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1

RP-HPLC and UV Spectrophotometric Methods for Estimation of Pirfenidone in Pharmaceutical Formulations.  

PubMed

High-performance liquid chromatographic and UV spectrophotometric methods were developed and validated for the quantitative determination of pirfenidone, a novel antifibrotic agent used in idiopathic pulmonary fibrosis. Chromatography was carried out by isocratic technique on a reversed-phase C18 Zorbax Eclipse plus column with mobile phase consisting of acetonitrile:water (35:65 %v/v) at flow rate of 0.7 ml/min. The UV spectrophotometric determinations were performed at 317 nm using methanol as a solvent. The proposed methods were validated according to International Conference on Harmonization ICH Q2 (R1) guidelines. The linearity range for pirfenidone was 0.2-5.0 and 3-25 ?g/ml for HPLC and UV method, respectively. Both the methods were accurate and precise with recoveries in the range of 98 and 102 % and relative standard deviation <2 %. The developed methods were successfully applied for determination of pirfenidone in tablets. PMID:25035534

Parmar, V K; Desai, S B; Vaja, T

2014-05-01

2

First-order derivative UV spectrophotometric method for simultaneous measurement of delapril and manidipine in tablets.  

PubMed

A first-order derivative spectrophotometric (1D-UV) method was developed and validated for simultaneous determination of delapril (DEL) and manidipine (MAN) in tablets. The 1D-UV spectra were obtained using change lambda = 4.0 nm and wavelength set at 228 nm for DEL and 246 nm for MAN. The method was validated in accordance with the ICH requirements, involving the specificity, linearity, precision, accuracy, robustness and limits of detection and quantitation. The method showed high specificity in the presence of two drugs and formulation excipients and was linear over the concentration range of 18-54 microg mL(-1) (r2 = 0.9994) for DEL and 6-18 microg mL(-1) (r2 = 0.9981) for MAN with adequate results for the precision (< or = 1.47%) and accuracy (98.98% for DEL and 100.50% for MAN). Moreover, the method proved to be robust by a Plackett-Burman experimental design evaluation. The proposed 'D-UV method was successfully applied for simultaneous analysis of DEL and MAN in tablets and can be used as alternative green method to separation techniques. The results were compared with the validated liquid chromatography, capillary electrophoresis and liquid chromatography-tandem mass spectrometry methods, showing non-significant difference. PMID:23878937

Todeschini, Vítor; Barden, Amanda Thomas; Sfair, Leticia Lenz; da Silva Sangoi, Maximiliano; Volpato, Nadia Maria

2013-01-01

3

Application of UV spectrophotometric method for easy and rapid estimation of lafutidine in bulk and pharmaceutical formulation  

PubMed Central

Introduction: The present research work discusses the development of a UV estimation method for lafutidine. Simple, accurate, cost efficient, and reproducible spectrophotometric method has been developed for the estimation of Lafutidine in bulk and pharmaceutical dosage form. Materials and Methods: The Stock solution was prepared in a mixture of water and methanol (1:1). Further dilutions were made in water. Results: The drug was determined at maximum wavelength (?max) 279 nm. Beers law was obeyed in the concentration range of 10–50 ?g/ml having line equation y = 0.0100x + 0.035 with correlation coefficient of 0.999. Results of the analysis were validated statistically and by recovery study. Conclusion: The result of analysis was validated as per ICH guidelines and this method can be used for the routine analysis of lafutidine formulation. PMID:23781468

Jadhav, Kiran; Dhamecha, Dinesh; Tate, Amol; Tambe, Harshad; Patil, Mrityunjaya B.

2011-01-01

4

Novel UV-spectrophotometric method for quantitative estimation of furazolidone using mixed hydrotropic agent.  

PubMed

A novel, eco friendly, accurate, sensitive, economic and safe spectrophotometric method was developed by application of mixed hydrotropy using 2 M sodium acetate, 8 M urea, 2 M niacinamide and 2 M sodium benzoate solution (25:25:25:25% V/V) as hydrotropic agent, for the solubalizing of poorly water-soluble Furazolidone (FZ) (solubility:- 3.64e-01 mg/mL in water). There were more than 32 times enhancements in the solubility of FZ were found in mixed hydrotropic solution as compared to solubilities in distilled water. FZ shows maximum absorbance at 360 nm where sodium acetate, urea, niacinamide, sodium benzoate and other tablets excipients did not show any absorbance above 300 nm, and thus no interference in the estimation was seen. FZ was obeyed Beers law in the concentration range of 10 to 50 ?g/ml (r(2)=0.9992) in mixed hydrotropic solvent with mean recovery ranging from 97.32% to 98.9%. Proposed method is new, simple, economic, safe, rapid, accurate and reproducible and was validated according to ICH guidelines and values of accuracy, precision and other statistical analysis were found to be in good accordance with the prescribed values. PMID:23261742

Jain, Nilesh; Jain, Ruchi; Jain, Deepak Kumar; Maheshwari, Rajesh Kumar; Jain, Surendra

2013-01-01

5

Comparison of UV spectrophotometric method and high performance liquid chromatography for the analysis of flunarizine and its application for the dissolution test.  

PubMed

This study aimed to develop a simple UV spectrophotometric method for the analysis and the dissolution test of flunarizine in capsules. The UV absorbance was both measured directly and by the first derivative measurements at 254 and 268 nm, respectively. The developed methods were validated for their linearity, accuracy, precision, limit of detection (LOD) and limit of quantitation (LOQ) in comparison with the reported HPLC method. The UV spectrophotometric method illustrated excellent linearity (r2 > 0.9999) in the concentration range of 6-24 microg/mL. Precision (%R.S.D. < 1.50) and recoveries were good (%R > 99.62). The LOD of direct UV and first derivative measurements were 0.09 and 0.84 microg/mL, respectively, and the LOQ were 0.26 and 2.55 microg/mL, respectively. Results from the assay of flunarizine in capsules by the UV spectrophotometric methods, both direct and first derivative measurements were not significantly different from those of the HPLC method (P > 0.05). Additionally, the method was successfully used for the dissolution test of flunarizine capsule and was found to be reliable, simple, fast, and inexpensive. PMID:16352415

Busaranon, Kesarin; Suntornsuk, Worapot; Suntornsuk, Leena

2006-04-11

6

Chlorine Dioxide-Iodide-Methyl Acetoacetate Oscillation Reaction Investigated by UV-Vis and Online FTIR Spectrophotometric Method  

PubMed Central

In order to study the chemical oscillatory behavior and mechanism of a new chlorine dioxide-iodide ion-methyl acetoacetate reaction system, a series of experiments were done by using UV-Vis and online FTIR spectrophotometric method. The initial concentrations of methyl acetoacetate, chlorine dioxide, potassium iodide, and sulfuric acid and the pH value have great influence on the oscillation observed at wavelength of 289?nm. There is a preoscillatory or induction period, and the amplitude and the number of oscillations are associated with the initial concentration of reactants. The equations for the triiodide ion reaction rate changing with reaction time and the initial concentrations in the oscillation stage were obtained. Oscillation reaction can be accelerated by increasing temperature. The apparent activation energies in terms of the induction period and the oscillation period were 26.02?KJ/mol and 17.65?KJ/mol, respectively. The intermediates were detected by the online FTIR analysis. Based upon the experimental data in this work and in the literature, a plausible reaction mechanism was proposed for the oscillation reaction. PMID:22454614

Shi, Laishun; Wang, Xiaomei; Li, Na; Liu, Jie; Yan, Chunying

2012-01-01

7

New, simple and validated UV-spectrophotometric methods for the estimation of gatifloxacin in bulk and formulations.  

PubMed

New, simple and cost effective UV-spectrophotometric methods were developed for the estimation of gatifloxacin in bulk and pharmaceutical formulations. Gatifloxacin was estimated at 286 nm in 100 mM phosphate buffer (pH 7.4) and 292 nm in 100 mM hydrochloric acid (pH 1.2). Linearity range was found to be 1-18 mug ml(-1) (regression equation: absorbance=0.0684 x Concentration in microg ml(-1) + 0.0050; r2 = 0.9998) in the phosphate buffer (pH 7.4) and 1-14 microg ml(-1) (regression equation: absorbance = 0.0864 x Concentration in microg ml(-1) + 0.0027; r2 = 0.9999) in hydrochloric acid medium (pH 1.2). The apparent molar absorptivity was found to be 2.62 x 10(4) l mol(-1) cm(-1) in the phosphate buffer and 3.25 x 10(4) l mol(-1) cm(-1) in hydrochloric acid media. In both the proposed methods sandell's sensitivity was found to be about 0.01 microg cm(-2)/0.001A. These methods were tested and validated for various parameters according to ICH guidelines and USP. The quantitation limits were found to be 0.312 and 0.3 microg ml(-1) in the phosphate buffer and hydrochloric acid medium, respectively. The proposed methods were successfully applied for the determination of gatifloxacin in pharmaceutical formulations (tablets, injection and ophthalmic solution). The results demonstrated that the procedure is accurate, precise and reproducible (relative standard deviation <2%), while being simple, cheap and less time consuming and can be suitably applied for the estimation of gatifloxacin in different dosage forms and dissolution studies. PMID:16226753

Venugopal, K; Saha, Ranendra N

2005-01-01

8

Development and Validation of UV-Visible Spectrophotometric Method for Simultaneous Determination of Eperisone and Paracetamol in Solid Dosage Form  

PubMed Central

Purpose: Eperisone Hydrochloride (EPE) is a potent new generation antispasmodic drug which is used in the treatment of moderate to severe pain in combination with Paracetamol (PAR). Both drugs are available in tablet dosage form in combination with a dose of 50 mg for EPE and 325 mg PAR respectively. Methods: The method is based upon Q-absorption ratio method for the simultaneous determination of the EPE and PAR. Absorption ratio method is used for the ratio of the absorption at two selected wavelength one of which is the iso-absorptive point and other being the ?max of one of the two components. EPE and PAR shows their iso-absorptive point at 260 nm in methanol, the second wavelength used is 249 nm which is the ?max of PAR in methanol. Results: The linearity was obtained in the concentration range of 5-25 ?g/mL for EPE and 2-10 ?g/mL for PAR. The proposed method was effectively applied to tablet dosage form for estimation of both drugs. The accuracy and reproducibility results are close to 100% with 2% RSD. Results of the analysis were validated statistically and found to be satisfactory. The results of proposed method have been validated as per ICH guidelines. Conclusion: A simple, precise and economical spectrophotometric method has been developed for the estimation of EPE and PAR in pharmaceutical formulation. PMID:24312876

Khanage, Shantaram Gajanan; Mohite, Popat Baban; Jadhav, Sandeep

2013-01-01

9

Chemometrics-Assisted UV Spectrophotometric and RP-HPLC Methods for the Simultaneous Determination of Tolperisone Hydrochloride and Diclofenac Sodium in their Combined Pharmaceutical Formulation  

PubMed Central

Chemometrics-assisted UV spectrophotometric and RP-HPLC methods are presented for the simultaneous determination of tolperisone hydrochloride (TOL) and diclofenac sodium (DIC) from their combined pharmaceutical dosage form. Chemometric methods are based on principal component regression and partial least-square regression models. Two sets of standard mixtures, calibration sets, and validation sets were prepared. Both models were optimized to quantify each drug in the mixture using the information included in the UV absorption spectra of the appropriate solution in the range 241–290 nm with the intervals ? = 1 nm at 50 wavelengths. The optimized models were successfully applied to the simultaneous determination of these drugs in synthetic mixture and pharmaceutical formulation. In addition, an HPLC method was developed using a reversed-phase C18 column at ambient temperature with a mobile phase consisting of methanol:acetonitrile:water (60:30:10 v/v/v), pH-adjusted to 3.0, with UV detection at 275 nm. The methods were validated in terms of linearity, accuracy, precision, sensitivity, specificity, and robustness in the range of 3–30 ?g/mL for TOL and 1–10 ?g/mL for DIC. The robustness of the HPLC method was tested using an experimental design approach. The developed HPLC method, and the PCR and PLS models were used to determine the amount of TOL and DIC in tablets. The data obtained from the PCR and PLS models were not significantly different from those obtained from the HPLC method at 95% confidence limit. PMID:24482768

Gohel, Nikunj Rameshbhai; Patel, Bhavin Kiritbhai; Parmar, Vijaykumar Kunvarji

2013-01-01

10

Chemometrics-Assisted UV Spectrophotometric and RP-HPLC Methods for the Simultaneous Determination of Tolperisone Hydrochloride and Diclofenac Sodium in their Combined Pharmaceutical Formulation.  

PubMed

Chemometrics-assisted UV spectrophotometric and RP-HPLC methods are presented for the simultaneous determination of tolperisone hydrochloride (TOL) and diclofenac sodium (DIC) from their combined pharmaceutical dosage form. Chemometric methods are based on principal component regression and partial least-square regression models. Two sets of standard mixtures, calibration sets, and validation sets were prepared. Both models were optimized to quantify each drug in the mixture using the information included in the UV absorption spectra of the appropriate solution in the range 241-290 nm with the intervals ? = 1 nm at 50 wavelengths. The optimized models were successfully applied to the simultaneous determination of these drugs in synthetic mixture and pharmaceutical formulation. In addition, an HPLC method was developed using a reversed-phase C18 column at ambient temperature with a mobile phase consisting of methanol:acetonitrile:water (60:30:10 v/v/v), pH-adjusted to 3.0, with UV detection at 275 nm. The methods were validated in terms of linearity, accuracy, precision, sensitivity, specificity, and robustness in the range of 3-30 ?g/mL for TOL and 1-10 ?g/mL for DIC. The robustness of the HPLC method was tested using an experimental design approach. The developed HPLC method, and the PCR and PLS models were used to determine the amount of TOL and DIC in tablets. The data obtained from the PCR and PLS models were not significantly different from those obtained from the HPLC method at 95% confidence limit. PMID:24482768

Gohel, Nikunj Rameshbhai; Patel, Bhavin Kiritbhai; Parmar, Vijaykumar Kunvarji

2013-12-01

11

Second-Order Derivative UV Spectrophotometric Method for the Determination of Fesoterodine and Comparison with LC, CE and LC-MS/MS in Commercial Extended-Release Tablets.  

PubMed

The present work describes a second-order derivative UV spectrophotometric method for determination of a potent antimuscarinic drug, fesoterodine, in extended-release tablets. The method was developed and satisfactory validated according to ICH guideline with respect to specificity, linearity, precision, accuracy, and robustness. The response was linear in the concentration range of 2-24 µg mL-1 (r2 = 0.9999, n = 7) at wavelength 228 nm, which was the zero crossing point of excipient solutions. The detection and quantitation limits were 0.38 and 1.27 µg mL-1, respectively. Precision and accuracy data evaluated by relative standard deviation were lower than 2%. The method proved to be robust by a Plackett-Burman design evaluation. It is simple, it has low cost, and it has low use of polluting reagents. Therefore, the proposed method was successfully applied for the quantitative analysis of fesoterodine in commercial tablets, and the results were compared to validated methods by liquid chromatography, capillary electrophoresis and liquid chromatography-tandem mass spectrometry showing non-significant difference (P > 0.05). PMID:24061183

Sangoi, Maximiliano S; Todeschini, Vítor; Steppe, Martin

2012-03-01

12

Development of HPLC and UV spectrophotometric methods for the determination of ascorbic acid using hydroxypropyl-beta-cyclodextrin and triethanolamine as photostabilizing agents.  

PubMed

In this study, the effect of complex formation with triethanolamine (TEA) alone and in combination with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the photostability of ascorbic acid was evaluated for exposure to artificial and diffuse daylight. The first-order rate constants for the photodegradation reactions were determined. The data obtained showed that these complexes strongly reduced the photodegradation process with an 11- and 35-fold increase in the photostability of ascorbic acid, depending of the ligand concentration and the irradiation source. The multicomponent complex gave a significantly better stabilization for exposure to light than TEA alone. Due to the fact that the complexation extended the exposure of ascorbic acid to light (without molecular changes), UV spectrophotometric and reversed phase high performance liquid chromatographic (HPLC) methods were developed for the quantitative determination of the vitamin in pure form and in pharmaceutical preparations. These methods were statistically validated, all the validation parameters were found to be within the acceptance range. These results demonstrate that the proposed methods are suitable for the quality control of ascorbic acid, providing simple, rapid, precise, accurate and convenient approaches for routine analysis of bulk drug and pharmaceutical formulations. PMID:20103119

Garnero, Claudia; Longhi, Marcela

2010-02-01

13

Visible spectrophotometric method for amiodarone.  

PubMed

Amiodarone is an antiarrhythmic agent used for various types of tachyarrhythmia, both ventricular and supraventricular (atrial) arrhythmia. A spectrophotometric method for the assay of amiodarone was established. Based on the reduction of potassium ferricyanide in hydrochloric acid medium to potassium ferrocyanide forming a blue colored complex ferric ferrocyanide with Fe (III) ions. The compound was most stable in a mixture of ethylic alcohol and water (2:1, v/v) and it had an absorption maximum at 725 nm. The data were according to the Lambert-Beer Law in the concentration range of 0.5-5.0 microg/sample: correlation and coefficient R = 0.99977, R2 = 0.999541, slope of the line 0.12775, intercept 0.042077. The detection limit (DL) was 0.1032 microg/sample and the quantification limit (QL) 0.344 microg/ sample. PMID:23077917

Bosînceanu, Andreea; Popa, Gra?iela; Tântaru, Gladiola; Popovici, Iuliana

2012-01-01

14

Development and Validation of a UV Spectrophotometric Method for the Simultaneous Estimation of Eprosartan Mesylate and Hydrochlorothiazide in Bulk and Formulations  

PubMed Central

A simple, efficient, precise and accurate absorbance ratio method have been developed for the estimation of eprosartan mesylate and hydrochlorothiazide in pure and in fixed dose combination. In this method, UV spectra of eprosartan mesylate and hydrochlorothiazide were overlayed which involves the formation of Q-absorbance equation at 249.1 nm (isobestic point) and 274.5 nm, the max of hydrochlorothiazide. Both the drugs obeyed Beers law in the concentration range of 6-36 ?g/ml and 1-10 ?g/ml for eprosartan mesylate and hydrochlorothiazide, respectively. The accuracy of the method was determined by recovery studies and was found to be in the range of 102.29-103.10% and 99.52-101.60% for eprosartan mesylate and hydrochlorothiazide, respectively. The method was validated as per ICH guidelines and statistically. The method showed good reproducibility and recovery with % RSD less than 2. The method was found to be simple, economic, accurate and reproducible and can be used for routine analysis of eprosartan mesylate and hydrochlorothiazide in pure and in fixed dose combinations. PMID:22923871

Anandakumar, K.; Santhi, D. Vijaya; Jothieswari, D.; Subathrai, R.; Vetrichelvan, T.

2011-01-01

15

UV Spectrophotometric Simultaneous Determination of Paracetamol and Ibuprofen in Combined Tablets by Derivative and Wavelet Transforms  

PubMed Central

The application of first-order derivative and wavelet transforms to UV spectra and ratio spectra was proposed for the simultaneous determination of ibuprofen and paracetamol in their combined tablets. A new hybrid approach on the combined use of first-order derivative and wavelet transforms to spectra was also discussed. In this application, DWT (sym6 and haar), CWT (mexh), and FWT were optimized to give the highest spectral recoveries. Calibration graphs in the linear concentration ranges of ibuprofen (12–32?mg/L) and paracetamol (20–40?mg/L) were obtained by measuring the amplitudes of the transformed signals. Our proposed spectrophotometric methods were statistically compared to HPLC in terms of precision and accuracy. PMID:24949492

Hoang, Vu Dang; Ly, Dong Thi Ha; Tho, Nguyen Huu; Minh Thi Nguyen, Hue

2014-01-01

16

Comparative Study of RP-HPLC and UV Spectrophotometric Techniques for the Simultaneous Determination of Amoxicillin and Cloxacillin in Capsules  

PubMed Central

Reversed-phase HPLC and UV spectrophotometric techniques using water as solvent have been developed and validated for the simultaneous determination of amoxicillin and cloxacillin in capsules. For both techniques, the linearity range of 60.073x2013;140.0 µg/mL was studied. The spectrophotometric data show that non-derivative techniques, such as absorbance ratio and compensation, and ratio spectra first-order derivative could be successfully used for the co-assay of amoxicillin and cloxacillin. Based on the statistical comparison of spectrophotometric and chromatographic data, the interchangeability between HPLC and UV spectrophotometric techniques has been suggested for the routine analysis. PMID:21264124

Giang, Do T; Hoang, Vu D

2010-01-01

17

UV-spectrophotometric determination of imatinib mesylate and its application in solubility studies.  

PubMed

A new, simple and sensitive UV-spectrophotometric method was developed for the determination of imatinib mesylate in bulk and pharmaceutical formulations (tablets and nanoparticles). The developed spectroscopic method was validated for selectivity, linearity and range, precision, accuracy and sensitivity. The method has demonstrated excellent linearity over the range of 2.5-25 microg/mL with regression equation: absorbance (AU) = 0.047 x concentration (microg/mL) + 0.008 and r2 = 0.9998. The developed method demonstrated consistent high recoveries (99-102%) and low relative standard deviation (< 5%) at 285 nm. Moreover, the method was found to be highly sensitive with low limit of detection (0.57 microg/mL) and limit of quantitation (1.71 microg/mL). The apparent molar absorptivity and Sandell's sensitivity was found to be 2.75 x 10(3) L/M cm and 2.15 microg/cm2 respectively. The validated method was successfully employed for the drug content analysis from tablets and nanoparticles preparations. Additionally, the method was successfully employed for pH metric solubility analysis of the drug. PMID:18819515

Bende, G; Kollipara, S; Sekar, V; Saha, R

2008-09-01

18

Simple Spectrophotometric Methods for Standardizing Ayurvedic Formulation  

PubMed Central

Traditional medicines are effective but the standardization of Ayurvedic formulations is essential in order to assess the quality of drugs, based on the concentration of their active principles. Department of AYUSH has given preliminary guidelines for standardizing these conventional formulations, for uniformity of batches in production of Ayurvedic formulation and it is necessary to develop methods for evaluation. The present work is an attempt to standardize asav-arishta, the traditional Ayurvedic formulation using simple, non-expensive spectrophotometric methods. The various parameters performed included total phenolics, total flavonoids, total alkaloids and total saponins, also included pH, sugar %, alcohol content and specific gravity. The results obtained may be considered as tools for assistance to the regulatory authorities, scientific organizations and manufacturers for developing standards. PMID:23325998

Vador, N.; Vador, B.; Hole, Rupali

2012-01-01

19

UV-Vis spectrophotometrical and analytical methodology for the determination of singlet oxygen in new antibacterials drugs.  

PubMed

We have determined and quantified spectrophotometrically the capacity of producing reactive oxygen species (ROS) as (1)O(2) during the photolysis with UV-A light of 5 new synthesized naphthyl ester derivates of well-known quinolone antibacterials (nalidixic acid (1), cinoxacin (2), norfloxacin (3), ciprofloxacin (4) and enoxacin (5)). The ability of the naphthyl ester derivatives (6-10) to generate singlet oxygen were detecting and for the first time quantified by the histidine assay, a sensitive, fast and inexpensive method. The following tendency of generation of singlet oxygen was observed: compounds 7 > 10 > 6 > 8 > 9 > parent drugs 1-5. PMID:19662185

Zoltan, Tamara; Vargas, Franklin; Izzo, Carla

2007-01-01

20

Spectrophotometric and HPLC Methods for Simultaneous Estimation of Amlodipine Besilate, Losartan Potassium and Hydrochlorothiazide in Tablets  

PubMed Central

Two UV-spectrophotometric and one reverse phase high performance liquid chromatography methods have been developed for the simultaneous estimation of amlodipine besilate, losartan potassium and hydrochlorothiazide in tablet dosage form. The first UV spectrophotometric method was a determination using the simultaneous equation method at 236.5, 254 and 271 nm over the concentration range 5-25, 10-50 and 5-25 ?g/ml for amlodipine besilate, losartan potassium and hydrochlorothiazide, respectively. The second UV method was a determination using the area under curve method at 231.5-241.5, 249-259 and 266-276 nm over the concentration range of 5-25, 5-25 and 10-50 ?g/ml for amlodipine besilate, hydrochlorothiazide and losartan potassium, respectively. In reverse phase high performance liquid chromatography analysis is carried out using 0.025 M phosphate buffer (pH 3.7):acetonitrile (57:43 v/v) as the mobile phase and Kromasil C18 (4.6 mm i.d×250 mm) column as stationery phase with detection wavelength of 232 nm linearity was obtained in the concentration range of 2-14, 20-140 and 5-40 ?g/ml for amlodipine besilate, losartan potassium and hydrochlorothiazide, respectively. Both UV-spectrophotometric and reverse phase high performance liquid chromatography methods were statistically validated and can be used for analysis of combined dose tablet formulation containing amlodipine besilate, losartan potassium and hydrochlorothiazide. PMID:20582208

Wankhede, S. B.; Raka, K. C.; Wadkar, S. B.; Chitlange, S. S.

2010-01-01

21

Simple spectrophotometric method for estimation of disodium edetate in topical gel formulations  

PubMed Central

A simple, sensitive, cost-effective and reproducible UV-spectrophotometric method has been developed and validated for the estimation of disodium edetate in topical gel formulations. Solution of disodium edetate reacts with ferric chloride to form complex in 0.1 N HCl giving ?max at 270 nm. Beer's law was obeyed in the concentration range of 5–50 ?g/mL (r2= 0.9997). The limit of detection and limit of quantitation were found to be 1.190 and 3.608 ?g/mL, respectively. The results show that the procedure is accurate, precise, and reproducible (relative standard deviation < 1%), while being simple and less time consuming. The study concluded that the UV-spectrophotometric method could be used for the quantification of disodium edetate in pure form as well as in pharmaceutical formulations. PMID:23781446

Kamboj, Sunil; Sharma, Deepak; Nair, Anroop B.; Kamboj, Suman; Sharma, Rakesh Kumar; Ali, Javed; Pramod, K; Ansari, S. H.

2011-01-01

22

Alternative spectrophotometric method for standardization of chlorite aqueous solutions.  

PubMed

The chlorite ion is the principal by-product of the treatment of drinking water by chlorine dioxide. In function of the chlorite salt instability, standard solutions of this ion need standardization by iodometric titration, which is a reliable method although labor intensive and time consuming. An alternative method to standardization of aqueous chlorite solutions, based on its direct UV absorption measurement, was presented. Besides the maximum absorption (260 nm) generally used in other studies, the minimum (239 nm) and isosbestic (248 nm) wavelengths were proposed as supplementary points to chlorite quantification and their molar absorptivity coefficients were estimated (155.2+/-0.6, 104.5+/-1.0 and 69.0+/-1.2 L cm(-1) mol(-1), respectively). The direct spectrophotometric determination of chlorite could be made selectively even in the presence of high concentration of major contaminants (chorine dioxide, chloride and chlorate), being a simple and rapid method, consuming very low volume of sample and generating low quantities of laboratory wastes. PMID:17386686

Philippi, Marilia; dos Santos, Heldiane S; Martins, Aline O; Azevedo, Carla M N; Pires, Marçal

2007-03-01

23

Determination of Theobromine, Theophylline, and Caffeine in Various Food Products Using Derivative UV-Spectrophotometric Techniques and High-Performance Liquid Chromatography  

Microsoft Academic Search

Accurate, sensitive and precise derivative ultraviolet Spectrophotometric and high-performance liquid chromatographic (HPLC) methods are described for the simultaneous determination of three natural methyl xanthines (theobromine, theophylline and caffeine) in various food products. The derivative UV-spectro-photometry, with zero crrosing technique of measurement was selected for determination of theobromine and theophylline. First-derivative procedure (D1) was adopted for theobromine determination in the presence

Mustafa A. Abuirjeie; Mohie Sharaf El-Din; Ibrahim I. Mahmoud

1992-01-01

24

UV spectrophotometric simultaneous determination of cefoperazone and sulbactam in pharmaceutical formulations by derivative, Fourier and wavelet transforms.  

PubMed

Signal processing methods based on the use of derivative, Fourier and wavelet transforms were proposed for the spectrophotometric simultaneous determination of cefoperazone and sulbactam in powders for injection. These transforms were successfully applied to UV spectra and ratio spectra to find suitable working wavelengths. Wavelet signal processing was proved to have distinct advantages (i.e. higher peak intensity obtained, additional smooth function and scaling factor process eliminated) over derivative and Fourier transforms. Especially, a better resolution of spectral overlapping bands was obtained by the use of double signal transform in the sequences such as (i) spectra pre-processed by Fractional Wavelet Transform and subsequently subjected to Continuous Wavelet Transform or Discrete Wavelet Transform, and (ii) derivative - wavelet transforms combined. Calibration graphs for cefoperazone and sulbactam were recorded for the range 10-35 mg/L. Good accuracy and precision were reported for all proposed methods by analyzing synthetic mixtures of cefoperazone and sulbactam. Furthermore, these methods were statistically comparable to RP-HPLC. PMID:24374557

Hoang, Vu Dang; Loan, Nguyen Thi; Tho, Vu Thi; Nguyen, Hue Minh Thi

2014-01-01

25

Spectrophotometric and liquid chromatographic determination of fenofibrate and vinpocetine and their hydrolysis products  

Microsoft Academic Search

Several spectrophotometric and HPLC methods are presented for the determination of fenofibrate, vinpocetine and their hydrolysis products. The resolution of either fenofibrate or vinpocetine and their hydrolysis products has been accomplished by using numerical spectrophotometric methods as partial least squares (PLS-1) and principal component regression (PCR) applied to UV spectra; and graphical spectrophotometric methods as first derivative of ratio spectra

Alaa El-Gindy; Samy Emara; Mostafa K. Mesbah; Ghada M. Hadad

2005-01-01

26

Determination of mimosine by a sensitive indirect spectrophotometric method.  

PubMed

A simple and sensitive indirect spectrophotometric method is described for the determination of mimosine based on its reaction with diazotized sulfanilamide (DZSAM). DZSAM couples with N-(1-naphthyl)ethylenediamine (NEDA) forming a pink colored azodye, absorbing maximally at 540nm (epsilon(max)=27mM(-1)cm(-1)). In the present method, mimosine was first reacted with known excess of DZSAM and the unreacted DZSAM was determined by coupling with NEDA. The reaction of mimosine with DZSAM proceeded optimally at neutral pH. The decrease in absorbance of the DZSAM-NEDA-coupled product obeyed Beer's law in the concentration range of 0.005-0.15mugml(-1) of mimosine. The present method was applied to estimate mimosine in plant extracts containing lesser than 0.05mugml(-1) with recovery at 99+/-0.41%. The method described is superior to other reported methods in terms of ease of adaptability and sensitivity. PMID:18969480

Lalitha, K; Rajendra Kulothungan, S

2004-06-17

27

Extractive spectrophotometric method for the determination of tropicamide.  

PubMed

Two simple, rapid, and extractive spectrophotometric methods were developed for the determination of tropicamide (TPC). These methods are based on the formation of ionpair complexes between the basic nitrogen of the drug with bromocresol purple (BCP) and methyl orange (MO) in acidic buffer solution. The formed complexes were extracted with chloroform and measured at 408 and 427 nm using BCP and MO, respectively. Beer's law was obeyed in the range 1.0-16 ?g ml(-1) with correlation coefficient (n=6) ?0.9991. The molar absorpitivity, Sandell sensitivity, detection, and quantification limits were also calculated. The composition of the ion pairs was found 1:1 by Job's method. The proposed methods have been applied successfully for the analysis of TPC in pure and in its eye drops. PMID:22523460

Shoaibi, Za; Gouda, Aa

2012-01-01

28

Extractive Spectrophotometric Method for the Determination of Tropicamide  

PubMed Central

Two simple, rapid, and extractive spectrophotometric methods were developed for the determination of tropicamide (TPC). These methods are based on the formation of ionpair complexes between the basic nitrogen of the drug with bromocresol purple (BCP) and methyl orange (MO) in acidic buffer solution. The formed complexes were extracted with chloroform and measured at 408 and 427 nm using BCP and MO, respectively. Beer's law was obeyed in the range 1.0–16 ?g ml–1 with correlation coefficient (n=6) ?0.9991. The molar absorpitivity, Sandell sensitivity, detection, and quantification limits were also calculated. The composition of the ion pairs was found 1:1 by Job's method. The proposed methods have been applied successfully for the analysis of TPC in pure and in its eye drops. PMID:22523460

Shoaibi, ZA; Gouda, AA

2012-01-01

29

Spectrophotometric methods to differentiate beers and evaluate beer ageing  

Microsoft Academic Search

The methodology most widely used to detect the antioxidant capacity (indirectly by ABTS+ discoloration) has been modified to be applied to beer samples due to signal instabilities. A new and direct method to follow beer ageing has been developed based on a simple organic solvent extraction follow by molecular absorption spectrophotometry UV–VIS (MAS) measurement. Polyphenols and Maillard reaction products (MRPs)

A. Oñate-jaén; D. Bellido-milla; M. P. Hernández-artiga

2006-01-01

30

A new spectrophotometric method for the determination of methyldopa.  

PubMed

A new, simple and low cost spectrophotometric method for the determination of methyldopa in pharmaceutical preparations was developed. The method was based on the coupling of methyldopa with 2,6-dichloroquinone-4-chlorimide (DCQ). The absorbance maximum (? max) of the resulted colored product was at 400 nm. Different buffers were used to determine the optimal pH for the reaction. About 1% w/v acetate buffer with pH 8.0 gave the optimal pH required for the reaction. Of the different solvents tried, water and ethanol were found to be the most suitable solvents. Beer's law was obeyed in concentration range of 4-20 ?g/ml methyldopa. The correlation coefficient was found to be (r = 0.9975). The limit of detection and limit of quantification were 1.1 ?g/ml and 3.21 ?g/ml, respectively. The reaction ratio between methyldopa and DCQ was studied and found to be 1:3. The work included the study of the possible interference of hydrochlorothiazide found in combination with methyldopa tablets. The method was validated and results obtained for the assay of two different brands of methyldopa tablets were compared with the BP method (colorimetric). The repeatability and reproducibility of the developed method were evaluated and the obtained results quoted. The derivative formed as a result of the reaction of methyldopa with DCQ was isolated and its possible mechanistic pathway was suggested. PMID:23960712

Gadkariem, E A; Ibrahim, K E E; Kamil, N A A; Haga, M E M; El-Obeid, H A

2009-10-01

31

A new spectrophotometric method for the determination of methyldopa  

PubMed Central

A new, simple and low cost spectrophotometric method for the determination of methyldopa in pharmaceutical preparations was developed. The method was based on the coupling of methyldopa with 2,6-dichloroquinone-4-chlorimide (DCQ). The absorbance maximum (?max) of the resulted colored product was at 400 nm. Different buffers were used to determine the optimal pH for the reaction. About 1% w/v acetate buffer with pH 8.0 gave the optimal pH required for the reaction. Of the different solvents tried, water and ethanol were found to be the most suitable solvents. Beer’s law was obeyed in concentration range of 4–20 ?g/ml methyldopa. The correlation coefficient was found to be (r = 0.9975). The limit of detection and limit of quantification were 1.1 ?g/ml and 3.21 ?g/ml, respectively. The reaction ratio between methyldopa and DCQ was studied and found to be 1:3. The work included the study of the possible interference of hydrochlorothiazide found in combination with methyldopa tablets. The method was validated and results obtained for the assay of two different brands of methyldopa tablets were compared with the BP method (colorimetric). The repeatability and reproducibility of the developed method were evaluated and the obtained results quoted. The derivative formed as a result of the reaction of methyldopa with DCQ was isolated and its possible mechanistic pathway was suggested. PMID:23960712

Gadkariem, E.A.; Ibrahim, K.E.E.; Kamil, N.A.A.; Haga, M.E.M.; El-Obeid, H.A.

2009-01-01

32

Spectrophotometric analysis of Ellerman bombs in the Ca II, H?, and UV range  

NASA Astrophysics Data System (ADS)

Context: Even if Ellerman bombs have been observed in the H? line within emerging magnetic flux regions since the early 20th century, their origin and the mechanisms that lead to their formation have been strongly debated. Recently, new arguments in favor of chromospheric magnetic reconnection have been advanced. Ellerman bombs seem to be the signature of reconnections that take place during the emergence of the magnetic field. Aims: We have observed an active region presenting emergence of magnetic flux. We detected and studied Ellerman bombs in two chromospheric lines: Ca ii 8542 Å and H?. We investigated the link between Ellerman bombs and other structures and phenomena appearing in an emerging active region: UV bright points, arch filament systems, and magnetic topology. Methods: On August 3, 2004, we performed multi-wavelength observations of the active region NOAA 10655. This active region was the target of SoHO Joint Observation Program 157. Both SoHO/MDI and TRACE (195 Å and 1600 Å) were used. Simultaneously, we observed in the Ca ii and Na D1 lines with the spectro-imager MSDP mode of THEMIS. Alternately to the MSDP, we used the MTR spectropolarimeter on THEMIS to observe in H? and in the Fe i doublet at 6302 Å. We derived the magnetic field vectors around some Ellerman bombs. Results: We present the first images of EBs in the Ca ii line and confirm that Ellerman bombs can indeed be observed in the Ca ii line, presenting the same “moustache” geometry profiles as in the H? line, but with a narrower central absorption in the Ca ii line, in which the peaks of emission are around ±0.35 Å. We noticed that the Ellerman bombs observed in the wings of Ca ii line have an elongated shape - the length about 50% greater than the width. We derived mean semi-axis lengths of 1.4'' × 2.0''. In the UV time profiles of the Ellerman bombs, we noticed successive enhanced emissions. The distribution of lifetimes of these individual impulses presents a strong mode around 210 s. Study of the magnetic topology shows that 9 out of the 13 EBs are located on the inversion line of the longitudinal field and that some typical examples might be associated with a bald patch topology. Conclusions: We provide new arguments in favor of the reconnection origin of Ellerman bombs. The different individual impulses observed in UV may be related to a bursty mode of reconnection. We also show that this Ca ii 8542 Å chromospheric line is a good indicator of Ellerman bombs and can bring new information about these phenomena.

Pariat, E.; Schmieder, B.; Berlicki, A.; Deng, Y.; Mein, N.; López Ariste, A.; Wang, S.

2007-10-01

33

A simple Ultraviolet spectrophotometric method for the determination of etoricoxib in dosage formulations.  

PubMed

The present study was undertaken to develop a validated, rapid, simple, and low-cost ultraviolet (UV) spectrophotometric method for estimating Etoricoxib (ETX) in pharmaceutical formulations. The analysis was performed on ? max 233 nm using 0.1 M HCl as blank/diluent. The proposed method was validated on International Conference on Harmonization (ICH) guidelines including parameters as linearity, accuracy, precision, reproducibility, and specificity. The proposed method was also used to access the content of the ETX in two commercial brands of Indian market. Beer's law was obeyed in concentration range of 0.1-0.5 ?g/ml, and the regression equation was Y = 0.418x + 0.018. The mean accuracy values for 0.1 ?g/ml and 0.2 ?g/ml concentration of ETX were found to be 99.76 ± 0.52% and 99.12 ± 0.84, respectively, and relative standard deviation (RSD) of interday and intraday was less than 2%. The developed method was suitable and specific to the analysis of ETX even in the presence of common excipients. The method was applied on two different marketed brands and ETX contents were 98.5 ± 0.56 and 99.33 ± 0.44, respectively, of labeled claim. The proposed method was validated as per ICH guidelines and statistically good results were obtained. This method can be employed for routine analysis of ETX in bulk and commercial formulations. PMID:23378945

Singh, Shipra; Mishra, Amrita; Verma, Anurag; Ghosh, Ashoke K; Mishra, Arun K

2012-10-01

34

Validation of different spectrophotometric methods for determination of vildagliptin and metformin in binary mixture.  

PubMed

New, simple, specific, accurate, precise and reproducible spectrophotometric methods have been developed and subsequently validated for determination of vildagliptin (VLG) and metformin (MET) in binary mixture. Zero order spectrophotometric method was the first method used for determination of MET in the range of 2-12 ?g mL(-1) by measuring the absorbance at 237.6 nm. The second method was derivative spectrophotometric technique; utilized for determination of MET at 247.4 nm, in the range of 1-12 ?g mL(-1). Derivative ratio spectrophotometric method was the third technique; used for determination of VLG in the range of 4-24 ?g mL(-1) at 265.8 nm. Fourth and fifth methods adopted for determination of VLG in the range of 4-24 ?g mL(-1); were ratio subtraction and mean centering spectrophotometric methods, respectively. All the results were statistically compared with the reported methods, using one-way analysis of variance (ANOVA). The developed methods were satisfactorily applied to analysis of the investigated drugs and proved to be specific and accurate for quality control of them in pharmaceutical dosage forms. PMID:24548810

Abdel-Ghany, Maha F; Abdel-Aziz, Omar; Ayad, Miriam F; Tadros, Mariam M

2014-05-01

35

Traceability methods comparison of broadband UV radiometers  

NASA Astrophysics Data System (ADS)

Broadband UV radiometers are widely used for measuring UV irradiance or radiant exposure in various areas of health, industry, and science, such as in weather aging of materials, semiconductor lithography, non-destructive testing, UV curing, catalytic process, environmental monitoring, atmospheric research, water purification, medical diagnostics and therapy, space-based astrophysical observations and other applications. The accuracy of measurement is influenced by many factors such as the characteristics of the radiometer, operating conditions, environmental conditions and the UV sources to be measured. Due to the lack of spectral resolving power, significant measurement errors may occur if the radiometer has poor quality. Five different calibration and traceability methods of UV radiometers were realized and analyzed at National Institute of Metrology (NIM), including absolute spectral irradiance method based on standard lamps, absolute spectral power responsivity method of detectors, absolute thermoelectric radiometer method, electrically calibrated pyroelectric radiometer method and method of comparing with the standard radiometer. The above methods were used to realize the irradiance responsivity of a broadband UVA meter independently. Compared to absolute spectral irradiance method based on standard lamps, relative deviation of these traceability methods are 0%, 0.18%, 2.50%, -3.04% and 4.11% respectively. Absolute spectral power responsivity method of detectors is adopted by the most national metrology institute to realize UV irradiance responsivity. The deviation of absolute thermoelectric radiometer method results from poor signal-to-noise of the combination of radiation source and a UV filter, near to the sensitivity limit of the absolute radiometer. The largest deviation of method of comparing with the standard radiometer comes from different response wavelength, different receiving area between the standard radiometer and the test radiometer. Spectral irradiance method based on standard lamps is the principal traceability method of NIM tracing to the national spectral irradiance primary standard directly. This method was proved by international comparison of "Irradiance Responsivity of UVA Detectors APMP PR-S1". The comparison results showed that the consistency between the NIMs' value and the international reference one is the best among the seven participants. On the basis of the above theories and methods, the uncertainty of broadband ultraviolet irradiance standard under the defined conditions was cut down to 2.0% (k=1) from 10% (k=1).

