sets. Features include both simple and sophisticated methods for gene searches, colorimetric and fluorescent ISH image viewers, graphical displays of ISH, microarray and RNA sequencing data, Brain Explorer software for 3D navigation of anatomy and gene expression, and an interactive reference atlas viewer. In addition, cross data set searches enable users to query multiple Allen Brain Atlas data sets simultaneously. All of the Allen Brain Atlas resources can be accessed through the Allen Brain Atlas data portal. PMID:23193282

Hue discrimination in Iberoamerican Observers

NASA Astrophysics Data System (ADS)

Carranza, Jazmín; Medina, Juana

2008-04-01

In this work we analyze the Farnsworth Munsell 100 Hue Test results, this test offers a simple method for testing color discrimination and was applied to a sample of 129 observers, with natural daylight in the same conditions (the observers were men and women), all of these were participants in colorimetric training courses, and aged 20 to 76, with two to twenty five years experience in the color control manufacturer laboratories (of plastics, rugs, dyes, textiles, and paints). Their job titles included mixers, inspectors, shaders, matchers, passers, and dyers. The test was applied twice and the results here presented are the comparison between both tests, taking into account errors by mistakes incidence in each hue position, as well as the redeeming of each participant in both test. The comparison shows us that most of the mistakes are in the green hue in both tests, but in the second test, approximately 20 percent of the observers reduced those. Also we can to separate persons with normal color vision of those which have zones of color confusion. In this work it is show some ones results of the comparison between men and women.

A novel biphenolic ligand for selective Mg2+ and Zn2+ ions sensing followed by colorimetric, spectroscopic and cell imaging methods.

PubMed

Maheswari, Palanisamy Uma; Renuga, Duraisamy; Henry, Linda Jeeva Kumari; Ruckmani, Kandasamy

2018-04-30

The (E)-2-((2-hydrohy-5-methylphenylimino) methyl) phenol ligand was synthesized. The receptor was characterized by IR, 1 H and 13 C NMR and CHN analysis. The ligand exhibits colorimetric and fluorometric sensing of Zn 2+ and Mg 2+ ions in semi-aqueous medium (DMSO-H2O). The receptor was tested with series of transition metal ions (Cr 2+ , Fe 2+ , Ni 2+ , Co 2+ , Cu 2+ , Zn 2+ ) and heavy metal ions (Sn 2+ , Pd 2+ , Ce 2+ , Hg 2+ , Cd 2+ ) and the essential human body elements like Ca 2+ , Mg 2+ , Na + and K + ions. The naked eye colorimetric sensing was absorbed only for Zn 2+ and Mg 2+ . Both ions (ZnCl 2 and MgCl 2 in H 2 O), when added to the colorless solutions of the receptor of about 1 equivalence in incremental additions turn the solution into bright turmeric yellow. All other ions remain inactive, in colorimetric sensing. Further the Zn 2+ and Mg 2+ ions were probed by absorption and emission spectroscopy through incremental addition of respective metal ions. The in-situ deprotonation of the ligand on both Mg 2+ and Zn 2+ ions binding was confirmed by 1 H NMR titration studies. The imino nitrogen of the receptor is not coordinated to the metal ions. The Job's plot studies reveal the 1:2 binding ratio of metal ions to the receptor. The high fold fluorescence output on metal ions binding was positively used to sense the Zn 2+ and Mg 2+ ions, separately and together in HeLa cancer cells through cell imaging. Copyright © 2018 Elsevier B.V. All rights reserved.

Detection and Spatial Mapping of Mercury Contamination in Water Samples Using a Smart-Phone

DTIC Science & Technology

2014-01-20

Au NP) and aptamer based colorimetric transmission assay that is implemented in disposable test tubes. With this smart-phone attachment that weighs...detection . colorimetric sensor . gold nanoparticles . aptamers A RTIC LE Terms of Use WEI ET AL. VOL. 8 ’ NO. 2 ’ 1121–1129 ’ 2014 www.acsnano.org 1122...a colorimetric assay utilizing citrate-stabilized plasmonic AuNPs and aptamers (Apt) mixed within disposable test tubes. Due to the shift in the

Real-time colorimetric detection of DNA methylation of the PAX1 gene in cervical scrapings for cervical cancer screening with thiol-labeled PCR primers and gold nanoparticles

PubMed Central

Huang, Jin; Liou, Yu-Ligh; Kang, Ya-Nan; Tan, Zhi-Rong; Peng, Ming-Jing; Zhou, Hong-Hao