Dai, Caihong; Huang, Bo; Wu, Zhifeng; OuYang, Huiquan; Yu, Jialin

2011-11-01

36

Stability-indicating methods for the spectrophotometric determination of norfloxacin  

Microsoft Academic Search

Two spectrophotometric procedures for the selective determination of norfloxacin (NF) in the presence of its decarboxylated degradant are described. The first depends upon measurement of the pH-induced absorbance difference (?A) of the drug solution between 0.1 N HCl and 0.1 N NaOH at 280 nm. The second involves chelation of the intact drug with iron(II) in acetate buffer solution (pH

Sonia Z. El Khateeb; Sawsan A. Abdel Razek; M. M. Amer

1998-01-01

37

Spectrophotometric method for simultaneous estimation of atenolol in combination with losartan potassium and hydrochlorothiazide in bulk and tablet formulation  

PubMed Central

Aim: To develop a simple, accurate, rapid and precise UV spectrophotometric method for the estimation of atenolol in combination with losartan potassium and hydrochlorothiazide. Materials and Methods: The method employs formation and solving simultaneous equation using 251.60 nm and 224.20 nm for losartan potassium and atenolol, 224.20 and 271.60 for atenolol and hydrochlorothiazide as two analytical wavelengths, using methanol water as a solvent. Results and Conclusion: The linearity was observed in the concentration range of 5-30 µg/ml (r=0.9991) for losratan pottassium, 2 - 12 µg/ml (r = 0.9995) for atenolol and 2 - 14 µg/ml (r = 0.9993) for hydrochlorothiazide. The results of the method were validated statistically and by recovery studies. PMID:21180476

Bari, Sanjay; Sathe, Shital; Jain, Pritam; Surana, Sanjay

2010-01-01

38

Three different spectrophotometric methods manipulating ratio spectra for determination of binary mixture of Amlodipine and Atorvastatin  

Microsoft Academic Search

Three simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra are developed for the simultaneous determination of Amlodipine besylate (AM) and Atorvastatin calcium (AT) in tablet dosage forms. The first method is first derivative of the ratio spectra (1DD), the second is ratio subtraction and the third is the method of mean centering of ratio spectra. The calibration curve

Hany W. Darwish; Said A. Hassan; Maissa Y. Salem; Badr A. El-Zeiny

2011-01-01

39

A New Spectrophotometric Method for the Determination of Arsenic in Environmental and Biological Samples  

Microsoft Academic Search

A simple and selective spectrophotometric method has been developed for the determination of trace amounts of arsenic using azure B as a chromogenic reagent. The proposed method is based on the reaction of arsenic(III) with potassium iodate in acid medium to liberate iodine. The liberated iodine bleaches the violet color of azure B and is measured at 644 nm. This decrease

Tom Cherian; B. Narayana

2005-01-01

40

Novel spectrophotometric methods for simultaneous determination of timolol and dorzolamide in their binary mixture.  

PubMed

Two smart and novel spectrophotometric methods namely; absorbance subtraction (AS) and amplitude modulation (AM) were developed and validated for the determination of a binary mixture of timolol maleate (TIM) and dorzolamide hydrochloride (DOR) in presence of benzalkonium chloride without prior separation, using unified regression equation. Additionally, simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of the binary mixture namely; simultaneous ratio subtraction (SRS), ratio difference (RD), ratio subtraction (RS) coupled with extended ratio subtraction (EXRS), constant multiplication method (CM) and mean centering of ratio spectra (MCR). The proposed spectrophotometric procedures do not require any separation steps. Accuracy, precision and linearity ranges of the proposed methods were determined and the specificity was assessed by analyzing synthetic mixtures of both drugs. They were applied to their pharmaceutical formulation and the results obtained were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there is no significant difference between the proposed methods and the reported one regarding both accuracy and precision. PMID:24607469

Lotfy, Hayam Mahmoud; Hegazy, Maha A; Rezk, Mamdouh R; Omran, Yasmin Rostom

2014-05-21

41

Spectrophotometric and high performance liquid chromatographic methods for sensitive determination of bisphenol A.  

PubMed

A new spectrophotometric method for the determination of trace amounts of bisphenol A based on a diazotization-coupling reaction was developed. In acidic solution, clenbuterol was first diazotized with sodium nitrite, then coupled with bisphenol A to from an azo-compound [I] in NH3-NH4Cl buffer, which shows a maximum absorption at 410 nm. The effects of the amount of sodium nitrite, diazo reaction time, the amount of clenbuterol, coupling reaction time and coupling reaction temperature have been examined. Under the optional conditions, the determination of the linear range of bisphenol A is 0.24-8.4 ?g/mL, correlation coefficient is 0.9905 and detection limit of this method is 0.15 ?g/mL. The spectrophotometric method is simple, rapid, high sensitivity with better accuracy. High performance liquid chromatography (HPLC) technique combined with this new spectrophotometric method has been also developed for the measurement of bisphenol A. The analysis was achieved on a C18 column using water and methanol as a mobile phase and the detection was done spectrophotometrically at 410 nm. These reported methods were applied to the determination of bisphenol A in hot water in contact with commercially available table-water bottle samples. PMID:24309176

Zhuang, Yafeng; Zhou, Meng; Gu, Jia; Li, Xiangmei

2014-03-25

42

UV-visible microscope spectrophotometric polarization and dichroism with increased discrimination power in forensic analysis  

NASA Astrophysics Data System (ADS)

Microanalysis of transfer (Trace) evidence is the application of a microscope and microscopical techniques for the collection, observation, documentation, examination, identification, and discrimination of micrometer sized particles or domains. Microscope spectrophotometry is the union of microscopy and spectroscopy for microanalysis. Analytical microspectroscopy is the science of studying the emission, reflection, transmission, and absorption of electromagnetic radiation to determine the structure or chemical composition of microscopic-size materials. Microscope spectrophotometry instrument designs have evolved from monochromatic illumination which transmitted through the microscope and sample and then is detected by a photometer detector (photomultiplier tube) to systems in which broad-band (white light) illumination falls incident upon a sample followed by a non-scanning grating spectrometer equipped with a solid-state multi-element detector. Most of these small modern spectrometers are configured with either silicon based charged-couple device detectors (200-950 nm) or InGaAs based diode array detectors (850-2300 nm) with computerized data acquisition and signal processing being common. A focus of this research was to evaluate the performance characteristics of various modern forensic (UV-Vis) microscope photometer systems as well as review early model instrumental designs. An important focus of this research was to efficiently measure ultraviolet-visible spectra of microscopically small specimens for classification, differentiation, and possibly individualization. The first stage of the project consisted of the preparation of microscope slides containing neutral density filter reference materials, molecular fluorescence reference materials, and dichroic reference materials. Upon completion of these standard slide preparations analysis began with measurements in order to evaluate figures of merit for comparison of the instruments investigated. The figures of merit investigated included: 1) wavelength accuracy, 2) wavelength precision, 3) wavelength resolution stability, 4) photometric accuracy, 5) photometric precision, 6) photometric linearity, 7) photometric noise, and 8) short-term baseline stability. In addition, intrinsic instrument polarization effects were investigated to determine the impact of these properties on spectral interpretation and data quality. Finally, a set of recommendations were developed which describe instrument performance characteristics for microscope and spectrometer features and functions, and specific instrument parameters that must be controlled in order to acquire high quality data from an ultraviolet-visible forensic microscope spectrophotometer system for increased discrimination power.

Purcell, Dale Kevin

43

Investigation of sorption properties of tetrazole-containing acrylic copolymers by spectrophotometric method  

NASA Astrophysics Data System (ADS)

In this work sorption of tetrazole-containing acrylic copolymers in water solutions of copper chloride were investigated with help of gravimetric and spectrophotometric methods. Sorption properties in dependence of copolymer composition and ion strength of the outer electrolyte were found. Fields of application of the synthesized copolymers were proposed, including cleaning of sewage, photocolorimetry, production of sensor micro sphere gel particles.

Uspenskaya, Maya V.; Sirotinkin, Nikolay V.; Kabakova, Marina M.; Thiel, E.

2006-09-01

44

SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF SCANDIUM WITH PONTACHROME AZURE BLUE B  

Microsoft Academic Search

A new method for the spectrophotometric determination of scandium was ; studied, using Pontachrome Azure Blue B (Color index 43830) as a reagent. ; Scandium reacts with the reagent at pH 6 approximates 7 to form a complex, of ; which composition seems to be ScRâ. The complex shows an absorption band ; with a maximum at 610 m mu

T. Shigematsu; K. Uesugi; M. Tabushi

1963-01-01

45

Spectrophotometric and Reversed-Phase High-Performance Liquid Chromatographic Method for the Determination of Doxophylline in Pharmaceutical Formulations  

PubMed Central

Two methods are described for determination of Doxophylline in a solid dosage form. The first method was based on ultraviolet (UV)-spectrophotometric determination of the drug. It involves absorbance measurement at 274 nm (?max of Doxophylline) in 0.1 N hydrochloric acid. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.20–30 mg/ml for the drug. The second method was based on high-performance liquid chromatography (HPLC) separation of the drug in reverse-phase mode using the Hypersil ODS C18 column (250 × 4.6 mm, 5 mm). The mobile phase constituted of buffer acetonitrile (80:20) and pH adjusted to 3.0, with dilute orthophosphoric acid delivered at a flow rate 1.0 ml/min. Detection was performed at 210 nm. Separation was completed within 7 min. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.165–30 mg/ml for the drug. The relative standard deviation was found to be <2.0% for the UV-spectrophotometry and HPLC methods. Both these methods have been successively applied to the solid dosage pharmaceutical formulation, and were fully validated according to ICH guidelines. PMID:21042488

Joshi, HR; Patel, AH; Captain, AD

2010-01-01

46

Antioxidant capacity of bovine milk as assayed by spectrophotometric and amperometric methods  

Microsoft Academic Search

The total antioxidant capacity (TAC) of bovine milk, whey, and low-molecular-weight (LMW) fractions of whey was investigated using spectrophotometric methods including an ABTS-based method (reduction of the cation radical of 2,2?-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid)) and a FRAP method (reduction of Fe3+). Significant antioxidant capacity in milk and whey was demonstrated by the ABTS method (TAC(ABTS)), and it apparently increased with increasing pH.

J Chen; H Lindmark-Månsson; L Gorton; B Åkesson

2003-01-01

47

Simultaneous determination of some cholesterol-lowering drugs in their binary mixture by novel spectrophotometric methods  

NASA Astrophysics Data System (ADS)

Four simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of simvastatin (SM) and ezetimibe (EZ) namely; extended ratio subtraction (EXRSM), simultaneous ratio subtraction (SRSM), ratio difference (RDSM) and absorption factor (AFM). The proposed spectrophotometric procedures do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined, and the methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the cited drugs. The four methods were applied for the determination of the cited drugs in tablets and the obtained results were statistically compared with each other and with those of a reported HPLC method. The comparison showed that there is no significant difference between the proposed methods and the reported method regarding both accuracy and precision.

Lotfy, Hayam Mahmoud; Hegazy, Maha Abdel Monem

2013-09-01

48

First order derivative spectrophotometric and HPLC methods for determination of moexipril hydrochloride in the pure form, pharmeceutical formulations and evaluation of its stability.  

PubMed

A rapid, linear (over a concentration range of 0.00012-0.0012% and with correlation coefficient r = 0.999), accurate (an average recovery of 100%), precise (an average standard deviation < 1.5%) and economical first derivative UV spectrophotometric assay method (lambda(max) = 238 nm) was developed for the determination of moexipril hydrochloride (MOXL) in a pharmaceutical formulation. The method was investigated for its utility for the determination of MOXL in commercially available tablets and as a stability-indicative assay in solid state. The results obtained by means of the investigated method were statistically compared (t-Student test and F-Snedecor test) with the results obtained by means of the reference method--HPLC, which evidenced that both methods are equally precise and accurate. It was finally concluded that first derivative UV spectrophotometry is selective with reference to excipients used for the tablets' formulation, however, it is not selective with reference to MOXL degradation products. PMID:22594252

Stanisz, Beata; Regulska, Katarzyna; Ratajczak, Tomasz

2012-01-01

49

A spectrophotometric method for the determination of neptunium and plutonium in process solutions  

Microsoft Academic Search

A method is described for the determination of neptunium and plutonium in process solutions. This involves the separation\\u000a of these elements followed by their spectrophotometric determination as Arsenazo III complexes. Neptunium(IV) and plutonium(IV)\\u000a are separated using TTA extraction method and the separated Np(IV) and Pu(IV) are then determined as their Arzenazo III complexes\\u000a in 5M HNO3. A few solutions obtained

P. R. Vasudeva Rao; S. K. Patil

1978-01-01

50

Spectrophotometric method for determination of germanium in foods with new color reagent trimethoxylphenylfluorone  

Microsoft Academic Search

A high sensitive and selective spectrophotometric method for determination of germanium has been developed. The method is based on the reaction of germanium with a new reagent trimethoxylphenylfluorone (TMPF) in the presence of Triton X-100. The absorbency of the complex (?max=505nm) increases linearly with concentration up to 0.24?gml?1 germanium in aqueous solution with a relative standard deviation (R.S.D.) of 1.02%.

Li Zaijun; Pan Jiaomai; Tang Jan

2001-01-01

51

Spectrophotometric methods for the determination of lansoprazole and pantoprazole sodium sesquihydrate  

Microsoft Academic Search

Spectrophotometric procedures for determination of two irreversible proton pump inhibitors, lansoprazole (I) and pantoprazole sodium sesquihydrate (II) are presented. Two methods were based on charge transfer complexation reaction of these drugs, where they act as n-donors, with either ? acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and with ? acceptor as iodine. A third method was also investigated depending on ternary complex formation with

Azza A. M Moustafa

2000-01-01

52

Spectrophotometric determination of Zineb (a dithiocarbamate fungicide) by the methylene blue method  

Microsoft Academic Search

A spectrophotometric method has been developed for the determination of Zineb in water and vegetables. The method is based on the liberation of hydrogen sulphide from Zineb, which is trapped in an absorbing solution of triethanolamine, sodium hydroxide and ethylenediamine tetraacetic acid. The absorbing solution is treated with N-N-dimethyl-p-phenylene diamine sulphonate and ferric chloride to form methylene blue. Beer's law

V. Agrawal; P. Shivhare; V. K. Gupta

1992-01-01

53

Sensitive spectrophotometric method for the determination of superoxide dismutase activity in tissue extracts  

Microsoft Academic Search

Superoxide dismutase (EC 1.15.1.1) has been assayed by a spectrophotometric method based on the inhibition of a superoxide-driven NADH oxidation. The assay consists of a purely chemical reaction sequence which involves EDTA. Mn(II), mercaptoethanol, and molecular oxygen, requiring neither auxiliary enzymes nor sophisticated equipment. The method is very flexible and rapid and is applicable with high sensitivity to the determination

F. Paoletti; D. Aldinucci; A. Mocali; A. Caparrini

1986-01-01

54

Development and Validation of Derivative Spectrophotometric Method for Determination of Rabeprazole Sodium in Pharmaceutical Formulation  

Microsoft Academic Search

The aim of this work is to develop and validate the derivative spectrophotometric method for determination of the proton pump inhibitor rabeprazole sodium in pharmaceutical formulations. The technique was applied using water (pH 10.0) as diluent. The first?order derivative spectra were obtained at N=5, ??=4.0 nm, and determinations were made at 304 nm. The method showed high specificity in the presence of

C. V. Garcia; J. Sippel; M. Steppe; E. E. S. Schapoval

2006-01-01

55

HPLC and chemometrics-assisted UV-spectroscopy methods for the simultaneous determination of ambroxol and doxycycline in capsule  

NASA Astrophysics Data System (ADS)

High-performance liquid chromatography (HPLC) and multivariate spectrophotometric methods are described for the simultaneous determination of ambroxol hydrochloride (AM) and doxycycline (DX) in combined pharmaceutical capsules. The chromatographic separation was achieved on reversed-phase C 18 analytical column with a mobile phase consisting of a mixture of 20 mM potassium dihydrogen phosphate, pH 6-acetonitrile in ratio of (1:1, v/v) and UV detection at 245 nm. Also, the resolution has been accomplished by using numerical spectrophotometric methods as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS-1) applied to the UV spectra of the mixture and graphical spectrophotometric method as first derivative of the ratio spectra ( 1DD) method. Analytical figures of merit (FOM), such as sensitivity, selectivity, analytical sensitivity, limit of quantitation and limit of detection were determined for CLS, PLS-1 and PCR methods. The proposed methods were validated and successfully applied for the analysis of pharmaceutical formulation and laboratory-prepared mixtures containing the two component combination.

Hadad, Ghada M.; El-Gindy, Alaa; Mahmoud, Waleed M. M.

2008-08-01

56

Spectrophotometric and spectrofluorimetric methods for analysis of tramadol, acebutolol and dothiepin in pharmaceutical preparations  

NASA Astrophysics Data System (ADS)

Sensitive spectrophotometric and spectrofluorimetric methods are described for the determination of tramadol, acebutolol and dothiepin (dosulepin) hydrochlorides. The two methods are based on the condensation of the cited drugs with the mixed anhydrides of malonic and acetic acids at 60 °C for 25-40 min. The coloured condensation products are suitable for the spectrophotometric and spectrofluorimetric determination at 329-333 and 431-434 nm (excitation at 389 nm), respectively. For the spectrophotometric method, Beer's law was obeyed from 0.5 to 2.5 ?g ml -1 for tramadol, dothiepin and 5-25 ?g ml -1 for acebutolol. Using the spectrofluorimetric method linearity ranged from 0.25 to 1.25 ?g ml -1 for tramadol, dothiepin and 1-5 ?g ml -1 for acebutolol. Mean percentage recoveries for the spectrophotometric method were 99.68 ± 1.00, 99.95 ± 1.11 and 99.72 ± 1.01 for tramadol, acebutolol and dothiepin, respectively and for the spectrofluorimetric method, recoveries were 99.5 ± 0.844, 100.32 ± 0.969 and 99.82 ± 1.15 for the three drugs, respectively. The optimum experimental parameters for the reaction has been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drugs in their pharmaceutical preparations with good recoveries. The procedures were accurate, simple and suitable for quality control application.

Abdellatef, Hisham E.; El-Henawee, Magda M.; El-Sayed, Heba M.; Ayad, Magda M.

2006-12-01

57

Development and validation of column high-performance liquid chromatographic and derivative spectrophotometric methods for determination of levofloxacin and ornidazole in combined dosage forms.  

PubMed

The manuscript describes validated reversed-phase column high-performance liquid chromatographic (RP-HPLC) and first-derivative UV spectrophotometric methods for the estimation of levofloxacin (LFX) and ornidazole (ORNI) in combined dosage forms. The RP-HPLC separation was achieved on a Phenomenex C18 column (250 mm x 4.6 mm id, 5 microm) using KH2PO4 buffer (pH 6.8)-methanol-acetonitrile (70 + 15 + 15, v/v/v) mobile phase at a flow rate of 1.5 mL/min and ambient temperature (25 +/- 2 degrees C). Quantification was achieved with photodiode array detection at 295 nm over the concentration range of 1-10 microg/mL for both LFX and ORNI, with mean recovery of 101.7 +/- 0.23 and 99.23 +/- 1.57%, respectively, by the RP-HPLC method. The derivative spectrophotometric method was based on the determination of both the drugs at their respective zero crossing point (ZCP). The first-order derivative spectra were obtained at N = 1 (scaling factor), Deltalambda = 2.0 nm (wavelength interval), and the determinations were made at 310 nm (ZCP of ORNI) for LFX and 295 nm (ZCP of LFX) for ORNI over the concentration range of 2-40 microg/mL for both LFX and ORNI. Mean recovery was 99.46 +/- 0.96 and 100.9 +/- 0.72%, respectively, by the first-derivative UV spectrophotometric method. Standard and sample solutions were prepared with methanol as the solvent in both of the methods. These methods were found to be simple, accurate, precise, and sensitive and were applicable for the simultaneous determination of LFX and ORNI in combined dosage forms. PMID:18727534

Patel, Satish A; Prajapati, Arun M; Patel, Paresh U; Patel, Natubhai J; Vaghmasi, Jayesh B

2008-01-01

58

UV spectrophotometric flow-injection assay of tetracycline antibiotics retained on Sephadex QAE A-25 in drug formulations  

Microsoft Academic Search

A flow injection analysis system with solid phase spectrophotometric transduction has been developed for the assay of tetracycline (TC), doxycicline (DTC), oxycicline (OTC) and chlortetracycline (CTC). The packing material of the flow-through cell consists of Sephadex QAE A-25 resin on which tetracyclines are temporarily retained. The carrier itself acts as the desorbing solution. The measurements of the intrinsic absorbance of

A. Ruiz Medina; M. G. Garc??a Mar??n; M. L. Fernández de Córdova; A. Molina D??az

2000-01-01

59

A spectrophotometric method for determination of chemical oxygen demand using home-made reagents  

Microsoft Academic Search

A novel spectrophotometric assay method using home-made reagents that can be used to determine the chemical oxygen demand (COD) in real wastewater is described. The home-made reagents were used instead of the American Hach reagents. The principle of measurement was based on direct determination of the concentration change that Cr6+ is reduced intensely to Cr3+ resulting from potassium dichromate oxidation

Jun Li; Tao Tao; Xue-bin Li; Jiao-lan Zuo; Tong Li; Jin Lu; Shu-hui Li; Li-zhen Chen; Chun-yang Xia; Yong Liu; Yan-li Wang

2009-01-01

60

A simple spectrophotometric method for determination of sodium diclofenac in pharmaceutical formulations.  

PubMed

A new, simple, rapid and accurate spectrophotometric method is proposed for determination of sodium diclofenac (SD) in pharmaceutical preparations based on its reaction with concentrated nitric acid (63% w/v). The reaction product is a yellowish compound with maximum absorbance at 380 nm. The corresponding calibration curve is linear over the range of 1-30 mg l(-1), while the limit of detection is 0.46 mg l(-1). PMID:16125178

Matin, A A; Farajzadeh, M A; Jouyban, A

2005-10-01

61

Simultaneous determination of retinoic acid and hydroquinone in skin ointment using spectrophotometric technique (ratio difference method)  

PubMed Central

An innovative spectrophotometric method was developed for simultaneous determination of compounds with interfering spectra in binary mixtures without previous separation, showing significant advantages over the conventional methods regarding minimal data manipulation and applicability. The proposed method was applied for the determination of retinoic acid and hydroquinone in laboratory-prepared mixtures with mean percentage recoveries 100.13 ± 0.31 and 99.99 ± 0.04, respectively, and in their pharmaceutical formulation with mean percentage recoveries 100.13 ± 0.86 and 100.07 ± 0.58, respectively. The method was validated according to USP guidelines and can be applied for routine quality control testing. PMID:23960798

Elzanfaly, Eman S.; Saad, Ahmed S.; Abd-Elaleem, Abd-Elaziz B.

2012-01-01

62

A spectrophotometric method for the evaluation of vegetable oil colors  

Microsoft Academic Search

Summary  A means for evaluating oil color on the basis of an optical density measurement at 500 millimicrons has been proposed. The\\u000a amount of chlorophyll would be taken into account by present methods or an adaptation of these methods.\\u000a \\u000a The advantages of the proposed means of evaluating oil color are that it expresses more exactly the amount of color in the

W. D. Pohle; S. E. Tierney

1957-01-01

63

Spectrophotometric methods for simultaneous determination of ternary mixture of amlodipine besylate, olmesartan medoxomil and hydrochlorothiazide.  

PubMed

Four, accurate, precise, and sensitive spectrophotometric methods are developed for the simultaneous determination of a ternary mixture containing amlodipine besylate (AM), olmesartan medoxomil (OL) and hydrochlorothiazide (HZ), where AM is determined at its ?(max) 364.6 nm ((0)D), while (OL) and (HZ) are determined by different methods. Method (A) depends on determining OL and HZ by measuring the second derivative of the ratio spectra ((2)DD) at 254.4 and 338.6 nm, respectively. Method (B) is first derivative of the double divisor ratio spectra (D-(1)DD) at 260.4 and 273.0 nm for OL and HZ, respectively. Method (C) based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method then measuring OL and HZ at their isoabsorptive point at 260.0 nm, while HZ is measured using the amplitude of first derivative at 335.2 nm. Method (D) is mean centering of the ratio spectra (MCR) at 252.0 nm and 220.0 nm for OL and HZ, respectively. The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs and their combined dosage form. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p=0.05. PMID:24534425

Merey, Hanan A; Ramadan, Nesrin K; Diab, Sherine S; Moustafa, Azza A

2014-05-01

64

Spectrophotometric methods for simultaneous determination of ternary mixture of amlodipine besylate, olmesartan medoxomil and hydrochlorothiazide  

NASA Astrophysics Data System (ADS)

Four, accurate, precise, and sensitive spectrophotometric methods are developed for the simultaneous determination of a ternary mixture containing amlodipine besylate (AM), olmesartan medoxomil (OL) and hydrochlorothiazide (HZ), where AM is determined at its ?max 364.6 nm (0D), while (OL) and (HZ) are determined by different methods. Method (A) depends on determining OL and HZ by measuring the second derivative of the ratio spectra (2DD) at 254.4 and 338.6 nm, respectively. Method (B) is first derivative of the double divisor ratio spectra (D-1DD) at 260.4 and 273.0 nm for OL and HZ, respectively. Method (C) based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method then measuring OL and HZ at their isoabsorptive point at 260.0 nm, while HZ is measured using the amplitude of first derivative at 335.2 nm. Method (D) is mean centering of the ratio spectra (MCR) at 252.0 nm and 220.0 nm for OL and HZ, respectively. The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs and their combined dosage form. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Merey, Hanan A.; Ramadan, Nesrin K.; Diab, Sherine S.; Moustafa, Azza A.

65

Determination of niobium in rocks by an isotope dilution spectrophotometric method  

USGS Publications Warehouse

Rocks and minerals are fused with sodium peroxide in the presence of carrierfree 95Nb. The fusion cake is leached with water and the precipitate dissolved in hydrofluoric-sulfuric acid mixture. Niobium is extracted into methyl isobutyl ketone and further purified by ion exchange. The amount of niobium is determined spectrophotometrically with 4-(2-pyridylazo)-resorcinol, and the chemical yield of the separations determined by counting 95Nb. This procedure is faster and less sensitive to interferences than previously proposed methods for determining niobium in rocks.The high purity of the separated niobium makes the method applicable to nearly all matrices. ?? 1970.

Greenland, L.P.; Campbell, E.Y.

1970-01-01

66

Titrimetric and Spectrophotometric Methods for the Assay of Ketotifen Using Cerium(IV) and Two Reagents.  

PubMed

One titrimetric and two spectrophotometric methods are described for the determination of ketotifen fumarate (KTF) in bulk drug and in tablets using cerium(IV) as the oxidimetric agent. In titrimetry (method A), the drug was treated with a measured excess of cerium(IV) in H2SO4 medium and after a standing time of 10 min, the surplus oxidant was determined by back titration with iron(II). The spectrophotometric procedures involve addition of a known excess of cerium(IV) to KTF in acid medium followed by the determination of unreacted oxidant by reacting with either p-dimethyl amino benzaldehyde and measuring the resulting colour at 460?nm (method B) or o-dianisidine and subsequent measurement of the absorbance of coloured product at 470?nm (method C). Titrimetric assay is based on a 1?:?2 reaction stoichiometry between KTF and cerium(IV) and the method is applicable over 2-18?mg range. In spectrophotometry, regression analysis of Beer's law plots showed a good correlation in 0.4-8.0 and 0.4-10.0?g?mL(-1) KTF ranges for method B and method C, respectively, and the corresponding molar absorptivity coefficients are calculated to be 4.0 × 10(4) and 3.7 × 10(4)?L?mol(-1)?cm(-1). PMID:24324496

Raghu, Madihalli Srinivas; Basavaiah, Kanakapura; Prashanth, Kudige Nagaraj; Vinay, Kanakapura Basavaiah

2013-01-01

67

Development and validation of simultaneous spectrophotometric methods for drotaverine hydrochloride and aceclofenac from tablet dosage form.  

PubMed

Two simple spectrophotometric methods have been developed for simultaneous estimation of drotaverine hydrochloride and aceclofenac from tablet dosage form. Method I is a simultaneous equation method (Vierodt's method), wavelengths selected are 306.5 and 276 nm. Method II is the absorbance ratio method (Q-Analysis), which employs 298.5 nm as ?(1) and 276 nm as ?(2) (?max of AF) for formation of equations. Both the methods were found to be linear between the range of 8-32 ?g/ml for drotaverine and 10-40 ?g/ml for aceclofenac. The accuracy and precision were determined and found to comply with ICH guidelines. Both the methods showed good reproducibility and recovery with % RSD in the desired range. The methods were found to be rapid, specific, precise and accurate and can be successfully applied for the routine analysis of drotaverine and aceclofenac in their combined tablet dosage form. PMID:22457554

Shah, S A; Shah, D R; Chauhan, R S; Jain, J R

2011-05-01

68

Spectrophotometric and complexometric methods for the determination of thorium and fluoride using bromocresol orange reagent.  

PubMed

The ternary purple coloured complex formed between Th(4+), bromocresol orange (BCO) and cetylpyridinium bromide (CPB) in acidic medium was investigated spectrophotometrically. Results obtained revealed the formation of 1:1:1, Th:BCO:CPB complex in aqueous solution at pH approximately 0.5 with a logarithmic conditional stability constant of 12.04+/-0.1, I=0.1 at 25 degrees C. The colour of the ternary complex was used for the determination of thorium(IV) in the range of 0.02-2.6 mug ml(-1) Th(4+), =9.2x10(4) l mol(-1) cm(-1) at 560 nm. Beside its high sensitivity, the reaction was also proved to be highly selective for Th(4+). Thorium(IV) was determined in presence of great number of transition metal ions, rare earths and different anions. Th(4+) was also determined with high accuracy and precision by its titration with disodium ethylenediaminetetraacetate (Na(2)EDTA) using BCO as an indicator at pH approximately 0.5. The endpoint was detected either visually or spectrophotometrically (lambda=550 nm). The proposed procedures were successfully applied for the determination of Th(4+) in standard Th-U ores and in a series of naturally occurring ores or minerals containing thorium. A spectrophotometric method was also described for the determination of fluoride ion, which was based upon the decrease in colour intensity of the Th-BCO complex on mixing it with F(-) ion. The proposed method was convenient, rapid and sensitive for fluoride. It could be used for the determination of fluoride ion in the 0.02-3.00 mug ml(-1) range (S.D.+/-0.9%). The proposed method was successfully applied for direct determination of F(-) ion in water obtained from different origins and the results were satisfactory. PMID:18967357

Khalifa, M E; Hafez, M A

1998-11-01

69

Simultaneous determination of some anti-hypertensive drugs in their binary mixture by novel spectrophotometric methods.  

PubMed

Three simple, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of Irbesartan (IRB) and Hydrochlorothiazide (HCT) without prior separation namely; ratio subtraction coupled with constant multiplication (RS-CM), ratio difference (RD) and constant center (CC). The accuracy, precision and linearity ranges of the proposed methods were determined, and the methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the cited drugs. The three methods were applied for the determination of the cited drugs in tablets and the obtained results were statistically compared with each other and with those of official methods. The comparison showed that there is no significant difference between the proposed methods and the official methods regarding both accuracy and precision. PMID:24887506

Fayez, Yasmin Mohammed

2014-11-11

70

Simultaneous determination of some anti-hypertensive drugs in their binary mixture by novel spectrophotometric methods  

NASA Astrophysics Data System (ADS)

Three simple, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of Irbesartan (IRB) and Hydrochlorothiazide (HCT) without prior separation namely; ratio subtraction coupled with constant multiplication (RS-CM), ratio difference (RD) and constant center (CC). The accuracy, precision and linearity ranges of the proposed methods were determined, and the methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the cited drugs. The three methods were applied for the determination of the cited drugs in tablets and the obtained results were statistically compared with each other and with those of official methods. The comparison showed that there is no significant difference between the proposed methods and the official methods regarding both accuracy and precision.

Fayez, Yasmin Mohammed

2014-11-01

71

Optimized and Validated Spectrophotometric Methods for the Determination of Enalapril Maleate in Commercial Dosage Forms  

PubMed Central

Four simple, rapid and sensitive spectrophotometric methods have been proposed for the determination of enalapril maleate in pharmaceutical formulations. The first method is based on the reaction of carboxylic acid group of enalapril maleate with a mixture of potassium iodate (KIO3) and iodide (KI) to form yellow colored product in aqueous medium at 25 ± 1°C. The reaction is followed spectrophotometrically by measuring the absorbance at 352 nm. The second, third and fourth methods are based on the charge transfer complexation reaction of the drug with p-chloranilic acid (pCA) in 1, 4-dioxan-methanol medium, 2, 3-dichloro 5, 6-dicyano 1, 4-benzoquinone (DDQ) in acetonitrile-1,4 dioxane medium and iodine in acetonitrile-dichloromethane medium. Under optimized experimental conditions, Beer’s law is obeyed in the concentration ranges of 2.5–50, 20–560, 5–75 and 10–200 ?g mL?1, respectively. All the methods have been applied to the determination of enalapril maleate in pharmaceutical dosage forms. Results of analysis are validated statistically. PMID:19609388

Rahman, Nafisur; Haque, Sk Manirul

2008-01-01

72

Determination of lead(II) in fly ash leachate using a newly developed simple spectrophotometric method  

NASA Astrophysics Data System (ADS)

A new simple method for the spectrophotometric determination of Pb(II) in fly ash leachates was developed. These leachates tend to contain a large amount of Ca(II) and Zn(II); this interferes with spectrophotometric determination of Pb(II) when conventional colorimetric agents are used. A copolymer consisting of protoporphyrin IX disodium salt and acrylamide was synthesized as a colorimetric agent. A measuring reagent containing ethylenediamine-N,N'-dipropionic acid (EDDP) as a masking agent for Zn(II) and an appropriate amount of Ca(II) together with the copolymer was applied to determine Pb(II). The temporal change in the absorption spectrum of the measuring reagent was acquired with a newly developed portable spectrophotometer for this method. The composition of EDDP and Ca(II) in the measuring reagent was optimized to measure leachates contaminated with Ca(II) and Zn(II). The detection limit and relative standard deviation of Pb(II) measured using the optimized method were 0.05 mg L -1 and 2.3%, respectively. The tolerance limits for Ca(II) and Zn(II) contaminants, where errors of less than 10% were allowed at a concentration of 0.5 mg L -1 Pb(II), were 4000 and 4 mg L -1, respectively. The determination of Pb(II) in various samples of actual leachates from incinerator fly ash was examined with this method. The obtained values correlated well with those obtained by flame atomic absorption spectroscopy.

Asano, Takaharu; Yabusaki, Katsumi; Wang, Pi-Chao; Iwasaki, Akio

2010-02-01

73

Development and Validation of Spectrophotometric, Atomic Absorption and Kinetic Methods for Determination of Moxifloxacin Hydrochloride  

PubMed Central

Three simple spectrophotometric and atomic absorption spectrometric methods are developed and validated for the determination of moxifloxacin HCl in pure form and in pharmaceutical formulations. Method (A) is a kinetic method based on the oxidation of moxifloxacin HCl by Fe3+ ion in the presence of 1,10 o-phenanthroline (o-phen). Method (B) describes spectrophotometric procedures for determination of moxifloxacin HCl based on its ability to reduce Fe (III) to Fe (II), which was rapidly converted to the corresponding stable coloured complex after reacting with 2,2? bipyridyl (bipy). The formation of the tris-complex formed in both methods (A) and (B) were carefully studied and their absorbance were measured at 510 and 520 nm respectively. Method (C) is based on the formation of ion- pair associated between the drug and bismuth (III) tetraiodide in acidic medium to form orange—red ion-pair associates. This associate can be quantitatively determined by three different procedures. The formed precipitate is either filtered off, dissolved in acetone and quantified spectrophotometrically at 462 nm (Procedure 1), or decomposed by hydrochloric acid, and the bismuth content is determined by direct atomic absorption spectrometric (Procedure 2). Also the residual unreacted metal complex in the filtrate is determined through its metal content using indirect atomic absorption spectrometric technique (procedure 3). All the proposed methods were validated according to the International Conference on Harmonization (ICH) guidelines, the three proposed methods permit the determination of moxifloxacin HCl in the range of (0.8–6, 0.8–4) for methods A and B, (16–96, 16–96 and 16–72) for procedures 1–3 in method C. The limits of detection and quantitation were calculated, the precision of the methods were satisfactory; the values of relative standard deviations did not exceed 2%. The proposed methods were successfully applied to determine the drug in its pharmaceutical formulations without interference from the common excipients. The results obtained by the proposed methods were comparable with those obtained by the reference method. PMID:22219661

Abdellaziz, Lobna M.; Hosny, Mervat M.

2011-01-01

74

A new spectrophotometric method for quantification of potassium solubilized by bacterial cultures.  

PubMed

A new spectrophotometric method was developed for the quantification of potassium in the culture broth supernatant of K-solubilizing bacteria. The standard curve of potassium with the new method, which is based on the measurement of cobalt, showed a regression coefficient (R2) of 0.998. The quantification values of potassium obtained with flame photometric method and the newly developed method showed a significant correlation (r) of 0.978. The new method depends on the precipitation of sodium cobaltinitrite with solubilized potassium in liquid medium as potassium sodium cobaltinitrite, which develops bluish green colour by the addition of conc. HCl. The intensity of developed colour can be recorded at 623 nm. This method involves less number of steps, is easy and time saving, and can be used for the reliable estimation of available potassium in culture broth supernatant of K-solubilizing bacteria. PMID:24669669

Rajawat, Mahendra Vikram Singh; Singh, Surender; Saxena, Anil Kumar

2014-03-01

75

Three different spectrophotometric methods manipulating ratio spectra for determination of binary mixture of Amlodipine and Atorvastatin.  

PubMed

Three simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra are developed for the simultaneous determination of Amlodipine besylate (AM) and Atorvastatin calcium (AT) in tablet dosage forms. The first method is first derivative of the ratio spectra ((1)DD), the second is ratio subtraction and the third is the method of mean centering of ratio spectra. The calibration curve is linear over the concentration range of 3-40 and 8-32 ?g/ml for AM and AT, respectively. These methods are tested by analyzing synthetic mixtures of the above drugs and they are applied to commercial pharmaceutical preparation of the subjected drugs. Standard deviation is <1.5 in the assay of raw materials and tablets. Methods are validated as per ICH guidelines and accuracy, precision, repeatability and robustness are found to be within the acceptable limit. PMID:21908232

Darwish, Hany W; Hassan, Said A; Salem, Maissa Y; El-Zeiny, Badr A

2011-12-01

76

A Comparative Study of Spectrophotometric and Iodometric Back Titration Methods for Hydrogen Sulfide Determination in Anoxic Basins  

Microsoft Academic Search

Iodometric Back Titration (IBT) and Spectrophotometric (SPM) methods are two common methods used in the determination of hydrogen sulfide concentrations in anoxic basins, like in the upper sections of the Black Sea anoxic waters. Although the results obtained by both methods are in agreement when the concentrations of sulfide are higher than 30 ?M\\/1, IBT analysis gives more reproducible results

Özden Batürk; Alexander Romanov; Serap Gokmen; Sergey Konovalov

2000-01-01

77

[Simultaneous determination of phenol and resorcinol by dual-wavelength spectrophotometric linear regression method].  

PubMed

Spectrophotometric simultaneous determination of phenol and resorcinol was studied. The absorption spectra of these two components severely overlap in ultraviolet spectral range. In the wavelength range of 250-290 nm, the absorbances of phenol and resorcinol were measured with an internal of 0.5 nm. Two wavelengths at 280.5 and 273.5 nm were chosen for the determination. Dual-wavelength linear regression method was used for the determination of phenol and resorcinol. Twenty five mixture standard solutions were prepared according to the orthogonal projection form L25 (5(6)). Two kinds of the components were linearly regressed. Meanwhile the contents of phenol and resorcinol in six synthetic mixture samples and simulation pharmaceutical preparations were measured. The measurement results showed that the relative error of phenol and resorcinol were less than 5%. The measurement system is stable and reliable. Therefore, the dual-wavelength spectrophotometric linear regression method may provide a new approach to the determintion of phenol and resorcinol in their compound preparations. PMID:17260769

Zhang, Qun; Zhan, Feng; Kai, Xiao-ming

2006-11-01

78

Determination of ametryn in sugarcane and ametryn-atrazine herbicide formulations using spectrophotometric method.  

PubMed

A sensitive spectrophotometric method has been developed for determination of ametryn in agricultural samples. The proposed method was based on reaction with pyridine and further coupling with sulfanilic acid to form a colored product. The absorbance was measured at 400 nm with a molar absorptivity of 2.1 x 10(5) L mol(-1) cm(-1). The method shows a linear range from 0.2-20 ?g mL(-1) with limit of detection and limit of quantification 0.16 and 0.54 ?g mL(-1), respectively. The method has been successfully applied to the determination of ametryn in sugarcane juice and commercial formulations after separation of ametryn from triazine herbicides based on solvent extraction. Recovery values were found to be in the range of 96.0 ± 0.2% to 98.4? ± ?0.1%. PMID:21713463

Shah, Jasmin; Jan, M Rasul; Ara, Behisht; Shehzad, Farhat-Un-Nisa

2012-06-01

79

Study on the determination of trace Ni (II) by the catalytic kinetic spectrophotometric method  

NASA Astrophysics Data System (ADS)

A new kinetic spectrophotometric method has been developed for the determination of trace Ni (II) in natural water. The method is based on the catalytic effect of Ni (II) on the oxidation of weak acid brilliant blue dye (RAWL) by KIO4 in acid medium. The concentration of nickel (II) can be determined spectrophotometrically by measuring the decrease of absorbance of RAWL at ? = 626 nm using the fix-time method. The influencing factors are investigated by the orthogonal experimental design. The obtained optimum analytical conditions are: pH = 2.00, c RAWL = 5.00×10-5 mol L-1, c KIO 4 = 2.00×10-5 mol L -1, the reaction time t = 10 min and the temperature T = 25°C. Under the optimum conditions, the developed method allows the measurement of Ni (II) in a range of 0-40.0 ng mL-1. The standard deviation of eleven independent measurements of blank reaction is S = 3.08×10-3 and the limit of detection is 2.20 ng mL-1. The relative standard deviations (RSDs) in six replicate determinations of 5 ng mL-1 and 8 ng mL-1 Ni (II) are 2.87% and 1.11%, respectively. Moreover, the experiments show few cations and anions can interfere with the measurement of Ni (II). The recovery efficiencies of this method are in a range of 97.0%-102.5% in freshwater samples. But there is a decreasing effect, which is about 0.2 times the added Ni (II) in seawater medium. After reasonable calibration this processing method is used for the determination of Ni (II) in seawater samples successfully. The results show this developed method has high accuracy and precision, high sensitivity, large range of linearity and high speed. The method can, therefore, be employed at room temperature.

Ji, Hongwei; Cao, Hengxia; Xin, Huizhen; Li, Shuang

2010-03-01

80

Novel sensitive spectrophotometric method for the trace determination of cyanide in industrial effluent.  

PubMed

The high toxicity of the cyanide ion at low concentration necessitates its analysis in a variety of environmental samples with a very low cyanide content. A new sensitive spectrophotometric method has been developed for the trace determination of cyanide with ninhydrin (NH) in an alkaline medium. Beer's law is obeyed in the range of cyanide concentration 0.04-0.24 microg cm(-3), and the molar absorptivity at 590 nm is 2.20 x 10(5) dm3 mol(-1) cm(-1). The Sandell's sensitivity of the product is 0.000118 microg cm(-2). The optimum reaction conditions and other important analytical parameters have been investigated. The results obtained by using the proposed method for environmental samples agree well with those obtained by the Aldridge standard method. PMID:12243398

Nagaraja, Padmarajaiah; Hemantha Kumar, Mattighatta S; Yathirajan, Hemmige S; Prakash, Jainara S

2002-09-01

81

Kinetic spectrophotometric method for the determination of trace amounts of oxalate by an activation effect.  

PubMed

A new, simple and inexpensive kinetic catalytic spectrophotometric method for the determination of oxalate is described. The method is based on an activation effect of oxalate on a catalytic effect of iron(II) on the oxidation of iodide by bromate. The reaction is monitored by measuring the absorbance of triiodide ion at lambda max = 352 nm. A calibration graph was obtained from 0.10 - 7.0 microg cm(-3) of oxalate with a detection limit of 0.080 microg cm(-3). The standard deviations for ten replicate determinations of 0.50, 1.0 and 5.0 microg cm(-3) of oxalate were 4.0, 2.6 and 1.8%, respectively. The applicability of the method was demonstrated by the determination of oxalate ion in real samples. PMID:16512434

Chamjangali, Mansour Arab; Keley, Vahid; Bagherian, Ghadamali

2006-02-01

82

Sensitive spectrophotometric method for the determination of superoxide dismutase activity in tissue extracts  

SciTech Connect

Superoxide dismutase (EC 1.15.1.1) has been assayed by a spectrophotometric method based on the inhibition of a superoxide-driven NADH oxidation. The assay consists of a purely chemical reaction sequence which involves EDTA. Mn(II), mercaptoethanol, and molecular oxygen, requiring neither auxiliary enzymes nor sophisticated equipment. The method is very flexible and rapid and is applicable with high sensitivity to the determination of both pure and crude superoxide dismutase preparations. The decrease of the rate of NADH oxidation is a function of enzyme concentration, and saturation levels are attainable. Fifty percent inhibition, corresponding to one unit of the enzyme, is produced by approximately 15 ng of pure superoxide dismutase. Experiments on rat liver cytosol have shown the specificity of the method for superoxide dismutase. Moreover, common cellular components do not interfere with the measurement, except for hemoglobin when present at relatively high concentrations. The assay is performed at physiological pH and is unaffected by catalase.

Paoletti, F.; Aldinucci, D.; Mocali, A.; Caparrini, A.

1986-05-01

83

Evaluation of spectrophotometric methods for screening of green rooibos (Aspalathus linearis) and green honeybush (Cyclopia genistoides) extracts for high levels of Bio-active compounds.  

PubMed

The potential of UV spectrophotometry and an aluminium chloride (AlCl(3)) colorimetric method to determine the dihydrochalcone (DHC) and mangiferin contents of green rooibos and honeybush (C. genistoides) extracts, respectively, was investigated. The DHC content of rooibos water extracts, determined using UV spectroscopy, correlated with the sum of the aspalathin and nothofagin contents as quantified using HPLC (r = 0.98). A correlation coefficient of 0.91 was obtained when correlating the mangiferin content of C. genistoides methanol extracts, determined by the AlCl(3) colorimetric method, with the results obtained by HPLC. Using the linear equations from the correlations it was possible to predict the DHC and mangiferin contents of extracts from the respective spectrophotometric measurements to a reasonable accuracy as an alternative to HPLC. The total polyphenol (TP) content of rooibos water extracts can also be determined using UV spectrophotometry and aspalathin as a standard (r = 0.99) as an alternative to the Folin-Ciocalteau method. The TP content of rooibos extracts correlated (r = 0.99) with its total antioxidant activity (TAA) as determined with the ABTS radical cation scavenging assay, but the TP content of C. genistoides water extracts is not a good indication of their TAA (r = 0.27). The aspalathin content of rooibos extracts correlated with their TAA (r = 0.96), but the mangiferin content of honeybush water extracts only gave a moderate correlation with their TAA (r = 0.75). PMID:17893845

Joubert, Elizabeth; Manley, Marena; Botha, Mariza

2008-01-01

84

New potentiometric and spectrophotometric methods for the determination of dextromethorphan in pharmaceutical preparations.  

PubMed

New, simple and convenient potentiometric and spectrophotometric methods are described for the determination of dextromethorphan hydrobromide (DXM) in pharmaceutical preparations. The potentiometric technique is based on developing a potentiometric sensor incorporating the dextromethorphan tetrakis(p-chlorophenyl)borate ion-pair complex as an electroactive species in a plasticized PVC matrix membrane with o-nitophenyl octyl ether or dioctyl phthalate. The sensor shows a rapid near Nernstian response of over 1 × 10(-5) - 1 × 10(-2) mol L(-1) dextromethorphan in the pH range of 3.0 - 9.0. The detection limit is 2 × 10(-6) mol L(-1) DXM and the response time is instantaneous (2 s). The proposed spectrophotometric technique involves the reaction of DXM with eriochrom black T (EBT) to form an ion-associate complex. Solvent extraction is used to improve the selectivity of the method. The optimal extraction and reaction conditions have been studied, and the analytical characteristics of the method have been obtained. Linearity is obeyed in the range of 7.37 - 73.7 × 10(-5) mol L(-1) DXM, and the detection limit of the method is 1.29 × 10(-5) mol L(-1). The relative standard deviation (RSD) and relative error for six replicate measurements of 3.685 × 10(-4) mol L(-1) are 0.672 and 0.855%, respectively. The interference effect of some excepients has also been tested. The drug contents in pharmaceutical preparations were successfully determined by the proposed methods by applying the standard-addition technique. PMID:24614739

Elmosallamy, Mohamed A F; Amin, Alaa S

2014-01-01

85

Direct and selective spectrophotometric method for the determination of vanadium in steel, environmental and biological samples.  

PubMed

A simple, direct and selective spectrophotometric method for determination of vanadium is described. The present methodology is based on the strong oxidizing power of vanadium (V). Vanadium (V) selectively oxidizes leucocrystal violet (LCV) to crystal violet in the presence of phosphoric acid. The violet colored dye obtained shows maximum absorbance at 590 nm. Beer's law is obeyed in the concentration range 0.06-0.6 ?g ml(-1). The molar absorptivity and Sandell's sensitivity are found to be 6.78×10(4) l mol(-1) cm(-1) and 0.0044 ?g cm(-2), respectively. The proposed method is simple, direct, and sensitive. It has been successfully applied for the determination of vanadium in various environmental, biological and steel samples. PMID:21764362

Mathew, Sunitha B; Pataila, Girija; Pillai, Ajai K; Gupta, V K

2011-10-15

86

Uncertainty in spectrophotometric analysis--"error propagation break up", a novel statistical method for uncertainty management.  

PubMed

In this work, is given the Combined Standard Uncertainty (CSU) calculation procedure, which can be applied in spectrophotometric measurements. For the assessment of the computations, different approaches are discussed, such as the contribution to the Combined Standard Uncertainty of the reproducibility, the repeatability, the total bias, the calibration curve, and the type of the measurand. Results of inter-laboratory measurements confirmed the assumptions. For the minimization of the errors propagation a controlled experimental procedure was applied by this laboratory, called "errors propagation break-up" (ERBs). The uncertainty of sample concentration from a reference curve dominates the Combined Standard Uncertainty. The contribution of the method and the laboratory bias (total bias) to the CSU is insignificant under controlled conditions of a measurement. This work develops a simple methodology that can be utilized to evaluate the uncertainty and errors control on routine methods used both by academic researchers or the industrial sector. PMID:21962657

Amanatidou, Elisavet; Trikoilidou, Eleni; Tsikritzis, Lazaros; Foteini, Katsiouli

2011-10-15

87

A facile spectrophotometric method for cobalt determination using alpha-benzilmonoxime in sodium dodecylsulfate micellar solutions.  

PubMed

Alpha-benzilmonoxime in sodium dodecylsulfate micellar media has been used for the spectrophotometric determination of cobalt at pH 9.0. The linear range of calibration is 0.05-1.50 microg cm(-3) of cobalt at 380 nm with molar absorptivity of 3.72 x 10(4) dm3 mol(-1) cm(-1), which is about 1.5-times greater than that of the alpha-benzilmonoxime extraction based method. The relative standard deviations, recoveries, detection limit and effects of diverse ions on the determination of cobalt were studied. These analytical results were satisfactory. The method was successfully applied to the determination of cobalt in the various samples. PMID:14640457

Eskandari, Habibollah; Karkaragh, Gholam Hassan Imanzadeh

2003-11-01

88

A Novel Spectrophotometric Method for Estimation of Fe in Metallurgical Samples Using Cyanex 301 as Extractant  

NASA Astrophysics Data System (ADS)

Iron(III) has been estimated spectrophotometrically at 425 nm following its quantitative extraction from Cl- medium by Cyanex 301 in redistilled colorless kerosene. Beer's law is valid provided (i) a 10-min phase agitation is allowed in extraction, (ii) [HCl] in the aqueous phase during extraction is kept at 0.10 mol/l or less, (iii) [Cyanex 301] is kept over 0.5% (v/v). It is observed that the linearity range of Beer's plot is increased with increasing (v/v)% of the Cyanex 301 used; the optimum ([Fe(III)], mg/l)/[Cyanex 301] in ((v/v)%) is 20:1. The color is stable for at least 10 days. The molar extinction coefficient ? is 7111 l/mol?cm. The method has been applied in the analysis of some metallurgical samples.

Biswas, R. K.; Karmakar, K.; Mondal, T. K.

2014-09-01

89

Derivative and Q-analysis Spectrophotometric Methods for Estimation of Hydrochlorothiazide and Olmesartan Medoxomil in Tablets  

PubMed Central

Two methods for simultaneous estimation of hydrochlorothiazide and olmesartan medoxomil in combined tablet dosage form have been developed. The first method is the application of Q–analysis method (absorbance ratio), which involves the formation of Q–absorbance equation at 264 nm (isobestic point) and at 271 nm, the maximum absorption of hydrochlorothiazide. The linearity ranges for hydrochlorothiazide and olmesartan medoxomil were 2.5-22.5 ?g/ml and 4-36 ?g/ml, respectively. The second method is based on the derivative spectrophotometric method at zero crossing wavelengths. The linearity ranges for hydrochlorothiazide and olmesartan medoxomil were 2.5-20 ?g/ml and 4-32 ?g/ml, respectively. The accuracy of the methods were assessed by recovery studies and was found to be 100.45% ±0.4215 and 100.24% ±0.3783 for absorbance ratio method and 99.39% ±0.221 and 99.72% ±0.11 for first derivative method, for hydrochlorothiazide and olmesartan medoxomil, respectively. These methods are simple, accurate and rapid, those require no preliminary separation and can therefore be used for routine analysis of both drugs in quality control laboratories. PMID:20502567

Bhusari, K. P.; Khedekar, P. B.; Dhole, Seema; Banode, V. S.

2009-01-01

90

Trace determination and chemical speciation of selenium in environmental water samples using catalytic kinetic spectrophotometric method.  

PubMed

A catalytic kinetic method is described for the determination of Se(IV), Se(VI) and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of bromate by hydrazine dihydrochloride in acidic media. The generated bromine decolorized methyl orange (MO) and the reaction was monitored spectrophotometrically at 507 nm as a function of time. The initial rate and fixed time methods were adopted for the determination and speciation of inorganic selenium. Under two optimum conditions, the calibration graphs are linear in the range 0-126.3 and 0-789.6 microg L(-1) of Se(IV) for the initial rate method and 0-315.8 and 0-789.6 microg L(-1) of Se(IV) for the fixed time method. The detection limits were 1.3 and 14.7 microg L(-1) for the initial rate and fixed time methods, respectively. The proposed methods were validated statistically and through recovery studies in environmental water samples. The relative standard deviation in the determination of 31.6-94.8 microg L(-1) of Se(IV) and Se(VI) was less than 6%. Analyses of standard reference materials for selenium using initial rate and fixed time methods showed that the proposed methods have good accuracy. Se(IV), Se(VI) and total inorganic selenium in environmental water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV). PMID:19091465

Chand, Vimlesh; Prasad, Surendra

2009-06-15

91

Spectrophotometric, septrofluorimetric and LC determination of lisinopril.  

PubMed

Three methods are described for the determination of lisinopril in the pharmaceutical tablets. The spectrophotometric method depends on the reaction of the lisinopril with sodium hypochlorite and phenyl hydrazine to form a condensation product measured at 362 nm. The spectrophotometric method was extended to develop a stability indicating method. The spectrofluorimetric method depends on reaction of the lisinopril with o-phthalaldehyde in the presence of 2-mercaptoethanol in borate buffer pH 9.5. The fluorescence of the reaction product was measured upon excitation at a maximum of 340 nm with emission wavelength at 455 nm. The HPLC method depends on using Hypersil silica column with a mobile phase consisting of methanol-water-triethylamine (50:50:0.1 v/v) and the pH was adjusted to 2.6 with 0.1 N perchloric acid. Quantitation was achieved with UV detection at 210 nm based on peak area. PMID:11377074

El-Gindy, A; Ashour, A; Abdel-Fattah, L; Shabana, M M

2001-07-01

92

New spectrophotometric methods for the determination of moxifloxacin in pharmaceutical formulations.  

PubMed

Two rapid, simple and sensitive spectrophotometric methods for the quantitative analysis of moxifloxacin (MOX) in pharmaceutical formulations have been described. The first method (A) involves reaction of MOX with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium (pH 11.0) which results in an orange-coloured product exhibiting maximum absorption (lambda(max)) at 411 nm. The second method (B) is based on the oxidation of the MOX with a known excess of cerium (IV) sulfate and the residual oxidant is determined by treating with a fixed amount of methyl orange, and measuring the absorbance at 507 nm. The molar absorptivities for methods A and B were 4.9 x 10(3) and 6.5 x 10(4) L mol(-1) cm(-1), respectively. Under the optimized reaction conditions, Beer's law correlation of the absorbance with MOX concentration was obtained in the range of 2.5-20 and 0.5-30 microgmL(-1) for method A and B respectively. The intra-day precision expressed as relative standard deviation (RSD) was < 1.6% for both methods. The methods were validated in terms of accuracy and precision and were successfully applied to the determination of MOX in its pharmaceutical dosage form. The proposed methods are useful for routine analysis of MOX in quality control laboratories. PMID:23841346

Elbashir, Abdalla A; Ebraheem, Sara A M; Elwagee, Alawia H E; Aboul-Enein, Hassan Y

2013-01-01

93

Simultaneous determination of Cinnarizine and Domperidone by area under curve and dual wavelength spectrophotometric methods  

NASA Astrophysics Data System (ADS)

Accurate, selective and sensitive spectrophotometric methods have been developed and validated for simultaneous determination of Cinnarizine and Domperidone, a binary mixture with overlapping spectra, without preliminary separation. These methods include area under the curve (AUC) and dual wavelength spectrophotometry. For the AUC method, the area under curve of mixture solutions in the wavelength ranges 241-258 nm and 280-292 nm were selected for determination of Cinnarizine and Domperidone and by applying Cramer's rule, concentration of each drug was obtained. In dual wavelength method, two wavelengths were selected for each drug in a way so that the difference in absorbance is zero for another drug. Domperidone shows equal absorbance at 240.2 nm and 273.2 nm, where the differences in absorbance were measured for the determination of Cinnarizine. Similarly, differences in absorbance at 230.8 nm and 259.2 nm were measured for determination of Domperidone. The proposed methods were applied for determination of Cinnarizine and Domperidone over the concentration ranges of 2-20 and 2-22 ?g mL-1, respectively. The suggested methods were validated as per USP guidelines and the results revealed that they are reliable, reproducible and precise for routine use with short analysis time. The results obtained by the proposed methods were statistically compared to the reported method, and there was no significant difference between them regarding both accuracy and precision.

Abdelrahman, Maha M.

2013-09-01

94

Simultaneous determination of Cinnarizine and Domperidone by area under curve and dual wavelength spectrophotometric methods.  

PubMed

Accurate, selective and sensitive spectrophotometric methods have been developed and validated for simultaneous determination of Cinnarizine and Domperidone, a binary mixture with overlapping spectra, without preliminary separation. These methods include area under the curve (AUC) and dual wavelength spectrophotometry. For the AUC method, the area under curve of mixture solutions in the wavelength ranges 241-258 nm and 280-292 nm were selected for determination of Cinnarizine and Domperidone and by applying Cramer's rule, concentration of each drug was obtained. In dual wavelength method, two wavelengths were selected for each drug in a way so that the difference in absorbance is zero for another drug. Domperidone shows equal absorbance at 240.2 nm and 273.2 nm, where the differences in absorbance were measured for the determination of Cinnarizine. Similarly, differences in absorbance at 230.8 nm and 259.2 nm were measured for determination of Domperidone. The proposed methods were applied for determination of Cinnarizine and Domperidone over the concentration ranges of 2-20 and 2-22 ?g mL(-1), respectively. The suggested methods were validated as per USP guidelines and the results revealed that they are reliable, reproducible and precise for routine use with short analysis time. The results obtained by the proposed methods were statistically compared to the reported method, and there was no significant difference between them regarding both accuracy and precision. PMID:23735208

Abdelrahman, Maha M

2013-09-01

95

Spectrophotometric methods manipulating ratio spectra for simultaneous determination of binary mixtures with sever overlapping spectra: a comparative study.  

PubMed

Three simple, specific and accurate spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of Rabeprazole sodium (RB) and Domperidone (DP) in their binary mixture without prior separation. Method A, is constant center spectrophotometric method (CC). Method B is a ratio difference spectrophotometric one (RD), while method C is a combined ratio isoabsorptive point-ratio difference method (RIRD). Linear correlations were obtained in range of 4-44?g/mL for both Rabeprazole sodium and Domperidone. The mean percentage recoveries of RB were 99.69±0.504 for method A, 99.83±0.483 for (B) and 100.31±0.499 for (C), respectively, and that of DP were 99.52±0.474 for method A, 100.12±0.505 for (B) and 100.16±0.498 for (C), respectively. Specificity was investigated by analysis of laboratory prepared mixtures containing the cited drugs and their combined tablet dosage form. The obtained results were statistically compared with those obtained by the reported methods, showing no significant difference with respect to accuracy and precision. The three methods were validated as per ICH guidelines and can be applied for routine analysis in quality control laboratories. PMID:24998682

Moustafa, H; Fayez, Y

2014-12-10

96

A Spectrophotometric Method to Determine the Inclination of Class I Objects  

E-print Network

A new method which enables us to estimate the inclination of Class I young stellar objects is proposed. Since Class I objects are not spherically symmetric, it is likely that the observed feature is sensitive to the inclination of the system. Thus, we construct a protostar model by carefully treating two-dimensional (2D) radiative transfer and radiative equilibrium. We show from the present 2D numerical simulations that the emergent luminosity L_SED,which is the frequency integration of spectral energy distribution (SED), depends strongly on the inclination of the system i, whereas the peak flux is insensitive to i. Based on this result, we introduce a novel indicator f_L, which is the ratio of L_SED to the peak flux, as a good measure for the inclination. By using f_L, we can determine the inclination regardless of the other physical parameters. The inclination would be determined by f_L within the accuracy of +- 5 degree, if the opening angle of bipolar outflows is specified by any other procedure. Since this spectrophotometric method is easier than a geometrical method or a full SED fitting method, this method could be a powerful tool to investigate the feature of protostars statistically with observational data which will be provided by future missions, such as SIRTF, ASTRO-F, and ALMA.

T. Nakazato; T. Nakamoto; M. Umemura

2002-10-11

97

An automated sequential injection spectrophotometric method for evaluation of tyramine oxidase inhibitory activity of some flavonoids.  

PubMed

An automated sequential injection (SI) spectrophotometric system has been developed for evaluation of tyramine oxidase (TOD) inhibitory activity. The method is based on the inhibition of TOD that catalyzes the oxidation of tyramine substrate to produce aldehyde and hydrogen peroxide (H?O?). The produced H?O? reacts with vanillic acid and 4-aminoantipyrine (4-AA) in the presence of peroxidase (POD) to form a quinoneimine dye, the absorbance of which is measured of absorbance at wavelength of 490 nm. The decrease of the quinoneimine dye is related to an increase of TOD inhibitory activity. Under the optimum conditions: 1.0 mM tyramine, 8 U mL(-1) TOD, 1.0 mM vanillic acid, 1.0 mM 4-AA and delay time of 10 s, some flavonoid compounds were examined for the TOD inhibitory activity expressed as IC?? value. It was found that flavonols (quercetin and myricetin) and flavans (epicatechin gallate (ECG) and epigallocatechin (EGC)) showed higher TOD inhibitory activity than flavones and flavanones. The results of IC?? values obtained from the proposed method and a batch-wise method were not significantly different from each other. Moreover, the SI system enabled automation of the analysis, leading to more convenient, more sensitive and faster analysis than the batch-wise method. A precise timing of the system also improves precision and accuracy of the assay, especially when the measurement of absorbance at non-steady state condition is involved. PMID:24720993

Moonrungsee, Nuntaporn; Shimamura, Tomoko; Kashiwagi, Takehiro; Jakmunee, Jaroon; Higuchi, Keiro; Ukeda, Hiroyuki

2014-05-01

98

Development and validation of sensitive spectrophotometric method for determination of two antiepileptics in pharmaceutical formulations  

NASA Astrophysics Data System (ADS)

Rapid, sensitive and validated spectrophotometric methods for the determination of two antiepileptics (gabapentin (GAB) and pregabalin (PRG)) in pure forms and in pharmaceutical formulations was developed. The method is based on the formation of charge transfer complex between drug and the chromogenic reagents quinalizarin (Quinz) and alizarin red S (ARS) producing charge transfer complexes in methanolic medium which showed an absorption maximum at 571 and 528 nm for GAB and 572 and 538 nm for PRG using Quinz and ARS, respectively. The optimization of the reaction conditions such as the type of solvent, reagent concentration and reaction time were investigated. Beer's law is obeyed in the concentration ranges 0.4-8.0 and 0.5-10 ?g mL-1 for GAB and PRG using Quinz and ARS, respectively. The molar absorptivity, Sandell sensitivity, detection and quantification limits are also calculated. The correlation coefficients were ?0.9992 with a relative standard deviation (RSD%) of ?1.76. The methods are successfully applied to the determination of GAB and PRG in pharmaceutical formulations and the validity assesses by applying the standard addition technique, which compared with those obtained using the reported methods.

Gouda, Ayman A.; Malah, Zakia Al

2013-03-01

99

Development and validation of sensitive spectrophotometric method for determination of two antiepileptics in pharmaceutical formulations.  

PubMed

Rapid, sensitive and validated spectrophotometric methods for the determination of two antiepileptics (gabapentin (GAB) and pregabalin (PRG)) in pure forms and in pharmaceutical formulations was developed. The method is based on the formation of charge transfer complex between drug and the chromogenic reagents quinalizarin (Quinz) and alizarin red S (ARS) producing charge transfer complexes in methanolic medium which showed an absorption maximum at 571 and 528 nm for GAB and 572 and 538 nm for PRG using Quinz and ARS, respectively. The optimization of the reaction conditions such as the type of solvent, reagent concentration and reaction time were investigated. Beer's law is obeyed in the concentration ranges 0.4-8.0 and 0.5-10 ?g mL(-1) for GAB and PRG using Quinz and ARS, respectively. The molar absorptivity, Sandell sensitivity, detection and quantification limits are also calculated. The correlation coefficients were ?0.9992 with a relative standard deviation (RSD%) of ?1.76. The methods are successfully applied to the determination of GAB and PRG in pharmaceutical formulations and the validity assesses by applying the standard addition technique, which compared with those obtained using the reported methods. PMID:23352920

Gouda, Ayman A; Malah, Zakia Al

2013-03-15

100

Development of surfactant assisted spectrophotometric method for determination of selenium in waste water samples.  

PubMed

A new, simple and highly selective method for spectrophotometric determination of selenium in waste water samples is described. Selenium(IV) oxidizes I(-) ions into I(2) which subsequently reacts with excess of I(-) ion in the acidic media to give tri-iodide ions (I(3)(-)), and it further reacts with cetylpyridinium cation (CP(+)) to give a violet colored species. The value of molar absorptivity of the ion-associate species in terms of selenium is 1.80 x 10(4) L mol(-1)cm(-1) at lambda(max) 510 nm. The detection limit of the method is 10 ng mL(-1) Se. The calibration curve is linear over 50-1000 ng mL(-1) Se with slope, intercept and co-relation coefficient of 0.23, -4.0 x 10(-4) and +0.99, respectively. None of the tested diverse ions interfered in the present method. The method has been tested for the determination of selenium in waste water samples. PMID:18541371

Agrawal, Kavita; Patel, Khageshwar Singh; Shrivas, Kamlesh

2009-01-30

101

Determination of vanadium in groundwater samples with an improved kinetic spectrophotometric method.  

PubMed

A kinetic catalytic method has been developed for the determination of vanadium based on its catalytic effect on the redox reaction of azorubin S and bromate in the presence of a sulphuric and nitric acid mixture. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at 515 nm. The fixed-time method was used for 0.5-5 min. Optimization of the reaction conditions regarding concentrations of acids, dye, oxidant, masking agent, etc. was investigated. The rate of decrease in absorbance of azorubin S was proportional to the concentration of vanadium in the range of 2.0-1.05 x 10(3) ng mL(-1). 3Sb/m was 0.0129 ng mL(-1) and 10 Sb/m was 0.0432 ng mL(-1). The catalytic method based on the oxidation reaction of azorubin S and bromate shows a good selectivity for vanadium over a wide variety of interference cations and anions. The proposed method was successfully applied to the determination of vanadium in groundwater samples and spiked-water samples. PMID:24701912

Ba?da, Esra

2014-01-01

102

A sensitive spectrophotometric method for the determination of propranolol HCl based on oxidation bromination reactions.  

PubMed

Three new, simple, sensitive, rapid and economical spectrophotometric methods (A, B and C) have been developed for the determination of propranolol hydrochloride (PRO) in bulk drug and dosage forms. These methods are based on oxidation-bromination reaction of PRO by bromine, generated in situ by the action of acid on a bromate-bromide mixture, followed by determination of unreacted bromine by three different reaction schemes. In method A, the determination of the residual bromine is based on its ability to bleach the indigo carmine dye and by measuring the absorbance at 610 nm. The residual bromine (in method B), is treated with excess of iron(II) and the resulting iron(III) is complexed with thiocyanate and the absorbance is measured at 480 nm. Method C involves treating the unreacted bromine with a measured excess of iron(II) and the remaining iron(II) is complexed with 1,10-phenanthroline and the increase in absorbance is measured at 510 nm. In all three methods, the amount of bromine reacted corresponds to the drug content. The different experimental parameters affecting the development and stability of the colour are carefully studied and optimized. Beer's Law is valid within a concentration range of 1-13, 4-12 and 2-9 µg ml?¹ for methods A, B, and C, respectively. The molar absorptivity, Sandell's sensitivity, detection and quantification limits are calculated. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods. The proposed methods have been successfully applied to the determination of PRO in pharmaceutical preparations and the results were statistically compared with those of the official method by applying the Student's t-test and F-test. PMID:20878893

El-Didamony, Akram M

2010-03-01

103

Extraction–Spectrophotometric Method for Determination of Fluoride in the Range of Microgram per Liter in Natural Waters  

Microsoft Academic Search

.  ?In this study a new extraction–spectrophotometric method for the determination of fluoride ion in natural waters has been\\u000a presented by use of octyl chemically bonded solid phase extraction (SPE) cartridge. In this method at first aluminium–oxinate\\u000a chelate is adsorbed on SPE cartridge, then the water sample (containing fluoride ion) is passed through the SPE device. The\\u000a excess of oxine on

Mir Ali Faraj-Zadeh; Ebrahim Ghorbani Kalhor

2001-01-01

104

A differential kinetic spectrophotometric method for determination of three sulphanilamide artificial sweeteners with the aid of chemometrics  

Microsoft Academic Search

A simple and sensitive spectrophotometric method for the simultaneous determination of acesulfame-K, sodium cyclamate and saccharin sodium sweeteners in foodstuff samples has been researched and developed. This analytical method relies on the different kinetic rates of the analytes in their oxidative reaction with KMnO4 to produce the green manganate product in an alkaline solution. As the kinetic rates of acesulfame-K,

Yongnian Ni; Weiqiang Xiao; Serge Kokot

2009-01-01

105

Determination of Arsenic in Environmental and Biological Samples Using Toluidine Blue or Safranine O by Simple Spectrophotometric Method  

Microsoft Academic Search

A simple spectrophotometric method has been developed for the determination of arsenic in various environmental and biological\\u000a samples. The method is based on the reaction of arsenic(III) with potassium iodate in acid medium to liberate iodine. This\\u000a liberated iodine bleaches the blue color of toluidine blue or pinkish red color of safranine O. The decrease in absorbance\\u000a at 628 or

Chand Pasha; Badiadka Narayana

2008-01-01

106

Analysis of residual solvents in ampicillin powder by headspace spectrophotometric method.  

PubMed

In this study a headspace spectrophotometric method is proposed for analysis of dichloromethane and isobutyl methyl keton (IBMK) residues in the ampicillin powder. Ampicillin is dissolved in 1 M NaOH in the vessel of an arsenic analyzer unit of an atomic absorption spectrophotometer. After 3-min stirring, the headspace has flowed by air into the flow-through cell and its absorbance is read at 196 nm, as emitted by a selenium hollow cathode lamp. The absorbance of the headspace is read in two cases (in the presence and absence of MnO4- ion). In the former case, the absorbance is only related to dichloromethane; in the latter, it is related to both solvents. By this method both solvents are determined in the ampicillin samples. The obtained results are compared with gas chromatography (GC) data. These results have good agreement. The proposed method is very rapid, selective and repeatable. Other solvents present, such as isopropyl alcohol, ethylacetate and triethylamine, are not interfering. PMID:11874121

Farajzadeh, Mirali; Mardani, Alireza

2002-02-01

107

Spectrophotometric methods for the determination of sitagliptin and vildagliptin in bulk and dosage forms.  

PubMed

Simple, accurate and precise spectrophotometric methods have been developed for the determination of sitagliptin and vildagliptin in bulk and dosage forms. The proposed methods are based on the charge transfer complexes of sitagliptin phosphate and vildagliptin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetrachloro-1,4-benzoquinone (p-chloranil). All the variables were studied to optimize the reactions conditions. For sitagliptin, Beer's law was obeyed in the concentration ranges of 50-300 ?g/ml, 20-120 ?g/ml and 100-900 ?g/ml with DDQ, TCNQ and p-chloranil, respectively. For vildagliptin, Beer's law was obeyed in the concentration ranges of 50-300 ?g/ml, 10-85 ?g/ml and 50-350 ?g/ml with DDQ, TCNQ and p-chloranil, respectively. The developed methods were validated and proved to be specific and accurate for the quality control of the cited drugs in pharmaceutical dosage forms. PMID:23675221

El-Bagary, Ramzia I; Elkady, Ehab F; Ayoub, Bassam M

2011-03-01

108

Spectrophotometric Methods for the Determination of Sitagliptin and Vildagliptin in Bulk and Dosage Forms  

PubMed Central

Simple, accurate and precise spectrophotometric methods have been developed for the determination of sitagliptin and vildagliptin in bulk and dosage forms. The proposed methods are based on the charge transfer complexes of sitagliptin phosphate and vildagliptin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetrachloro-1,4-benzoquinone (p-chloranil). All the variables were studied to optimize the reactions conditions. For sitagliptin, Beer’s law was obeyed in the concentration ranges of 50-300 ?g/ml, 20-120 ?g/ml and 100-900 ?g/ml with DDQ, TCNQ and p-chloranil, respectively. For vildagliptin, Beer’s law was obeyed in the concentration ranges of 50-300 ?g/ml, 10-85 ?g/ml and 50-350 ?g/ml with DDQ, TCNQ and p-chloranil, respectively. The developed methods were validated and proved to be specific and accurate for the quality control of the cited drugs in pharmaceutical dosage forms. PMID:23675221

El-Bagary, Ramzia I.; Elkady, Ehab F.; Ayoub, Bassam M.

2011-01-01

109

Development and validation of spectrophotometric method for simultaneous estimation of paracetamol and lornoxicam in different dissolution media  

PubMed Central

Background: Paracetamol and lornoxicam in combined tablet dosage form are available in the market. This combination is used to treat inflammatory diseases of the joints, osteoarthritis and sciatica. Spectrophotometric and high performance liquid chromatography (HPLC) methods have been reported for their simultaneous estimation in tablet dosage form in specific solvent. This paper presents simple, accurate and reproducible spectrophotometric method for simultaneous determination of paracetamol and lornoxicam in tablet dosage form in different dissolution media. The reported method is helpful in determination of paracetamol and lornoxicam during dissolution study. Materials and Methods: Simple, sensitive, accurate and economical spectrophotometric method based on an absorption correction equation was developed for the estimation of paracetamol and lornoxicam simultaneously in tablet dosage form in different dissolution media at different pH. Results: Paracetamol showed absorption maxima at 243 nm in 0.1N HCland phosphate buffer pH 6.8, while lornoxicam showed absorption maxima at 374 nm in 0.1N HCland phosphate buffer pH 6.8. The linearity was obtained in the concentration range of 4-12 ?g/ml for paracetamol and 4-16 ?g/ ml for lornoxicam. Discussion: The concentrations of the drugs were determined by an absorption correction equation method. The results of analysis have been validated statistically by recovery studies. PMID:23781487

Patel, Dasharath M.; Sardhara, Bhavesh M.; Thumbadiya, Diglesh H.; Patel, Chhagan N.

2012-01-01

110

Estimation of phytotoxic aluminum in soil solution using three spectrophotometric methods  

SciTech Connect

In the current investigation three spectrophotometric techniques -8-hydroxyquinoline, aluminon, and ferron- were compared for their ability to estimate phytotoxic Al in soil solution. Soil solution Al reacting with 8-hydroxyquinoline in 15 s, ferron in 30 s, and aluminon in 30 min were related to root and shoot growth of subterranean clover (Trifolium subterraneum L. cv. Mt. Barket) and switchgrass (Panicum virgatum L. cv. Cave-in-Rock) in limed and unlimed treatments of 10 acidic subsoil horizons. Across all 10 soils the amount of Al reacting with 8-hydroxyquinoline was generally the lowest, and that reacting with ferron the highest, although overlap among methods did occur. Manganese interference in several of the soil solutions limited the utility of the ferron method. The amounts of Al reacting with 8-hydroxyquinoline and aluminon were significantly related (P < 0.05) to root and shoot growth limitations exhibited by subterranean clover and switch-grass. Activities of Al/sup 3 +/ (a/sub Al/sup 3 +//) calculated from the GEOCHEM program using the Al reacting with 8-hydroxyquinoline and aluminon as the Al inputs were generally the best predictors of root and shoot growth.

Wright, R.J.; Wright, S.F.

1987-09-01

111

Investigation on the interaction of Safranin T with anionic polyelectrolytes by spectrophotometric method  

NASA Astrophysics Data System (ADS)

Understanding the role played by chemical additives such as NaCl salt, acid and Cetylpyridinium Chloride (CPC) surfactant on the interaction between dye and polyelectrolyte contributes to optimization of processes using polyelectrolytes in the removal of dye from aqueous solution. Herein we focus in the interaction between Safranin T, a cationic dye, with two anionic polyelectrolytes, poly(ammonium acrylate) and poly(acrylic acid) using spectrophotometric method and conductivity measurement. In aqueous solution, each of anionic polyelectrolytes forms a complex with the dye and induces a metachromasy indicated by the blue shift of the absorbance of the dye. The stoichiometry of complexes evaluated by the molar ratio method are 1:1 for Safranin T poly(ammonium acrylate) and 2:1 in the case of Safranin T poly(acrylic acid). The effect of additives on the stability of complexes has been studied by varying concentrations of the salt and the surfactant and pH of the solution. The thermodynamic parameters of interaction ?G, ?H and ?S at different temperatures were evaluated to determine the stability constant of the complexes.

Fradj, Anouar Ben; Lafi, Ridha; Hamouda, Sofiane Ben; Gzara, Lassaad; Hamzaoui, Ahmed Hichem; Hafiane, Amor

2014-10-01

112

A simple and highly sensitive spectrophotometric method for the determination of cyanide in equine blood.  

PubMed

An epidemiological association among black cherry trees (Prunus serotina), eastern tent caterpillars (Malacosoma americana), and the spring 2001 episode of mare reproductive loss syndrome in central Kentucky focused attention on the potential role of environmental cyanogens in the causes of this syndrome. To evaluate the role of cyanide (CN (-)) in this syndrome, a simple, rapid, and highly sensitive method for determination of low parts per billion concentrations of CN (-) in equine blood and other biological fluids was developed. The analytical method is an adaptation of methods commonly in use and involves the evolution and trapping of gaseous hydrogen cyanide followed by spectrophotometric determination by autoanalyzer. The limit of quantitation of this method is 2 ng/mL in equine blood, and the standard curve shows a linear relationship between CN (-) concentration and absorbance (r >. 99). The method throughput is high, up to 100 samples per day. Normal blood CN (-) concentrations in horses at pasture in Kentucky in October 2001 ranged from 3-18 ng/mL, whereas hay-fed horses showed blood CN (-) levels of 2-7 ng/mL in January 2002. Blood samples from a small number of cattle at pasture showed broadly similar blood CN (-) concentrations. Intravenous administration of sodium cyanide and oral administration of mandelonitrile and amygdalin yielded readily detectable increases in blood CN (-) concentrations. This method is sufficiently sensitive and specific to allow the determination of normal blood CN (-) levels in horses, as well as the seasonal and pasture-dependent variations. The method should also be suitable for investigation of the toxicokinetics and disposition of subacutely toxic doses of CN (-) and its precursor cyanogens in the horse as well as in other species. PMID:20021191

Hughes, Charlie; Lehner, Fritz; Dirikolu, Levent; Harkins, Dan; Boyles, Jeff; McDowell, Karen; Tobin, Thomas; Crutchfield, James; Sebastian, Manu; Harrison, Lenn; Baskin, Stephen I

2003-01-01

113

Application of spectrophotometric, densitometric, and HPLC techniques as stability indicating methods for determination of Zaleplon in pharmaceutical preparations  

Microsoft Academic Search

Spectrophotometric, spectrodensitometric and HPLC are stability indicating methods described for determination of Zaleplon in pure and dosage forms.As Zaleplon is easily degradable, the proposed techniques in this manuscript are adopted for its determination in presence of its alkaline degradation product, namely N-[4-(3-cyano-pyrazolo[1,5a]pyridin-7-yl)-phenyl]-N-ethyl-acetamide. These approaches are successfully applied to quantify Zaleplon using the information included in the absorption spectra of appropriate

Fadia H. Metwally; M. Abdelkawy; Nada S. Abdelwahab

2007-01-01

114

Flow injection kinetic spectrophotometric method for the determination of trace amounts of nitrite.  

PubMed

In this work, a new, simple and sensitive flow injection catalytic kinetic spectrophotometric determination of nitrite is reported based on catalytic effect of nitrite on the redox reaction between sulfonazo III and potassium bromate in acidic media. The reaction was monitored by measuring the decrease in the absorbance of sulfunazo III at 570 nm. Various chemical (such as the effect of acidity, reagents concentrations) and instrumental parameters (flow rate, reaction coil length, injection volume and temperature) were studied and were optimized. Under the optimum conditions calibration graph was linear in the nitrite concentration ranges of 8.00 x 10(-3)-3.00 x 10(-1) microg/ml (with slope of 2.40) and 3.50 x 10(-1)-1.80 microg/ml (with slope of 0.42). The detection limit was 6.00 x 10(-3) microg/ml of nitrite, the relative standard deviation (n=10) was 1.25% and 0.88% for 5.00 x 10(-2) and 2.00 x 10(-1)microg/ml of nitrite respectively. About 60 samples in 1h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of nitrite in food and environmental samples. PMID:19615524

Nouroozi, Siavash; Mirshafian, Razieh

2009-09-15

115

Determination of Trace Amounts of Lead Using the Flotation-spectrophotometric method.  

PubMed

The present study describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of extremely low concentrations of lead. It is based on flotation of a complex of Pb(2+) ions and Alizarin yellow between aqueous and n-hexane interface at pH = 6. The proposed procedure is also applied for determination of lead in both tap water and prepared sea water samples. Beer's Law was obeyed over the concentration range of 3.86 × 10(-8) To 8.20 × 10(-7) molL(-1) (8-170 ngmL(-1)) with an apparent molar absorptivity of 1.33 × 10(6) molL(-1) cm(-1) for a 100 mL aliquot of the water sample. The detection limit (n = 10) was 8.7 × 10(-9) molL(-1) (1.0 ngmL(-1)) and the Relative standard deviation (R.S.D), (n = 10) for 7.2 × 10(-7) molL(-1) (150 ngmL(-1)) of Pb (II) was 4.36%. A notable advantage of the method is that the determination of Pb (II) is free from the interference of almost all cations and ions found in the environment and waste water samples. The determination of Pb (II) in tap and synthetic seawater samples was also carried out by the present method. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples. PMID:21234287

Shiri, Sabah; Delpisheh, Ali; Haeri, Ali; Poornajaf, Abdolhossein; Golzadeh, Babak; Shiri, Sina

2010-01-01

116

Synthesis and Characterization of Potassium Tris(oxalato)ferrate(III) Trihydrate: A Spectrophotometric Method of Iron Analysis  

NASA Astrophysics Data System (ADS)

A previous Journal article [J. Chem. Educ. 1984, 61, 1098--1099] described a potassium tris(oxalato)ferrate(III) trihydrate empirical formula experiment that offered an excellent integrative experience in synthesis and characterization for general chemistry laboratory students. However, we have introduced a fast and accurate spectrophotometric method for the determination of iron in the product that takes the place of the photochemical-gravimetric procedure described in the article. Besides the pedagogic interest of bringing three different types of chemical analysis (titrimetric, gravimetric, and spectrophotometric) to bear on one compound, the new iron determination allows students to complete the experiment in 2, 3-hr laboratory periods rather than the 5 periods allotted in the original experiment.

Dallinger, Richard F.