2016-01-01

Background DNA methylation can induce carcinogenesis by silencing key tumor suppressor genes. Analysis of aberrant methylation of tumor suppressor genes can be used as a prognostic and predictive biomarker for cancer. In this study, we propose a colorimetric method for the detection of DNA methylation of the paired box gene 1 (PAX1) gene in cervical scrapings obtained from 42 patients who underwent cervical colposcopic biopsy. Methods A thiolated methylation-specific polymerase chain reaction (MSP) primer was used to generate MSP products labeled with the thiol group at one end. After bisulfite conversion and MSP amplification, the unmodified gold nanoparticles (AuNPs) were placed in a reaction tube and NaCl was added to induce aggregation of bare AuNPs without generating polymerase chain reaction products. After salt addition, the color of AuNPs remained red in the methylated PAX1 gene samples because of binding to the MSP-amplified products. By contrast, the color of the AuNP colloid solution changed from red to blue in the non-methylated PAX1 gene samples because of aggregation of AuNPs in the absence of the MSP-amplified products. Furthermore, PAX1 methylation was quantitatively detected in cervical scrapings of patients with varied pathological degrees of cervical cancer. Conventional quantitative MSP (qMSP) was also performed for comparison. Results The two methods showed a significant correlation of the methylation frequency of the PAX1 gene in cervical scrapings with severity of cervical cancer (n=42, P<0.05). The results of the proposed method showed that the areas under the receiver operating characteristic curve (AUCs) of PAX1 were 0.833, 0.742, and 0.739 for the detection of cervical intraepithelial neoplasms grade 2 and worse lesions (CIN2+), cervical intraepithelial neoplasms grade 3 and worse lesions (CIN3+), and squamous cell carcinoma, respectively. The sensitivity and specificity for detecting CIN2+ lesions were 0.941 and 0.600, respectively, with a cutoff value of 31.27%. The proposed method also showed superior sensitivity over qMSP methods for the detection of CIN2+ and CIN3+ (0.941 vs 0.824 and 1.000 vs 0.800, respectively). Furthermore, the novel method exhibited higher AUC (0.833) for the detection of CIN2+ than qMSP (0.807). Conclusion The results of thiol-labeled AuNP method were clearly observed by the naked eyes without requiring any expensive equipment. Therefore, the thiol-labeled AuNP method could be a simple but efficient strategy for cervical cancer screening. PMID:27789946

A novel colorimetric aptasensor for ultrasensitive detection of cocaine based on the formation of three-way junction pockets on the surfaces of gold nanoparticles.

PubMed

Abnous, Khalil; Danesh, Noor Mohammad; Ramezani, Mohammad; Taghdisi, Seyed Mohammad; Emrani, Ahmad Sarreshtehdar

2018-08-22

Herein, a novel colorimetric aptasensor was introduced for detection of cocaine based on the formation of three-way junction pockets on the surfaces of gold nanoparticles (AuNPs) and the catalytic activity of the surfaces of AuNPs. Simplicity and detection of cocaine in a short time (only 35 min) are some of the unique features of the proposed sensing strategy. In the presence of cocaine, triple-fragment aptamer (TFA) forms on the surfaces of AuNPs, leading to a significant decrease of the catalytic activity of AuNPs and the color of samples remains yellow. In the absence of target, TFA does not form on the surfaces of AuNPs and 4-Nitrophenol, as a colorimetric agent, has more access to the surfaces of AuNPs, resulting in the reduction of 4-Nitrophenol and the color of sample changes from yellow to colorless. The sensing strategy showed good specificity, a limit of detection (LOD) of 440 pM and a dynamic range over 2-100 nM. The sensing method was also successfully applied to detect cocaine in spiked human serum samples with recovery of 94.71-98.63%. Copyright © 2018 Elsevier B.V. All rights reserved.

A visual water vapor photonic crystal sensor with PVA/SiO2 opal structure

NASA Astrophysics Data System (ADS)

Yang, Haowei; Pan, Lei; Han, Yingping; Ma, Lihua; Li, Yao; Xu, Hongbo; Zhao, Jiupeng

2017-11-01

In study, we proposed a simple yet fast optical sensing motif based on thimbleful of polyvinyl alcohol (PVA) infiltrated photonic crystal (PC), which allows for high efficiency in vapor sensing through changes in their inter-layer space. Linear response to a broad dynamic range of vapor concentration was realized. Ultrafast response time (<1 s) and excellent recyclability were also demonstrated. Selective response to a vapor was exhibited, reflecting well the characteristic sorption properties of PVA, with which colorimetric reporting was readily achieved. These substantial improvements in performance are attributed to the efficacy of signal transduction and the enhanced signal transduction because of thimbleful PVA infiltrated space between adjacent SiO2 nanospheres.