1995-10-01

117

Selective kinetic spectrophotometric method for determination of gatifloxacin based on formation of its N-vinyl chlorobenzoquinone derivative  

NASA Astrophysics Data System (ADS)

A selective and simple kinetic spectrophotometric has been developed, for the first time, for the determination of gatifloxacin (GAT) in its dosage forms. The method was based on the formation of a colored N-vinyl chlorobenzoquinone derivative of GAT by its reaction with 2,3,5,6-tetrachloro-1,4-benzoquinone in presence of acetaldehyde. The formation of the colored product was monitored spectrophotometrically by measuring the absorbances at 655 nm. The factors affecting the reaction were studied and optimized. The stoichiometry of the reaction was determined, and the reaction pathway was postulated. Under the optimized conditions, the initial rate and fixed time (at 5 min) methods were utilized for constructing the calibration graphs. The graphs were linear in the concentration ranges of 2-100 and 10-140 ?g ml -1 with limits of detection of 0.84 and 3.5 ?g ml -1 for the initial rate and fixed time methods, respectively. The analytical performance of both methods was fully validated, and the results were satisfactory. The proposed methods were successfully applied to the determination of GAT in its commercial dosage forms. The label claim percentages were 99.7-100.5 and 98.2-99.5% for the initial rate and fixed time methods, respectively. Statistical comparison of the results with those of the reference method showed excellent agreement and proved that there was no significant difference in the accuracy and precision between the reference and the proposed methods. The proposed methods are superior to all the previously reported spectrophotometric methods in terms of the procedure simplicity and assay selectivity.

Darwish, Ibrahim A.; Sultan, Maha A.; Al-Arfaj, Hessa A.

2010-01-01

118

Determination of thallium(I) by flotation-spectrophotometric method using iodide and rhodamine B.  

PubMed

A method for the trace amount determination of Tl(I), via its preconcentration, is proposed. The method is based on the reaction of iodide, Tl(I) and Rhodamine B in a weakly acidic medium. In this process an ion-associated complex is formed, which is floated at the interface of aqueous-cyclohexane layers. Various amounts of Tl(I) by a subsequent separation and dissolution of the floated complex in methanol could be determined, spectrophotometrically. Beer's law was obeyed for the Tl(I) content in the range of (0.8-8.0) x 10(-7) mol l(-1) with a correlation coefficient of 0.9974. The conditional molar absorptivity was found to be 1.0 x 10(6) l mol(-1) cm(-1) at 560 nm, which indicated the considerable sensitivity of the procedure. The detection limit (DL) was 4.7 x 10(-8) mol l(-1) and the RSD (n = 5) for 4 x 10(-7) mol l(-1) of Tl(I) was 3.34%. None of the alkaline cations was interfered, and the interference of many other metal ions was eliminated via ion-exchange separation using a cation-exchanger resin, Amberlite IR-120, before the flotation step. The reliability of the procedure was confirmed by determining the Tl(I) contents of synthetic laboratory waste water by both flotation spectrophotometry and graphite furnace atomic absorption spectrometry (GFAAS). The recovery was 92.3-95.4% for 1 x 10(-7) and 4 x 10(-7) mol l(-1), respectively. The precision and accuracy of the results were comparable via F and t tests at the 95% confidence level. PMID:14640448

Hosseini, Mohammad Said; Naseri, Yousef

2003-11-01

119

A PLS-based extractive spectrophotometric method for simultaneous determination of carbamazepine and carbamazepine-10,11-epoxide in plasma and comparison with HPLC  

NASA Astrophysics Data System (ADS)

Carbamazepine (CBZ) undergoes enzyme biotransformation through epoxidation with the formation of its metabolite, carbamazepine-10,11-epoxide (CBZE). A simple chemometrics-assisted spectrophotometric method has been proposed for simultaneous determination of CBZ and CBZE in plasma. A liquid extraction procedure was operated to separate the analytes from plasma, and the UV absorbance spectra of the resultant solutions were subjected to partial least squares (PLS) regression. The optimum number of PLS latent variables was selected according to the PRESS values of leave-one-out cross-validation. A HPLC method was also employed for comparison. The respective mean recoveries for analysis of CBZ and CBZE in synthetic mixtures were 102.57 (±0.25)% and 103.00 (±0.09)% for PLS and 99.40 (±0.15)% and 102.20 (±0.02)%. The concentrations of CBZ and CBZE were also determined in five patients using the PLS and HPLC methods. The results showed that the data obtained by PLS were comparable with those obtained by HPLC method.

Hemmateenejad, Bahram; Rezaei, Zahra; Khabnadideh, Soghra; Saffari, Maryam

2007-11-01

120

Derivative-ratio spectrophotometric method for the determination of ternary mixture of aspirin, paracetamol and salicylic acid  

NASA Astrophysics Data System (ADS)

A derivative spectrophotometric method was developed for the assay of a ternary mixture of aspirin (ASP), paracetamol (PAR) and salicylic acid (SAL). The method is based on the use of the first and second derivatives of the ratio spectra and measurement at zero-crossing wavelengths. The ratio spectra were obtained by dividing the absorption spectrum of the mixture by that of one of the components. The concentration of the other components are then determined from their respective calibration curves treated similarly. The described method was applied for the determination of these combinations in synthetic mixtures and dosage forms. The results obtained were accurate and precise.

El-Yazbi, Fawzi A.; Hammud, Hassan H.; Assi, Sulaf A.

2007-10-01

121

Net analyte signal standard addition method (NASSAM) as a novel spectrofluorimetric and spectrophotometric technique for simultaneous determination, application to assay of melatonin and pyridoxine  

NASA Astrophysics Data System (ADS)

In this work a new modification of the standard addition method called "net analyte signal standard addition method (NASSAM)" is presented for the simultaneous spectrofluorimetric and spectrophotometric analysis. The proposed method combines the advantages of standard addition method with those of net analyte signal concept. The method can be applied for the determination of analyte in the presence of known interferents. The accuracy of the predictions against H-point standard addition method is not dependent on the shape of the analyte and interferent spectra. The method was successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT) in synthetic mixtures and in a pharmaceutical formulation.

Asadpour-Zeynali, Karim; Bastami, Mohammad

2010-02-01

122

A simple and rapid spectrophotometric method for determination of thiophanate-methyl in commercial formulations and its residues in foodstuffs.  

PubMed

A new, simple, rapid, and sensitive spectrophotometric method for the determination of thiophanate-methyl, based on its reaction with cobalt(II) in the presence of triethylamine, has been developed. The yellowish green color that develops instantaneously on mixing the fungicide with the reagents in dimethylformamide is stable for at least 2 h and has maximum absorbance at 360 nm. The method has been successfully applied to the determination of thiophanate-methyl in its commercial formulations and residues on grains and apples. A photometric titration procedure for formulation analysis of the fungicide has also been developed. PMID:15295873

Verma, Balbir C; Sood, Sumita; Chauhan, Chetan; Sharma, Devender K

2004-01-01

123

UV partial least-squares calibration and liquid chromatographic methods for direct quantitation of levofloxacin in urine.  

PubMed

Levofloxacin was determined in human urine samples by application of a spectrophotometric multivariate calibration partial least-squares (PLS-1) method. A calibration set consisting of standards was prepared by using a multilevel multifactor experimental design. In order to ensure accurate results, the calibration matrix included a urine sample free of levofloxacin (i.e., urine blank). The components of the calibration matrix were levofloxacin and urine. The concentration of levofloxacin ranged from 0.5 to 16.5 microg/mL. Different urine concentrations were used as the second component of the calibration matrix in order to include the information inherent in the changes in the UV spectrum for urine upon dilution. In addition, a high-performance liquid chromatographic method was proposed. In this method, a Shim-pack amino column was used at ambient temperature with a mobile phase of 25 mM potassium dihydrogen phosphate (pH adjusted to 3.1 with phosphoric acid)-acetonitrile (70 + 30, v/v), and the flow rate was 1 mL/min. UV detection at 293 nm was used for quantitation. The proposed methods were applied to the determination of the dissolution rate for tablets containing levofloxacin. The urinary excretion pattern for the cumulative amount of levoflacin excreted was also calculated. PMID:17955970

El-Gindy, Alaa; Emara, Samy; Mostafa, Ahmed

2007-01-01

124

A spectrophotometric method for the quantification of an enzyme activity producing 4-substituted phenols: determination of toluene-4-monooxygenase activity.  

PubMed

A spectrophotometric method for the quantitative determination of an enzyme activity resulting in the accumulation of 4-substituted phenols is described in this article. Toluene-4-monooxygenase (T4MO) activity in whole cells of Pseudomonas mendocina KR1 is used to demonstrate this method. This spectrophotometric assay is based on the coupling of T4MO activity with tyrosinase activity. The 4-substituted phenol, produced by the action of T4MO on the aromatic ring of a substituted arene, is a substrate for tyrosinase, which converts phenols to o-quinones. The latter react with the nucleophile 3-methyl-2-benzothiazolinone hydrazone (MBTH) to produce intensely colored products that absorb light maximally at different wavelengths, depending on the phenolic substrate used. The incubation of whole cells of P. mendocina KRI with fluorobenzene resulted in the accumulation of 4-fluorophenol. The coupling of T4MO activity with tyrosinase activity in the presence of fluorobenzene resulted in the formation of a colored product absorbing maximally at 480 nm. The molar absorptivity (epsilon) value for the o-quinone-MBTH adduct formed from 4-fluorophenol was determined experimentally to be 12,827 M(-1) cm(-1) with a linear range of quantification between 2.5 and 75 microM. The whole cell assay was run as a continuous indirect assay. The initial rates of T4MO activity toward fluorobenzene, as determined spectrophotometrically, were 61.8+/-4.4 nmol/min/mg P. mendocina KR1 protein (using mushroom tyrosinase), 64.9+/-4.6 nmol/min/mg P. mendocina KR1 protein (using cell extracts Pseudomonas putida F6), and, as determined by HPLC analysis, 62.6+/-1.4 nmol/min/mg P. mendocina KR1 protein. PMID:16061193

Nolan, Louise C; O'Connor, Kevin E

2005-09-15

125

A New Spectrophotometric Method for Determination of Selenium in Cosmetic and Pharmaceutical Preparations after Preconcentration with Cloud Point Extraction  

PubMed Central

A simple, rapid, and sensitive spectrophotometric method for the determination of trace amounts of selenium (IV) was described. In this method, all selenium spices reduced to selenium (IV) using 6?M?HCl. Cloud point extraction was applied as a preconcentration method for spectrophotometric determination of selenium (IV) in aqueous solution. The proposed method is based on the complexation of Selenium (IV) with dithizone at pH?

Soruraddin, Mohammad Hosein; Heydari, Rouhollah; Puladvand, Morteza; Zahedi, Mir Mehdi

2011-01-01

126

Spectrophotometric information from the DIVA satellite  

NASA Astrophysics Data System (ADS)

The DIVA satellite will, in addition to the astrometry, obtain photometric data for about 40 million survey stars and spectral data for about a third of these. Relevant sections of the CCD-data stream will be transmitted to Earth to allow a photometric and a spectrophotometric analysis. The DIVA photometric (SM) data can be used to derive stellar colours. Colours are in particular required for the chromaticity correction of the astrometry. The UV telescope (UV) is designed to obtain information about the Balmer jump region of the spectral energy distribution. The spectrophotometric (SC) data consists of overlapping spectral orders in the cross-scan direction. From these SC images the dispi (dispersed position-coded intensity) will be derived. The information on all stellar parameters is, of course, contained in the dispi and can be extracted without deconvolution. CCDs of the type foreseen for DIVA are in the process of being tested for their performance under the special conditions of this space mission. Methods are being tested, like artificial neural networks (ANNs) and others, to derive the astrophysical parameters Teff, log g, [M/H], and E(B-V) from the dispi. We find that even with the relatively modest spectral resolution of the dispi the ANN can discriminate well in temperature, moderately well in gravity and extinction, and crudely in metallicity, all clearly dependent on the brightness of the star. Degeneracy in the temperature and extinction determination can be lifted especially using Balmer jump information from the DIVA UV telescope.

de Boer, K. S.; Willemsen, P. G.; Reif, K.; Poschmann, H.; Marien, K.-H.; Kaempf, T. A.; Hilker, M.; Evans, D. W.; Bailer-Jones, C. A. L.

2003-01-01

127

Spectrophotometric determination of mangiferin  

Microsoft Academic Search

Summary  A spectrophotometric method is proposed for determining mangiferin in a crystalline powder and in sweetvetch herbage. The\\u000a relative accuracy of the method is ± 0.34% for the powder and ± 2.63% for the herbage.

B. A. Krivut; N. A. Fedyunina; S. I. Kocherga; S. V. Rusakova

1976-01-01

128

Simultaneous spectrophotometric determination of paracetamol, ibuprofen and caffeine in pharmaceuticals by chemometric methods  

NASA Astrophysics Data System (ADS)

In this study, the simultaneous determination of paracetamol, ibuprofen and caffeine in pharmaceuticals by chemometric approaches using UV spectrophotometry has been reported as a simple alternative to using separate models for each component. Spectra of paracetamol, ibuprofen and caffeine were recorded at several concentrations within their linear ranges and were used to compute the calibration mixture between wavelengths 200 and 400 nm at an interval of 1 nm in methanol:0.1 HCl (3:1). Partial least squares regression (PLS), genetic algorithm coupled with PLS (GA-PLS), and principal component-artificial neural network (PC-ANN) were used for chemometric analysis of data and the parameters of the chemometric procedures were optimized. The analytical performances of these chemometric methods were characterized by relative prediction errors and recoveries (%) and were compared with each other. The GA-PLS shows superiority over other applied multivariate methods due to the wavelength selection in PLS calibration using a genetic algorithm without loss of prediction capacity. Although the components show an important degree of spectral overlap, they have been determined simultaneously and rapidly requiring no separation step. These three methods were successfully applied to pharmaceutical formulation, capsule, with no interference from excipients as indicated by the recovery study results. The proposed methods are simple and rapid and can be easily used in the quality control of drugs as alternative analysis tools.

Khoshayand, M. R.; Abdollahi, H.; Shariatpanahi, M.; Saadatfard, A.; Mohammadi, A.

2008-08-01

129

Speciation and analysis of arsenic(III) and arsenic(V) by electrochemical hydride generation spectrophotometric method.  

PubMed

A simple method was developed for speciation and spectrophotometric determination of inorganic As(III) and As(V) using an electrochemical hydride generation technique. For speciation of As(III) and As(V), a graphite rod was used as cathode to reduce As(III) to AsH(3), the rod was then replaced with a tin-lead alloy wire for reducing As(V) to AsH(3). The spectrophotometric determination was based on the reaction of AsH(3) with silver diethyldithiocarbamate to give an absorbing complex at 510 nm. Under the optimized conditions, the calibration curves were linear over the ranges of 0.1-5 microg ml(-1) for As(III) and 0.5-4.0 microg ml(-1) for As(V). The concentration detection limits of 0.02 and 0.06 microg ml(-1) were achieved for As(III) and As(V), respectively. The relative standard deviations for five replicate speciation and determination of 3.0 microg ml(-1) As(III) and As(V) were 0.8 and 7.2%, respectively. The accuracy and recovery of the method were evaluated by analyzing tap water spiked with As(III) and As(V). PMID:20065596

Arbab-Zavar, Mohammad Hossein; Chamsaz, Mahmoud; Heidari, Tahereh

2010-01-01

130

Development and validation of new spectrophotometric ratio H-point standard addition method and application to gastrointestinal acting drugs mixtures  

NASA Astrophysics Data System (ADS)

New, simple, specific, accurate and precise spectrophotometric technique utilizing ratio spectra is developed for simultaneous determination of two different binary mixtures. The developed ratio H-point standard addition method (RHPSAM) was managed successfully to resolve the spectral overlap in itopride hydrochloride (ITO) and pantoprazole sodium (PAN) binary mixture, as well as, mosapride citrate (MOS) and PAN binary mixture. The theoretical background and advantages of the newly proposed method are presented. The calibration curves are linear over the concentration range of 5-60 ?g/mL, 5-40 ?g/mL and 4-24 ?g/mL for ITO, MOS and PAN, respectively. Specificity of the method was investigated and relative standard deviations were less than 1.5. The accuracy, precision and repeatability were also investigated for the proposed method according to ICH guidelines.

Yehia, Ali M.

2013-05-01

131

Spectrophotometric methods based on charge transfer complexation reactions for the determination of saxagliptin in bulk and pharmaceutical preparation.  

PubMed

Simple, accurate and precise spectrophotometric methods have been developed for the determination of saxagliptin in bulk and dosage forms. The proposed methods are based on the charge transfer complexes of saxagliptin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). All the variables were studied to optimize the reactions' conditions. Beer's law was obeyed in the concentration ranges of 50-300 ?g/ml and 10-110 ?g/ml with DDQ and TCNQ, respectively. The developed methods were validated and proved to be precise and accurate for the quality control of the saxagliptinin its pharmaceutical dosage form. PMID:23675274

El-Bagary, Ramzia I; Elkady, Ehab F; Ayoub, Bassam M

2012-09-01

132

Novel spectrophotometric method for determination of cinacalcet hydrochloride in its tablets via derivatization with 1,2-naphthoquinone-4-sulphonate.  

PubMed

This study represents the first report on the development of a novel spectrophotometric method for determination of cinacalcet hydrochloride (CIN) in its tablet dosage forms. Studies were carried out to investigate the reaction between CIN and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 8.5), an orange red-colored product exhibiting maximum absorption peak (?max) at 490 nm was produced. The stoichiometry and kinetic of the reaction were investigated and the reaction mechanism was postulated. This color-developing reaction was employed in the development of a simple and rapid visible-spectrophotometric method for determination of CIN in its tablets. Under the optimized reaction conditions, Beer's law correlating the absorbance with CIN concentration was obeyed in the range of 3 - 100 ?g/ml with good correlation coefficient (0.9993). The molar absorptivity (?) was 4.2 × 105 l/mol/cm. The limits of detection and quantification were 1.9 and 5.7 ?g/ml, respectively. The precision of the method was satisfactory; the values of relative standard deviations (RSD) did not exceed 2%. No interference was observed from the excipients that are present in the tablets. The proposed method was applied successfully for the determination of CIN in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.80 - 102.23 ± 1.27 - 1.62%. The results were compared favorably with those of a reference pre-validated method. The method is practical and valuable in terms of its routine application in quality control laboratories. PMID:22305461

Darwish, Ibrahim A; Al-Shehri, Mona M; El-Gendy, Manal A

2012-01-01

133

Novel atomic absorption spectrometric and rapid spectrophotometric methods for the quantitation of paracetamol in saliva: application to pharmacokinetic studies.  

PubMed

A novel atomic absorption spectrometric method and two highly sensitive spectrophotometric methods were developed for the determination of paracetamol. These techniques based on the oxidation of paracetamol by iron (III) (method I); oxidation of p-aminophenol after the hydrolysis of paracetamol (method II). Iron (II) then reacts with potassium ferricyanide to form Prussian blue color with a maximum absorbance at 700 nm. The atomic absorption method was accomplished by extracting the excess iron (III) in method II and aspirates the aqueous layer into air-acetylene flame to measure the absorbance of iron (II) at 302.1 nm. The reactions have been spectrometrically evaluated to attain optimum experimental conditions. Linear responses were exhibited over the ranges 1.0-10, 0.2-2.0 and 0.1-1.0 mug/ml for method I, method II and atomic absorption spectrometric method, respectively. A high sensitivity is recorded for the proposed methods I and II and atomic absorption spectrometric method value indicate: 0.05, 0.022 and 0.012 mug/ml, respectively. The limit of quantitation of paracetamol by method II and atomic absorption spectrometric method were 0.20 and 0.10 mug/ml. Method II and the atomic absorption spectrometric method were applied to demonstrate a pharmacokinetic study by means of salivary samples in normal volunteers who received 1.0 g paracetamol. Intra and inter-day precision did not exceed 6.9%. PMID:20046743

Issa, M M; Nejem, R M; El-Abadla, N S; Al-Kholy, M; Saleh, Akila A

2008-01-01

134

Use of response surface methodology for development of new microwell-based spectrophotometric method for determination of atrovastatin calcium in tablets  

PubMed Central

Background Response surface methodology by Box–Behnken design employing the multivariate approach enables substantial improvement in the method development using fewer experiments, without wastage of large volumes of organic solvents, which leads to high analysis cost. This methodology has not been employed for development of a method for analysis of atorvastatin calcium (ATR-Ca). Results The present research study describes the use of in optimization and validation of a new microwell-based UV-Visible spectrophotometric method of for determination of ATR-Ca in its tablets. By the use of quadratic regression analysis, equations were developed to describe the behavior of the response as simultaneous functions of the selected independent variables. Accordingly, the optimum conditions were determined which included concentration of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), time of reaction and temperature. The absorbance of the colored-CT complex was measured at 460 nm by microwell-plate absorbance reader. The method was validated, in accordance with ICH guidelines for accuracy, precision, selectivity and linearity (r² = 0.9993) over the concentration range of 20–200 ?g/ml. The assay was successfully applied to the analysis of ATR-Ca in its pharmaceutical dosage forms with good accuracy and precision. Conclusion The assay described herein has great practical value in the routine analysis of ATR-Ca in quality control laboratories, as it has high throughput property, consumes minimum volume of organic solvent thus it offers the reduction in the exposures of the analysts to the toxic effects of organic solvents, environmentally friendly "Green" approach) and reduction in the analysis cost by 50-fold. PMID:23146143

2012-01-01

135

Comparative in vivo study of the efficacy and tolerance of exfoliating agents using reflectance spectrophotometric methods.  

PubMed

The aim of the present study was to compare the effectiveness and the safety of different topical agents (glycolic acid, mandelic acid, and grape juice acid mixture) in skin exfoliation by objective instrumental methods. To evaluate the exfoliating effects of these substances, a new experimental in vivo protocol based on DHA (dihydroxyacetone)-induced skin pigmentation was used. Skin acceptability towards acid application was investigated by the evaluation of skin erythema induced by topical application of these substances at increased concentrations. Furthermore, their photosensitizing effects were evaluated by determining the increase in sensitivity to UV-light exposure in cutaneous sites previously treated with acids. These in vivo evaluations were monitored by reflectance spectophotometry. From the results obtained, we observed the differing capacities of the tested acids to increase the rate of skin regeneration, with a significant reduction in the time required to obtain skin renewal. The study pointed out that glycolic acid (10% w/w) induced a faster skin exfoliation, a more intense erythema, and a higher photosensitizing effect in comparison with the mandelic acid and grape juice acid mixtures. Further evidence showed that the mandelic acid and grape juice acid mixtures were able to induce a slower and safer peeling action in comparison with glycolic acid. Finally, our results suggest that the methodologies and protocols used in this study may help in choosing the most appropriate topical agents for skin exfoliating treatments. PMID:20587353

Rizza, Luisa; Frasca, Giuseppina; Bonina, Claudia; Puglia, Carmelo

2010-01-01

136

Research on UV radiation measurements and correction methods  

Microsoft Academic Search

The widely use of UV radiation led to the demand for improved understanding of the properties of instrumentation used to measure this radiation. The UV radiometers are mainly influenced by the factors as operating conditions, environmental conditions and the UV sources to be calibrated and measured. In addition, large errors can occur due to out-of-band, non-linear, and non-ideal cosine or

Bo Huang; Cai-Hong Dai; Jai-Lin Yu; Zhi-Feng Wu; Hui-Quan Ouyang

2011-01-01

137

Spectrophotometric study of total protein-albumin methods applied to cerebrospinal fluid.  

PubMed

A spectrophotometric study was carried out for three proteins assays when modification of their serum procedures using bromcresol green, bromcresol purple and biuret reagents were applied to the determinations of total proteins and albumin in cerebrospinal fluids. A novel concentration device wherein the sample itself was used as the primary diluent for the three reagents concentrated to contain the proper amounts of chemicals in smaller volumes than suggested in their serum procedures allowed reasonable absorbance signals to be obtained. Low molecular weight molecules were separated from the albumin and globulins of the fluids by centrifugal ultrafiltration using a 25K cutoff and spectra were obtained for both high and low molecular weight fractions. Some materials were obtained in the separated ultrafiltrates which gave reactions with all three reagents, reactions which either overlapped the spectra of the albumin reactions or superimposed the spectra obtained with the total protein reaction. A screening procedure for cerebrospinal fluid total proteins or centrifugally ultrafiltered albumin appears reasonable as an inference from studies made, although further elucidation of the low molecular weight fractions in needed as a confirmation device. PMID:7237740

Artiss, J D; Thibert, R J; Zak, B

1981-02-01

138

Accelerated UV Test Methods for Encapsulants of Photovoltaic Modules: Preprint  

SciTech Connect

This paper asserts that materials used for PV encapsulation must be evaluated for their ability to transmit light and to maintain mechanical integrity for extended periods of time under long term UV exposure.

Kempe, M. D.

2008-05-01

139

Selective Spectrophotometric and Spectrofluorometric Methods for the Determination of Amantadine Hydrochloride in Capsules and Plasma via Derivatization with 1,2-Naphthoquinone-4-sulphonate  

PubMed Central

New selective and sensitive spectrophotometric and spectrofluorometric methods have been developed and validated for the determination of amantadine hydrochloride (AMD) in capsules and plasma. The methods were based on the condensation of AMD with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product. The spectrophotometric method involved the measurement of the colored product at 460 ?nm. The spectrofluorometric method involved the reduction of the product with potassium borohydride, and the subsequent measurement of the formed fluorescent reduced AMD-NQS product at 382 ?nm after excitation at 293 ?nm. The variables that affected the reaction were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9972–0.9974) and low LOD (1.39 and 0.013??g?mL?1) were obtained in the ranges of 5–80 and 0.05–10? ?g?mL?1 for the spectrophotometric and spectrofluorometric methods, respectively. The precisions of the methods were satisfactory; RSD ?2.04%. Both methods were successfully applied to the determination of AMD in capsules. As its higher sensitivity, the spectrofluorometric method was applied to the determination of AMD in plasma; the recovery was 96.3–101.2 ± 0.57–4.2%. The results obtained by the proposed methods were comparable with those obtained by the official method PMID:20140080

Mahmoud, Ashraf M.; Khalil, Nasr Y.; Darwish, Ibrahim A.; Aboul-Fadl, Tarek

2009-01-01

140

Novel spectrophotometric method for determination of some macrolide antibiotics in pharmaceutical formulations using 1,2-naphthoquinone-4-sulphonate.  

PubMed

New, simple and rapid spectrophotometric method has been developed and validated for the assay of two macrolide drugs, azithromycin (AZT) and erythromycin (ERY) in pure and pharmaceutical formulations. The proposed method was based on the reaction of AZT and ERY with sodium 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium at 25 °C to form an orange-colored product of maximum absorption peak at 452 nm. All variables were studied to optimize the reaction conditions and the reaction mechanism was postulated. Beer's law was obeyed in the concentration range 1.5-33.0 and 0.92-8.0 ?g mL(-1) with limit of detection values of 0.026 and 0.063 ?g mL(-1) for AZT and ERY, respectively. The calculated molar absorptivity values are 4.3 × 10(4) and 12.3 × 10(4) L mol(-1) cm(-1) for AZT and ERY, respectively. The proposed methods were successfully applied to the determination of AZT and ERY in formulations and the results tallied well with the label claim. The results were statistically compared with those of an official method by applying the Student's t-test and F-test. No interference was observed from the concomitant substances normally added to preparations. PMID:23041925

Ashour, Safwan; Bayram, Roula

2012-12-01

141

Novel spectrophotometric method for determination of some macrolide antibiotics in pharmaceutical formulations using 1,2-naphthoquinone-4-sulphonate  

NASA Astrophysics Data System (ADS)

New, simple and rapid spectrophotometric method has been developed and validated for the assay of two macrolide drugs, azithromycin (AZT) and erythromycin (ERY) in pure and pharmaceutical formulations. The proposed method was based on the reaction of AZT and ERY with sodium 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium at 25 °C to form an orange-colored product of maximum absorption peak at 452 nm. All variables were studied to optimize the reaction conditions and the reaction mechanism was postulated. Beer's law was obeyed in the concentration range 1.5-33.0 and 0.92-8.0 ?g mL-1 with limit of detection values of 0.026 and 0.063 ?g mL-1 for AZT and ERY, respectively. The calculated molar absorptivity values are 4.3 × 104 and 12.3 × 104 L mol-1 cm-1 for AZT and ERY, respectively. The proposed methods were successfully applied to the determination of AZT and ERY in formulations and the results tallied well with the label claim. The results were statistically compared with those of an official method by applying the Student's t-test and F-test. No interference was observed from the concomitant substances normally added to preparations.

Ashour, Safwan; Bayram, Roula

2012-12-01

142

Quick spectrophotometric identification of synthetic food colorants by linear regression analysis  

Microsoft Academic Search

A quick spectrophotometric method for the identification of artificial food colorants, following isolation by adsorption\\u000a on wool, is described. The method is based on a computational comparison of a measured UV\\/VIS colorant spectrum with a series\\u000a of reference spectra. A calculated spectrum, which shows the best fit to the measured spectrum, is obtained from the reference\\u000a spectra by means of

Klaus Hofer; Dieter Jenewein

1997-01-01

143

Measurement of phenols dearomatization via electrolysis: The UV-Vis solid phase extraction method  

Microsoft Academic Search

Dearomatization levels during electrochemical oxidation of p-methoxyphenol (PMP) and p-nitrophenol (PNP) have been determined through UV-Vis spectroscopy using solid phase extraction (UV-Vis\\/SPE). The results show that the method is satisfactory to determine the ratio between aromatic compounds and aliphatic acids and reaction kinetics parameters during treatment of wastewater, in agreement with results obtained from numerical deconvolution of UV-Vis spectra. Analysis

Ronald Vargas; Carlos Borrás; Jorge Mostany; Benjamin R. Scharifker

2010-01-01

144

Spectrophotometric probe  

DOEpatents

A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

Prather, William S. (Augusta, GA); O'Rourke, Patrick E. (Martinez, GA)

1994-01-01

145

pH and buffering capacity problems involved in the determination of ammonia in saline water using the indophenol blue spectrophotometric method  

Microsoft Academic Search

Magnesium ions in brackish water or sea water complex with the citrate reagent (CIT) and thus interfere with the indophenol blue spectrophotometric method for ammonia measurement by altering the final pH of the color solution. The complex system, possibly Mg(CIT)?+OH??Mg(OH)(CIT)2?, shows buffer characteristics and can be identified by acid–base titration. A maximum capacity of ca. 40?eqpH?1ml?1 was found at pH

Su-Cheng Pai; Yung-Jin Tsau; Tai-I Yang

2001-01-01

146

Spectrophotometric methods for the simultaneous analysis of meclezine hydrochloride and pyridoxine hydrochloride in bulk drug and pharmaceutical formulations.  

PubMed

Three new spectrophotometric procedures for the simultaneous determination of pyridoxine hydrochloride and meclezine hydrochloride are described. The first method depends on the application of simultaneous equation to resolve the interference due to spectral overlapping. The analytical signals were measured at 231 and 220 nm. Calibration graphs were established for 1 to 20 microGmL(-1) for pyridoxine hydrochloride and 0.5 to 10 microGmL(-1) for meclezine hydrochloride in binary mixture. In the second method, the determination of pyridoxine hydrochloride and meclezine hydrochloride was performed by measuring the absorbances at 290 and 235 nm in the simple absorbance spectra of their mixture. In third method a yellowish orange complex of pyridoxine hydrochloride was formed with ferric chloride, which absorbs in the visible region with lambda(max) at 445 nm. Calibration curve of complex formation range was conducted in between 20 to 250 microGmL(-1). These methods were validated with respect to accuracy, precision, linearity, limit of detection and quantification. Regression analysis of Beer's plot showed good correlation in a general concentration range of 1 to 20 microGml(-1) with correlation coefficient (r = 0.9999 and 0.9999; CV < 0.858) for pyridoxine hydrochloride, whereas meclezine hydrochloride concentration range 0.5 to 10 microGmL(-1) with correlation coefficient (r = 0.9998 and 0.9998; CV < 0.826). These methods can be readily applied, without any interference from the excipients. The suggested procedures were successfully applied to the determination of these compounds in synthetic mixtures and in pharmaceutical preparations, with high percentage of recovery, good accuracy and precision. PMID:17416572

Arayne, M Saeed; Sultana, Najma; Siddiqui, Farhan Ahmed; Zuberi, M Hashim; Mirza, Agha Zeeshan

2007-04-01

147

Measured UV spectra compared with discrete ordinate method simulations  

SciTech Connect

A comprehensive radiative transfer model is used to calculate surface spectral ultraviolet irradiance under cloud-free conditions. The results are compared with measurements made at Lauder, New Zealand (45 deg S, 170 deg E) before and after the eruption of Mount Pinatubo and including a snow-covered surface. There is reasonable agreement between measured and calculated diffuse, direct, and global irradiances over the range 300 to 450 nm. Discrepancies may be due to calibration errors in the UV measurements, or in the extra terrestrial irradiances input to the model. Ratios of diffuse/direct irradiances are independent of such calibration uncertainties and therefore provide a sensitive test of the model. If appropriate ozonesonde data, surface albedo, and aerosol optical properties are used, the model ratios are in satisfactory agreement with measurements over a wide range of observing conditions. For cases in which the atmospheric optical properties are best known the agreement is better than 8% in the UV-B range, and for wavelengths 320 to 450 nm the deviation is smaller. The comparison suggests that the ultraviolet radiation exposure can be computed with confidence for clear sky conditions if the appropriate atmospheric molecular density profiles, ozonesonde data, surface albedo, and aerosol optical properties are available. The UV radiation model is used to investigate the impact of changes in solar zenith angle, ozone abundance, surface albedo, and aerosol loading on UV radiation reaching the surface of the Earth. The ratios of diffuse to direct irradiance depend critically on solar zenith angle, surface albedo, and aerosol extinction. Ozone changes have pronounced effects on the global UVB irradiance but have only a minor effect on these ratios.

Zeng, J.; Mckenzie, R.; Stamnes, K.; Wineland, M.; Rosen, J. [Univ. of Alaska, Fairbanks, AK (United States)]|[Univ. of Wyoming, Laramie, WY (United States)

1994-11-01

148

Liquid chromatography and chemometric-assisted spectrophotometric methods for the analysis of two multicomponent mixtures containing cough suppressant drugs.  

PubMed

Three methods were applied for the analysis of 2 multicomponent mixtures containing dextromethorphan hydrobromide, phenylephrine hydrochloride, chlorpheniramine maleate, methylparaben, and propylparaben, together with either sodium benzoate (Mix 1) or ephedrine hydrochloride and benzoic acid (Mix 2). In the first method, liquid chromatography was used for their simultaneous determination using an ODS column with a mobile phase consisting of acetonitrile-phosphate buffer, pH 2.7 (40 + 60, v/v), containing 5mM heptanesulfonic acid sodium salt and ultraviolet (UV) detection at 214 nm. Also, 2 chemometric methods, principal component regression, and partial least squares were used. For both chemometric calibrations, a concentration set of the mixture consisting of each compound in each mixture was prepared in distilled water. The absorbance data in the UV spectra were measured for the 76 or 71 wavelength points in the spectral region 210-240 or 210-224 nm considering the intervals of deltagamma = 0.4 or 0.2 nm for Mix 1 and Mix 2, respectively. The 2 chemometric methods did not require any separation step. These methods were successfully applied for the analysis of the 2 multicomponent combinations in synthetic mixtures and in commercial syrups, and the results were compared with each other. PMID:16152922

El-Gindy, Alaa; Emara, Samy; Mesbah, Mostafa K; Hadad, Ghada M

2005-01-01

149

Sensitive and rapid titrimetric and spectrophotometric methods for the determination of stavudine in pharmaceuticals using bromate-bromide and three dyes.  

PubMed

Four sensitive and rapid methods for the determination of stavudine (STV) in bulk drug and in dosage forms were developed and optimized. In titrimetry, aqueous solution of STV was treated with a known excess of bromate-bromide in HCl medium followed by estimation of unreacted bromine by iodometric back titration. Spectrophotometric methods involve the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange, indigocarmine or thymol blue followed by measurement of absorbance at 520 nm (method A), 610 nm (method B) or 550 nm (method C). In all the methods, the amount of bromate reacted corresponds to the amount of STV. Calculations in titrimetry were based on a 1:0.666 (STV:KBrO3) stoichiometry and the method was found to be applicable over 3.5-10 mg range. A linear increase in absorbance with concentration of STV was observed in the spectrophotometric methods, and the Beer's law was obeyed over the concentration ranges 0.125-1.75, 1-10 and 1-9.0 microg mL-1 STV for method A, method B and method C, respectively. The methods when applied to the determination of STV in tablets and capsules were found to give satisfactory results. PMID:18506251

Basavaiah, Kanakapura; Ramakrishna, Veeraiah; Somashekar, Chikkaswamy; Kumar, Urdigere R Anil

2008-06-01

150

Determination of phosphorus in food samples by X-ray fluorescence spectrometry and standard spectrophotometric method  

Microsoft Academic Search

The Wavelength Dispersive X-ray fluorescence (WD XRF) determination of phosphorus in GMO and non GMO food samples is proposed. The tested materials included commercially available transgenic, unmodified soya-foods and popular dairy products. The WD XRF method was compared with the standard molybdenum blue method. Matrix effects were minimised by using standard reference material. Obtained results were discussed in respect of

A Jastrz?bska; B Brudka; T Szyma?ski; E Sz?yk

2003-01-01

151

Quantitative analysis of a bacteria-derived antibiotic in nematode-infected insects using HPLC–UV and TLC–UV methods  

Microsoft Academic Search

3,5-Dihydroxy-4-isopropylstilbene (ST), an antibiotic produced by the bacterial symbiont Photorhabdus luminescens of the nematodes of the genus Heterorhabditis was determined quantitatively in nematode bacterium-infected insects using HPLC or TLC for separation and UV for quantification. Comparable and reproducible results were obtained with both HPLC–UV and TLC–UV methods. Several factors, including solvents for extraction of the antibiotic from the infected insects,

Kaiji Hu; Jianxiong Li; John M Webster

1997-01-01

152

A Rapid, Simple Spectrophotometric Method for Simultaneous Detection of Nitrate and Nitrite  

Microsoft Academic Search

Numerous methods are available for measurement of nitrate (NO?3). However, these assays can either be time consuming or require specialized equipment (e.g., nitrate reductase, chemiluminescent detector). We have developed a method for simultaneous evaluation of nitrate and nitrite concentrations in a microtiter plate format. The principle of this assay is reduction of nitrate by vanadium(III) combined with detection by the

Katrina M. Miranda; Michael G. Espey; David A. Wink

2001-01-01

153

Immunologic, spectrophotometric and nucleic acid based methods for the detection and quantification of airborne pollen.  

PubMed

Microscopic identification of pollen morphological phenotypes has been the traditional method used to identify and quantify pollen collected by air monitoring stations worldwide. Although this method has enabled a semi-standardized approach for the assessment of pollen exposure, limitations including labor intensiveness, required expertise, examiner bias, and the inability to differentiate species, genera, and in some cases families have limited data derived from the these stations. Recent advances in chemical, biochemical and molecular detection methods have provided standardized alternatives to this microscopic approach. In this review, we examine the applicability of alternative methodologies, in particular nucleic acid based assays involving the quantitative polymerase chain reaction, for the standardized detection of airborne pollen. PMID:22342607

Rittenour, William R; Hamilton, Robert G; Beezhold, Donald H; Green, Brett J

2012-09-28

154

Simultaneous spectrophotometric determination of four metals by two kinds of partial least squares methods  

NASA Astrophysics Data System (ADS)

Simultaneous determination of Ni(II), Cd(II), Cu(II) and Zn(II) was studied by two methods, kernel partial least squares (KPLS) and wavelet packet transform partial least squares (WPTPLS), with xylenol orange and cetyltrimethyl ammonium bromide as reagents in the medium pH = 9.22 borax-hydrochloric acid buffer solution. Two programs, PKPLS and PWPTPLS, were designed to perform the calculations. Data reduction was performed using kernel matrices and wavelet packet transform, respectively. In the KPLS method, the size of the kernel matrix is only dependent on the number of samples, thus the method was suitable for the data matrix with many wavelengths and fewer samples. Wavelet packet representations of signals provide a local time-frequency description, thus in the wavelet packet domain, the quality of the noise removal can be improved. In the WPTPLS by optimization, wavelet function and decomposition level were selected as Daubeches 12 and 5, respectively. Experimental results showed both methods to be successful even where there was severe overlap of spectra.

Gao, Ling; Ren, Shouxin

2005-10-01

155

Enzymatic spectrophotometric method for aflatoxin B detection based on acetylcholinesterase inhibition.  

PubMed

A new method for aflatoxin B (AFB) determination is proposed. The AFB determination is based on acetylcholinesterase (AChE) inhibition, and the AChE residual activity is determined using the colorimetric method (Ellman's method). Cholinesterases (ChEs) from various sources were tested using AFB1 as reference aflatoxin. AChE from electric eel has shown the highest sensitivity to AFB1, and it was chosen for the rest of the work. To select and optimize the analytical procedures, an investigation on the type of AChE inhibition by AFB1 was carried out. The AChE degree of inhibition by AFB1 was independent of the incubation time and the enzyme concentrations, showing the reversibility of the inhibition. This reversibility of the inhibition permits a rapid analysis of AFB1, requiring only 3 min. For the development of the AFB1 assay, the pH, the time of reaction, temperature, and substrate concentration were evaluated and optimized. The linear range of 10-60 ng mL-1 was determined. To evaluate the selectivity of this method, the cross-reactivity with other aflatoxins such as aflatoxin B2, aflatoxin G1, aflatoxin G2, and aflatoxin M1 was investigated. Finally, the suitability of the assay for AFB1 quantification in barley was evaluated. This study shows a new approach to detect aflatoxins based on enzyme inhibition and has advantages such as the ease of use, rapidity, and cost effectiveness. Thus, it could find a possible use as a screening method for this type of mycotoxins. PMID:17408242

Arduini, Fabiana; Errico, Ilenia; Amine, Aziz; Micheli, Laura; Palleschi, Giuseppe; Moscone, Danila

2007-05-01

156

Simultaneous determination of calcium and magnesium in water using artificial neural network spectro-photometric method  

NASA Astrophysics Data System (ADS)

A new analytical method using Back-Propagation (BP) artificial neural networks and spectrophotometry for simultaneous determination of calcium and magnesium in tap water, the Yellow River water and seawater is established. By condition experiment, the optimum analytical conditions for calcium, magnesium and Arsenazo (III) color reactions are obtained. Levenberg-Marquart (L-M) algorithm is used for calculation in BP neural network. The topological structure of three-layer BP ANN network architecture is chosen as 11-10-2 (nodes). The initial value of gradient coefficient ? is fixed at 0.001 and the increase factor and reduction factor of ? take the default values of the system. The data are processed by computers with our own programs written in MATLAB 7.0. The relative standard deviations of the calculated results for calcium and magnesium are 2.31% and 2.14%, respectively. The results of standard addition method show that the recoveries of calcium and magnesium are 103.6% and 100.8% in the tap water, 103.2% and 96.6% in the Yellow River water (Lijin district of Shandong Province), and 98.8%-103.3% and 98.43%-103.4% in seawater from Jiaozhou Bay of Qingdao. It is found that 14 common cations and anions do not interfere with the determination of calcium and magnesium under the optimum experimental conditions. The comparative experiments do not show any obvious difference between the results obtained by this new method and those obtained by the classical complexometric titration method in seawater medium. This method exhibits good reproducibility and high accuracy in the determination of calcium and magnesium and can be used for the simultaneous determination of Ca2+ and Mg2+ in tap water and natural water.

Ji, Hongwei; Li, Shuang; Xin, Huizhen; Cao, Hengxia

2010-09-01

157

Simultaneous determination of calcium and magnesium in water using artificial neural network spectro-photometric method  

Microsoft Academic Search

A new analytical method using Back-Propagation (BP) artificial neural networks and spectrophotometry for simultaneous determination\\u000a of calcium and magnesium in tap water, the Yellow River water and seawater is established. By condition experiment, the optimum\\u000a analytical conditions for calcium, magnesium and Arsenazo (III) color reactions are obtained. Levenberg-Marquart (L-M) algorithm\\u000a is used for calculation in BP neural network. The topological

Hongwei Ji; Shuang Li; Huizhen Xin; Hengxia Cao

2010-01-01

158

Two derivative spectrophotometric methods for the simultaneous determination of lovastatin combined with three antioxidants  

Microsoft Academic Search

A zero crossing and an algorithm bivariate calibration derivative method for the simultaneous determination of lovastatin combined separately with three antioxidants (ascorbic acid, quercetin and gallic acid) in synthetic mixtures are described. The aqueous or methanolic solutions obeyed Beer's law in the concentration ranges of 3.20–17.36 ?g\\/ml for lovastatin, 1.76–8.80 ?g\\/ml for ascorbic acid, 1.41–7.04 ?g\\/ml for gallic acid and

C. K Markopoulou; J. E Koundourelllis

2003-01-01

159

Derivative Spectrophotometric Method for Estimation of Antiretroviral Drugs in Fixed Dose Combinations  

PubMed Central

Purpose: Lamivudine is cytosine and zidovudine is cytidine and is used as an antiretroviral agents. Both drugs are available in tablet dosage forms with a dose of 150 mg for LAM and 300 mg ZID respectively. Method: The method employed is based on first order derivative spectroscopy. Wavelengths 279 nm and 300 nm were selected for the estimation of the Lamovudine and Zidovudine respectively by taking the first order derivative spectra. The conc. of both drugs was determined by proposed method. The results of analysis have been validated statistically and by recovery studies as per ICH guidelines. Result: Both the drugs obey Beer’s law in the concentration range 10-50 ?g mL-1,for LAM and ZID; with regression 0.9998 and 0.9999, intercept – 0.0677 and – 0.0043 and slope 0.0457 and 0.0391 for LAM and ZID, respectively.The accuracy and reproducibility results are close to 100% with 2% RSD. Conclusion: A simple, accurate, precise, sensitive and economical procedures for simultaneous estimation of Lamovudine and Zidovudine in tablet dosage form have been developed. PMID:24312779

P.B., Mohite; R.B., Pandhare; S.G., Khanage

2012-01-01

160

Liquid chromatographic-atomic absorption spectrophotometric method for determination of methyl mercury in seafood: collaborative study.  

PubMed

A previously developed method that uses a simplified sample preparation procedure and atomic absorption detection of liquid chromatographic eluates for the determination of methyl mercury in seafood has been collaboratively studied. The unique feature of the method involves the use of a specially designed interface for the generation of mercury vapor. Methyl mercury is isolated from the blended sample by chloroform elution from a diatomaceous earth-hydrochloric acid column. The organomercury compound is then extracted into a small volume of 0.01M sodium thiosulfate solution. An aliquot of this solution is injected onto a Zorbax ODS column and eluted with methanol-ammonium acetate solution (3 + 2), pH 5.7, containing 0.01% mercaptoethanol. Mercury is detected by flameless atomic absorption spectrophotometry using the interface. The samples analyzed in the study were unspiked swordfish, unspiked and spiked lobster, and unspiked and spiked tuna. The spiked samples contained methyl mercury both above and below the U.S. Food and Drug Administration guideline level of 1 microgram Hg/g. Reproducibility relative standard deviations ranged from 10.5% at 1 microgram Hg/g to 18.2% at about 0.1 microgram Hg/g. Accuracy, measured by comparison to reference values obtained by the Associate Referee, ranged from 94.4 to 99.6%. The method has been adopted official first action. PMID:2592315

Holak, W

1989-01-01

161

Four Derivative Spectrophotometric Methods for the Simultaneous Determination of Carmoisine and Ponceau 4R in Drinks and Comparison with High Performance Liquid Chromatography  

PubMed Central

Four simple, rapid, and accurate spectrophotometric methods were developed for the simultaneous determination of two food colorants, Carmoisine (E122) and Ponceau 4R (E124), in their binary mixtures and soft drinks. The first method is based on recording the first derivative curves and determining each component using the zero-crossing technique. The second method uses the first derivative of ratio spectra. The ratio spectra are obtained by dividing the absorption spectra of the binary mixture by that of one of the components. The third method, derivative differential procedure, is based on the measurement of difference absorptivities derivatized in first order of solution of drink samples in 0,1?N NaOH relative to that of an equimolar solution in 0,1?N HCl at wavelengths of 366 and 451?nm for Carmoisine and Ponceau 4R, respectively. The last method, based on the compensation method is presented for derivative spectrophotometric determination of E122 and E124 mixtures with overlapping spectra. By using ratios of the derivative maxima, the exact compensation of either component in the mixture can be achieved, followed by its determination. These proposed methods have been successfully applied to the binary mixtures and soft drinks and the results were statistically compared with the reference HPLC method (NMKL 130). PMID:24672549

Turak, Fatma; Dinc, Mithat; Dulger, Oznur; Ozgur, Mahmure Ustun

2014-01-01

162

Experimental Study of Closed System in the Chlorine Dioxide-Iodide-Sulfuric Acid Reaction by UV-Vis Spectrophotometric Method  

PubMed Central

The mole ratio r(r = [I?]0/[ClO2]0) has great influence on ClO2-I?-H2SO4 closed reaction system. By changing the initiate concentration of potassium iodide, the curve of absorbance along with the reaction time was obtained at 350?nm and 297?nm for triiodide ion, and 460?nm for iodine. The changing point of the absorbance curve's shape locates at r = 6.00. For the reaction of ClO2-I? in the absence of H2SO4, the curve of absorbance along with the reaction time can be obtained at 350?nm for triiodide ion, 460?nm for iodine. The mole ratio r is equal to 1.00 is the changing point of the curve's shape no matter at which wavelength to determine the reaction. For the reaction of ClO2-I?-H+ in different pH buffer solution, the curve of absorbance along with the reaction time was recorded at 460?nm for iodine. When r is greater than 1.00, the transition point of the curve's shape locates at pH 2.0, which is also the point of producing chlorite or chloride for chlorine dioxide at different pH. When r is less than 1.00, the transition point locates at pH 7.0. PMID:21808646

Li, Na; Shi, Laishun; Wang, Xiaomei; Guo, Fang; Yan, Chunying

2011-01-01

163

Field Application of a Rapid Spectrophotometric Method for Determination of Persulfate in Soil  

PubMed Central

Remediation of hydrocarbon contaminated soils can be performed both in situ and ex situ using chemical oxidants such as sodium persulfate. Standard methods for quantifying persulfate require either centrifugation or prolonged settling times. An optimized soil extraction procedure was developed for persulfate involving simple water extraction using a modified disposable syringe. This allows considerable saving of time and removes the need for centrifugation. The extraction time was reduced to only 5 min compared to 15 min for the standard approach. A comparison of the two approaches demonstrated that each provides comparable results. Comparisons were made using high (93 g kg?1 soil) and low (9.3 g kg?1 soil) additions of sodium persulfate to a petroleum hydrocarbon-contaminated soil, as well as sand spiked with diesel. Recoveries of 95±1% and 96±10% were observed with the higher application rate in the contaminated soil and spiked sand, respectively. Corresponding recoveries of 86±5% and 117±19% were measured for the lower application rate. Results were obtained in only 25 min and the method is well suited to batch analyses. In addition, it is suitable for application in a small field laboratory or even a mobile, vehicle-based system, as it requires minimal equipment and reagents. PMID:23776446

Cunningham, Colin J.; Pitschi, Vanessa; Anderson, Peter; Barry, D. A.; Patterson, Colin; Peshkur, Tanya A.

2013-01-01

164

Improved methods for adjusting the UV content of measurement instrument illumination for papermaking industry  

NASA Astrophysics Data System (ADS)

Optical brightening agents (OBAs) or fluorescent whitening agents (FWAs) are often used additives in paper and board products as they improve both whiteness and brightness of the products. When printed, OBAs can even contribute to colour tone reproduction. Fluorescent emissions of OBAs depend on the UV content of the illuminant (light source). Adequate adjustment (control or adjustment) of UV content of measurement apparatus (e.g. spectrophotometer) is essential for accurate colour measurement and printing colour reproduction. We proposed a method to adjust the UV content against assigned spectra rather than, as adopted in current ISO standards, against single assigned values. Demonstrations of applying this method to the CIE standard illuminants used in papermaking and graphic industries, D65, C and D50 have been given. Thanks to the well-established traceability of reference standards (IRs), the UV contents of a spectrophotometer corresponding to the standard CIE illuminants have been achieved.

Yang, Li

2014-09-01

165

Monitoring Escherichia coli growth in M63 media by ultrasonic noninvasive methods and correlation with spectrophotometric and HPLC techniques  

Microsoft Academic Search

A low-intensity ultrasonic technique (that is noninvasive, nondestructive, and online) has been developed to monitor the growth\\u000a of Escherichia coli in glucose minimal media under aerobic and anaerobic conditions. Ultrasonic time of flight (TOF) variations were correlated\\u000a with microorganism growth and the disappearance of nutrients and their subsequent conversion into different metabolites. Spectrophotometric\\u000a growth data and high-performance liquid chromatography (HPLC)

Carlos Sierra; Luis Elvira; José L. García; Pablo Resa; Beatriz Galán

2010-01-01

166

Simultaneous Spectrophotometric Determination of Iron, Titanium, and Aluminum by Partial Least-Squares Calibration Method in Micellar Medium  

Microsoft Academic Search

Simultaneous spectrophotometric determination of iron, titanium and aluminum was carried out using their morin (3,5,7,2?,4?-penta hydroxy flavone) complexes in Triton X-100 micellar medium. Partial least-squares regression was employed for the resolution of ternary mixtures of Fe, Ti, and Al. The presence of Triton X-100 micellar system avoids the solvent extraction step necessary for the formation of soluble morin complexes. The

Afsaneh Safavi; Mohammad Mirzaee; Hamid Abdollahi

2003-01-01

167

Flow injection spectrophotometric assay of ?-amylase activity  

Microsoft Academic Search

A spectrophotometric flow injection method for the determination of ?-amylase activity is proposed. The method is based on the analysis of the maltose obtained during the hydrolysis of amylose in the presence of ?-amylase and relies on the reaction of 3,5 dinitrosalicylic-acid and maltose at boiling temperatures to form a brick red coloured complex, monitored spectrophotometrically at 540nm. The method

J. F van Staden; L. V Mulaudzi

2000-01-01

168

Simultaneous spectrophotometric determination of Sn(II) and Sn(IV) by mean centering of ratio kinetic profiles and partial least squares methods.  

PubMed

Two spectrophotometric methods are described for the simultaneous determination of binary mixtures of Sn(II) and Sn(IV) in water samples and fruit juice samples, without prior separation steps, using the mean centering of ratio kinetic profiles and partial least squares (PLS) methods. The methods are based on the difference in the rate of the reactions of Sn(II) and Sn(IV) with pyrocatechol violet at pH 4.0. The methods allow rapid and accurate determination of Sn(II) and Sn(IV). The analytical characteristics of the methods for the simultaneous determination of binary mixtures of Sn(II) and Sn(IV) were calculated. The results showed that the methods were capable to simultaneous determination of 0.1-1.80 mg L(-1) each of cations. The proposed methods were successfully applied to the simultaneous determination of Sn(II) and Sn(IV)in an orange juice sample. PMID:19071842

Madrakian, Tayyebeh; Afkhami, Abbas; Moein, Roshanak; Bahram, Morteza

2007-07-31

169

Spectrophotometric Determination of Iron(II) and Cobalt(II) by Direct, Derivative, and Simultaneous Methods Using 2-Hydroxy-1-Naphthaldehyde-p-Hydroxybenzoichydrazone.  

PubMed

Optimized and validated spectrophotometric methods have been proposed for the determination of iron and cobalt individually and simultaneously. 2-hydroxy-1-naphthaldehyde-p-hydroxybenzoichydrazone (HNAHBH) reacts with iron(II) and cobalt(II) to form reddish-brown and yellow-coloured [Fe(II)-HNAHBH] and [Co(II)-HNAHBH] complexes, respectively. The maximum absorbance of these complexes was found at 405?nm and 425?nm, respectively. For [Fe(II)-HNAHBH], Beer's law is obeyed over the concentration range of 0.055-1.373??g?mL(-1) with a detection limit of 0.095??g?mL(-1) and molar absorptivity ?, 5.6 × 10(4)?L mol(-1) cm(-1). [Co(II)-HNAHBH] complex obeys Beer's law in 0.118-3.534??g?mL(-1) range with a detection limit of 0.04??g?mL(-1) and molar absorptivity, ? of 2.3 × 10(4)?L mol(-1) cm(-1). Highly sensitive and selective first-, second- and third-order derivative methods are described for the determination of iron and cobalt. A simultaneous second-order derivative spectrophotometric method is proposed for the determination of these metals. All the proposed methods are successfully employed in the analysis of various biological, water, and alloy samples for the determination of iron and cobalt content. PMID:22505925

Devi, V S Anusuya; Reddy, V Krishna

2012-01-01

170

Spectrophotometric Determination of Iron(II) and Cobalt(II) by Direct, Derivative, and Simultaneous Methods Using 2-Hydroxy-1-Naphthaldehyde-p-Hydroxybenzoichydrazone  

PubMed Central

Optimized and validated spectrophotometric methods have been proposed for the determination of iron and cobalt individually and simultaneously. 2-hydroxy-1-naphthaldehyde-p-hydroxybenzoichydrazone (HNAHBH) reacts with iron(II) and cobalt(II) to form reddish-brown and yellow-coloured [Fe(II)-HNAHBH] and [Co(II)-HNAHBH] complexes, respectively. The maximum absorbance of these complexes was found at 405?nm and 425?nm, respectively. For [Fe(II)-HNAHBH], Beer's law is obeyed over the concentration range of 0.055–1.373??g?mL?1 with a detection limit of 0.095??g?mL?1 and molar absorptivity ?, 5.6 × 104?L mol?1 cm?1. [Co(II)-HNAHBH] complex obeys Beer's law in 0.118–3.534??g?mL?1 range with a detection limit of 0.04??g?mL?1 and molar absorptivity, ? of 2.3 × 104?L mol?1 cm?1. Highly sensitive and selective first-, second- and third-order derivative methods are described for the determination of iron and cobalt. A simultaneous second-order derivative spectrophotometric method is proposed for the determination of these metals. All the proposed methods are successfully employed in the analysis of various biological, water, and alloy samples for the determination of iron and cobalt content. PMID:22505925

Devi, V. S. Anusuya; Reddy, V. Krishna

2012-01-01

171

G protein signaling in UV protection: methods for understanding the signals in young etiolated seedlings.  

PubMed

A seed is competent to respond to light soon after imbibition. A new developmental program begins in or on the ground where the young seedling may be exposed to heat, cold, drought, flooding (anoxia), salts, varying levels of visible light, and the topic of this paper, ultraviolet radiation. Herein what is described is a method for growing and maintaining seedlings, then methods of UV irradiation in order to measure discrete effects of UV wavelengths in signal transduction, very early in seedling development. The physiological response to an abiotic signal is partly dependent on the developmental state of the plant. Dark-grown seedlings of plant species possess young leaves or leaf primordia in a "suspended" state of development whereby exposure to sunlight, visible and UV, is required to initiate the leaf developmental program, including development of etioplasts or proplastids into fully functioning chloroplasts. In order for us to understand the initial and persisting effects of UV in seedlings, we "delay" light-induced development by carrying out all experiments in complete darkness between days 0 (seed) and day 7 (Arabidopsis). In this case, the UV regulation of a simple signaling pathway in Arabidopsis, G protein signaling in UV protection and acclimation early in development, is investigated with the use of several mutants and easily score-able phenotypes. PMID:23913039

Orozco-Nunnelly, Danielle A; Kaufman, Lon S; Warpeha, Katherine M

2013-01-01

172

Derivative spectrophotometric and liquid chromatographic methods for the simultaneous determination of metoclopramide hydrochloride and aspirin in pharmaceuticals.  

PubMed

Two simple analytical methods were developed and validated for the analysis of a binary mixture of metoclopramide (MET) and aspirin (ASP). The first method depends on measuring the first derivative amplitudes at 257 nm for MET and at 310 nm for ASP, respectively. The calibration graphs were linear in the range of 0.25-20.0 µg/mL for MET and 10.0-200.0 µg/mL for ASP. For the second method, good chromatographic separation was achieved using Promosil C18 column (250 × 4.6 mm i.d., 5 µm particle size). Mobile phase consisting of methanol and 0.02 M phosphate buffer in the ratio of 60:40 (v/v) at pH 4.0 was pumped at a flow rate of 1 mL/min with UV detection at 260 nm. Indapamide was used as an internal standard. The method showed good linearity over the concentration ranges of 0.20-10.0 and 10.0-200.0 ?g/mL with limits of detection of 0.06, 1.81 ?g/mL and limits of quantification of 0.17, 5.46 ?g/mL for MET and ASP, respectively. The results of the proposed methods were statistically compared with those obtained by the official United States Pharmacopeia method revealing non-significant differences in the performance of the methods regarding accuracy and precision. The suggested methods were successfully applied for the simultaneous analysis of the studied drugs in their co-formulated tablets as well as in their single dosage forms. PMID:24510919

Belal, Fathalla F; Sharaf El-Din, Mohie K; Tolba, Manar M; Elmansi, Heba

2014-11-01

173

Spectrophotometric and HPTLC-densitometric determination of lisinopril and hydrochlorothiazide in binary mixtures.  

PubMed

Different spectrophotometric and HPTLC-densitometric methods are presented for the simultaneous determination of lisinopril and hydrochlorothiazide in pharmaceutical tablets. The spectrophotometric methods include third derivative (3D) ultraviolet spectrophotometry with zero crossing measurement at 217.4 and 233.4 nm, second derivative of the ratio spectra with measurement at 214.3 and 228.0 nm; both classical least squares and principal component regression were applied to the UV absorption and first derivative spectra of the mixture. The HPTLC method was based on separation of both drugs followed by densitometric measurements of their spots at 210 and 275 nm for lisinopril and hydrochlorothiazide, respectively. The separation was carried out on Merck HPTLC aluminum plates of silica gel 60 F254, using chloroform-ethylacetate-acetic acid (10:3:2 by vol.) as mobile phase. The linear and second order polynomial were used for the regression equation of lisinopril and hydrochlorothiazide, respectively. PMID:11377075

El-Gindy, A; Ashour, A; Abdel-Fattah, L; Shabana, M M

2001-07-01

174

A simple and rapid in situ preconcentration method for trace ammonia nitrogen in environmental water samples using a solid-phase extraction followed by spectrophotometric determination.  

PubMed

A simple and rapid in situ preconcentration method for the spectrophotometric determination of trace ammonia nitrogen in environmental water samples has been developed based on solid-phase extraction using a small column packed with octadecyl group-bonded silica gel (Sep-Pak C18 cartridge). A water sample was taken into a graduated syringe for easy and simple operation and prevention of contamination immediately after sample collection. Ammonia in the sample was reacted with hypochlorite and thymol to be converted into indothymol blue; then the formed indothymol blue was collected as an ion pair between indothymol blue and tetrabutylammonium ion on a Sep-Pak C18 cartridge. The indothymol blue on the cartridge was stable for 4 days. The retained indothymol blue was easily eluted with a mixture of methanol and 0.01 mol/l sodium hydroxide solution. The color intensity due to the indothymol blue was spectrophotometrically measured at 725 nm. The proposed method was successfully applied to environmental water samples such as river water. PMID:16363488

Okumura, Minoru; Honda, Sachiko; Fujinaga, Kaoru; Seike, Yasushi

2005-09-01

175

Improving Spectrophotometric Carbon System Measurements.  

E-print Network

??This work provides improved procedures for spectrophotometric carbon system measurements. Indicator dyes used for routine spectrophotometric pH measurements in seawater suffer from impurity issues, which… (more)

Patsavas, Mark

2014-01-01

176

Development and validation of a rapid stability indicating HPLC-method using monolithic stationary phase and two spectrophotometric methods for determination of antihistaminic acrivastine in capsules  

NASA Astrophysics Data System (ADS)

Simple, rapid and accurate high performance liquid chromatographic (HPLC) and spectrophotometric methods are described for determination of antihistaminic acrivastine in capsules. The first method (method A) is based on accurate, sensitive and stability indicating chromatographic separation method. Chromolith® Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, was used as stationary phase applying isocratic binary mobile phase of ACN and 25 mM NaH2PO4 pH 4.0 in the ratio of 22.5:77.5 at flow rate of 5.0 mL/min and 40 °C. A diode array detector was used at 254 nm for detection. The elution time of acrivastine was found to be 2.080 ± 0.032. The second and third methods (methods B and C) are based on the oxidation of acrivastine with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilic acid (?max: 520 nm) or amaranth dye (?max: 530 nm). The reacted oxidant corresponds to the drug content. Beer’s law is obeyed over the concentration range 1.563-50, 2.0-20 and 1.0-10 ?g mL-1 for methods A, B and C, respectively. The limits of detection and quantitation were 0.40, 0.292 and 0.113 ?g mL-1 and 0.782, 0.973 and 0.376 ?g mL-1 for methods A, B and C, respectively. The HPLC method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. Stability tests were done through exposure of the analyte solution for four different stress conditions and the results indicate no interference of degradants with HPLC-method. The proposed methods was favorably applied for determination of acrivastine in capsules formulation. Statistical comparison of the obtained results from the analysis of the studied drug to those of the reported method using t- and F-tests showed no significant difference between them.

Gouda, Ayman A.; Hashem, Hisham; Jira, Thomas

2014-09-01

177

Solidphase ultraviolet absorbance spectrophotometric multisensor for the simultaneous determination of butylated hydroxytoluene and co-existing antioxidants  

Microsoft Academic Search

Continuous flow injection and UV spectrophotometric detection have been proposed for simultaneous determination of the two binary mixtures, butylated hydroxytoluene (BHT)\\/n-propyl gallate (n-PG) and butylated hydroxytoluene (BHT)\\/butylated hydroxyanisole (BHA), in food and cosmetics samples. The method is based on the different residence times of each antioxidant when the flow cell is packed to a height of 25mm with silica C18

L. F. Capitán-Vallvey; M. C. Valencia; E. Arana Nicolás

2004-01-01

178

Simultaneous Spectrophotometric Estimation of Tenofovir Disoproxil Fumarate and Lamivudine in Three Component Tablet Formulation Containing Efavirenz  

PubMed Central

Three UV spectrophotometric methods have been developed, simultaneous equation method, multicomponent analysis (II) and derivative spectroscopy method (III). The absorption maxima of the drugs were found to be 247, 259 and 272 nm, respectively for efavirenz, tenofovir disoproxil fumarate and lamivudine in methanol:water (50:50) solvent system. Efavirenz, tenofovir disoproxil fumarate and lamivudine obeyed Beer’s law in the concentration range of 10-60, 5-30 and 5-30 ?g/ml, respectively. Results of analysis for all the three methods were analyzed and validated for various parameters according to ICH guidelines. PMID:21218073

Sharma, R.; Mehta, K.

2010-01-01

179

An experimental method for determining the UV susceptibility of airborne microorganisms using an upper room UV field  

Microsoft Academic Search

With the global rise in tuberculosis cases, coupled with the emergence of strains of Mycobacterium tuberculosis which are multiply-antibiotic resistant, interest has been renewed in the use of upper-room UV systems to control the spread of airborne infection. Whilst a number of researchers have demonstrated that upper-room UV fields might be effective, it is technically difficult to determine the performance

CB Beggs; LA Fletcher; PA Sleigh; KG Kerr; CJ Noakes

180

A UV spectroscopic method for monitoring aromatic hydrocarbons dissolved in water  

Microsoft Academic Search

An enhanced UV spectrometric method is applied to trace measurements of aromatic hydrocarbons dissolved in water. This approach gains selectivity and sensitivity by the use of optically generated first and second derivatives of transmission spectra. The augmented spectroscopic technique is combined with chemometric algorithms like principal component regression or partial least squares which are used for calibration of the spectrometer

F. Vogt; M. Tacke; M. Jakusch; B. Mizaikoff

2000-01-01

181

An in vivo method to assess the photostability of UV filters in a sunscreen.  

PubMed

An in vivo method was developed in order to study the photostability of UV filters in a sunscreen. This method assesses sunscreen photostability in the emulsion after direct interaction with the skin. For this purpose UV filters were recovered from volunteers' forearms by using the stripping technique, then extracted from tapes and quantified by high-performance liquid chromatography (HPLC). The photostability of the filters tested was evaluated by comparing the amount of filters recovered from the strippings of UV-irradiated skin (40 minimal erythema dose, or MED) versus non-irradiated skin. Sequential analysis of several successive tapes reflected the distribution profile of the filters in the stratum corneum. Photochemical change was observed for one filter: it was shown to undergo a photochemical modification with the appearance of an additional HPLC peak. Moreover, UV filters tested displayed a high affinity for the stratum corneum but presented different distribution profiles. This in vivo method takes into account the interaction of the sunscreen agents with the stratum corneum. Furthermore, unlike spectrometric methods usually used for photostability assessment, it gives quantitative data for each individual filter of a finished product by using an HPLC technique. PMID:11382839

Cambon, M; Issachar, N; Castelli, D; Robert, C

2001-01-01

182

Microwave-assisted of dispersive liquid-liquid microextraction and spectrophotometric determination of uranium after optimization based on Box-Behnken design and chemometrics methods.  

PubMed

In this study an analytical procedure based on microwave-assisted dispersive liquid-liquid microextraction (MA-DLLME) and spectrophotometric coupled with chemometrics methods is proposed to determine uranium. In the proposed method, 4-(2-pyridylazo) resorcinol (PAR) is used as a chelating agent, and chloroform and ethanol are selected as extraction and dispersive solvent. The optimization strategy is carried out by using two level full factorial designs. Results of the two level full factorial design (2(4)) based on an analysis of variance demonstrated that the pH, concentration of PAR, amount of dispersive and extraction solvents are statistically significant. Optimal condition for three variables: pH, concentration of PAR, amount of dispersive and extraction solvents are obtained by using Box-Behnken design. Under the optimum conditions, the calibration graphs are linear in the range of 20.0-350.0ngmL(-1) with detection limit of 6.7ngmL(-1) (3?B/slope) and the enrichment factor of this method for uranium reached at 135. The relative standard deviation (R.S.D.) is 1.64% (n=7, c=50ngmL(-1)). The partial least squares (PLS) modeling was used for multivariate calibration of the spectrophotometric data. The orthogonal signal correction (OSC) was used for preprocessing of data matrices and the prediction results of model, with and without using OSC, were statistically compared. MA-DLLME-OSC-PLS method was presented for the first time in this study. The root mean squares error of prediction (RMSEP) for uranium determination using PLS and OSC-PLS models were 4.63 and 0.98, respectively. This procedure allows the determination of uranium synthesis and real samples such as waste water with good reliability of the determination. PMID:25062051

Niazi, Ali; Khorshidi, Neda; Ghaemmaghami, Pegah

2015-01-25

183

Simultaneous Determination of 6-Mercaptopurine and its Oxidative Metabolites in Synthetic Solutions and Human Plasma using Spectrophotometric Multivariate Calibration Methods  

PubMed Central

Introduction 6-Mercaptopurine (6MP) is an important chemotherapeutic drug in the conventional treatment of childhood acute lymphoblastic leukemia (ALL). It is catabolized to 6-thiouric acid (6TUA) through 8-hydroxo-6-mercaptopurine (8OH6MP) or 6-thioxanthine (6TX) intermediates. Methods High-performance liquid chromatography (HPLC) is usually used to determine the contents of therapeutic drugs, metabolites and other important biomedical analytes in biological samples. In the present study, the multivariate calibration methods, partial least squares (PLS-1) and principle component regression (PCR) have been developed and validated for the simultaneous determination of 6MP and its oxidative metabolites (6TUA, 8OH6MP and 6TX) without analyte separation in spiked human plasma. Mixtures of 6MP, 8-8OH6MP, 6TX and 6TUA have been resolved by PLS-1 and PCR to their UV spectra. Results Recoveries (%) obtained for 6MP, 8-8OH6MP, 6TX and 6TUA were 94.5-97.5, 96.6-103.3, 95.1-96.9 and 93.4-95.8, respectively, using PLS-1 and 96.7-101.3, 96.2-98.8, 95.8-103.3 and 94.3-106.1, respectively, using PCR. The NAS (Net analyte signal) concept was used to calculate multivariate analytical figures of merit such as limit of detection (LOD), selectivity and sensitivity. The limit of detections for 6MP, 8-8OH6MP, 6TX and 6TUA were calculated to be 0.734, 0.439, 0.797 and 0.482 ?mol L-1, respectively, using PLS and 0.724, 0.418, 0783 and 0.535 ?mol L-1, respectively, using PCR. HPLC was also applied as a validation method for simultaneous determination of these thiopurines in the synthetic solutions and human plasma. Conclusion Combination of spectroscopic techniques and chemometric methods (PLS and PCR) has provided a simple but powerful method for simultaneous analysis of multicomponent mixtures PMID:23678408

Sorouraddin, Mohammad-Hossein; Khani, Mohammad-Yaser; Amini, Kaveh; Naseri, Abdolhossein; Asgari, Davoud; Rashidi, Mohammad-Reza

2011-01-01

184

Quantitative HPLC-UV method for the determination of firocoxib from horse and dog plasma  

Microsoft Academic Search

A sensitive reversed-phase HPLC-UV method was developed for the determination of firocoxib, a novel and highly selective COX-2 inhibitor, in plasma. A 1.0mL dog or horse plasma sample is mixed with water and passed through a hydrophobic–lipophilic copolymer solid-phase extraction column to isolate firocoxib. Quantitation is based on an external standard curve. The method has a validated limit of quantitation

Valerie Kvaternick; Thomas Malinski; Jill Wortmann; James Fischer

2007-01-01

185

Spectrophotometric Determination of Steroid Oximes  

Microsoft Academic Search

A spectrophotometric procedure for the determination of steroid oximes is described utilizing 11?-hydroxy-iia-methyl-5?-pregnane -3, 20 -dione dioxime (I) and iia-hydroxy-progesterone dioxime (II) as models. The method is based on (a) acid hydrolysis to release hydroxylamine, (b) oxidation of hydroxylamine to nitrous acid with iodine, (c) diazotization of sulfanilic acid with the nitrous acid, (d) coupling of the diazonium compound with

Arlington A. Forist; Ray W. Judy

1974-01-01

186

Kinetics and reaction pathways of formaldehyde degradation using the UV-fenton method.  

PubMed

This study was based on the purpose of investigating the reaction rules of formaldehyde (HCHO) as an intermediate product in the degradation of many other organic wastewaters. The process conditions of UV-Fenton method for the degradation of the low concentrations of HCHO were studied in a batch photochemical reactor. The results showed that, when the original HCHO concentration was 30 mg/L, at an operating temperature of 23 degrees C, pH = 3, an H202 dosage of 68 mg/L, and an H2O2-to-Fe2+ mole ratio (H2O2:Fe2+) of 5, 91.89% of the HCHO was removed after 30 minutes. The degradation of HCHO in the UV-Fenton system was basically in accordance with the exponential decay. The kinetic study results showed that the reaction orders of HCHO, Fe2+, and H2O2 in the system were 1.054, 0.510, and 0.728, respectively, and the activation energy (Ea) was 9.85 kJ/mol. The comparison of UV/H2O2, Fenton, and UV-Fenton systems for the degradation of HCHO, and the results of iron catalyst tests showed that the mechanism of UV-Fenton on the degradation of HCHO was through a synergistic effect of Fe2+ and UV light to catalyze the decomposition of H2O2. The introduction of UV irradiation to the Fenton system largely increased the degradation rate of HCHO, mainly as a result of the accelerating effect on the formation of the Fe2+/Fe3+ cycle. The reaction products were analyzed by gas chromatography-mass spectrometry and a chemical oxygen demand (COD) analyzer. The effluent gases also were analyzed by gas chromatography. Based on those results, the reaction pathways of HCHO in the UV-Fenton system were proposed. The qualitative and quantitative analysis of the reaction products and the COD showed that the main intermediate product of the reaction was formic acid, and the further oxidation of it was the rate-limiting step for the degradation of HCHO. PMID:21657193

Liu, Xiangxuan; Liang, Jiantao; Wang, Xuanjun

2011-05-01

187

A simple spectrophotometric method for the determination of arsenic in industrial and environmental samples using 2,4-Dihydroxy benzophenone-2-amino thiophenol.  

PubMed

2,4-Dihydroxy benzophenone-2-amino thiophenol (BPBT) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of arsenic. The reagent reacts with arsenic in acidic medium (pH=6.0, sodium acetate-acetic acid buffer) to form light greenish yellow colored 1:1 (M:L) complex. Maximum absorbance was obtained at 343 nm and remains constant for over 24 h. The molar absorptivity and Sandell's sensitivity of BPBT are found to be 6.01×10(4) L mol(-1)cm(-1) and 0.0016 ?g cm(-2) respectively. The system obeys Beer's law in the range of 0.125-2.637 ?g/ml of As (III). Since BPBT method is more sensitive, it was applied for the determination of arsenic in some environmental water samples. PMID:24468982

Deepa, K; Lingappa, Y

2014-04-24

188

Stability indicating HPLC-UV method for determination of dapoxetine HCl in pharmaceutical product.  

PubMed

A stability-indicating HPLC-UV method for the determination of dapoxetine hydrochloride in solution and pharmaceutical product was developed. The mobile phase was composed of acetonitrile and 0.2 M ammonium acetate buffer at 50 : 50 ratio. The chromatographic parameters, theoretical plates (N), tailing factor (T), capacity factor (k') and peak asymmetry factor (As) were calculated. Stress degradation studies, namely, acid, alkali, oxidation, heat and UV light, were performed. The analyte was eluted at 5.8 min using gradient system at a flow rate of 1.5 mL/min. The theoretical plates count was > 2000, tailing factor < 1.54, capacity factor > 5.38 and peak asymmetry factor was < 1.10. The method was linear from 1 to 40 microg/mL with a correlation coefficient of 0.9994. The intraday precision and accuracy values were 0.14-1.54% and 0.63-1.83%, respectively. On the other hand, the interday precision and accuracy results were 0.49-1.83% and 1.15-1.85%, respectively. The drug solution was stable at ambient room temperature (26 degrees C) for 48 h. Dapoxetine HCI was found susceptible to oxidation and degraded slightly under acid and alkali conditions but was stable under UV light and heat. No interference from tablet excipiets and degradation products was found. Hence, the method can be employed as a stability-indicating method for the determination of dapoxetine HCl in pharmaceutical products. PMID:25265818

Liew, Kai Bin; Peh, Kok Khiang

2014-01-01

189

Simultaneous determination of Allura Red and Ponceau 4R in drinks with the use of four derivative spectrophotometric methods and comparison with high-performance liquid chromatography.  

PubMed

Four simple, rapid, sensitive, and accurate spectrophotometric methods were developed for the simultaneous determination of Allura Red (AR) and Ponceau 4R (P) without previous chemical separation. The first method, derivative spectrophotometry, depends on first derivative spectrophotometry with zero-crossing and peak-to-base measurement. The second method, derivative ratio spectrophotometry, uses the first derivative of the ratio spectra. The ratio spectra are obtained by dividing the absorption spectra of a binary mixture by that of one of the components. The third method, differential derivative spectrophotometry, is based on the measurement of the difference absorptivities derivatized in the first order of a sample extract in 0.1 M NaOH relative to that of an equimolar solution in 0.1 M HCl. The fourth method, based on the compensation technique, is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra by using ratios of the derivative maximum or minimum; the exact compensation of either component in the mixture can be achieved, followed by its determination. All the proposed methods were successfully applied to the determination of the colorants in their laboratory mixtures and granulated drinks without any interference by the ingredients. AR and P showed good linearity, with regression coefficients of 0.9994-0.9999. The LOD and LOQ values ranged from 0.059 to 0.102 and 0.198 to 0.341 microg/mL, respectively. The intraday and interday precision tests produced good RSD values (<1.37%); recoveries ranged from 98.75 to 100.37% for all four methods. The common ingredients and additives did not interfere in the AR and P determination. The results of the proposed methods were statistically compared with the results of an HPLC method given in the literature (Nordic Committee on Food Analysis; NMKL 130) at the 95% confidence level by Student's test and the variance ratio F-test. No statistically significant difference was found among these methods. PMID:24645518

Turak, Fatma; Ozgur, Mahmure Ustun

2013-01-01

190

Development of an reliable analytical method for synergistic extractive spectrophotometric determination of cobalt(II) from alloys and nano composite samples by using chromogenic chelating ligand.  

PubMed

A synergistic simple and selective spectrophotometric method was developed for the determination of cobalt(II) with 1-(2',4'-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2',4'-dinitro APTPT] as a chromogenic reagent. The proposed method has been described on the basis of synergistic effective extraction of cobalt(II) in presence of pyridine at pH range 9.5-10.2, showed orange-red coloured ternary complex having molar ratio 1:2:2 (M:L:Py). The equilibrium time is 10 min for extraction of cobalt(III) from organic phase. The absorbance of coloured organic layer in chloroform is measured spectrophotometrically at 490 nm against reagent blank. The Beer's law was obeyed in the concentration range 2.5-15 ?g mL(-1) of cobalt(II) and optimum concentration range was 5-12.5 ?g mL(-1) of cobalt(II) and it was evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of cobalt(II)-2',4'-dinitro APTPT-pyridine complex in chloroform are 1.109×10(3) L mol(-1) cm(-1) and 0.053 ?g cm(-2), respectively while molar absorptivity and Sandell's sensitivity of cobalt(II)-2',4'-dinitro APTPT complex in chloroform are 6.22×10(2) L mol(-1) cm(-1) and 0.096 ?g cm(-2), respectively. The composition of cobalt(II)-2',4'-dinitro APTPT-pyridine complex (1:2:2) was established by slope ratio method, mole ratio method and Job's method of continuous variation. The ternary complex was stable for more than 48 h. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The method is successfully applied for the determination of cobalt(II) in binary, synthetic mixtures and real samples. A repetition of the method was checked by finding relative standard deviation (R.S.D.) for n=5 which was 0.15%. The reliability of the method is confirmed by comparison of experimental results with atomic absorption spectrophotometer. PMID:21978559

Kamble, Ganesh S; Ghare, Anita A; Kolekar, Sanjay S; Han, Sung H; Anuse, Mansing A

2011-12-15

191

Synthesis and Characterization of Silver\\/Clay\\/Chitosan Bionanocomposites by UV-Irradiation Method  

Microsoft Academic Search

Problem statement: Silver\\/Montmorillonite\\/Chitosan Bionanocomposites (Ag\\/MMT\\/Cts BNCs) have been synthesized by UV-irradiation reduction method in the absence of any reducing agent or heat treatment which is used to antibacter ial application and medical devices. Approach: MMT, Chitosan and AgNO 3 were used as a solid support, stabilizer and silve r precursor, respectively. The properties of Ag\\/MMT\\/Cts BNCs were studied as a

Mansor Bin Ahmad; Kamyar Shameli; Majid Darroudi

192

Development and validation of an high-performance liquid chromatographic, and a ultraviolet spectrophotometric method for determination of Ambroxol hydrochloride in pharmaceutical preparations  

PubMed Central

A high-performance liquid chromatographic (HPLC) and ultraviolet (UV) methods were developed and validated for the quantitative determination of Ambroxol hydrochloride (AMH) in pharmaceutical dosage form. HPLC was carried out by reversed phase (RP) technique on an RP-18 column with a mobile phase composed of acetonitrile and water (pH 3.5 adjusted with orthophosphoric acid [60:40, v/v]). UV method was performed with the ?max at 250 nm. Both the methods showed good linearity, reproducibility, and precision. No spectral or chromatographic interferences from the tablet excipients were found in UV and HPLC. The method was successfully applied to commercial tablets. Validation parameters such as linearity, precision, accuracy, and specificity were determined. The HPLC Limit of detection (LOD) and Limit of quantification (LOQ) for Ambroxol were found to be 1 and 5 ng/ml, respectively. The UV LOD and LOQ for Ambroxol were found to be 1 and 4 ?g/ml, respectively. The results were statistically compared using one-way analysis of variance. The proposed economical method could be applicable for routine analysis of AMH and monitoring of the quality of marketed drugs. PMID:23662284

Muralidharan, Selvadurai; Kumar, Jaya Raja; Dhanara, Sokkalingam Arumugam

2013-01-01

193

Development and validation of an high-performance liquid chromatographic, and a ultraviolet spectrophotometric method for determination of Ambroxol hydrochloride in pharmaceutical preparations.  

PubMed

A high-performance liquid chromatographic (HPLC) and ultraviolet (UV) methods were developed and validated for the quantitative determination of Ambroxol hydrochloride (AMH) in pharmaceutical dosage form. HPLC was carried out by reversed phase (RP) technique on an RP-18 column with a mobile phase composed of acetonitrile and water (pH 3.5 adjusted with orthophosphoric acid [60:40, v/v]). UV method was performed with the ?max at 250 nm. Both the methods showed good linearity, reproducibility, and precision. No spectral or chromatographic interferences from the tablet excipients were found in UV and HPLC. The method was successfully applied to commercial tablets. Validation parameters such as linearity, precision, accuracy, and specificity were determined. The HPLC Limit of detection (LOD) and Limit of quantification (LOQ) for Ambroxol were found to be 1 and 5 ng/ml, respectively. The UV LOD and LOQ for Ambroxol were found to be 1 and 4 ?g/ml, respectively. The results were statistically compared using one-way analysis of variance. The proposed economical method could be applicable for routine analysis of AMH and monitoring of the quality of marketed drugs. PMID:23662284

Muralidharan, Selvadurai; Kumar, Jaya Raja; Dhanara, Sokkalingam Arumugam

2013-01-01

194

Cisapride a green analytical reagent for rapid and sensitive determination of bromate in drinking water, bread and flour additives by oxidative coupling spectrophotometric methods.  