Gas diffusion as a new fluidic unit operation for centrifugal microfluidic platforms.

PubMed

Ymbern, Oriol; Sández, Natàlia; Calvo-López, Antonio; Puyol, Mar; Alonso-Chamarro, Julian

2014-03-07

A centrifugal microfluidic platform prototype with an integrated membrane for gas diffusion is presented for the first time. The centrifugal platform allows multiple and parallel analysis on a single disk and integrates at least ten independent microfluidic subunits, which allow both calibration and sample determination. It is constructed with a polymeric substrate material and it is designed to perform colorimetric determinations by the use of a simple miniaturized optical detection system. The determination of three different analytes, sulfur dioxide, nitrite and carbon dioxide, is carried out as a proof of concept of a versatile microfluidic system for the determination of analytes which involve a gas diffusion separation step during the analytical procedure.

Dual-Modal Colorimetric/Fluorescence Molecular Probe for Ratiometric Sensing of pH and Its Application.

PubMed

Wu, Luling; Li, Xiaolin; Huang, Chusen; Jia, Nengqin

2016-08-16

As traditional pH meters cannot work well for minute regions (such as subcellular organelles) and in harsh media, molecular pH-sensitive devices for monitoring pH changes in diverse local heterogeneous environments are urgently needed. Here, we report a new dual-modal colorimetric/fluorescence merocyanine-based molecular probe (CPH) for ratiometric sensing of pH. Compared with previously reported pH probes, CPH bearing the benzyl group at the nitrogen position of the indolium group and the phenol, which is used as the acceptor for proton, could respond to pH changes immediately through both the ratiometric fluorescence signal readout and naked-eye colorimetric observation. The sensing process was highly stable and reversible. Most importantly, the suitable pKa value (6.44) allows CPH to presumably accumulate in lysosomes and become a lysosome-target fluorescent probe. By using CPH, the intralysosomal pH fluctuation stimulated by antimalaria drug chloroquine was successfully tracked in live cells through the ratiometric fluorescence images. Additionally, CPH could be immobilized on test papers, which exhibited a rapid and reversible colorimetric response to acid/base vapor through the naked-eye colorimetric analysis. This proof-of-concept study presents the potential application of CPH as a molecular tool for monitoring intralysosomal pH fluctuation in live cells, as well as paves the way for developing the economic, reusable, and fast-response optical pH meters for colorimetric sensing acid/base vapor with direct naked-eye observation.

Rapid detection of Puccinia triticina causing leaf rust of wheat by PCR and loop mediated isothermal amplification

PubMed Central

Kulshreshtha, Deepika; Gupta, Sangeeta; Singh, Kartar; Bhardwaj, Subhash C.

2018-01-01

Leaf rust of wheat caused by Puccinia triticina has significant impact on wheat production worldwide. Effective and quick detection methodologies are required to mitigate yield loss and time constraints associated with monitoring and management of leaf rust of wheat. In the present study, detection of P. triticina has been simplified by developing a rapid, reliable, efficient and visual colorimetric method i.e., loop mediated isothermal amplification of DNA (LAMP). Based on in silico analysis of P. triticina genome, PTS68, a simple sequence repeat was found highly specific to leaf rust fungus. A marker (PtRA68) was developed and its specificity was validated through PCR technique which gave a unique and sharp band of 919 bp in P. triticina pathotypes only. A novel gene amplification method LAMP which enables visual detection of pathogen by naked eye was developed for leaf rust pathogen. A set of six primers was designed from specific region of P. triticina and conditions were optimised to complete the observation process in 60 minutes at 65o C. The assay developed in the study could detect presence of P. triticina on wheat at 24 hpi (pre-symptomatic stage) which was much earlier than PCR without requiring thermal cycler. Sensitivity of LAMP assay developed in the study was 100 fg which was more sensitive than conventional PCR (50 pg) and equivalent to qPCR (100 fg). The protocol developed in the study was utilized for detection of leaf rust infected samples collected from different wheat fields. LAMP based colorimetric detection assay showed sky blue color in positive reaction and violet color in negative reaction after addition of 120 μM hydroxyl napthol blue (HNB) solution to reaction mixture. Similarly, 0.6 mg Ethidium bromide/ml was added to LAMP products, placed on transilluminator to witness full brightness in positive reaction and no such brightness could be seen in negative reaction mixture. Further, LAMP products spread in a ladder like banding pattern in gel electrophoresis. Our assay is significantly faster than the conventional methods used in the identification of P. triticina. The assay developed in the study shall be very much useful in the development of diagnostic kit for monitoring disease, creation of prediction model and efficient management of disease. PMID:29698484

Multifunctional Nanomaterials Utilizing Hybridization Chain Reaction for Molecular Diagnostics and Bioanalytical Applications

NASA Astrophysics Data System (ADS)

Rana, Md. Muhit

DNA nanotechnology has shown great promise in molecular diagnostic, bioanalytical and biomedical applications. The great challenge of detecting target analytes, biomarkers and small molecules, in molecular diagnostics is low yield sensitivity. To address this challenge, different nanomaterials have been used for a long time and to date there is no such cost-effective bioanalytical technique which can detect these target biomarkers (DNA, RNA, circulating DNA/miRNA) or environmental heavy metal ions (Hg2+ and Ag+) in a cost-effective and efficient manner. Herein, we initially discuss two possible bioanalytical detection methods- a) colorimetric and b) fluorometric assays which are very popular nowadays due to their distinctive spectroscopic properties. Finally, we report the promising colorimetric assay using a novel DNA based amplification strategy know as hybridization chain reaction (HCR) for potential application in the visual detection of low copies of biomarkers (miRNAs as little as 20 femtomole in an RNA pool and cell extracts in seven different combinations and Ebola virus DNA as low as 400 attomoles in liquid biopsy mimics in sixteen different combinations), environmental and biological heavy metal ions (mercury and silver concentrations as low as 10 pM in water, soil and urine samples) and also successfully applied to a molecular logic gate operation to distinguish OR and AND logic gates. No results showed any false-positive or false-negative information. On the other hand, we also discuss the future possibilities of HCR amplification technology, which is very promising for fluorometric bioanalysis. The HCR based nanoprobe technology has numerous remarkable advantages over other methods. It is re-programmable, simple, inexpensive, easy to assemble and operate and can be performed with visual and spectroscopic read-outs upon recognition of the target analytes. This rapid, specific and sensitive approach for biomarkers and heavy metal ion detection generates an on-site signal while eliminating the use of sophisticated high-maintenance instrumentation. We demonstrate that this state-of-the-art technology and methodology can potentially serve as an alternative approach to detect novel disease biomarkers, small molecules and inorganic compounds. This approach can be combined with the current existing methods for real-time point-of-care molecular diagnostics and is significant for preclinical or clinical studies.

Rapid detection of Puccinia triticina causing leaf rust of wheat by PCR and loop mediated isothermal amplification.

PubMed

Manjunatha, C; Sharma, Sapna; Kulshreshtha, Deepika; Gupta, Sangeeta; Singh, Kartar; Bhardwaj, Subhash C; Aggarwal, Rashmi

2018-01-01

Leaf rust of wheat caused by Puccinia triticina has significant impact on wheat production worldwide. Effective and quick detection methodologies are required to mitigate yield loss and time constraints associated with monitoring and management of leaf rust of wheat. In the present study, detection of P. triticina has been simplified by developing a rapid, reliable, efficient and visual colorimetric method i.e., loop mediated isothermal amplification of DNA (LAMP). Based on in silico analysis of P. triticina genome, PTS68, a simple sequence repeat was found highly specific to leaf rust fungus. A marker (PtRA68) was developed and its specificity was validated through PCR technique which gave a unique and sharp band of 919 bp in P. triticina pathotypes only. A novel gene amplification method LAMP which enables visual detection of pathogen by naked eye was developed for leaf rust pathogen. A set of six primers was designed from specific region of P. triticina and conditions were optimised to complete the observation process in 60 minutes at 65o C. The assay developed in the study could detect presence of P. triticina on wheat at 24 hpi (pre-symptomatic stage) which was much earlier than PCR without requiring thermal cycler. Sensitivity of LAMP assay developed in the study was 100 fg which was more sensitive than conventional PCR (50 pg) and equivalent to qPCR (100 fg). The protocol developed in the study was utilized for detection of leaf rust infected samples collected from different wheat fields. LAMP based colorimetric detection assay showed sky blue color in positive reaction and violet color in negative reaction after addition of 120 μM hydroxyl napthol blue (HNB) solution to reaction mixture. Similarly, 0.6 mg Ethidium bromide/ml was added to LAMP products, placed on transilluminator to witness full brightness in positive reaction and no such brightness could be seen in negative reaction mixture. Further, LAMP products spread in a ladder like banding pattern in gel electrophoresis. Our assay is significantly faster than the conventional methods used in the identification of P. triticina. The assay developed in the study shall be very much useful in the development of diagnostic kit for monitoring disease, creation of prediction model and efficient management of disease.