PubMed

Green analytical methods using Cisapride (CPE) as green analytical reagent was investigated in this work. Rapid, simple, and sensitive spectrophotometric methods for the determination of bromate in water sample, bread and flour additives were developed. The proposed methods based on the oxidative coupling between phenoxazine and Cisapride in the presence of bromate to form red colored product with max at 520 nm. Phenoxazine and Cisapride and its reaction products were found to be environmentally friendly under the optimum experimental condition. The method obeys beers law in concentration range 0.11-4.00 g ml(-1) and molar absorptivity 1.41 × 10(4) L mol(-1)cm(-1). All variables have been optimized and the presented reaction sequences were applied to the analysis of bromate in water, bread and flour additive samples. The performance of these method was evaluated in terms of Student's t-test and variance ratio F-test to find out the significance of proposed methods over the reference method. The combination of pharmaceutical drugs reagents with low concentration create some unique green chemical analyses. PMID:23261631

Al Okab, Riyad Ahmed

2013-02-15

195

Kinetic spectrophotometric H-point standard addition method for the simultaneous determination of diloxanide furoate and metronidazole in binary mixtures and biological fluids.  

PubMed

Simple, reliable, and sensitive kinetic spectrophotometric method has been developed for the simultaneous determination of diloxanide furoate and metronidazole using H-point standard addition method (HPSAM). The method is based on the oxidation rate difference of diloxanide and metronidazole by potassium permanganate in basic medium. A green color has been developed and measured at 610 nm. Different experimental parameters were carefully optimized. The limiting logarithmic and the initial-rate methods were adopted for the construction of the calibration curve of each individual reaction with potassium permanganate. Under the optimum conditions, Beer's law was obeyed in the range of 1.0-20.0 and 5.0-25.0 ?g ml(-1) for diloxanide furoate and metronidazole, respectively. The detection limits were 0.22 ?g ml(-1) for diloxanide furoate and 0.83 ?g ml(-1) for metronidazole. Correlation coefficients of the regression equations were greater than 0.9970 in all cases. The precision of the method was satisfactory; the maximum value of relative standard deviation did not exceed 1.06% (n=5). The accuracy, expressed as recovery was between 99.4% and 101.4% with relative error of 0.12 and 0.14 for diloxanide furoate and metronidazole, respectively. The proposed method was successfully applied for the simultaneous determination of both drugs in pharmaceutical dosage forms and human urine samples and compared with alternative HPLC method. PMID:23807049

Issa, Mahmoud Mohamed; Nejem, R'afat Mahmoud; Abu Shanab, Alaa Mohamed; Shaat, Nahed Talab

2013-10-01

196

Cisapride a green analytical reagent for rapid and sensitive determination of bromate in drinking water, bread and flour additives by oxidative coupling spectrophotometric methods  

NASA Astrophysics Data System (ADS)

Green analytical methods using Cisapride (CPE) as green analytical reagent was investigated in this work. Rapid, simple, and sensitive spectrophotometric methods for the determination of bromate in water sample, bread and flour additives were developed. The proposed methods based on the oxidative coupling between phenoxazine and Cisapride in the presence of bromate to form red colored product with max at 520 nm. Phenoxazine and Cisapride and its reaction products were found to be environmentally friendly under the optimum experimental condition. The method obeys beers law in concentration range 0.11-4.00 g ml-1 and molar absorptivity 1.41 × 104 L mol-1 cm-1. All variables have been optimized and the presented reaction sequences were applied to the analysis of bromate in water, bread and flour additive samples. The performance of these method was evaluated in terms of Student's t-test and variance ratio F-test to find out the significance of proposed methods over the reference method. The combination of pharmaceutical drugs reagents with low concentration create some unique green chemical analyses.

Al Okab, Riyad Ahmed

2013-02-01

197

Spectrophotometric determination of ethacridine lactate in infusion  

PubMed Central

Aim: A simple, rapid, selective, accurate, and precise UV spectrophotometric method has been developed for the estimation of ethacridine lactate from bulk and pharmaceutical formulation. Materials and Methods: Appropriate aliquot portions of stock standard solution of ethacridine lactate were transferred into five separate 10 ml volumetric flasks, and the volume was adjusted to the mark with double distilled water to obtain concentrations of 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 ?g/ml. The ?max of ethacridine lactate in double distill water was found to be 271 nm with an apparent molar absorptivity of 59.781 × 103 l/mol cm. The drug follows linearity in the concentration range 2–12 ?g/ml with a correlation coefficient value of 0.998. Results: The proposed method was applied to pharmaceutical formulation and % amount of drug estimated 99.71% was found to be in good agreement with the label claim. The accuracy of the method was checked by recovery experiment performed at three different levels, i.e., 80%, 100%, and 120%. The % recovery was found to be in the range 99.26–100.25%. The low values of % RSD are indicative of the accuracy and reproducibility of the method. The precision of the method was studied as intraday, interday variations and repeatability. The % RSD value less than 2 indicates that the method is precise. Ruggedness of the proposed method was studied with the help of two analysts. Conclusion: The results indicated that the method could be used for the routine estimation of ethacridine lactate from tablet formulations. PMID:23781454

Jain, Pritam S.; Surana, S. J.

2011-01-01

198

Spectrophotometric catalogs and databases  

NASA Astrophysics Data System (ADS)

An overview is given of different spectrophotometric catalogs, including a brief description of the applications of absolute spectrophotometry in evolutionary population synthesis. Observational data for different stars are given. A list of catalogs is presented, including those containing intrinsic energy distributions for stars of different temperatures and luminosities, spectrophotometric standards, extragalactic sources, and theoretically calculated spectra. A number of useful links and Internet resources are provided.

Burnashev, V. I.; Burnasheva, B. A.

2014-06-01

199

A membraneless gas-diffusion unit-multisyringe flow injection spectrophotometric method for ammonium determination in untreated environmental samples.  

PubMed

A new design of a membraneless gas-diffusion (MGD) unit coupled to a multisyringe flow injection system is proposed. The spectrophotometric determination of ammonium using an acid-base indicator was chosen to show the feasibility of this approach. Hence, in alkaline medium, ammonium ions are transformed into ammonia (donor channel) which diffuses through the headspace into the acceptor stream (bromothymol blue solution), causing a pH change and subsequently a colour change. The exploitation of the enhanced potentialities of this re-designed MGD device was the main purpose of the present work. Hence, several strategies concerning flow management were studied seeking to characterize and improve the analytical features of the methodology and moreover, untreated environmental samples were analysed without previous filtration. Consequently, stopped flow in acceptor channel with continuous flow in donor channel was chosen for the application to wastewater and spiked river water samples. A linear concentration range between 10.0 and 50.0 mg L(-1) of NH(4)(+), a limit of detection of 2.20 mg L(-1) and a determination frequency of 11h(-1) were obtained. PMID:21641433

Almeida, M Inês G S; Estela, José Manuel; Segundo, Marcela A; Cerdà, Víctor

2011-06-15

200

Extractive Spectrophotometric Determination of Ambrisentan  

PubMed Central

Purpose: Ambrisentan (ABS) is an antihypertensive drug used in the treatment of pulmonary atrial hypertension. The survey of literature for ABS revealed only two spectrophotometric methods for its quantification. The reported methods lack the sensitivity. This study is aimed at developing two sensitive extractive spectrophotometric methods for the determination of ABS in bulk and in tablets. Methods: The proposed methods are based on the formation of colored chloroform extractable ion-pair complexes of ABS with methylene blue (MB method) and safranine O (SO method) in buffered solution at pH 9.8. The extracted complexes showed maximum absorbance at 525 and 515 nm for methylene blue and safranine O, respectively. Results: In both the methods, the calibration curve was linear from 1–15 µg mL-1 of drug. Apparent molar absorpitivities were 1.7911 x 105, 2.3272 x 105 L mol-1 cm-1; Sandell’s sensitivities were 0.0215, 0.0162 µg cm-2; LOD were 0.182, 0.175 µg mL-1; LOQ were 0.551, 0.531 µg mL-1 for methods MB and SO, respectively. The relative standard deviation and percent recovery ranged from 0.206–1.310% and 99.0–101.5%, respectively. Conclusion: The results demonstrate that the proposed methods are sensitive, precise, accurate and inexpensive. These methods can easily be used for the assay of ABS in quality control laboratories. PMID:24312841

Kumar, Namasani Santhosh; Rani, Avula Prameela; Visalakshi, Telu; Sekharan, Chandra Bala

2013-01-01

201

An improved UHPLC-UV method for separation and quantification of carotenoids in vegetable crops.  

PubMed

Carotenoid identification and quantitation is critical for the development of improved nutrition plant varieties. Industrial analysis of carotenoids is typically carried out on multiple crops with potentially thousands of samples per crop, placing critical needs on speed and broad utility of the analytical methods. Current chromatographic methods for carotenoid analysis have had limited industrial application due to their low throughput, requiring up to 60 min for complete separation of all compounds. We have developed an improved UHPLC-UV method that resolves all major carotenoids found in broccoli (Brassica oleracea L. var. italica), carrot (Daucus carota), corn (Zea mays), and tomato (Solanum lycopersicum). The chromatographic method is completed in 13.5 min allowing for the resolution of the 11 carotenoids of interest, including the structural isomers lutein/zeaxanthin and ?-/?-carotene. Additional minor carotenoids have also been separated and identified with this method, demonstrating the utility of this method across major commercial food crops. PMID:25038701

Maurer, Megan M; Mein, Jonathan R; Chaudhuri, Swapan K; Constant, Howard L

2014-12-15

202

A Novel Dry Develop Method Of Photoresist - "Unzipping Development" By Flood UV Irradiation  

NASA Astrophysics Data System (ADS)

A novel dry develop method of photoresist - "unzipping development" by flood UV irradiation is described. Evaluated resist consisted of poly-methyl methacrylate (PMMA) and unzipping inhibitors such as p-benzoquinone (p-BQ) and 4,4'-diazide diphenylmethane(4,4'-DDM). As a preliminary experiment has shown that 4,4'-DDM was superior to p-BQ as an unzipping inhibitor, a resist : PMMA added with 40 wt% was mainly evaluated. At patterning exposure (600 ~ 1200 mJ/m2 at 210 ~ 280 nm), 4,4'-DDM in the exposed area fixed into polymer. Then, 4,4'-DDM in the unexposed area was removed in vacuo (0.4 mmHg at 120°C for 1 hr). Finally, negative resist pattern of 1.6 ?m was developed by flood UV irradiation (24 J/cm2 at 254 nm) at 90 ~ 130°C without using any solvent. Mechanistic studies were carried out by using IR and UV analyses.

Katsuragi, Hayato; Miyazaki, Masao; Ishikawa, Norio; Mori, Kiyoto; Yamada, Hitomi; Morita, Shinzo; Hattori, Shuzo

1988-01-01

203

Multiwavelength spectrophotometric determination of acid dissociation constants of ionizable drugs  

Microsoft Academic Search

A multiwavelength spectrophotometric approach has been developed to determine acid dissociation constants (pKa values) of sparingly soluble drug compounds. UV absorption spectra of the drug solution are acquired using a versatile device based on a fiber optics dip probe, a light source and a photodiode array (PDA) detector while the pH and the ionic strength of the chemical system is

R. I. Allen; K. J. Box; J. E. A. Comer; C. Peake; K. Y. Tam

1998-01-01

204

Method validation using weighted linear regression models for quantification of UV filters in water samples.  

PubMed

This paper describes the validation of a method consisting of solid-phase extraction followed by gas chromatography-tandem mass spectrometry for the analysis of the ultraviolet (UV) filters benzophenone-3, ethylhexyl salicylate, ethylhexyl methoxycinnamate and octocrylene. The method validation criteria included evaluation of selectivity, analytical curve, trueness, precision, limits of detection and limits of quantification. The non-weighted linear regression model has traditionally been used for calibration, but it is not necessarily the optimal model in all cases. Because the assumption of homoscedasticity was not met for the analytical data in this work, a weighted least squares linear regression was used for the calibration method. The evaluated analytical parameters were satisfactory for the analytes and showed recoveries at four fortification levels between 62% and 107%, with relative standard deviations less than 14%. The detection limits ranged from 7.6 to 24.1ngL(-1). The proposed method was used to determine the amount of UV filters in water samples from water treatment plants in Araraquara and Jau in São Paulo, Brazil. PMID:25281096

da Silva, Claudia Pereira; Emídio, Elissandro Soares; de Marchi, Mary Rosa Rodrigues

2015-01-01

205

CATALYTIC SPECTROPHOTOMETRIC DETERMINATION OF HEXAVALENT CHROMIUM  

Microsoft Academic Search

A simple, highly selective and sensitive catalytic method is presented for the determination of Cr in natural and highly polluted waste-waters. The method is based on the catalytic effect of Cr on the oxidation of 2-aminophenol (AP) with hydrogen peroxide. The reaction is followed spectrophotometrically by tracing the oxidation product at 430 nm after 10 minutes of mixing the reagents.

Ashraf A. Mohamed; Saleh A. Ahmed; Mohamed F. El-Shahat

2001-01-01

206

Simultaneous Determination of Potassium Clavulanate and Amoxicillin Trihydrate in Bulk, Pharmaceutical Formulations and in Human Urine Samples by UV Spectrophotometry.  

PubMed

A simple and sensitive UV spectrophotometric method was developed and validated for the simultaneous determination of Potassium Clavulanate (PC) and Amoxicillin Trihydrate (AT) in bulk, pharmaceutical formulations and in human urine samples. The method was linear in the range of 0.2-8.5 ?g/ml for PC and 6.4-33.6 ?g/ml for AT. The absorbance was measured at 205 and 271 nm for PC and AT respectively. The method was validated with respect to accuracy, precision, specificity, ruggedness, robustness, limit of detection and limit of quantitation. This method was used successfully for the quality assessment of four PC and AT drug products and in human urine samples with good precision and accuracy. This is found to be simple, specific, precise, accurate, reproducible and low cost UV Spectrophotometric method. PMID:23675211

Gujral, Rajinder Singh; Haque, Sk Manirul

2010-12-01

207

Simultaneous Determination of Potassium Clavulanate and Amoxicillin Trihydrate in Bulk, Pharmaceutical Formulations and in Human Urine Samples by UV Spectrophotometry  

PubMed Central

A simple and sensitive UV spectrophotometric method was developed and validated for the simultaneous determination of Potassium Clavulanate (PC) and Amoxicillin Trihydrate (AT) in bulk, pharmaceutical formulations and in human urine samples. The method was linear in the range of 0.2–8.5 ?g/ml for PC and 6.4–33.6 ?g/ml for AT. The absorbance was measured at 205 and 271 nm for PC and AT respectively. The method was validated with respect to accuracy, precision, specificity, ruggedness, robustness, limit of detection and limit of quantitation. This method was used successfully for the quality assessment of four PC and AT drug products and in human urine samples with good precision and accuracy. This is found to be simple, specific, precise, accurate, reproducible and low cost UV Spectrophotometric method. PMID:23675211

Gujral, Rajinder Singh; Haque, Sk Manirul

2010-01-01

208

Detection of ibuprofen and ciprofloxacin by solid-phase extraction and UV/Vis spectroscopy  

NASA Astrophysics Data System (ADS)

A simple and economic solid-phase extraction coupled with UV/Vis spectrophotometric method is described for the analysis of ibuprofen and ciprofloxacin. Following solid-phase extraction from model wastewater samples containing standard ibuprofen or ciprofloxacin, elutes were analyzed by a UV/Vis spectrophotometer at 225 nm for ibuprofen and 280 nm for ciprofloxacin. The assay was linear for both compounds with good coefficients of correlation. This method shows good recoveries for both compounds with 101.0 ± 9.8% for ibuprofen and 99.4 ± 11.8% ciprofloxacin.

Zhou, Zhengwei; Jiang, Jia Qian

2012-07-01

209

A simple spectrophotometric method for the determination of cobalt in industrial, environmental, biological and soil samples using bis(salicylaldehyde)orthophenylenediamine.  

PubMed

Bis(salicylaldehyde)orthophenylenediamine (BSOPD) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of cobalt. It reacts with cobalt in slightly acidic (0.0002-0.001 M H(2)SO(4)) 50% 1,4-dioxanic medium to form a red-orange chelate with a molar ratio 1:1. The reaction is instantaneous and the maximum absorbance was obtained at 458 nm and remains constant for over 24h. The average molar absorption coefficient and Sandell's sensitivity were found to be 1.109 x 10(4)l mol(-1)cm(-1) and 20 ng cm(-2) of Co(II), respectively. Linear calibration graph was obtained for 0.1-15 mg l(-1) of Co(II) with a correlation coefficient value of 0.995 for Co-BSOPD complex. Large excess of 44 cations, anions and complexing agents do not interfere in the determination. The method was successfully used in the determination of cobalt(II) from synthetic mixture and certified reference materials for the purpose of validating the method and the results of analyses were found to be excellent agreement with those of actual values. This developed method was also used for determination of cobalt in some environmental waters (potable and polluted), biological (blood and urine) and soil samples and solution containing both cobalt(II) and cobalt(III). The results of the proposed method for biological samples were comparable with AAS and were found to be in good agreement. The method has high precision and accuracy (s=+/-0.01 for 0.5 mg l(-1)). PMID:17215023

Ahmed, M Jamaluddin; Uddin, M Nasir

2007-05-01

210

Minor polar compounds in extra virgin olive oil: correlation between HPLC-DAD-MS and the Folin-Ciocalteu spectrophotometric method.  

PubMed

Minor polar compounds of 88 extra virgin olive oils were analyzed by HPLC-DAD-MS (high-performance liquid chromatography-diode array detector-mass spectrometry) and by the Folin-Ciocalteu (FC) spectrophotometric method, to validate and evaluate, for olive oils, the linear association between FC and HPLC data. The Pearson correlation coefficients were calculated between HPLC and FC results. The highest, positive R were related with deacetoxyoleuropein aglycone (R = 0.93) and oleuropein aglycone (R = 0.93) as single compounds and with the sum of orthodiphenols (R = 0.94) and the sum of all compounds (R = 0.95), showing that both estimations of total phenols content are reliably correlated, regardless for the absolute contents and are independent of the relative composition of the phenolic fraction. On the other hand the HPLC quantifications of apigenin and lignans showed no significant correlation with FC. These results, supported also by principal component analysis, may suggest caution about the interpretation of FC results to compare olive oils with very different phenolic profiles. PMID:24405086

Alessandri, Stefano; Ieri, Francesca; Romani, Annalisa

2014-01-29

211

UV differential optical absorption method for measuring sulfur content in coal  

NASA Astrophysics Data System (ADS)

Determining the sulfur content in coal rapidly and accurately can provide a technical basis for the enterprises and the environmental administration departments. A novel method for measuring the sulfur content in coal based on UV differential optical absorption is presented in this paper. However, compared with the applications in atmosphere monitoring, the UV differential optical absorption spectroscopy (DOAS) for the sulfur content measurement in coal has the problems that the concentration range of SO2 in the flue gas is wider and the optical path-length of the gas cell is shorter. To solve these problems, an improved DOAS algorithm based on a finite impulse response (FIR) filter and a nonlinear compensation technique is proposed. An experimental measurement system based on the modified DOAS is designed and established. The standard SO2 gas and five kinds of standard coals are experimentally tested. Theoretical and experimental results show that the lower detection limit of the system is better than 0.014%, and the repeatability of the measurement system fairly meets the national standard of China. The system has advantages of low maintenance and shorter measurement duration (4 min).

Song, Feihu; Xu, Chuanlong; Wang, Shimin

2012-02-01

212

A novel method to calculate solar UV exposure relevant to vitamin D production in humans.  

PubMed

We present a novel method to calculate vitamin D3 -weighted exposure by integrating the incident solar spectral radiance over all relevant parts of the human body. Earlier investigations are based on the irradiance on surfaces, whereas our calculated exposure of a voxel model of a human takes into account the complex geometry of the radiation field. Assuming that sufficient vitamin D3 (1000 international units) can be produced within the human body in one minute for a completely uncovered body in vertical posture in summer at midlatitudes (e.g. Rome, June 21, noon, UV index of 10), we calculate the exposure times needed in other situations or seasons to gain enough vitamin D3 . Our calculations show that the UV index is not a good indicator for the exposure which depends on the orientation of the body (e.g. vertical (standing) or horizontal (lying down) posture). Without clothing the exposure is dominated by diffuse sky radiation and it is nearly irrelevant how the body in vertical posture is oriented toward the sun. At the winter solstice (December 21, noon, cloudy) at least in central Europe sufficient vitamin D3 cannot be obtained with realistic clothing, even if the exposure were extended to all daylight hours. PMID:23517086

Seckmeyer, Gunther; Schrempf, Michael; Wieczorek, Anna; Riechelmann, Stefan; Graw, Kathrin; Seckmeyer, Stefan; Zankl, Maria

2013-01-01

213

Reliability-targeted HPLC-UV method validation--a protocol enrichment perspective.  

PubMed

Method validation is important in analytical chemistry to obtain the reliability of an analytical method. Guidelines provided by the regulatory bodies can be used as a general framework to assess the validity of a method. Since these guidelines do not focus on the reliability of analytical results exclusively, this study was aimed to combine a few recently evolved strategies that may render analytical method validation more reliable and trustworthy. In this research, the analytical error function was determined by appropriate polynomial regression statistics that determine the range of analyte concentration that may lead to more accurate measurements by producing the least possible total error in the assay and can be regarded as a reliable weighting method. The reliability of the analytical results over a particular concentration range has been proposed by a Bayesian probability study. In order to ensure the applicability of this approach, it was applied for the validation of an HPLC-UV assay method dedicated to the quantification of cefepime and tazobactam in human plasma. A comparison between the newer approach and the usual method validation revealed that the application of analytical error function and Bayesian analysis at the end of the validation process can produce significant improvements in the analytical results. PMID:24302678

Dharuman, Joghee Gowder; Vasudevan, Mahalingam

2014-02-01

214

A rapid spectrophotometric method for the determination of molybdenum in industrial, environmental, biological and soil samples using 5,7-dibromo-8-hydroxyquinoline.  

PubMed

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amount of molybdenum(VI) using 5,7-dibromo-8-hydroxyquinoline (DBHQ) has been developed. 5,7-Dibromo-8-hydroxyquinoline reacts in a slightly acidic solution (0.05 - 1.0 M H2SO4) with molybdenum(VI) to give a deep greenish-yellow chelate which has an absorption maximum at 401 nm. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 4.13 x 10(3) L mol(-1) cm(-1) and 7 ng cm(-2) of molybdenum(VI), respectively. Linear calibration graphs were obtained for 0.1 - 50 microg mL(-1) of molybdenum(VI). The stoichiometric composition of the chelate is 1:3 (Mo:DBHQ). A large excess of over 50 cations, anions and some common complexing agents (e.g. EDTA, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere with the determination. The method was successfully used in the determination of molybdenum in several Standard Reference Materials (alloys, steels and waters) as well as in some environmental waters (inland and surface), biological samples (human blood and urine), soil samples, solution containing both molybdenum(V) and molybdenum(VI) and complex synthetic mixtures. The method has high precision and accuracy (S = +/-0.01 for 0.5 microg mL(-1)). PMID:11999518

Ahmed, M Jamaluddin; Haque, M Enamul

2002-04-01

215

Quantification of protein concentration using UV absorbance and Coomassie dyes.  

PubMed

The measurement of a solubilized protein concentration in solution is an important assay in biochemistry research and development labs for applications ranging from enzymatic studies to providing data for biopharmaceutical lot release. Spectrophotometric protein quantification assays are methods that use UV and visible spectroscopy to rapidly determine the concentration of protein, relative to a standard, or using an assigned extinction coefficient. Where multiple samples need measurement, and/or the sample volume and concentration is limited, preparations of the Coomassie dye commonly known as the Bradford assay can be used. PMID:24423263

Noble, James E

2014-01-01

216

A Bayesian-Adaptive Decision Method for the V/UV/S Classification of Segments of a  

E-print Network

, a method forvoiced (V), unvoiced (UV), or silence (S) classification of speechsegments,based on the maximum. It is assumed that the vector x has an L-dimensional Gaussian dis- tribution with an expected random value also the probability density function(pdf) of the expected random values. I. INTRODUCTION In the past, various methods

Di Benedetto, Maria-Gabriella

217

Simultaneous determination of moexipril hydrochloride and hydrochlorothiazide in tablets by derivative spectrophotometric and high-performance liquid chromatographic methods.  

PubMed

Two new simple and selective assay methods have been presented for the binary mixtures of moexipril hydrochloride (MOEX) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations. The first method depends on second-derivative ultraviolet spectrophotometry with zero-crossing measurements at 215 and 234 nm for MOEX and HCTZ, respectively. The assay was linear over the concentration ranges 1.0-11.0 microg ml(-1) for MOEX and 0.5-9.0 microg ml(-1) for HCTZ. The determination limits for MOEX and HCTZ were found to be 1.0 and 0.5 microg ml(-1), respectively; while the detection limits were 0.2 microg ml(-1) for MOEX and 0.1 microg ml(-1) for HCTZ. The second method was based on isocratic reversed-phase liquid chromatography by using a mobile phase acetonitrile-20 mM phosphate buffer (pH 4.0) (50:50, v/v). Lisinopril was used as an internal standard (IS) and the substances were detected at 212 nm. The linearity range for both drugs was 0.5-12.0 microg ml(-1). The determination and detection limits were found to be 0.100 and 0.010 microg ml(-1) for MOEX and 0.025 and 0.005 microg ml(-1) for HCTZ, respectively. The proposed methods were successfully applied to the determination of these drugs in synthetic mixtures and commercially available tablets with a high percentage recovery, good accuracy and precision. PMID:14550868

Ertürk, Sidika; Cetin, Sevil Müge; Atmaca, Sedef

2003-10-15

218

A spectrophotometric assay method for vanadium in biological and environmental samples using 2,4-dinitrophenylhydrazine with imipramine hydrochloride.  

PubMed

A simple, rapid, and sensitive method involving the interaction of 2,4-dinitrophenylhydrazine with imipramine hydrochloride in presence of vanadium (V) in sulfuric acid medium has been proposed for the determination of vanadium. The purple-colored product developed showed an absorption maximum at 560 nm and was stable for 24 h. The working curve was linear over the concentration range of 0.1-2.8 ?g ml(?-?1), with sensitivity of detection of 0.0124 ?g ml(?-?1). Molar absorptivity and Sandell's sensitivity were found to be 2.6 × 10(4) l/mol cm and 0.0039 ?g cm(?-?1), respectively. The accuracy of the proposed method was assessed by Student's t test and variance ratio F test, and the results were on par with the reported method. The method was successfully used in the determination of V in water, human urine, soil, and plant samples, and it was free from interference by various concomitant ions. PMID:21625927

Al-Tayar, Naef Ghllab Saeed; Nagaraja, P; Vasantha, R A; Shresta, Ashwinee Kumar

2012-01-01

219

Differential spectrophotometric determination of mixed uranium(VI) and thorium(IV) by the stop-flow method  

SciTech Connect

From a study of the kinetics of the reaction between Th(IV) and U(VI) and Arsenazo III a method, based on the time-selection principle, has been developed for the differential deterential determination of these ions in a mixture in the ratio of 5:1.

Pogonin, V.I.; Likhonin, E.A.; Savvin, S.B.; Chibisov, A.K.

1986-10-20

220

A rapid spectrophotometric method for the determination of trace level lead using 1,5-diphenylthiocarbazone in aqueous micellar solutions.  

PubMed

A very simple, ultra-sensitive and fairly selective direct spectrophotmetric method is presented for the rapid determination of lead(II) at ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) in micellar media. The presence of the micellar system avoids the previous steps of solvent extraction and reduces the cost and toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The molar absorptivities of the lead-dithizone complex formed in the presence of the cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost ten times the value observed in the standard method, resulting in an increase in the sensitivity of the method. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption coefficient was found to be 3.99 x 10(5) L mol(-1) cm(-1) and Sandell's sensitivity was 30 ng cm(-2) of Pb. Linear calibration graphs were obtained for 0.06-60 mg L(-1) of Pb(II); the stoichiometric composition of the chelate is 1:2 (Pb:dithizone). The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L(-1) of Pb(II). The method was successfully used in the determination of lead in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), biological samples (human blood and urine), soil samples and solutions containing both lead(II) and lead(IV) and complex synthetic mixtures. The method has high precision and accuracy (sigma = +/-0.01 for 0.5 mg L(-1)). PMID:17297232

Khan, Humaira; Ahmed, M Jamaluddin; Bhanger, M Iqbal

2007-02-01

221

Quantitative HPLC-UV method for the determination of firocoxib from horse and dog plasma.  

PubMed

A sensitive reversed-phase HPLC-UV method was developed for the determination of firocoxib, a novel and highly selective COX-2 inhibitor, in plasma. A 1.0 mL dog or horse plasma sample is mixed with water and passed through a hydrophobic-lipophilic copolymer solid-phase extraction column to isolate firocoxib. Quantitation is based on an external standard curve. The method has a validated limit of quantitation of 25 ng/mL and a limit of detection of 10 ng/mL. The validated upper limit of quantitation was 2500 ng/mL for horses and 10,000 ng/mL for dogs. The average recoveries ranged from 88-93% for horse plasma and 96-103% for dog plasma. The coefficient of variation in all cases was less than 10%. This method is suitable for the analysis of clinical samples from pharmacokinetic and bioequivalence studies and drug monitoring. PMID:17537684

Kvaternick, Valerie; Malinski, Thomas; Wortmann, Jill; Fischer, James

2007-07-01

222

A Simple and Selective Spectrophotometric Method for the Determination of Trace Gold in Real, Environmental, Biological, Geological and Soil Samples Using Bis (Salicylaldehyde) Orthophenylenediamine  

PubMed Central

A simple high sensitive, selective, and rapid spectrophotometric method for the determination of trace gold based on the rapid reaction of gold(III) with bis(salicylaldehyde)orthophenylenediamine (BSOPD) in aqueous and micellar media has been developed. BSOPD reacts with gold(III) in slightly acidic solution to form a 1:1 brownish-yellow complex, which has an maximum absorption peak at 490 nm in both aqueous and micellar media. The most remarkable point of this method is that the molar absorptivities of the gold-BSOPD complex form in the presence of the nonionic TritonX-100 surfactant are almost a 10 times higher than the value observed in the aqueous solution, resulting in an increase in the sensitivity and selectivity of the method. The apparent molar absorptivities were found to be 2.3 × 104 L mol?1 cm?1 and 2.5 × 105 L mol?1 cm?1 in aqueous and micellar media, respectively. The reaction is instantaneous and the maximum absorbance was obtained after 10 min at 490 nm and remains constant for over 24 h at room temperature. The linear calibration graphs were obtained for 0.1–30 mg L?1 and 0.01–30 mg L?1 of gold(III) in aqueous and surfactant media, respectively. The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L?1 of Au(III); most metal ions can be tolerated in considerable amounts in aqueous micellar solutions. The Sandell’s sensitivity, the limit of detection and relative standard deviation (n = 9) were found to be 5 ng cm?2, 1 ng mL?1 and 2%, respectively in aqueous micellar solutions. Its sensitivity and selectivity are remarkably higher than that of other reagents in the literature. The proposed method was successfully used in the determination of gold in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), and biological samples (blood and urine), geological, soil and complex synthetic mixtures. The results obtained agree well with those samples analyzed by atomic absorption spectrophotometry (AAS). PMID:19609392

Soomro, Rubina; Ahmed, M. Jamaluddin; Memon, Najma; Khan, Humaira

2008-01-01

223

Determination of partition coefficients of diazepam and flurazepam between phosphatidylcholine bilayer vesicles and water by second derivative spectrophotometric method.  

PubMed

Second derivative spectrophotometry allowed the establishment of a simple and accurate method for the determination of partition coefficients of benzodiazepine drugs in a liposome/water system. The absorption spectra of diazepam (DZ) and flurazepam (FZ) in phosphatidylcholine (egg yolk) bilayer vesicle suspensions showed small spectral changes depending on the concentration of phosphatidylcholine vesicles. However, the intense background signals caused by the light scattering of the phosphatidylcholine vesicles made it difficult to yield a correct base line, thus the quantitative spectral data could not be obtained. In the second derivative spectra, the spectral changes were enhanced and three derivative isosbestic points were observed for each drug indicating the entire elimination of the residual background signal effects. The derivative intensity change of each drug (DeltaD) induced by its interaction with phosphatidylcholine bilayers was measured at a specific wavelength. From the relationship between the DeltaD value and the lipid concentration, the molar partition coefficients (K(p)s) of DZ and FZ were calculated and obtained with a good precision of R.S.D below 10%. The fractions of the partitioned DZ and FZ calculated by using the obtained K(p) values agreed well with the experimental values. The results prove that the derivative method can be usefully and easily applied to the determination of partition coefficients of benzodiazepines in the liposomes/water system without any separation procedures. PMID:11275439

Omran, A A; Kitamura, K; Takegami, S; El-Sayed, A A; Abdel-Mottaleb, M

2001-05-01

224

Hypothesis testing for the validation of the kinetic spectrophotometric methods for the determination of lansoprazole in bulk and drug formulations via Fe(III) and Zn(II) chelates.  

PubMed

Point and interval hypothesis tests performed to validate two simple and economical, kinetic spectrophotometric methods for the assay of lansoprazole are described. The methods are based on the formation of chelate complex of the drug with Fe(III) and Zn(II). The reaction is followed spectrophotometrically by measuring the rate of change of absorbance of coloured chelates of the drug with Fe(III) and Zn(II) at 445 and 510 nm, respectively. The stoichiometric ratio of lansoprazole to Fe(III) and Zn(II) complexes were found to be 1:1 and 2:1, respectively. The initial-rate and fixed-time methods are adopted for determination of drug concentrations. The calibration graphs are linear in the range 50-200 µg ml?¹ (initial-rate method), 20-180 µg ml?¹ (fixed-time method) for lansoprazole-Fe(III) complex and 120-300 (initial-rate method), and 90-210 µg ml?¹ (fixed-time method) for lansoprazole-Zn(II) complex. The inter-day and intra-day precision data showed good accuracy and precision of the proposed procedure for analysis of lansoprazole. The point and interval hypothesis tests indicate that the proposed procedures are not biased. PMID:20878895

Rahman, Nafisur; Kashif, Mohammad

2010-03-01

225

Spectrophotometric titration of zirconium in siliceous materials.  

PubMed

An accurate and selective complexometric titration procedure based upon a spectrophotometrically detected end-point has been developed for the determination of zirconium in glasses, glass-ceramics and refractories. A p-bromomandelic acid separation step for zirconium imparts excellent selectivity to the procedure. The method is particularly important for the 1-5% concentration range where a simple, accurate and selective method for the determination of zirconium has been lacking. PMID:18962344

Sugawara, K F; Su, Y S; Strzegowski, W R

226

Low-level luminescence as a method of detecting the UV influence on biological systems  

NASA Astrophysics Data System (ADS)

It is well known that low-level luminescence is correlated to many physiological and biological parameters, e.g. cell cycle, temperature, oxidation- and UV-stress. We report some new approaches on low-level luminescence measurements and UV influence on different biological systems. One example concerns yeast cultures, which show an increasing intensity of luminescence after UV-treatment with a maximum after 1.5 h. Investigations on normal human fibroblasts and keratinocytes display different longtime kinetics: The former show no changes of the luminescence in time, the latter an increase that reaches the maximum after 9 h. The time-dependent spectral measurement on xeroderma pigmentosum after UV-treatment displays a time-shift of the action-spectra shifting the maximum from 400 nm to 420 nm in 12 h. Some results on neutrophils reveals spectral UV influence on respiratory burst and the cellular repair system. The results on human skin display spectral changes of low-level luminescence after UV-treatment. These results provide a useful tool of analyzing UV influence on human skin.

Mei, Wei-Ping; Popp, Fritz A.

1995-02-01

227

A vacuum ultraviolet spectrophotometric system  

NASA Technical Reports Server (NTRS)

The development of a vacuum ultraviolet spectrophotometric system for measuring transmittance and reflectance at variable angles is presented. Using various detectors and sources, the spectrophotometric system has been used for wavelengths from 80 nm to 300 nm with optical components up to 80 mm in diameter. The capability exists to make measurements through the visible range.

Spann, James F.; Keffer, Charles E.; Zukic, Muamer

1993-01-01

228

Photolytic decolorization of Rose Bengal by UV/H(2)O(2) and data optimization using response surface method.  

PubMed

Rose Bengal (C.I. name is Acid Red 94) was irradiated with UV light in the presence of hydrogen peroxide. The photoinduced decolorization of the dye was monitored spectrophotometrically. The apparent rate of decolorization was calculated from the observed absorption data and was found to be pseudo first order. A systematic study of the effect of dye concentration and H(2)O(2) concentration on the kinetics of dye decolorization was also carried out. Dye decolorization increased with increasing H(2)O(2) concentration and decreasing dye concentration. The maximum dye decolorization was determined as 90% with 0.005 mM dye at optimum 0.042 M H(2)O(2) and pH 6.6. Additionally, the effect on decolorization of this dye in the presence of some additives (ions) was also investigated. It was seen that sulphite caused a maximum effect on % decolorization of the dye solution. A plausible explanation involving the probable radical initiated mechanism was given to explain the dye decolorization. The experimental data was also optimized using the response surface methodology (RSM). According to ANOVA results, the proposed model can be used to navigate the design space. It was found that the response of Rose Bengal degradation is very sensitive to the independent factors of dye concentration, H(2)O(2) concentration, pH and reaction time. The proposed model for D-optimal design fitted very well with the experimental data with R(2) and R(adj)(2) correlation coefficients of 0.85 and 0.80, respectively. PMID:18395977

Rauf, M A; Marzouki, N; Körbahti, Bahadir K

2008-11-30

229

Determination of p K a Values of Cefdinir and Cefixime by LC and Spectrophotometric Methods and Their Analysis in Pharmaceutical Dosage Forms  

Microsoft Academic Search

The pK\\u000a a values of cefdinir and cefixime, which are used in the treatment of bacterial infections, have been determined precisely\\u000a in water and methanol–water binary mixtures (20% v\\/v) using spectrophotometric titration and LC, respectively. A simple, fast and precise isocratic high-performance liquid chromatographic\\u000a (LC) procedure has been developed for the determination of cefdinir and cefixime in drug formulations. This

Nurullah Sanli; Senem Sanli; Umit S?z?r; Mehmet Gumustas; Sibel A. Ozkan

2011-01-01

230

Monolayer polystyrene micro-spheres array master derived by spin-coating method for UV nanoimprint.  

PubMed

Polystyrene micro-spheres aqueous suspensions were obtained by an emulsifier-free polymerization method. Fourier transform infrared spectroscopy and laser particle size distribution were used to characterize the colloidal solutions. Results indicate that the polystyrene micro-spheres colloidal solution has a good dispersion and the micro-spheres have a uniform size and smooth surface. The as-prepared polystyrene micro-spheres colloidal solution was spun onto glass substrates and then the coated sample was heated at 70 degrees C for 1 h to form close-packed monolayer polystyrene microspheres arrays, which are used as a master. Scanning electron microscopy was used to observe the morphological properties of the polystyrene micro-spheres array. A relative good result can be easily obtained by a spinning speed of 2000 rpm for 30 second, when the solution concentration is around 10 wt.%. Furthermore, the polydimethylsiloxane soft mold was replicated from the-fabricated polystyrene micro-spheres array master and was then imprinted onto the photosensitive hybrid film under UV-irradiation and thus the micro-lens arrays built in the photosensitive hybrid sol-gel film were obtained. PMID:22962781

Zhang, X H; Que, Wenxiu; Gao, T X

2012-08-01

231

Determination of sotolon content in South African white wines by two novel HPLC-UV and UPLC-MS methods.  

PubMed

Sotolon has been reported to play an important role in the atypical ageing and aroma character of many wines. A number of analytical techniques for sotolon analysis in wine have been reported, but these often require extensive sample preparation. In this work we report a HPLC-UV method and a novel UPLC-MS method to determine sotolon concentrations in white wines with little sample preparation applied for the first time for the evaluation of sotolon levels in South African wines. The validation showed that the instrumental methods had good accuracy, repeatability and linearity, but the UPLC-MS method proved more sensitive. For both methods, quantification limits were lower than the sotolon odour threshold in wine (10?g/L), 0.86?g/L and 0.013?g/L, for HPLC-UV and UPLC-MS methods, respectively. Sotolon levels in 65 South African white wines were often found to be lower than the reported odour threshold, with the highest concentration being 9.11?g/L. However, for low levels (<1?g/L), unknown interferences in certain wines led to sotolon not being quantified with the HPLC-UV method, which made the UPLC-MS method more suitable. PMID:25236214

Gabrielli, Mario; Buica, Astrid; Fracassetti, Daniela; Stander, Marietjie; Tirelli, Antonio; du Toit, Wessel J

2015-02-15

232

Multiwavelength spectrophotometric determination of acid dissociation constants  

Microsoft Academic Search

The acid-base equilibria of several diprotic amphoteric drugs, namely, niflumic acid, norfloxacin, piroxicam, pyridoxine and 2-methyl-4-oxo-3H-quinazoline-3-acetic acid have been characterized in terms of microconstants and tautomeric ratios. A multiwavelength spectrophotometric (WApH) titration method for determination of acid dissociation constants (pKa values) of ionizable compounds developed previously was applied for this purpose. Microspeciation was investigated by three approaches: (1) selective monitoring

Krisztina Takács-Novák; Kin Y. Tam

2000-01-01

233

UV-Visible Spectroscopic Method and Models for Assessment and Monitoring of Harmful Algal Blooms  

NASA Technical Reports Server (NTRS)

The development of an enhanced predictive and early warning capability for the occurrence and impact of harmful algal blooms (HABs) would be of great benefit to coastal communities. A critical issue for early detection and monitoring of HABs is the need to detect harmful algal species within a mixed-species phytoplankton assemblage. Possession of UV-absorbing compounds called mycosporine-like amino acids (MAAs) may be one factor that allows HAB species to out-compete their phytoplankton neighbors. Possession of MAAs, which we believe can be inferred from strong UV-absorption signals in phytoplankton absorption coefficients, can be used as a flag for potential HAB outbreak. The goal of this project was to develop a solar simulating UV-visible incubator to grow HAB dinoflagellates, to begin MAA analysis of samples collected on global cruises, and to carry out initial experiments on HAB dinoflagellate species in pure culture. Our scientific objectives are to quantify MAA production and spectral induction mechanisms in HAB species, to characterize spectral absorption of MAAs, and to define the ecological benefit of MAAs (i.e. photoprotection). Data collected on cruises to the global oceans will be used to parameterize phytoplankton absorption in the UV region, and this parameterization could be incorporated into existing models of seawater optical properties in the UV spectral region. Data collected in this project were used for graduate fellowship applications by Elizabeth Frame. She has been awarded an EPA STAR fellowship to continue the work initiated by this project.