Trace vapor detection of hydrogen peroxide: An effective approach to identification of improvised explosive devices

NASA Astrophysics Data System (ADS)

Xu, Miao

Vapor detection has been proven as one of the practical, noninvasive methods suitable for explosives detection among current explosive detection technologies. Optical methods (especially colorimetric and fluorescence spectral methods) are low in cost, provide simple instrumentation alignment, while still maintaining high sensitivity and selectivity, these factors combined facilitate broad field applications. Trace vapor detection of hydrogen peroxide (H2O2) represents an effective approach to noninvasive detection of peroxide-based explosives, though development of such a sensor system with high reliability and sufficient sensitivity (reactivity) still remains challenging. Three vapor sensor systems for H2O2 were proposed and developed in this study, which exploited specific chemical reaction towards H2O2 to ensure the selectivity, and materials surface engineering to afford efficient air sampling. The combination of these features enables expedient, cost effective, reliable detection of peroxide explosives. First, an expedient colorimetric sensor for H2O2 vapor was developed, which utilized the specific interaction between Ti(oxo) and H2O2 to offer a yellow color development. The Ti(oxo) salt can be blended into a cellulose microfibril network to produce tunable interface that can react with H2O2. The vapor detection limit can reach 400 ppb. To further improve the detection sensitivity, a naphthalimide based fluorescence turn-on sensor was designed and developed. The sensor mechanism was based on H2O2-mediated oxidation of a boronate fluorophore, which is nonfluorescent in ICT band, but becomes strongly fluorescent upon conversion into the phenol state. The detection limit of this sensory material was improved to be below 10 ppb. However, some technical factors such as sensor concentration, local environment, and excitation intensity were found difficult to control to make the sensor system sufficiently reproducible. To solve the problem, we developed a ratiometric fluorescence sensor, which allows for dual-band emission monitoring and thus enhances the detection reliability. Moreover, the significant spectral overlap between the fluorescence of the pristine sensor and the absorption of the reacted state enables effective Foster Resonance Energy Transfer (FRET). This FRET process can significantly enhance the fluorescence sensing efficiency in comparison to the normal single-band sensor system, for which the sensing efficiency is solely determined by the stoichiometric conversion of sensor molecules.

Identification of human flavin-containing monooxygenase 3 substrates by a colorimetric screening assay.

PubMed

Catucci, Gianluca; Polignano, Isabelle; Cusumano, Debora; Medana, Claudio; Gilardi, Gianfranco; Sadeghi, Sheila J

2017-04-01

Human hepatic flavin-containing monooxygenase 3 is a phase I drug-metabolizing enzyme that is responsible for the oxidation of a variety of drugs and xenobiotics. This work reports on a high throughput rapid colorimetric assay for the screening of substrates or inhibitors of this enzyme. The method is based on the competition of two substrates for access to the active site of hFMO3 whereby the enzymatic product of the first drug converts nitro-5-thiobenzoate (TNB, yellow) to 5,5'-dithiobis (2-nitrobenzoate) (DTNB, colourless). Upon addition of a competing substrate, the amount of detected DNTB is decreased. The assay is validated testing three known substrates of hFMO3, namely benzydamine, tozasertib and tamoxifen. The latter drugs resulted in 41%-55% inhibition. In addition, two other drugs also classified as doping drugs, selegiline and clomiphene, were selected based on their chemical structure similarity to known substrates of hFMO3. These drugs showed 21% and 60% inhibition in the colorimetric assay and therefore were proven to be hFMO3 substrates. LC-MS was used to confirm their N-oxide products. Further characterisation of these newly identified hFMO3 substrates was performed determining their K m and k cat values that resulted to be 314 μM and 1.4 min -1 for selegiline and, 18 μM and 0.1 min -1 for clomiphene. This method paves the way for a rapid automated high throughput screening of nitrogen-containing compounds as substrates/inhibitors of hFMO3. Copyright © 2017 Elsevier Inc. All rights reserved.