Mitchell, B. Greg

2000-01-01

234

A Simple Sample Preparation with HPLC-UV Method for Estimation of Clomipramine from Plasma.  

PubMed

Clomipramine is a tricyclic antidepressant. Different methods for determination of clomipramine hydrochloride in plasma have been described. Most of these procedures favor the use of acidic back-extraction in extraction procedure and HPLC as the analytical technique. In this study, the clomipramine extraction procedure was modified and a direct injection to the column was performed to shorten the time of sample preparation considerably. Furthermore, the method was applied in bioequivalence study of new formulations of clomipramine in comparison with reference tablets. THE DRUG AND INTERNAL STANDARD WERE EXTRACTED FROM PLASMA WITH HEPTAN : isoamyl alcohol (95:5) and re-extracted with 200 ?L of orthophosphoric acid (0.3% v/v). The organic layer was discharged and analysis was performed on C8 reverse phase ODS2 HPLC column with a mobile phase, acetonitrile : water (75:25) and UV detection set at 215 nm. Additionally, a single dose study was carried out with a two-sequence, crossover block-randomized design for bioequivalence study. Clomipramine tablets (3 × 25 mg) of either formulations (reference or test products) were administered separately in two occasions to 12 fasting healthy male volunteers. Blood samples were taken prior to and at 9 points within 48 h after dose administration. The retention time of internal standard (cisapride), clomipramine, and desmethyl clomipramine were 5.6 ± 0.2, 10.3 ± 0.3, and 9.5 ± 0.3 min, respectively. The standard curve covering the concentration ranges of 2.5-120 ng/mL was linear (r(2) = 0.9950 and 0.9979) for clomipramine and desmethyl clomipramine. The co-efficient of variation for intra-day and inter-day accuracy and precision was less than 18.3%. The pharmacokinetic parameters Cmax and Tmax were obtained directly from plasma clomipramine concentrations. Kel was estimated by log-linear regression and AUC was calculated by the linear trapezoidal rule. The pharmacokinetic parameters AUC and Cmax were tested for equivalence after log-transformation of data. The 90% standard confidence intervals of the mean values for the test/reference ratios, AUC, and Cmax were within the acceptable bioequivalence limits of 0.80-1.20. These results indicated that the analytical method was linear and accurate. Test and reference formulations were found to be bioequivalent and therefore interchangeable. PMID:24363733

Mostafavi, Sayed Abolfazl; Tahvilian, Reza; Dehghani Poudeh, Masoumeh; Rafeepour, Zeinab

2010-01-01

235

Quantitative determination of levofloxacin hemihydrate in bulk and tablets by UV-spectrophotometry and first order derivative methods.  

PubMed

Two simple, rapid, accurate and economical 'UV Spectrophotometry' and 'First Order Derivative' methods have been developed for determination of levofloxacin hemihydrate in bulk and tablets. In (10% v/v) acetonitrile, the lambdamax of the drug was found to be 288 nm. The same spectrum was derivatised into first order derivative, using UV probe software of instrument (Shimadzu-2450), at Deltalambda=4. The amplitude of the trough was recorded at 297 nm. In both the proposed methods, levofloxacin hemihydrate follows linearity in the concentration range 2-12 microg/ml with a correlation coefficient of 0.9999. Assay results were in good agreement with label claim. The methods were validated statistically and by recovery studies. The relative standard deviation were found to be less than 2% with excellent precision and accuracy. PMID:19553178

Shirkhedkar, A A; Surana, S J

2009-07-01

236

Two methods for retrieving UV index for all cloud conditions from sky imager products or total SW radiation measurements.  

PubMed

Cloud effects on UV Index (UVI) and total solar radiation (TR) as a function of cloud cover and sunny conditions (from sky images) as well as of solar zenith angle (SZA) are assessed. These analyses are undertaken for a southern-hemisphere mid-latitude site where a 10-years dataset is available. It is confirmed that clouds reduce TR more than UV, in particular for obscured Sun conditions, low cloud fraction (<60%) and large SZA (>60°). Similarly, local short-time enhancement effects are stronger for TR than for UV, mainly for visible Sun conditions, large cloud fraction and large SZA. Two methods to estimate UVI are developed: (1) from sky imaging cloud cover and sunny conditions, and (2) from TR measurements. Both methods may be used in practical applications, although Method 2 shows overall the best performance, as TR allows considering cloud optical properties. The mean absolute (relative) differences of Method 2 estimations with respect to measured values are 0.17 UVI units (6.7%, for 1 min data) and 0.79 Standard Erythemal Dose (SED) units (3.9%, for daily integrations). Method 1 shows less accurate results but it is still suitable to estimate UVI: mean absolute differences are 0.37 UVI units (15%) and 1.6 SED (8.0%). PMID:24645969

Badosa, Jordi; Calbó, Josep; Mckenzie, Richard; Liley, Ben; González, Josep-Abel; Forgan, Bruce; Long, Charles N

2014-01-01

237

A Reverse Phase HPLC-UV and HPTLC Methods for Determination of Plumbagin in Plumbago indica and Plumbago zeylanica.  

PubMed

A reverse phase HPLC method with UV detection has been developed and validated in order to quantify plumbagin, the bioactive marker of the roots of P. indica and P. zeylanica. A quantitative HPTLC method was also developed using hexane: ethyl acetate (8:2) as the mobile phase. The plumbagin content in the roots were determined using both the methods. P. indica was found to contain significantly higher amount of plumbagin than P. zeylanica. The HPLC and HPTLC methods described here are simple, rapid, accurate and sensitive. PMID:21369461

Unnikrishnan, K P; Raja, S Sudhakar; Balachandran, Indira

2008-11-01

238

An environmentally friendly (“green”) reversed-phase liquid chromatography method for UV filters determination in cosmetics  

Microsoft Academic Search

A green procedure based on reversed-phase liquid chromatography with gradient elution using environmentally friendly solvents, has been developed to determine 18 UV filters, which are most used in Europe nowadays as sunscreen in cosmetics. Samples were weighed and dissolved in ethanol. Two aliquots were taken from the initial sample solution to prepare two solutions, so analytes could be determined chromatographically

A. Salvador; A. Chisvert

2005-01-01

239

Liquid chromatography–UV diode-array detection method for multi-residue determination of macrolide antibiotics in sheep's milk  

Microsoft Academic Search

A rapid, simple and sensitive liquid chromatography–UV diode-array detection method was developed for the simultaneous determination of seven macrolides (erythromycin, oleandomycin, roxithromycin, josamycin, spiramycin, tylosin and ivermectin) in sheep's milk. The column, mobile phase, temperature and flow rate were optimised to provide the best resolution of these analytes. The extraction of the antibiotic residues involves the treatment of protein-free samples

M. A. García-Mayor; R. M. Garcinuño; P. Fernández-Hernando; J. S. Durand-Alegría

2006-01-01

240

FORCED DEGRADATION AND PH STABILITY STUDIES OF LYSERGOL: AN ERGOLIC ALKALOID BY STABILITY INDICATING RP HPLC-UV METHOD  

Microsoft Academic Search

A simple HPLC-UV method was developed and validated for the analysis of lysergol, its stress degradation profile, and pH stability studies. Instrument used was Agilent HPLC 1120 autosampler with a C18 reversed phase column and a mobile phase comprised of methanol and water (1% acetic acid) with isocratic flow. Flow rate was kept constant at 1 mL\\/min throughout the experiment and

Shamama Javed; Kanchan Kohli; Mushir Ali

2012-01-01

241

A new method of chlorophenols decomposition based on UV-irradiation by XeBr-excilamp and their subsequent biodegradation  

NASA Astrophysics Data System (ADS)

The combined decomposition method of chlorophenols (CP) is offered. The method is based on photolysis of CP through XeBr-excilamp UV irradiation at 283 nm in a flow photoreactor with subsequent treatment of photolysis products by microorganism-destructor B. cereus isolated from an aeration pond of Baikal pulp-and-paper mill. At initial concentration of CP of 20 mg/l the polluted solutions can be utilized directly by means of biological treatment using B. cereus under aerobic conditions. However, if the initial CP concentration is higher than 20 mg/l, the polluted solutions are low biodegradable. It is shown, that the combined treatment is most effective method in this case. At initial CP concentration of 50 mg/l and higher it is suggested to use the deep preliminary UV-treatment with the purpose of removal 80-90 % of initial CP. It is revealed, that 4-CP is relatively persistent compound for B. cereus, easily decomposed by UV-radiation of XeBr-excilamp. As a result of subsequent biological treatment during 10 days the utilization of basic CP photoproducts is obtained. Experimentally, the preliminary UV-processing time was essentially less than that found earlier by E. Tamer, Z. Hamid, Aly A. (Chemosphere, 2006), where the half-life periods of initial CP were from 2.2 to 54 hours at the same value of initial concentration of CP. Correspondingly, the total CP decomposition process was accompanied by high power inputs. It is suggested to use mentioned above method for effective CP decomposition at high concentration values.

Sosnin, E. A.; Matafonova, G. G.; Batoev, V. B.; Christofi, N.

2008-01-01

242

Simultaneous spectrophotometric determination of trace amounts of uranium, thorium, and zirconium using the partial least squares method after their preconcentration by alpha-benzoin oxime modified Amberlite XAD-2000 resin.  

PubMed

A new solid phase extraction method for separation and preconcentration of trace amounts of uranium, thorium, and zirconium in water samples is proposed. The procedure is based on the adsorption of U(VI), Th(IV) and Zr(IV) ions on a column of Amberlite XAD-2000 resin loaded with alpha-benzoin oxime prior to their simultaneous spectrophotometric determination with Arsenazo III using orthogonal signal correction partial least squares method. The enrichment factor for preconcentration of uranium, thorium, and zirconium was found to be 100. The detection limits for U(VI), Th(IV) and Zr(IV) were 0.50, 0.54, and 0.48microgL(-1), respectively. The precision of the method, evaluated as the relative standard deviation obtained by analyzing a series of 10 replicates, was below 4% for all elements. The practical applicability of the developed sorbent was examined using synthetic seawater, natural waters and ceramic samples. PMID:20006073

Ghasemi, Jahan B; Zolfonoun, E

2010-01-15

243

Stability indicating HPLC-UV method for detection of curcumin in Curcuma longa extract and emulsion formulation.  

PubMed

A stability-indicating HPLC-UV method for the determination of curcumin in Curcuma longa extract and emulsion was developed. The system suitability parameters, theoretical plates (N), tailing factor (T), capacity factor (K'), height equivalent of a theoretical plate (H) and resolution (Rs) were calculated. Stress degradation studies (acid, base, oxidation, heat and UV light) of curcumin were performed in emulsion. It was found that N>6500, T<1.1, K' was 2.68-3.75, HETP about 37 and Rs was 1.8. The method was linear from 2 to 200?g/mL with a correlation coefficient of 0.9998. The intra-day precision and accuracy for curcumin were ?0.87% and ?2.0%, while the inter-day precision and accuracy values were ?2.1% and ?-1.92. Curcumin degraded in emulsion under acid, alkali and UV light. In conclusion, the stability-indicating method could be employed to determine curcumin in bulk and emulsions. PMID:25306352

Syed, Haroon Khalid; Liew, Kai Bin; Loh, Gabriel Onn Kit; Peh, Kok Khiang

2015-03-01

244

Removal of organic matter from a variety of water matrices by UV photolysis and UV\\/H 2O 2 method  

Microsoft Academic Search

A re-circulated flow-through photoreactor was used to evaluate the ultraviolet (UV) photolysis and UV\\/H2O2 oxidation process in the purification of three different water matrices. Chemically coagulated and electrocoagulated surface water, groundwater contaminated with creosote wood preservative and 1,2-dichloroethane (DCE) containing washing water from the plant manufacturing tailor-made ion-exchange resins were used as sample waters. The organic constituents of creosote consist

Sari Vilhunen; Miia Vilve; Mikko Vepsäläinen; Mika Sillanpää

2010-01-01

245

TLC-UV and VIS Densitometric Detection Method for Determination of Oxyphenonium Bromide and its Degradation Products in Tablets  

Microsoft Academic Search

A chromatographic-densitometric method was developed for determination of oxyhyphenonium bromide and its degradation products under UV\\/VIS spectra. Silica gel TLCF254 plates were used as stationary phase and butanol-1–glacial acetic acid–water (12.8:2:2.8 v\\/v\\/v) as mobile phase. Densitometric measurements were done at ? ? 225 nm and ? ? 530 nm. Degradation products ?-cyclohexyl-?-hydroxybenzeneacetic acid and N,N-diethyl-N-methylaminethanol were determined by HNMR method. The chromatographic-densitometric method is specific for

Urszula Hubicka; Jan Krzek; Olga Szczyrbowska

2009-01-01

246

Apparatus and method for treating pollutants in a gas using hydrogen peroxide and UV light  

NASA Technical Reports Server (NTRS)

An apparatus for treating pollutants in a gas may include a source of hydrogen peroxide, and a treatment injector for creating and injecting dissociated hydrogen peroxide into the flow of gas. The treatment injector may further include an injector housing having an inlet, an outlet, and a hollow interior extending therebetween. The inlet may be connected in fluid communication with the source of hydrogen peroxide so that hydrogen peroxide flows through the hollow interior and toward the outlet. At least one ultraviolet (UV) lamp may be positioned within the hollow interior of the injector housing. The at least one UV lamp may dissociate the hydrogen peroxide flowing through the tube. The dissociated hydrogen peroxide may be injected into the flow of gas from the outlet for treating pollutants, such as nitrogen oxides.

Cooper, Charles David (Inventor); Clausen, Christian Anthony (Inventor)

2005-01-01

247

APPARATUS AND METHOD FOR TREATING POLLUTANTS IN A GAS USING HYDROGEN PEROXIDE AND UV LIGHT  

NASA Technical Reports Server (NTRS)

An apparatus for treating pollutants in a gas may include a source of hydrogen peroxide, and a treatment injector for creating and injecting dissociated hydrogen peroxide into the flow of gas. The treatment injector may further include an injector housing having an inlet, an outlet, and a hollow interior extending there between. The inlet may be connected in fluid communication with the source of hydrogen peroxide so that hydrogen peroxide flows through the hollow interior and toward the outlet. At least one ultraviolet (UV) lamp may be positioned within the hollow interior of the injector housing. The at least one UV lamp may dissociate the hydrogen peroxide flowing through the tube. The dissociated hydrogen peroxide may be injected into the flow of gas from the outlet for treating pollutants, such as nitrogen oxides.

Cooper, Charles David (Inventor); Clauseu, christian Anthony (Inventor)

2005-01-01

248

Rapid, sensitive and on-line measurement of chemical oxygen demand by novel optical method based on UV photolysis and chemiluminescence  

Microsoft Academic Search

A novel on-line method based on the combination of UV photolysis and chemiluminescence detection was established and experimentally validated for the determination of chemical oxygen demand (COD). A quantitative amount of free radicals can be produced by analytes in the UV irradiation process. By utilizing the phenomenon that luminol can be oxidized by the free radicals to produce luminescence, COD

Yingying Su; Xiaohong Li; He Chen; Yi Lv; Xiandeng Hou

2007-01-01

249

Green synthesis of silver/montmorillonite/chitosan bionanocomposites using the UV irradiation method and evaluation of antibacterial activity  

PubMed Central

In this study, silver nanoparticles (Ag-NPs) were synthesized using a green physical synthetic route into the lamellar space of montmorillonite (MMT)/chitosan (Cts) utilizing the ultraviolet (UV) irradiation reduction method in the absence of any reducing agent or heat treatment. Cts, MMT, and AgNO3 were used as the natural polymeric stabilizer, solid support, and silver precursor, respectively. The properties of Ag/MMT/Cts bionanocomposites (BNCs) were studied as the function of UV irradiation times. UV irradiation disintegrated the Ag-NPs into smaller sizes until a relatively stable size and size distribution were achieved. Meanwhile, the crystalline structure and d-spacing of the MMT interlayer, average size and size distribution, surface morphology, elemental signal peaks, functional groups, and surface plasmon resonance of Ag/MMT/Cts BNCs were determined by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, Fourier transform infrared, and UV-visible spectroscopy. The antibacterial activity of Ag-NPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria (ie, Escherichia coli) by the disk diffusion method on Muller–Hinton Agar at different sizes of Ag-NPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biologic research and biomedical applications, such as surgical devices and drug delivery vehicles. PMID:21116328

Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Rustaiyan, Abdolhossein; Ibrahim, Nor Azowa; Zargar, Mohsen; Abdollahi, Yadollah

2010-01-01

250

[Method validation according to ISO 15189 and SH GTA 04: application for the extraction of DNA and its quantitative evaluation by a spectrophotometric assay].  

PubMed

According to the French legislation on medical biology (January 16th, 2010), all biological laboratories must be accredited according to ISO 15189 for at least 50% of their activities before the end of 2016. The extraction of DNA from a sample of interest, whether solid or liquid is one of the critical steps in molecular biology and specifically in somatic or constitutional genetic. The extracted DNA must meet a number of criteria such quality and also be in sufficient concentration to allow molecular biology assays such as the detection of somatic mutations. This paper describes the validation of the extraction and purification of DNA using chromatographic column extraction and quantitative determination by spectrophotometric assay, according to ISO 15189 and the accreditation technical guide in Human Health SH-GTA-04. PMID:24113450

Harlé, Alexandre; Lion, Maëva; Husson, Marie; Dubois, Cindy; Merlin, Jean-Louis

2013-01-01

251

A validated spectrophotometric and liquid chromatography method for determination and purity evaluation of 4-methoxy-2-[2-hydroxy-3(4-phenyl-1-piperazinyl)]propyl-2,3-dihydro-6-methyl-1,3-dioxo-1 H-pyrrolo[3,4-c]pyridine  

Microsoft Academic Search

A spectrophotometric analysis of the UV-spectrum of 4-methoxy-2-[2-hydroxy-3(4-phenyl-1-piperazinyl)]propyl-2,3-dihydro-6-methyl-1,3-dioxo-1H-pyrrolo[3,4-c]pyridine (I) in 0.01 M HCl was performed by determining the values of specific absorption coefficients at the following analytical wavelengths: 224, 285 and 348 nm. The separation by means of TLC of compound I and of its five decomposition products was also studied. Silica gel coated plates (60 F254) were used and

Izabela Muszalska; Helena ?adowska; Dominika Szkatula

2003-01-01

252

Spectrophotometric estimation of cobalt with ninhydrin  

PubMed Central

A violet coloured complex was developed when cobalt metal reacts with ninhydrin at pH 8.2, using sodium acetate buffer solution. Absorbance of the complex was measured at 395 nm. Various factors, such as volume of the ligand used, solution pH, stability of the complex with time and interference of other metals, which effect the complex formation have been studied in detail. Present developed method can be used for the spectrophotometric estimation of cobalt with ninhydrin complex. The method is simple, selective and cheap for the determination of cobalt in very less time. PMID:23961185

Mahmood, Karamat; Wattoo, Feroza Hamid; Wattoo, Muhammad Hamid Sarwar; Imran, Muhammad; Asad, Muhammad Javaid; Tirmizi, Syed Ahmed; Wadood, Abdul

2012-01-01

253

Combined cloud point-solid phase extraction by dispersion of TiO? nanoparticles in micellar media followed by semi-microvolume UV-vis spectrophotometric detection of zinc.  

PubMed

A new approach is presented in this paper by using dispersed TiO2 nanoparticles (TiO2-NPs) in a combined cloud point and solid phase extraction for the efficient preconcentration and determination of Zn(2+) in various samples. In this method Zn(2+) ions are adsorbed on TiO2-NPs and transferred into surfactant rich phase. Subsequently the Zn(2+) ions are desorbed from TiO2-NPs by a dithizone solution via forming a color complex which could be detected colorimetrically. The influence of chemical variables such as pH of the sample solution, electrolyte, amount of TiO2-NPs, type and volume of the eluent on the extraction system was studied. The calibration graph was linear in the range of 0.5-90.0 µg L(-1) of Zn(2+) (r=0.9996). An enrichment factor of 80 was achieved and the limit of detection for Zn(2+) was 0.33 µg L(-1). The relative standard deviation (RSD) for eight replicate measurements of 10 µg L(-1) and 60 µg L(-1) of Zn(2+) was 1.8% and 1.5% respectively. The proposed method was successfully applied to the quantitative determination of Zn(2+) in tap water, powder milk and Zinc sulfate tablet with satisfactory results. PMID:25059144

Pourreza, Nahid; Naghdi, Tina

2014-10-01

254

Highly sensitive catalytic spectrophotometric determination of ruthenium  

NASA Astrophysics Data System (ADS)

A new and highly sensitive catalytic kinetic method (CKM) for the determination of ruthenium(III) has been established based on its catalytic effect on the oxidation of L-phenylalanine ( L-Pheala) by KMnO 4 in highly alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance at 526 nm. The proposed CKM is based on the fixed time procedure under optimum reaction conditions. It relies on the linear relationship where the change in the absorbance (? At) versus added Ru(III) amounts in the range of 0.101-2.526 ng ml -1 is plotted. Under the optimum conditions, the sensitivity of the proposed method, i.e. the limit of detection corresponding to 5 min is 0.08 ng ml -1, and decreases with increased time of analysis. The method is featured with good accuracy and reproducibility for ruthenium(III) determination. The ruthenium(III) has also been determined in presence of several interfering and non-interfering cations, anions and polyaminocarboxylates. No foreign ions interfered in the determination ruthenium(III) up to 20-fold higher concentration of foreign ions. In addition to standard solutions analysis, this method was successfully applied for the quantitative determination of ruthenium(III) in drinking water samples. The method is highly sensitive, selective and very stable. A review of recently published catalytic spectrophotometric methods for the determination of ruthenium(III) has also been presented for comparison.

Naik, Radhey M.; Srivastava, Abhishek; Prasad, Surendra

2008-01-01

255

An HPLC-UV method for the measurement of permeability of marker drugs in the Caco-2 cell assay.  

PubMed

The Caco-2 cell line has been used as a model to predict the in vitro permeability of the human intestinal barrier. The predictive potential of the assay relies on an appropriate in-house validation of the method. The objective of the present study was to develop a single HPLC-UV method for the identification and quantitation of marker drugs and to determine the suitability of the Caco-2 cell permeability assay. A simple chromatographic method was developed for the simultaneous determination of both passively (propranolol, carbamazepine, acyclovir, and hydrochlorothiazide) and actively transported drugs (vinblastine and verapamil). Separation was achieved on a C18 column with step-gradient elution (acetonitrile and aqueous solution of ammonium acetate, pH 3.0) at a flow rate of 1.0 mL/min and UV detection at 275 nm during the total run time of 35 min. The method was validated and found to be specific, linear, precise, and accurate. This chromatographic system can be readily used on a routine basis and its utilization can be extended to other permeability models. The results obtained in the Caco-2 bi-directional transport experiments confirmed the validity of the assay, given that high and low permeability profiles were identified, and P-glycoprotein functionality was established. PMID:21584437

Kratz, J M; Teixeira, M R; Koester, L S; Simões, C M O

2011-06-01

256

Simple spectrophotometric determination of cinnarizine in its dosage forms  

Microsoft Academic Search

A direct, extraction-free spectrophotometric method has been developed for the determination of cinnarizine in pharmaceutical preparations. The method is based on ion-pair formation between the drug and three acidic (sulphonphthalein) dyes; namely bromocresol green (BCG), bromocresol purple (BCP) and bromophenol blue (BPB) which induces an instantaneous bathochromic shift of the maximum in the drug spectrum. Conformity to Beer's law enabled

H. Abdine; F. Belal; N. Zoman

2002-01-01

257

Characteristics of photoconductive UV photodetector based on ZnO nanorods grown on polyethylene naphthalate substrate by chemical bath deposition method  

NASA Astrophysics Data System (ADS)

Vertically aligned ZnO nanorods were synthesized on a polyethylene naphthalate (PEN) substrate using a chemical bath deposition method at a low temperature. The structural and optical investigations revealed the high quality of the fabricated ZnO nanorods on flexible substrate. A metal-semiconductor-metal UV photodetector based on ZnO nanorods was fabricated on the PEN substrate. The optoelectronic characteristics of fabricated UV photodetector were studied in the dark and under 325 nm UV light illumination at -3 V and 3 V bias voltages. The responsivity and photosensitivity of the ZnO nanorod UV photodetector were 2.856 A/W and 1175% at 3 V bias voltage, respectively. Moreover, the response and the recovery times measured during the turn-on and turnoff of UV illumination were 1.2 s and 1.8 s, respectively.

Shabannia, R.; Hassan, H. Abu

2014-07-01

258

Spectrophotometric determination of paracetamol with iodylbenzene.  

PubMed

Paracetamol (N-acetyl-4-aminophenol) has been determined spectrophotometrically by its oxidation with iodylbenzene in acetone to produce the yellow-orange N-acetyl-1,4-benzoquinoneimine, which attains maximum colour intensity within 1 min and absorbs maximally at 430 nm. The maximum molar absorptivity is 1.58 x 10(3) l.mole(-1).cm(-1). The method is simple and rapid and has been found to be unaffected by the presence of salicylamide, oxyphenbutazone, acetylsalicylic acid, dipyrone and a number of other excipients. PMID:18963836

Verma, K K; Jain, A

1985-03-01

259

Effects of UV assistance on the properties of al-doped ZnO thin films deposited by sol-gel method  

NASA Astrophysics Data System (ADS)

We report here the preparation of aluminum doped zinc oxide transparent conductive thin films by a UV-assisted sol-gel method. It was found that UV irradiation creates ozone, which promotes the conductivity and transparency of the films. Boro-silicate glasses are used as substrates; an PGME is used as a solvent; after spin-coating, the films are dried and radiated with UV and then heated to 400°C for decarburization and 500°C for annealing under air. The surface morphologies of the prepared films are observed by FE-SEM and AFM. It was found that the films irradiated with UV-C are smoother and denser. An XRD analysis shows that the films have a typical wurtzite crystalline structure with a c-axis orientation normal to the surface. The electric resistance values measured with a four-point probe show that the films irradiated with UV have better conductivity (at approximately 3.4 × 10-3?-cm) than the films that did not undergo UV irradiation. An analysis by visible light spectrometry indicates that the AZO films irradiated with UV are more transparent than the films without UV-irradiation.

Tseng, Yung-Kuan; Pai, Feng-Ming; Chen, Yan-Cheng; Wu, Chao-Hsien

2013-11-01

260

Spectrophotometric multicomponent determination of sunset yellow, tartrazine and allura red in soft drink powder by double divisor-ratio spectra derivative, inverse least-squares and principal component regression methods.  

PubMed

Double divisor-ratio spectra derivative (graphical method), classical least-squares and principal component regression (two numerical methods) methods were developed for the spectrophotometric multicomponent analysis of soft drink powders and synthetic mixtures containing three colorants without any chemical separation. The graphical method is based on the use of derivative signals of the ratio spectra using double divisor. In this method, the linear determination ranges were 2-8 mug ml(-1) sunset yellow, 4-18 mug ml(-1) tartrazine and 2-8 mug ml(-1) allura red in 0.1 M HCl. In the numerical methods, a training set was randomly prepared by using 18 samples containing between 0 and 8 mug ml(-1) of sunset yellow, 0-18 mug ml(-1) of tartrazine and 0-8 mug ml(-1) of allura red. The chemometric calibrations were calculated by using the prepared training set and its absorbances at seven points (from 375.0 to 550.0 nm) in the spectral region 325-584 nm. The proposed methods were validated by using synthetic ternary mixtures and applied to the simultaneous determination of three colorants in soft drink powders. The obtained results were statistically compared with each other. PMID:18968786

Dinç, Erdal; Baydan, Emine; Kanbur, Murat; Onur, Feyyaz

2002-09-12

261

An analytical method for determination of fullerenes and functionalized fullerenes in soils with high performance liquid chromatography and UV detection.  

PubMed

Fullerenes are carbon-based nanomaterials expected to play a major role in emerging nanotechnology and produced at an increasing rate for industrial and household applications. In the last decade a number of novel compounds (i.e. fullerene derivatives) is being introduced into the market and specific analytical methods are needed for analytical purposes as well as environmental and safety issues. In the present work eight fullerenes (C60 and C70) and functionalized fullerenes (C60 and C70 exohedral-derivatives) were selected and a novel liquid chromatographic method was developed for their analysis with UV absorption as a method of detection. The resulting HPLC-UV method is the first one suitable for the analysis of all eight compounds. This method was applied for the analysis of fullerenes added to clayish, sandy and loess top-soils at concentrations of 20, 10 and 5 ?g kg(-1) and extracted with a combination of sonication and shaking extraction. The analytical method limits of detection (LoD) and limits of quantification (LoQ) were in the range of 6-10 ?g L(-1) and 15-24 ?g L(-1) respectively for the analytical solutions. The extraction from soil was highly reproducible with recoveries ranging from 47±5 to 71±4% whereas LoD and LoQ for all soils tested were of 3 ?g kg(-1) and 10 ?g kg(-1) respectively. No significant difference in the extraction performance was observed depending of the different soil matrices and between the different concentrations. The developed method can be applied for the study of the fate and toxicity of fullerenes in complex matrices at relatively low concentrations and in principle it will be suitable for the analysis of other types of functionalized fullerenes that were not included in this work. PMID:24356233

Carboni, Andrea; Emke, Erik; Parsons, John R; Kalbitz, Karsten; de Voogt, Pim

2014-01-01

262

Adverse Effects of UV-B Radiation on Plants Growing at Schirmacher Oasis, East Antarctica  

PubMed Central

This study aimed to assess the impacts of ultraviolet-B (UV-B) radiation over a 28-day period on the levels of pigments of Umbilicaria aprina and Bryum argenteum growing in field. The depletion of stratospheric ozone is most prominent over Antarctica, which receives more UV-B radiation than most other parts of the planet. Although UV-B radiation adversely affects all flora, Antarctic plants are better equipped to survive the damaging effects of UV-B owing to defenses provided by UV-B absorbing compounds and other screening pigments. The UV-B radiations and daily average ozone values were measured by sun photometer and the photosynthetic pigments were analyzed by the standard spectrophotometric methods of exposed and unexposed selected plants. The daily average atmospheric ozone values were recorded from 5 January to 2 February 2008. The maximum daily average for ozone (310.7 Dobson Units (DU)) was recorded on 10 January 2008. On that day, average UV-B spectral irradiances were 0.016, 0.071, and 0.186 W m-2 at wavelengths of 305, 312, and 320 nm, respectively. The minimum daily average ozone value (278.6 DU) was recorded on 31 January 2008. On that day, average UV-B spectral irradiances were 0.018, 0.085, and 0.210 W m-2 at wavelengths of 305, 312, and 320 nm, respectively. Our results concludes that following prolonged UV-B exposure, total chlorophyll levels decreased gradually in both species, whereas levels of UV-B absorbing compounds, phenolics, and carotenoids gradually increased. PMID:24748743

Singh, Jaswant; Singh, Rudra P.

2014-01-01

263

88—A SPECTROPHOTOMETRIC STUDY OF YELLOWING IN WOOL FABRIC  

Microsoft Academic Search

The differential spectrophotometric method of measuring colour in wool fabric reveals that the fabric yellows much more slowly when heated in air than in aqueous solution. Yellowing by heating in buffer solutions increases with pH value and is also markedly affected by the nature of the buffer ions, glycine and related nitrogen compounds causing least yellowing and pyrophosphate most when

F. G. Lennox

1960-01-01

264

A method of laser micro-polishing for metallic surface using UV nano-second pulse and CW lasers  

E-print Network

During laser micro-polishing, the constant control of laser energy density is a key technology to improve the surface roughness. In this paper, a method which controls the energy density of UV(ultraviolet) pulse laser in real time with the control of CW(continuous wave) laser spot size in laser micro-polishing for metallic surface was presented. The experimental and analytical considerations of several influence factors such as laser spot size, fusion zone and focal offset were investigated. In addition, using a laser micro-polishing system manufactured with this method, the laser micro-polishing experiments on the two different surface shapes of stainless steel 316L were conducted. For the inclined or curved surface, the surface roughness improvements of up to 56.4% and 57.3% were respectively obtained, and the analysis of the results were discussed.

Jang, Pong-Ryol; Ji, Kum-Hyok; Kim, Nam-Chol

2014-01-01

265

[A quantitative method for evaluating the structure and conformational stability of proteins by second derivative UV-spectroscopy].  

PubMed

A quantitative method is suggested for estimating the structure and conformational stability of proteins based on the individual absorbance of Tyr residues in the second derivative UV spectra. Subtilisins Carlsberg, BPN' and 72 were chosen as the model proteins. The values of the increase of the Tyr absorption at 282.3 nm upon the total denaturation of the proteins made it possible to calculate the number of the exposed and "buried" tyrosine residues in the native proteins. A mathematical model of spectrum changes during the transition of Tyr residues from the "buried" to exposed form is suggested. The method is useful for the determination of the denaturation constants of proteins bearing "buried" tyrosine residues. PMID:8166752

Shevchenko, A A; Kost, O A; Kazanskaia, N F

1994-03-01

266

Spectrophotometric and high performance liquid chromatographic determination of cetirizine dihydrochloride in pharmaceutical tablets.  

PubMed

Derivative spectrophotometric, colorimetric and high performance liquid chromatographic methods, for the determination of the antihistaminic cetirizine dihydrochloride in tablet form were described. Spectrophotometrically, cetirizine was determined by the measurement of its first (1D) and second (2D) derivative amplitudes at 239 (peak) and 243-233 nm (peak-to-trough), respectively. The aqueous solutions obeyed Beer's law in the concentration ranges of 1.2-10.0 and 0.8-10.0 micrograms ml-1 for 1D and 2D measurements, respectively. The colorimetric procedure was based on measuring the absorbency of the coloured chromogen resulted from the reaction between cetirizine sodium salt in polar solvent (DMF) and chloranil at 556 nm. The relation with concentrations was linear over 120-250 micrograms ml-1. Optimization of the reaction conditions was studied. At the same time, investigation of the complex formed was made with respect to its composition and the associated constant. A simple liquid chromatographic assay has been developed for the determination of cetirizine dihydrochloride in the presence of one of its synthesis precursor (hydroxyzine hydrochloride). A Bondapak-C18 column was used with a mobile phase consisting of acetonitrile/0.01 M ammonium dihydrogen phosphate (32:68, v/v) containing 0.1% w/v tetrabutyl ammonium hydrogen sulphate adjusted to pH 3 with phosphoric acid at a flow rate of 2 ml min-1. With salicylic acid as internal standard, quantitation was achieved with UV detection at 230 nm based on the peak height ratios. Beer's law was obeyed in a concentration range of 3-35 micrograms ml-1 and the regression line equation was derived with a correlation coefficient of 0.9999. The validity of the methods was further confirmed using the standard addition method. The proposed procedures were successfully applied to the determination of cetirizine in bulk and tablet form, with high percentage of recovery, good accuracy and precision. PMID:9656155

el Walily, A F; Korany, M A; el Gindy, A; Bedair, M F

1998-07-01

267

Development of a reliable analytical method for extraction spectrophotometric determination of ruthenium(III) from catalyst and fissium alloy using o-methylphenyl thiourea as a chromogenic chelating ligand.  

PubMed

A simple and selective method is developed for the extraction spectrophotometric determination of ruthenium(III) using o-methylphenyl thiourea (OMPT) as a chromogenic chelating ligand. The basis of the proposed method is ruthenium(III)-OMPT complex formation in aqueous hydrochloric acid media (3.0molL(-1)) after 5.0min heating on a boiling water bath and the complex formed is extracted into chloroform. The absorbance of green colored ruthenium(III)-OMPT complex is measured at 590nm against the reagent blank. Beer's law was obeyed up to 42.5?gmL(-1) of ruthenium(III) and the optimum concentration range is 7.56-39.81?gmL(-1) of ruthenium(III) as evaluated by Ringbom's plot. Molar absorptivity and Sandell's sensitivity of ruthenium(III)-OMPT complex in chloroform are 2.34×10(3)Lmol(-1) cm(-1) and 0.043?gcm(-2) respectively. The composition of ruthenium(III):OMPT complex (1:2) was established from slope ratio method, mole ratio method and Job's continuous variation method. Complex was stable for more than 48h. The interfering effect of various foreign ions was studied and suitable masking agents are used wherever necessary to enhance the selectivity of the method. Proposed method is successfully applied for determination of ruthenium(III) from binary and ternary synthetic mixtures, synthetic mixtures corresponding to fissium alloy and ruthenium catalyst. Repetition of the method was checked by finding relative standard deviation (R.S.D) for 10 determinations which was 0.23%. A scheme for sequential separation of palladium(II), ruthenium(III), rhodium(III) and platinum(IV) has been developed. PMID:23353761

Kuchekar, Shashikant R; Shelar, Yogesh S; Aher, Haribhau R; Han, Sung H

2013-04-01

268

Quantification of doxycycline hyclate in tablets by HPLC-UV method.  

PubMed

An accurate, sensitive, precise and rapid gradient reversed-phase high-performance liquid chromatographic method was successfully developed and validated for the determination of doxycycline hyclate in bulk drug and tablets. The best separation was achieved on a 250 × 4.6 mm, 5.0 µm particle size CN Luna column with water + 0.1% TFA-acetonitrile + 0.1% TFA, 60:40 (v/v) as the mobile phase at a flow rate of 1.0 mL/min. Ultraviolet detection was performed at 360 nm at ambient column temperature (25°C). The method was linear over the concentration range of 50-100 µg/mL (r = 0.9999) with limits of detection and quantification of 2.83 and 8.59 µg/mL, respectively. The drug was subjected to oxidation, acid, base and neutral degradation, photolysis and heat as stress conditions. Degradation products were found interfering with the assay of doxycycline hyclate, therefore the method can be regarded as suitable. The method was applied for the determination of doxycycline hyclate in standard and pharmaceutical products, with excellent recoveries. The method can be used for the quality control of doxycycline hyclate. PMID:23192739

Kogawa, Ana Carolina; Salgado, Hérida Regina Nunes

2013-01-01

269

Determination of the overlapping pKa values of resorcinol using UV-visible spectroscopy and DFT methods.  

PubMed

In this paper we determine the overlapping pK(a) values of resorcinol in water, applying a UV-Vis spectroscopic method that uses absorbance diagrams. On the other hand, in order to explain the pK(a) values obtained, we also investigate the molecular conformations and solute-solvent interactions of the resorcinate anions, using ab initio and density functional theory methods. Several ionization reactions and equilibria in protic solvents, which possess a high hydrogen-bond-donor capability, are proposed. The mentioned reactions and equilibria constituted the indispensable theoretical basis to calculate the acidity constants of resorcinol. Basis sets at the HF/6-31 + G(d) and B3LYP/6-31 + G(d) levels of theory were used for calculations. Tomasi's method was used to analyze the formation of intermolecular hydrogen bonds between the resorcinate anions and water molecules. In this way, it was determined that in alkaline aqueous solutions the monoanion and dianion of resorcinol are solvated with two and four molecules of water, respectively. The agreement between the experimentally determined pK(a) values and those reported in the literature demonstrates the applicability and accurateness of the spectroscopic method here used. On the other hand, the agreement between the experimental and theoretically calculated pK(a) values provides solid support for the acid-base reactions proposed in this work. PMID:15556426

Blanco, S E; Almandoz, M C; Ferretti, F H

2005-01-01

270

Spectrophotometric determination of ofloxacin in pharmaceuticals by redox reaction  

Microsoft Academic Search

Two simple spectrophotometric methods have been developed to analyze ofloxacin (OFX) in pharmaceuticals. The methods are based on the oxidation of OFX by a measured excess of cerium(IV) sulfate in H2SO4 medium. This was followed by the determination of the unreacted oxidant by reacting it with either p-toluidine ( p-TD) and measuring the absorbance at 525 nm (method A) or

P. J. Ramesh; K. Basavaiah; N. Rajendraprasad; O. Zenita Devi; K. B. Vinay

2011-01-01

271

Spectrophotometric determination of ofloxacin in pharmaceuticals by redox reaction  

Microsoft Academic Search

Two simple spectrophotometric methods have been developed to analyze ofloxacin (OFX) in pharmaceuticals. The methods are based\\u000a on the oxidation of OFX by a measured excess of cerium(IV) sulfate in H2SO4 medium. This was followed by the determination of the unreacted oxidant by reacting it with either p-toluidine (p-TD) and measuring the absorbance at 525 nm (method A) or o-dianisidine (o-DA)

P. J. Ramesh; K. Basavaiah; N. Rajendraprasad; O. Zenita Devi; K. B. Vinay

272

Evaluation of UV-HPLC and mass spectrometry methods for specific activity determination.  

PubMed

The specific activity (SA) values determined using two different methods were compared for a set of tritium-labeled and carbon-14-labeled compounds. The methods employed were as follows: (a) liquid chromatography/mass spectrometry (LC/MS) isotopic peak intensity distribution, and (b) determination of the tracer mass concentration using ultraviolet-high-performance liquid chromatography analysis coupled with the radioactive solution concentration measured by liquid scintillation counting. In general, at lower SA, the accuracy and or precision of the LC/MS-determined SA value decreased significantly. Because of this decrease in accuracy, a rough guideline of ~10% of the theoretical maximum SA is recommended as the lower cutoff for MS-based SA measurements. If the tracer contains heteroatoms that possess significant percentages of heavy isotopes at natural abundance (e.g. Cl and Br), then the MS-based SA cutoff recommendation is approximately 25-30% of the fully labeled compound in the tracer mixture. Additionally, IsoPat(2) was found to be the preferred calculation method for LC/MS-based SA determination because SA values via this program were more consistent with those obtained by ultraviolet concentration calibration with solution count. PMID:25223538

Elmore, Charles S; Schenk, David J; Arent, Robert; Kingston, Lee

2014-09-01

273

Simultaneous determination of amoxicillin and diclofenac in pharmaceutical formulations using UV spectral data and the PLS chemometric method.  