Visualisation of gas-liquid mass transfer around a rising bubble in a quiescent liquid using an oxygen sensitive dye

NASA Astrophysics Data System (ADS)

Dietrich, Nicolas; Hebrard, Gilles

2018-02-01

An approach for visualizing and measuring the mass transfer around a single bubble rising in a quiescent liquid is reported. A colorimetric technique, developed by (Dietrich et al. Chem Eng Sci 100:172-182, 2013) using an oxygen sensitive redox dye was implemented. It was based on the reduction of the colorimetric indicator in presence of oxygen, this reduction being catalysed by sodium hydroxide and glucose. In this study, resazurin was selected because it offered various reduced forms with colours ranging from transparent (without oxygen) to pink (in presence of oxygen). These advantages made it possible to visualize the spatio-temporal oxygen mass transfer around rising bubbles. Images were recorded by a CCD camera and, after post-processing, the shape, size, and velocity of the bubbles were measured and the colours around the bubbles mapped. A calibration, linking the level of colour with the dissolved oxygen concentration, enabled colour maps to be converted into oxygen concentration fields. A rheoscopic fluid was used to visualize the wake of the bubbles. A calculation method was also developed to determine the transferred oxygen fluxes around bubbles of two sizes (d = 0.82 mm and d = 2.12 mm) and the associated liquid-side mass transfer coefficients. The results compared satisfactorily with classical global measurements made by oxygen micro-sensors or from the classical models. This study thus constitutes a striking example of how this new colorimetric method could become a remarkable tool for exploring gas-liquid mass transfer in fluids.

Visualisation of gas-liquid mass transfer around a rising bubble in a quiescent liquid using an oxygen sensitive dye

NASA Astrophysics Data System (ADS)

Dietrich, Nicolas; Hebrard, Gilles

2018-07-01

An approach for visualizing and measuring the mass transfer around a single bubble rising in a quiescent liquid is reported. A colorimetric technique, developed by (Dietrich et al. Chem Eng Sci 100:172-182, 2013) using an oxygen sensitive redox dye was implemented. It was based on the reduction of the colorimetric indicator in presence of oxygen, this reduction being catalysed by sodium hydroxide and glucose. In this study, resazurin was selected because it offered various reduced forms with colours ranging from transparent (without oxygen) to pink (in presence of oxygen). These advantages made it possible to visualize the spatio-temporal oxygen mass transfer around rising bubbles. Images were recorded by a CCD camera and, after post-processing, the shape, size, and velocity of the bubbles were measured and the colours around the bubbles mapped. A calibration, linking the level of colour with the dissolved oxygen concentration, enabled colour maps to be converted into oxygen concentration fields. A rheoscopic fluid was used to visualize the wake of the bubbles. A calculation method was also developed to determine the transferred oxygen fluxes around bubbles of two sizes (d = 0.82 mm and d = 2.12 mm) and the associated liquid-side mass transfer coefficients. The results compared satisfactorily with classical global measurements made by oxygen micro-sensors or from the classical models. This study thus constitutes a striking example of how this new colorimetric method could become a remarkable tool for exploring gas-liquid mass transfer in fluids.

Fabricating a UV-Vis and Raman Spectroscopy Immunoassay Platform.

PubMed

Hanson, Cynthia; Israelsen, Nathan D; Sieverts, Michael; Vargis, Elizabeth

2016-11-10

Immunoassays are used to detect proteins based on the presence of associated antibodies. Because of their extensive use in research and clinical settings, a large infrastructure of immunoassay instruments and materials can be found. For example, 96- and 384-well polystyrene plates are available commercially and have a standard design to accommodate ultraviolet-visible (UV-Vis) spectroscopy machines from various manufacturers. In addition, a wide variety of immunoglobulins, detection tags, and blocking agents for customized immunoassay designs such as enzyme-linked immunosorbent assays (ELISA) are available. Despite the existing infrastructure, standard ELISA kits do not meet all research needs, requiring individualized immunoassay development, which can be expensive and time-consuming. For example, ELISA kits have low multiplexing (detection of more than one analyte at a time) capabilities as they usually depend on fluorescence or colorimetric methods for detection. Colorimetric and fluorescent-based analyses have limited multiplexing capabilities due to broad spectral peaks. In contrast, Raman spectroscopy-based methods have a much greater capability for multiplexing due to narrow emission peaks. Another advantage of Raman spectroscopy is that Raman reporters experience significantly less photobleaching than fluorescent tags 1 . Despite the advantages that Raman reporters have over fluorescent and colorimetric tags, protocols to fabricate Raman-based immunoassays are limited. The purpose of this paper is to provide a protocol to prepare functionalized probes to use in conjunction with polystyrene plates for direct detection of analytes by UV-Vis analysis and Raman spectroscopy. This protocol will allow researchers to take a do-it-yourself approach for future multi-analyte detection while capitalizing on pre-established infrastructure.

3D flower-like ferrous(II) phosphate nanostructures as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose at nanomolar level.

PubMed

Guo, Jingjing; Wang, Yan; Zhao, Min

2018-05-15

Ferrous(II) phosphate nanoflowers (Fe 3 (PO 4 ) 2 ·8H 2 O NFs) were synthesized by a facial co-precipitation method. The structure, composition and morphology were characterized by XRD, EDX, element mapping and FESEM. The as-prepared Fe 3 (PO 4 ) 2 ·8H 2 O NFs exhibited excellent intrinsic peroxidase-like activity. Steady-state kinetic studies showed that Fe 3 (PO 4 ) 2 ·8H 2 O NFs exhibited stronger affinities with 3,3,5,5-tetramethylbenzidine (TMB) and H 2 O 2 as the substrates compared with the natural horseradish peroxidase (HRP) and the catalytic constant (k cat ) value was even higher than HRP and other reported nanomaterial based peroxidase mimics. The investigation of the catalytic mechanism by cyclic voltammetry, fluorescence spectroscopy and ESR displayed the catalytic activity of Fe 3 (PO 4 ) 2 ·8H 2 O NFs originated from the generation of •OH. The Fe 3 (PO 4 ) 2 ·8H 2 O NFs also exhibited higher robustness and better storage stability than HRP. Then, a Fe 3 (PO 4 ) 2 ·8H 2 O NFs-based colorimetric platform was developed to determine H 2 O 2 and glucose. The linear range of H 2 O 2 and glucose was as broad as 1 × 10 -5 -2.5 mM and 8 × 10 -4 -1.2 mM, and the detection limit (LOD) was as low as 5 nM and 35 nM, respectively. This simple assay offered a highly sensitive and specific strategy for H 2 O 2 and glucose determination, which had been successfully utilized for real sample analysis with good reproducibility and accuracy. Copyright © 2018 Elsevier B.V. All rights reserved.

High sensitivity, loop-mediated isothermal amplification combined with colorimetric gold-nanoparticle probes for visual detection of high risk human papillomavirus genotypes 16 and 18.

PubMed

Kumvongpin, Ratchanida; Jearanaikool, Patcharee; Wilailuckana, Chotechana; Sae-Ung, Nattaya; Prasongdee, Prinya; Daduang, Sakda; Wongsena, Metee; Boonsiri, Patcharee; Kiatpathomchai, Wansika; Swangvaree, Sukumarn Sanersak; Sandee, Alisa; Daduang, Jureerut

2016-08-01

High-risk human papillomavirus (HR-HPV) causes cervical cancer. HPV16 and HPV18 are the most prevalent strains of the virus reported in women worldwide. Loop-mediated isothermal amplification (LAMP) is an alternative method for DNA detection under isothermal conditions. However, it results in a turbid amplified product which is not easily detected by the naked eye. This study aimed to develop an improved technique by using gold nanoparticles (AuNPs) attached to a single-stranded DNA probe for the detection of HPV16 and HPV18. Detection of the LAMP product by AuNP color change was compared with detection by visual turbidity. The optimal conditions for this new LAMP-AuNP assay were an incubation time of 20min and a temperature of 65°C. After LAMP amplification was complete, its products were hybridized with the AuNP probe for 5min and then detected by the addition of magnesium salt. The color changed from red to blue as a result of aggregation of the AuNP probe under high ionic strength conditions produced by the addition of the salt. The sensitivity of the LAMP-AuNP assay was greater than the LAMP turbidity assay by up to 10-fold for both HPV genotypes. The LAMP-AuNP assay showed higher sensitivity and ease of visualization than did the LAMP turbidity for the detection of HPV16 and HPV18. Additionally, AuNP-HPV16 and AuNP-HPV18 probes were stable for over 1year. The combination of LAMP and the AuNP-probe colorimetric assay offers a simple, rapid and highly sensitive alternative diagnostic tool for the detection of HPV16 and HPV18 in district hospitals or field studies. Copyright © 2016 Elsevier B.V. All rights reserved.

On-Board Monitoring of Engine Oil

DTIC Science & Technology

2011-04-01

Viscosity of Transparent and Opaque Liquids at 40°C Infracal Soot Meter Karl Fischer Titration ASTM D 664 Standard Test Method for Acid Number of... methods involve potentiometric and colorimetric titrations, respectively. For both tests, a titration solvent is prepared and added to the oil. The...ASTM D 2896 and ASTM D 4739 [17]. Both methods involve potentiometric titrations. ASTM D 2896 uses a stronger acid and more polar solvent than ASTM D

Colorimetric values of esthetic stainless steel crowns.

PubMed

Hosoya, Yumiko; Omachi, Koichi; Staninec, Michal

2002-01-01

The colorimetric values of two different kinds of esthetic stainless steel crowns were measured and compared with the colorimetric values of primary anterior teeth in Japanese children. The colorimetric values of resin composite-faced stainless steel crowns (Kinder Krown) and epoxy-coated stainless steel crowns (White Steel Crown) were measured with a color difference meter. The Commission Internationale de Eclairage L*, a*, b*, and delta E*ab values and Munsell value, chroma, and hue were calculated. The data were compared with previously reported colorimetric values of Japanese primary anterior teeth measured with the same color difference meter used in this study. Compared to Japanese primary anterior teeth, Kinder Krown Pedo I and Pedo II showed much higher L* values and lower hue; on the other hand, White Steel Crown showed much higher L*, a*, b* values, much higher value and chroma, and much lower hue. Color analysis revealed that the colors of the White Steel Crown and Kinder Krown Pedo I were substantially different from the color of Japanese primary anterior teeth. The color difference between Pedo II crowns and Japanese primary anterior teeth was relatively high, but the color of Pedo II might be acceptable for clinical use.

NAA For Human Serum Analysis: Comparison With Conventional Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, Laura C.; Zamboni, Cibele B.; Medeiros, Jose A. G.

2010-08-04

Instrumental and Comparator methods of Neutron Activation Analysis (NAA) were applied to determine elements of clinical relevancy in serum samples of adult population (Sao Paulo city, Brazil). A comparison with the conventional analyses, Colorimetric for calcium, Titrymetric for chlorine and Ion Specific Electrode for sodium and potassium determination were also performed permitting a discussion about the performance of NAA methods for clinical chemistry research.

Assessment of Remaining Lubricant Life

DTIC Science & Technology

1986-11-01

tioxidant, inexpensive spectrophotometers are used. However, the greatest advantage of the Mitsubishi chemical stressing technique was the fact that it uses...samples, the method’s main advantage over the thermal stressing techniques is eliminated. The colorimetric method had the advantage over induction period...decrease of 18 torr. The main advantage of defining the induction period in this manner is that it eliminates any need for interpretation by the

Oxalate analysis methodology for decayed wood

Treesearch

Carol A. Clausen; William Kenealy; Patricia K. Lebow

2008-01-01

Oxalate from partially decayed southern pine wood was analyzed by HPLC or colorimetric assay. Oxalate extraction efficiency, assessed by comparing analysis of whole wood cubes with ground wood, showed that both wood geometries could be extracted with comparable efficiency. To differentiate soluble oxalate from total oxalate, three extraction methods were assessed,...

A net fishing enrichment strategy for colorimetric detection of E. coli O157:H7

USDA-ARS?s Scientific Manuscript database

The strict regulatory requirements for pathogen monitoring in food systems to ensure safety demands that the detection method can recognize small numbers of pathogens. Although significant efforts on the development of biosensors have been reported with marked improvement in sensitivity, appropriate...

40 CFR 63.323 - Test methods and monitoring.

Code of Federal Regulations, 2012 CFR

2012-07-01

... downstream from any flow disturbance such as a bend, expansion, contraction, or outlet; downstream from no other inlet; and 2 stack or duct diameters upstream from any flow disturbance such as a bend, expansion... monitoring by inserting the colorimetric detector or PCE gas analyzer tube into the open space above the...

40 CFR 63.323 - Test methods and monitoring.

Code of Federal Regulations, 2014 CFR

2014-07-01

... downstream from any flow disturbance such as a bend, expansion, contraction, or outlet; downstream from no other inlet; and 2 stack or duct diameters upstream from any flow disturbance such as a bend, expansion... monitoring by inserting the colorimetric detector or PCE gas analyzer tube into the open space above the...

40 CFR 63.323 - Test methods and monitoring.

Code of Federal Regulations, 2013 CFR

2013-07-01

... downstream from any flow disturbance such as a bend, expansion, contraction, or outlet; downstream from no other inlet; and 2 stack or duct diameters upstream from any flow disturbance such as a bend, expansion... monitoring by inserting the colorimetric detector or PCE gas analyzer tube into the open space above the...

Rapid quantification of proanthocyanidins (condensed tannins) with a continuous flow analyzer

Treesearch

James K. Nitao; Bruce A. Birr; Muraleedharan G. Nair; Daniel A. Herms; William J. Mattson

2001-01-01

Proanthocyanidins (condensed tannins) frequently need to be quantified in large numbers of samples in food, plant, and environmental studies. An automated colorimetric method to quantify proanthocyanidins with sulfuric acid (H2SO4) was therefore developed for use in a continuous flow analyzer. Assay conditions were...