PubMed

A new method for the simultaneous determination of amoxicillin trihydrate (AMT) and sodium diclofenac (DIC) in pharmaceutical formulations is proposed. The resolution of binary mixtures of these drugs has been accomplished by using partial least squares (PLS) regression analysis. The model was obtained from UV spectral data and validated by internal cross-validation; it was used to find the concentration of analytes in some commercial samples. The method was applied in the concentration ranges of 0-120.0 mg L(-1) for AMT and 0-16.0 mg L(-1) for DIC, allowing a rapid, accurate and precise simultaneous estimation of the concentration of both analytes of interest in the presence of small amounts of different, unmodelled, absorbing excipients, in spite of their important spectral overlapping. The accuracy, precision and figures of merit (FOM) for AMT and DIC were calculated. This new method proved to be useful for a fast and simultaneous determination of AMT and DIC in pharmaceutical formulations. PMID:21233564

Cantarelli, Miguel A; Pellerano, Roberto G; Marchevsky, Eduardo J; Camiña, Jose M

2011-01-01

274

Fabrication of a bilayer wire grid polarizer in the near infrared wavelength region by using a UV curing nanoimprinting method  

NASA Astrophysics Data System (ADS)

In this study, we have designed and fabricated an Al bilayer wire grid polarizer (B-WGP) in the near-infrared wavelength region. A finite difference time domain method was employed to design and analyze the subwavelength B-WGP with a period of 450 nm, a grating height of 150 nm, and a duty cycle of 0.5. The high polarization extinction ratio of 1200 indicates that the B-WGP may be used as a normal incidence polarization beam splitter. A subwavelength polymer pattern was fabricated by using an UV curing nanoimprinting method, and an Al thin film was deposited by using a thermal evaporation method. The experimental results show that the transmittance of the TM-wave of the B-WGP is over 50% at wavelengths in the range 1000 ˜ 2000 nm wavelength while the transmittance of the TE-wave is less than 1%, and that the polarization extinction ratio 250. The discrepancies between the simulated and the experimental results are discussed.

Lee, Yong Ho; Peranantham, Pazhanisami; Hwangbo, Chang Kwon; Kim, Seok-Min

2012-11-01

275

Screening method for the detection of artificial colours in saffron using derivative UV-Vis spectrometry after precipitation of crocetin.  

PubMed

A screening method for the detection of artificial colours (naphthol yellow, tartrazine, quinoline yellow, Sunset yellow, Allura red, amaranth, azorubine, Ponceau 4R and Red 2G) in saffron is described. The method involves removal of crocins by precipitation of crocetin (pH 0.1, 90 degrees C) before adsorption of the artificial colours on polyamide SPE cartridges (pH 2). After washing with methanol, acetone and methanol, elution was done with a methanol:ammonia solution (95:5 v/v), and detection was performed by derivative spectrometry. Sample pretreatment changes the UV-Vis saffron extract profile in such a way that second derivative spectra can be used to identify the presence of added colours. Erythrosine, which was found to be pH dependent, could not be detected under the above conditions. The lowest detectable amount for each colour was strongly dependent on chemical structure. The recovery of carminic acid was very low possibly due to irreversible retention on the polyamide. This procedure can replace the current ISO TLC method (2003) and be used alternatively or in combination with HPLC procedures adopted in the same standard. PMID:16019836

Zalacain, A; Ordoudi, S A; Blázquez, I; Díaz-Plaza, E M; Carmona, M; Tsimidou, M Z; Alonso, G L

2005-07-01

276

An interlaboratory study on the suitability of a gradient LC-UV method as a compendial method for the determination of erythromycin and its related substances.  

PubMed

A liquid chromatographic (LC) method for the analysis of erythromycin and related substances has been adapted from an isocratic method developed by Chepkwony et al. (2001). The suitability of the method for general application as a compendial (pharmacopoeia) method has been assessed by means of an interlaboratory (collaborative) study. The method involves LC separation on a XTerra C18 column kept at 65 degrees C and UV detection at 210 nm. Five laboratories, located in Europe and the United States (US), participated in the study. Four erythromycin samples were tested. The main components (erythromycin A (EA), erythromycin B (EB), erythromycin C (EC)) and the impurities were determined. The analysis of variance was carried out on the results of the five laboratories to evaluate the between-laboratory consistencies and the laboratory-sample interaction. The estimates for the repeatability and reproducibility of the method, expressed as relative standard deviation (RSD) of the result of the determination of EA, were calculated to be 0.8% and 1.4% respectively. It is concluded that the method examined is a good replacement for the methods currently described in the European Pharmacopoeia (Ph. Eur.) and the United States Pharmacopoeia (USP), especially for its enhanced selectivity. PMID:20381987

Van den Bossche, L; Lodi, A; Schaar, J; Shaakov, S; Zorzan, M; Tranquillini, M E; Overballe-Petersen, C; Hoogmartens, J; Adams, E

2010-09-21

277

Screening of conditions controlling spectrophotometric sequential injection analysis  

PubMed Central

Background Despite its potential benefits over univariate, chemometrics is rarely utilized for optimizing sequential injection analysis (SIA) methods. Specifically, in previous vis-spectrophotometric SIA methods, chemometrically optimized conditions were confined within flow rate and reagent concentrations while other conditions were ignored. Results The current manuscript reports, for the first time, a comprehensive screening of conditions controlling vis-spectrophotometric SIA. A new diclofenac assay method was adopted. The method was based on oxidizing diclofenac by permanganate (a major reagent) with sulfuric acid (a minor reagent). The reaction produced a spectrophotometrically detectable diclofenac form. The 26 full-factorial design was utilized to study the effect of volumes of reagents and sample, in addition to flow rate and concentrations of reagents. The main effects and all interaction order effects on method performance, i.e. namely sensitivity, rapidity and reagent consumption, were determined. The method was validated and applied to pharmaceutical formulations (tablets, injection and gel). Conclusions Despite 64 experiments those conducted in the current study were cumbersome, the results obtained would reduce effort and time when developing similar SIA methods in the future. It is recommended to critically optimize effective and interacting conditions using other such optimization tools as fractional-factorial design, response surface and simplex, rather than full-factorial design that used at an initial optimization stage. In vis-spectrophotometric SIA methods those involve developing reactions with two reagents (major and minor), conditions affecting method performance are in the following order: sample volume > flow rate ? major reagent concentration >> major reagent volume ? minor reagent concentration >> minor reagent volume. PMID:21333024

2011-01-01

278

Separation via flotation, spectrophotometric speciation, and determination of vanadium(IV) in wastes of power stations.  

PubMed

1-(2-Hydroxy-4-methoxybenzophenone)-4-phenylthiosemicarbazone (HMBPT) was investigated as a new reagent for the flotation of vanadium(IV). At pH approximately 1.5, vanadium(IV) forms a 1:1 pale-violet complex with HMBPT in aqueous solution. An intense clear violet layer was formed after flotation, by adding an oleic acid (HOL) surfactant. The composition of the float was 1:1 [V(IV)]:[HMBPT]. A highly selective and sensitive spectrophotometric procedure was proposed for the determination of microamounts of V(IV) as its floated complex. The molar absorptivities of the V(IV)-HMBPT and V(IV)-HMBPT-HOL systems were 0.4 x 10(4) and 0.12 x 10(5) L mol(-1) cm(-1) at 560 nm, respectively. The formation constants of the species formed in the presence and absence of HOL were 4.6 x 10(7) and 8.7 x 10(5) L mol(-1), respectively. Beer's law was obeyed up to 1 x 10(-4) mol L(-1) in the aqueous layer as well as in the oleic acid layer. The HMBPT-V(IV) complexes formed in the aqueous solution and scum layer were characterized by elemental analysis, infrared and UV spectrophotometric studies. The mode of chelation between V(IV) and HMBPT is proposed to be due to a reaction between the protonated bidentate HMBPT ligand and V(IV) through the S=C and N=C groups. Interferences from various foreign ions were avoided by adding excess HMBPT and/or Na2S2O3 as a masking agent. The proposed flotation method was successfully applied to the analysis of V(IV) in synthetic mixtures, wastes of power stations, simulated samples and in real ores. The separation mechanism is discussed. PMID:16317901

Akl, Magda Ali; El-Asmy, Ahmed A; Yossef, Wafaa M

2005-11-01

279

Selective spectrophotometric determination of p-aminophenol and acetaminophen  

Microsoft Academic Search

A specific spectrophotometric method was developed for the determination of p-aminophenol and acetaminophen. The method is based on the reaction of p-aminophenol at ambient temperature with sodium sulphide in presence of an oxidant to produce a methylene blue-like dye. Different oxidizing agents were tried, e.g. Ce(IV) and Fe(III). The colour developed within 10 min and remained stable for at least

Fardous A. Mohamed; Mohamed A. AbdAllah; Soad M. Shammat

1997-01-01

280

Hybrid hard- and soft-modeling of spectrophotometric data for monitoring of ciprofloxacin and its main photodegradation products at different pH values  

NASA Astrophysics Data System (ADS)

A simple and fast on line spectrophotometric method combined with a hybrid hard-soft modeling multivariate curve resolution (HS-MCR) was proposed for the monitoring of photodegradation reaction of ciprofloxacin under UV radiation. The studied conditions attempt to emulate the effect of sunlight on these antibiotics that could be eventually present in the environment. The continuous flow system made it possible to study the ciprofloxacin degradation at different pH values almost at real time, avoiding errors that could arise from typical batch monitoring of the reaction. On the base of a concentration profiles obtained by previous pure soft-modeling approach, reaction pathways have been proposed for the parent compound and its photoproducts at different pH values. These kinetic models were used as a constraint in the HS-MCR analysis. The kinetic profiles and the corresponding pure response profile (UV-Vis spectra) of ciprofloxacin and its main degradation products were recovered after the application of HS-MCR analysis to the spectra recorded throughout the reaction. The observed behavior showed a good agreement with the photodegradation studies reported in the bibliography. Accordingly, the photodegradation reaction was studied by high performance liquid chromatography coupled with UV-Vis diode array detector (HPLC-DAD). The spectra recorded during the chromatographic analysis present a good correlation with the ones recovered by UV-Vis/HS-MCR method.

Razuc, Mariela; Garrido, Mariano; Caro, Yamile S.; Teglia, Carla M.; Goicoechea, Héctor C.; Fernández Band, Beatriz S.

2013-04-01

281

Hybrid hard- and soft-modeling of spectrophotometric data for monitoring of ciprofloxacin and its main photodegradation products at different pH values.  

PubMed

A simple and fast on line spectrophotometric method combined with a hybrid hard-soft modeling multivariate curve resolution (HS-MCR) was proposed for the monitoring of photodegradation reaction of ciprofloxacin under UV radiation. The studied conditions attempt to emulate the effect of sunlight on these antibiotics that could be eventually present in the environment. The continuous flow system made it possible to study the ciprofloxacin degradation at different pH values almost at real time, avoiding errors that could arise from typical batch monitoring of the reaction. On the base of a concentration profiles obtained by previous pure soft-modeling approach, reaction pathways have been proposed for the parent compound and its photoproducts at different pH values. These kinetic models were used as a constraint in the HS-MCR analysis. The kinetic profiles and the corresponding pure response profile (UV-Vis spectra) of ciprofloxacin and its main degradation products were recovered after the application of HS-MCR analysis to the spectra recorded throughout the reaction. The observed behavior showed a good agreement with the photodegradation studies reported in the bibliography. Accordingly, the photodegradation reaction was studied by high performance liquid chromatography coupled with UV-Vis diode array detector (HPLC-DAD). The spectra recorded during the chromatographic analysis present a good correlation with the ones recovered by UV-Vis/HS-MCR method. PMID:23376269

Razuc, Mariela; Garrido, Mariano; Caro, Yamile S; Teglia, Carla M; Goicoechea, Héctor C; Fernández Band, Beatriz S

2013-04-01

282

Schrödinger method as N-body double and UV completion of dust  

NASA Astrophysics Data System (ADS)

We investigate large-scale structure formation of collisionless dark matter in the phase space description based on the Vlasov (or collisionless Boltzmann) equation whose nonlinearity is induced solely by gravitational interaction according to the Poisson equation. Determining the time evolution of density and peculiar velocity demands solving the full Vlasov hierarchy for the moments of the phase space distribution function. In the presence of long-range interaction no consistent truncation of the hierarchy is known apart from the pressureless fluid (dust) model, which is incapable of describing virialization due to the occurrence of shell-crossing singularities and the inability to generate vorticity and higher cumulants like velocity dispersion. Our goal is to find a simple ansatz for the phase space distribution function that approximates the full Vlasov distribution function without pathologies in a controlled way and therefore can serve as theoretical N-body double and as a replacement for the dust model. We argue that the coarse-grained Wigner probability distribution obtained from a wave function fulfilling the Schrödinger-Poisson equation (SPE) is the sought-after function. We show that its evolution equation approximates the Vlasov equation and therefore also the dust fluid equations before shell crossing, but cures the shell-crossing singularities and is able to describe regions of multistreaming and virialization. This feature was already employed in cosmological simulations of large-scale structure formation by Widrow and Kaiser (1993). The coarse-grained Wigner ansatz allows us to calculate all higher moments from density and velocity analytically, thereby incorporating nonzero higher cumulants in a self-consistent manner. On this basis we are able to show that the Schrödinger method automatically closes the corresponding hierarchy such that it suffices to solve the SPE in order to directly determine density and velocity and all higher cumulants.

Uhlemann, Cora; Kopp, Michael; Haugg, Thomas

2014-07-01

283

Indirect spectrophotometric determination of arbutin, whitening agent through oxidation by periodate and complexation with ferric chloride  

Microsoft Academic Search

A simple and accurate spectrophotometric method for the determination of arbutin (glycosylated hydroquinone) is described. It is based on the oxidation of arbutin by periodate in presence of iodate. Excess periodate causes liberation of iodine at pH 8.0. The unreacted periodate is determined by measurement of the liberated iodine spectrophotometrically in the wavelength range (300–500nm).A calibration curve was constructed for

B. N. Barsoom; A. M. E. Abdelsamad; N. M. Adib

2006-01-01

284

Chromatography with Spectrophotometric Detection  

Microsoft Academic Search

We describe a method for determining uric acid in serum by reversed-phase liquid chromatography with spectro- photometric detection at 280 nm. Serum, 100 ulis mixed with 100 u1of a solution containing, per liter, 70 ml of acetonitrile in sodium acetate (20 mmol\\/Iiter, pH 4.0) and 500 mg of the internal standard, adenine. The mixture is allowed to stand in an

Ernest J. Kiser; George F. Johnson; David L. Witte

285

Quantification of dissolved organic carbon at very low levels in natural ice samples by a UV-induced oxidation method.  

PubMed

The study of chemical impurities trapped in solid precipitation and accumulated in polar ice sheets and high-elevation, midlatitude cold glaciers over the last several hundreds of years provides a unique way to reconstruct our changing atmosphere from the preindustrial era to the present day. Numerous ice core studies of inorganic species have already evaluated the effects of growing anthropogenic emissions of SO(2) or NO(x) on the chemical composition of the atmosphere in various regions of the world. While it was recently shown that organic species dominate the atmospheric aerosol mass, the contribution of anthropogenic emissions to their budget remains poorly understood. The study of organics in ice is at the infancy stage, and it still is difficult to draw a consistent picture of the organic content of polar ice from sparse available data. A UV oxidation method and IR quantification of CO(2) was optimized to obtain measurements of dissolved organic carbon content as low as a few ppbC. Stringent working conditions were defined to prevent contamination during the cleaning of ice. Measurements in various ice cores corresponding to preindustrial times revealed dissolved organic carbon content of less than 10 ppbC in Antarctica and up to 75 ppbC in alpine ice. PMID:21142062

Preunkert, S; Legrand, M; Stricker, P; Bulat, S; Alekhina, I; Petit, J R; Hoffmann, H; May, B; Jourdain, B

2011-01-15

286

Preclinical Monitoring of Drug Association in Experimental Chemotherapy of Chagas' Disease by a New HPLC-UV Method  

PubMed Central

A combination of drugs in experimental chemotherapy of Chagas' disease may increase the effectiveness of treatment. To evaluate the possible mechanisms that influence the improvement of therapy, we investigated the pharmacokinetic interaction between benznidazole and itraconazole in a murine model treated orally with single doses of 5 mg of each compound separately or together. Blood samples from treated mice were collected at different intervals for 48 h, and a high-performance liquid chromatography (HPLC)-UV method was used to quantify both drugs in the plasma. A decrease of 1.5-fold in the maximum drug concentration in the plasma (Cmax) and an increase of 2.66-fold in the volume of distribution (V) and 7.5-fold in the elimination half-life (t1/2?) of benznidazole when coadministered with itraconazole were observed. The parameters area under the curve (AUC0-t), area under the curve extrapolated to infinity (AUC0-?), time to maximum concentration of drug in serum (Tmax), and clearance (CL) for benznidazole were not significantly different in this therapeutic regime. None of the evaluated parameters for ITC demonstrated a significant difference between isolated and associated administration. These results suggest that the main effect of this interaction leads to accumulation of benznidazole in the biological system. This effect may contribute to the improved therapeutic efficacy of this combination of drugs, in addition to synergism of the different mechanisms of action of benznidazole and itraconazole against Trypanosoma cruzi in vivo. PMID:22450981

Moreira da Silva, Rodrigo; Oliveira, Liliam Teixeira; Silva Barcellos, Neila Marcia; de Souza, Jacqueline

2012-01-01

287

The determination of kaolinite clay content in limestones of western Tamil Nadu by methylene blue adsorption using UV-vis spectroscopy  

NASA Astrophysics Data System (ADS)

The clay index values of 60 different limestone samples collected from western Tamil Nadu were determined using UV-vis spectrophotometric method with the help of the absorbance value at 663 nm of a known concentration of methylene blue. The type of clay was determined as kaolinite through the FTIR technique. The applicability of this approach and advantages over the current methods in cement and chemical industries are demonstrated. According to the clay index values, the quality of the samples obtained from Padaivedu area of Namakkal district is better than the other samples.

Ramasamy, V.; Anandalakshmi, K.

2008-06-01

288

Spectrophotometric determination of Pb(II), Fe(III) and Bi(III) in complexes with 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (DACT).  

PubMed

A UV spectrophotometric method was developed for simultaneous determination of ions: Pb(II), Fe(III) and Bi(III) in complexes with DACT. Zero-order and derivative spectra were used for the determinations. Under the established experimental conditions the described method furnished reliable results with low limit of detection (from 0.09 microg x mL(-1) to 1.75 microg x mL(-1)), high recovery (from 96.08% to 97.81%) and broad range of linearity for the analyzed ions. Good precision of the method was confirmed in experiments on model solutions containing mixtures of ions studied at different concentrations and in statistical analysis of the data obtained. PMID:17665844

Krzek, Jan; Apola, Anna; Stolarczyk, Mariusz; Rzeszutko, W?odzimierz

2007-01-01

289

Spectrophotometric determination of Diclofenac sodium with Methylene Blue  

Microsoft Academic Search

A sensitive spectrophotometric method was established for the determination of Diclofenac sodium (DS) with Methylene Blue (MB) as analytical reagent. It was found that DS reacts with an excess of MB in the pH range 9.2–9.4, to form a chloroform-extractable blue ion-association complex. Good agreement with Beer's law was found in the range of DS concentrations of 0.8–6.4 ?g\\/ml with

Julio C. Botello; Guadalupe Pérez-Caballero

1995-01-01

290

Extraction and Spectrophotometric Determination of Lead in the Environment  

Microsoft Academic Search

A rapid method for the extraction and spectrophotometric determination of lead in the environment is described. The lead forms a yellow complex with PBHA at pH 9.5 which is extracted from chloroform. The molar absorptivity was found 4.0 × 10 mol cm at 390 nm. The phenylfluorone is used as a synergestic. Pb-PBHA complex is back extracted with 0.01 M

S. K. Patke; Y. K. Agrawal

1980-01-01

291

New 1,2,4-triazole-based azo-azomethine dye. Part III: Synthesis, characterization, thermal property, spectrophotometric and computational studies.  

PubMed

A new 1,2,4-triazole-based azo-azomethine compound, H2L, has been prepared by condensation reaction of 1-(3-formyl-4-hydroxyphenylazo)-4-ethylbenzene with prepared triazole-based diamine. The structure of H2L was characterized by using FT-IR, UV-Vis and (1)H NMR spectroscopic methods as well as elemental analysis. Hard model chemometrics method has been used to determine the formation constants of zinc(II), copper(II), nickel(II) and cobalt(II) complexes of H2L in DMSO by UV-Vis spectrophotometric method. Solvatochromic behavior of the dye has been also investigated in some organic solvents with different polarities. Thermal properties of the prepared dye was examined by thermogravimetric analysis. Results indicated that the framework of the dye was stable up to 245 °C. Furthermore,(1)H chemical shifts and UV-Vis of H2L were studied by the gauge independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and time-dependent density functional theory (TD-DFT) methods respectively at the level of density functional theory using B3LYP/6-311+G(d) basis sets in DMSO. The computational data are in reasonably good agreement with the experimental data. PMID:24577255

Erfantalab, Malihe; Khanmohammadi, Hamid

2014-05-01

292

MIR\\/NIR\\/VIS spectrophotometric investigation of absorbing thin-film materials based on error function minimization by the method of conjugated gradients  

Microsoft Academic Search

A flexible numerical procedure for the calculation of thin film optical constants from specular transmittance and reflectance data is presented. The method is based on the minimization of an error function, which may be adapted to the specifics of the optical behavior of the given sample (or set of samples), and the given wavenumber region. The flexibility in choosing an

Olaf Stenzel; Ralf Petrich

1994-01-01

293

Comparison of two methods, UHPLC-UV and UHPLC-MS/MS, for the quantification of polyphenols in cider apple juices.  

PubMed

The aim of this study was to develop faster and more efficient phenotyping methods for in-depth genetic studies on cider apple progeny. The UHPLC chromatographic system was chosen to separate polyphenolic compounds, and quantifications were then simultaneously performed with a UV-PDA detector and an ESI-triple quadrupole mass analyzer (SRM mode). Both quantification methods were validated for 15 major compounds using two apple juice samples, on the basis of linearity, limits of detection and quantification, recovery and precision tests. The comparison between UV and SRM quantifications in 120 different samples of a cider apple progeny showed an excellent correlation for major compounds quantified with both methods. However, an overestimation was revealed for five compounds with the UV detector and the mass analyzer. Co-elution and matrix effects are discussed to explain this phenomenon. SRM methods should therefore be considered with restrictions in some cases for quantification measurements when several phenolic compounds are simultaneously quantified in complex matrices such as apple juices. For both methods, analyses were carried out over short periods of time while maintaining a high quality for the simultaneous quantification of phenolic compounds in apple juice. Each method is relevant for more in-depth genetic studies of the polyphenol content of apple juice. PMID:23973994

Verdu, Cindy F; Gatto, Julia; Freuze, Ingrid; Richomme, Pascal; Laurens, François; Guilet, David

2013-01-01

294

New spectrophotometric methods for the determinations of hydrogen sulfide present in the samples of lake water, industrial effluents, tender coconut, sugarcane juice and egg.  

PubMed

The new methods are working on the principle that iron(III) is reduced to iron(II) by hydrogen sulfide, catechol and p-toluidine the system 1/hydrogen sulfide the system 2, in acidic medium followed by the reduced iron forming complex with 1,10-phenanthroline with ?(max) 510 nm. The other two methods are based on redox reactions between electrolytically generated manganese(III) sulfate taken in excess and hydrogen sulfide followed by the unreacted oxidant oxidizing diphenylamine ?(max) 570 the system 3/barium diphenylamine sulphonate ?(max) 540 nm, the system 4. The increase/decrease in the color intensity of the dye products of the systems 1 and 2 or 3 and 4 are proportional to the concentration of hydrogen sulfide with its quantification range 0.035-1.40 ?g ml(-1)/0.14-1.40 ?g ml(-1). PMID:22889607

Shyla, B; Nagendrappa, G

2012-10-01

295

MIR/NIR/VIS spectrophotometric investigation of absorbing thin-film materials based on error function minimization by the method of conjugated gradients  

NASA Astrophysics Data System (ADS)

A flexible numerical procedure for the calculation of thin film optical constants from specular transmittance and reflectance data is presented. The method is based on the minimization of an error function, which may be adapted to the specifics of the optical behavior of the given sample (or set of samples), and the given wavenumber region. The flexibility in choosing an appropriate form of the error function minimized, in combination with the powerful minimization method of conjugated gradients, allowed us to investigate the optical constants of very different types of novel thin film materials with a complicated absorption behavior. In particular, the results concerning the investigation of single- and two-layer-systems based on the following optical thin film materials are presented: amorphous silicon, phthalocyanine layers, hydrogenated amorphous carbon, and as-deposited (rough) CVD diamond layers.

Stenzel, Olaf; Petrich, Ralf

1994-09-01

296

New spectrophotometric methods for the determinations of hydrogen sulfide present in the samples of lake water, industrial effluents, tender coconut, sugarcane juice and egg  

NASA Astrophysics Data System (ADS)

The new methods are working on the principle that iron(III) is reduced to iron(II) by hydrogen sulfide, catechol and p-toluidine the system 1/hydrogen sulfide the system 2, in acidic medium followed by the reduced iron forming complex with 1,10-phenanthroline with ?max 510 nm. The other two methods are based on redox reactions between electrolytically generated manganese(III) sulfate taken in excess and hydrogen sulfide followed by the unreacted oxidant oxidizing diphenylamine ?max 570 the system 3/barium diphenylamine sulphonate ?max 540 nm, the system 4. The increase/decrease in the color intensity of the dye products of the systems 1 and 2 or 3 and 4 are proportional to the concentration of hydrogen sulfide with its quantification range 0.035-1.40 ?g ml-1/0.14-1.40 ?g ml-1.

Shyla, B.; Nagendrappa, G.

2012-10-01

297

Simultaneous spectrophotometric determination of Tartrazine, Sunset Yellow and Ponceau 4R in commercial products by partial least squares and principal component regression multivariate calibration methods  

Microsoft Academic Search

Three multivariate calibration methods, partial least squares (PLS-1 and PLS-2) and principal component regression (PCR),\\u000a were proposed and successfully applied to the simultaneous determination of three dyes, Tartrazine (E-102), Sunset Yellow\\u000a (E-110) and Ponceau 4R (E-124) in mixtures by ultraviolet-visible absorption spectrophotometry. The designed and optimized\\u000a training set of calibration was applied to the determination of the three dyes in

J. J. Berzas Nevado; J. Rodríguez Flores; M. J. Villaseñor Llerena

1998-01-01

298

Improving the spectrophotometric determination of the alkylating activity of anticancer agents: A new insight into the mechanism of the NBP method  

Microsoft Academic Search

In this paper, the mechanism of the nitrobenzylpyridine (NBP) method to measure the alkylating activity of drugs originally described by Epstein et al. [J. Epstein, R.W. Rosenthal, R.J. Ess, Anal. Chem. 27 (1955) 1435–1439] and modified later by others was revisited using melphalan, m-sarcolysin, chlorambucil, cyclophosphamide and ifosfamide. Its direct application to determine the activity of these drugs in human

Karen M. E. Dierickx; Fabrice Journé; Pascal Gerbaux; Renato Morandini; Jean-Michel Kauffmann; Ghanem E. Ghanem

2009-01-01

299

Ambient formic acid in southern California air: A comparison of two methods, Fourier transform infrared spectroscopy and alkaline trap-liquid chromatography with UV detection  

SciTech Connect

Formic acid is an ubiquitous component of urban smog. Sources of formic acid in urban air include direct emissions from vehicles and in situ reaction of ozone with olefins. Ambient levels of formic acid in southern California air were first measured some 15 years ago by Hanst et al. using long-path Fourier transform infrared spectroscopy (FTIR). All subsequent studies of formic acid in the Los Angeles area have involved the use of two methods, either FTIR or collection on alkaline traps followed by gas chromatography, ion chromatography, or liquid chromatography analysis with UV detection, ATLC-UV. The Carbon Species Methods Comparison Study (CSMCS), a multilaboratory air quality study carried out in August 1986 at a southern California smog receptor site, provided an opportunity for direct field comparison of the FTIR and alkaline trap methods. The results of the comparison are presented in this brief report.

Grosjean, D. (DGA, Inc., Ventura, CA (USA)); Tuazon, E.C. (Univ. of California, Riverside (USA)); Fujita, E. (California Air Resources Board, Sacramento (USA))

1990-01-01

300

In-situ spectrophotometric probe  

DOEpatents

A spectrophotometric probe is described for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and co-terminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focusing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid. 5 figs.

Prather, W.S.

1992-12-15

301

In-situ spectrophotometric probe  

DOEpatents

A spectrophotometric probe for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and coterminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focussing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid.

Prather, William S. (2419 Dickey Rd., Augusta, GA 30906)

1992-01-01

302

A direct spectrophotometric method for the simultaneous determination of zinc and cobalt in metalloproteins using 4-(2-pyridylazo)resorcinol.  

PubMed

An assay involving the direct and simultaneous determination of low micromolar concentrations (1-10 microM) of both zinc and cobalt ions suitable for metal content analyses of metalloproteins is described. The procedure exploits differences in the visible absorption spectra of the chromophoric chelator 4-(2-pyridylazo)resorcinol (PAR) resulting from its complexation to Zn2+ and/or Co2+ ions and is based on the fit of experimental spectra to a linear addition of Beer-Lambert law. The method eliminates the need for separating or masking one of the metal ions prior to their quantification and could prove to be particularly useful in studies on Co2+-substituted zinc proteins. PMID:19435594

Säbel, Crystal E; Shepherd, Jeffrey L; Siemann, Stefan

2009-08-01

303

Simultaneous spectrophotometric determination of Fe(III) and Al(III) using orthogonal signal correction-partial least squares calibration method after solidified floating organic drop microextraction.  

PubMed

A solidified floating organic drop microextraction (SFODME) procedure was developed for the simultaneous extraction and preconcentration of Fe(III) and Al(III) from water samples. The method was based on the formation of cationic complexes between Fe(III) and Al(III) and 3,5,7,2',4'-pentahydroxyflavone (morin) which were extracted into 1-undecanol as ion pairs with perchlorate ions. The absorbance of the extracted complexes was then measured in the wavelength range of 300-450 nm. Finally, the concentration of each metal ion was determined by the use of the orthogonal signal correction-partial least squares (OSC-PLS) calibration method. Several experimental parameters that may be affected on the extraction process such as the type and volume of extraction solvent, pH of the aqueous solution, morin and perchlorate concentration and extraction time were optimized. Under the optimum conditions, Fe(III) and Al(III) were determined in the ranges of 0.83-27.00 ?g L(-1) (R(2)=0.9985) and 1.00-32.00 ?g L(-1) (R(2)=0.9979) of Fe(III) and Al(III), respectively. The relative standard deviations (n=6) at 12.80 ?g L(-1) of Fe(III) and 17.00 ?g L(-)(1) of Al(III) were 3.2% and 3.5%, respectively. An enhancement factors of 102 and 96 were obtained for Fe(III) and Al(III) ions, respectively. The procedure was successfully applied to determination of iron and aluminum in steam and water samples of thermal power plant; and the accuracy was assessed through the recovery experiments and independent analysis by electrothermal atomic absorption spectroscopy (ETAAS). PMID:25168229

Rohani Moghadam, Masoud; Haji Shabani, Ali Mohammad; Dadfarnia, Shayessteh

2015-01-25

304

Spectrophotometric estimation of individual flavone glycosides in three Euphorbia species.  

PubMed

Two spectrophotometric methods (conventional and differential) are carried out for the estimation of flavone glycosides (hyperoside and/or kaempferol-3-beta-glucoside) in Euphorbia paralias L., and Euphorbia helioscopia L. The glycosides are extracted with methanol from the aerial parts of the different Euphorbia species, separated on silica gel chromatoplates, and eluted by refluxing with methanol (80%). The absorbance value (conventional method) and the delta absorbance value (differential method) of the prepared glycosidal solutions are measured. The results of both methods are of conveinent reproducibility. PMID:1161795

Abdel-Salam, N A; El-Sayed, M; Khafagy, S M

1975-06-01

305

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

Microsoft Academic Search

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers

J. L. Garnett; G. Major

1982-01-01

306

Biologically weighted personal UV dosimetry.  

PubMed

People are exposed to natural or artificial UV radiation in different ways; unintentionally or intentionally, at their workplace on their spare time. To quantify the amount of individual UV exposure, a personal dosimetry is necessary. In research, polysulphone film (PSF) dosimeters are the most frequently used personal UV dosimeters. We use calculated weighting factors in the measurement processing of polysulphone film dosimeters. The special weighting factor transforms the dosimeter reading from an equivalent UV dose to the biologically effective UV dose. The factor depends on the investigated problem (action spectrum of the photobiological effect and spectral distribution of the incident UV source), the calibration of PSF was carried out once by a monochromatic radiation (gamma = 295 nm). The equivalent dose readings are available from this calibration curve for any investigated question. A presented result of this method is the seasonal measurement of erythemally effective UV exposure by ambient solar radiation, and the individual exposure level in a "normal" person concerning UV exposure and also in groups with the risk of a lack of sunshine. Further applications are occupational measurements of the risk of health damage by UV radiation (with respect to the limit of the maximum permissible 8 h-exposure according to IRPA/INIRC-guidelines). We controlled the extent of UV exposure in workers in the area of arc welding workplaces. The biological weighting of PSF readings simplifies a routine use of PSF in personal UV monitoring to investigators without the expending special measurement technology (e.g. spectroradiometer). PMID:8988614

Knuschke, P; Barth, J

1996-10-01

307

Forced Degradation Study on Gliclazide and Application of Validated Stability-Indicating HPLC-UV Method in Stability Testing of Gliclazide Tablets  

Microsoft Academic Search

Forced degradation study on gliclazide was conducted under the conditions of hydrolysis, oxidation, dry heat and photolysis\\u000a and an isocratic stability-indicating HPLC-UV method was developed and validated. All the seven degradation products (I–VII)\\u000a formed under different conditions were optimally resolved on a C18 column with mobile phase composed of 40% acetonitrile and 60% ammonium acetate solution (0.025 M, pH 3.5) at

Gulshan Bansal; Manjeet Singh; Kaur Chand Jindal

2007-01-01

308

Quantitation of the main constituents of vanilla by reverse phase HPLC and ultra-high-pressure-liquid-chromatography with UV detection: method validation and performance comparison.  

PubMed

Vanilla's main constituents, i. e., vanillin, para-hydroxybenzaldehyde, and their corresponding acids, can be easily quantified by RP LC with UV detection and external calibration. This paper describes two methods that were developed using HPLC and ultra-high-pressure LC (UHPLC), respectively, and validated according to the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). Both methods were highly specific, exhibited good linearities with high precision, and achieved good accuracies of quantitative results. The UHPLC method was more sensitive, five times shorter, and gave better peak resolutions than the HPLC alternative. PMID:19714659

Cicchetti, Esmeralda; Chaintreau, Alain

2009-09-01

309

Effect of UV irradiation on detection of cocaine hydrochloride and crack vapors by IMIS and API-MS methods.  

PubMed

Detection of drug vapors and volatile products of their decomposition is an important, and sometimes the only way to determine the presence of illegal drug traces at the surface of mail items, documents, hands and banknotes. This paper gives the results of experimental studies on the effect of UV irradiation on the sensitivity of a vapor phase detection of cocaine of different origin by a technology of ion mobility increment spectrometry (IMIS). It is shown that the influence of UV irradiation on the surface of cocaine hydrochloride and crack increases the amplitude of IMIS signals by about eight times. We analyzed ions emerged by photolysis of tested cocaine samples using mass-spectrometry with atmospheric pressure ionization (API-MS). The assumption is made about structural formula of volatile products of photolysis of crack and cocaine hydrochloride. By the results of API-MS and IMIS studies on photolysis of cocaine samples it is assumed that compound C(10)H(15)NO(3) with a molecular weight of 197 amu and ecgonidine methyl ester with a molecular weight of 181 amu are responsible for the increase of an amplitude of IMIS signals upon UV irradiation of samples of crack and cocaine hydrochloride. PMID:19203621

Kolomiets, Yuri N; Pervukhin, Viktor V

2009-04-30

310

Sterilization Using 365 nm UV-LED  

Microsoft Academic Search

There are several methods used for sterilization. In those methods chlorine, heat and UV rays are traditionally used. In recent years, the UV sterilization is taken notice as a sterilization method that the sterilized object does not change in quality and is environment-friendly. In this paper, an UV-LED is focused because it does not contain harmful substance and has longer

Noriyuki YAGI; Mirei MORI; Akiko HAMAMOTO; Masayuki NAKANO; Masatake AKUTAGAWA; Souko TACHIBANA; Akira TAKAHASHI; Toshitaka IKEHARA; Yohsuke KINOUCHI

2007-01-01

311

Spectrophotometric analysis of aqueous mixtures of some chromium (III) complexes. Thesis  

NASA Technical Reports Server (NTRS)

Several methods of determining the relative concentrations of Cr(H2O)5C1(+2) and Cr(H2O)6(+3) are described. The three methods studied are curved resolving methods, used in evaluating spectrophotometric results, mixture results, used in verifying curve resolving techniques, and chromium analysis.

Stevens, G.

1983-01-01

312

Spectrophotometric determination of phosphorus acid  

SciTech Connect

A number of procedures have been proposed to determine phosphorus acid and its salts, the phosphites, in the presence of hypophosphorus acid and its salts, the hypophosphites. Among these procedures, iodometric back-titration has produced the most reliable results. In this paper, the authors propose an improved iodometric determination of phosphorus acid that enables the sensitivity to be increased by at least two orders of magnitude. The essence of this improvement is that excess iodine that did not react with phosphite ion is determined not volumetrically but spectrophotometrically. To eliminate the effect of iodine ion that is liberated when iodine reacts with phosphite ion on the optical density of the solution, a 200-fold excess of potassium iodide is added before the photometric measurement. The working iodine solution is prepared by diluting 10 m of 0.025 N iodine titrant and 50 ml of phosphate buffer, pH 6.7-7.2, to 1 liter with distilled water in a coulometric flask. To construct the calibration curve, 5, 10, 15, 20, and 25 ml, respectively of working iodine solution, and 10 ml of 2% aqueous potassium iodide are placed into five 100-ml volumetric flasks, and the solutions are made up to volume with water. After 10 min the photometric measurements are carried out at 380 nm using curvets and the reference solution is obtained by diluting 10 ml of 2% aqueous potassium iodide to 100 ml with distilled water.

Domin, A.V.; Domina, N.G.; Zakharov, Yu.A.; Shechkov, G.T.

1987-03-01

313

A simple spectrophotometric determination of solid supported amino groups.  

PubMed

A simple spectrophotometric method for the quantitative determination of solid phase supported amino groups is described. The method involves reacting the solid support with an excess of activated acylating agent, N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) and an efficient acylation catalyst, 4-dimethylaminopyridine, and after thoroughly removing the unreacted SPDP, the solid support is reacted with an excess of dithiothreitol to quantitatively release pyridine-2-thione from the solid support to the solution. After an appropriate dilution, the released pyridine-2-thione which has a strong absorbance at 343 nm, is quantified by reading its absorbance in a spectrophotometer at 343 nm. PMID:3734326

Ngo, T T

1986-06-01

314

Are You UV Safe?  

NSDL National Science Digital Library

Students may be slathered with SPF 30 sunscreen all summer at the beach or pool, but what do they know about ultraviolet (UV) light radiation and absorption? How could we help them find out the science behind this important health precaution? We found the perfect opportunity when we developed this series of practical strategies to promote students' investigation skills. We integrated several scientific processes into a lesson on UV light radiation and absorption for fourth-grade students and preservice elementary methods students. These teaching tools help students develop their abilities to ask testable questions, plan and design investigations, and interpret what they find.

Capobianco, Brenda; Thiel, Elizabeth A.

2006-09-01

315

Systematic mutagenesis method for enhanced production of bacitracin by Bacillus licheniformis Mutant Strain UV-MN-HN-6  

PubMed Central

The purpose of the current study was intended to obtain the enhanced production of bacitracin by Bacillus licheniformis through random mutagenesis and optimization of various parameters. Several isolates of Bacillus licheniformis were isolated from local habitat and isolate designated as GP-35 produced maximum bacitracin production (14±0.72 IU ml-1). Bacitracin production of Bacillus licheniformis GP-35 was increased to 23±0.69 IU ml-1 after treatment with ultraviolet (UV) radiations. Similarly, treatment of vegetative cells of GP-35 with chemicals like N-methyl N’-nitro N-nitroso guanidine (MNNG) and Nitrous acid (HNO2) increased the bacitracin production to a level of 31±1.35 IU ml-1 and 27±0.89 IU ml-1respectively. Treatment of isolate GP-35 with combined effect of UV and chemical treatment yield significantly higher titers of bacitracin with maximum bacitracin production of 41.6±0.92 IU ml-1. Production of bacitracin was further enhanced (59.1±1.35 IU ml-1) by optimization of different parameters like phosphate sources, organic acids as well as temperature and pH. An increase of 4.22 fold in the production of bacitracin after mutagenesis and optimization of various parameters was achieved in comparison to wild type. Mutant strain was highly stable and produced consistent yield of bacitracin even after 15 generations. On the basis of kinetic variables, notably Yp/s (IU/g substrate), Yp/x (IU/g cells), Yx/s(g/g), Yp/s, mutant strain B. licheniformis UV-MN-HN-6 was found to be a hyperproducer of bacitracin. PMID:24031806

Aftab, Muhammad Nauman; Ikram-ul-Haq; Baig, Shahjahan

2012-01-01

316

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

SciTech Connect

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers and oligomers used in both grafting and rapid cure systems is outlined. The experimental conditions where grafting may occur during radiation rapid cure processing are discussed. Possible future developments of the technique are outlined. 1 figure, 8 tables.

Garnett, J.L. (Univ. of New South Wales, Kensington, Australia); Major, G.

1982-01-01

317

Comparative Study of Three Methods for Affinity Measurements: Capillary Electrophoresis Coupled with UV Detection and Mass Spectrometry, and Direct Infusion Mass Spectrometry  

NASA Astrophysics Data System (ADS)

We present affinity capillary electrophoresis and mass spectrometry (ACE-MS) as a comprehensive separation technique for label-free solution-based affinity analysis. The application of ACE-MS for measuring affinity constants between eight small molecule drugs [ibuprofen, s-flurbiprofen, diclofenac, phenylbutazone, naproxen, folic acid, resveratrol, and 4,4'-(propane-1,3-diyl) dibenzoic acid] and ?-cyclodextrin is described. We couple on-line ACE with MS to combine the separation and kinetic capability of ACE together with the molecular weight and structural elucidation of MS in one system. To understand the full potential of ACE-MS, we compare it with two other methods: Direct infusion mass spectrometry (DIMS) and ACE with UV detection (ACE-UV). After the evaluation, DIMS provides less reliable equilibrium dissociation constants than separation-based ACE-UV and ACE-MS, and cannot be used solely for the study of noncovalent interactions. ACE-MS determines apparent dissociation constants for all reacting small molecules in a mixture, even in cases when drugs overlap with each other during separation. The ability of ACE-MS to interact, separate, and rapidly scan through m/z can facilitate the simultaneous affinity analysis of multiple interacting pairs, potentially leading to the high-throughput screening of drug candidates.

Mironov, Gleb G.; Logie, Jennifer; Okhonin, Victor; Renaud, Justin B.; Mayer, Paul M.; Berezovski, Maxim V.

2012-07-01

318

A fast tree-based method for estimating column densities in Adaptive Mesh Refinement codes Influence of UV radiation field on the structure of molecular clouds  

E-print Network

Context. Ultraviolet radiation plays a crucial role in molecular clouds. Radiation and matter are tightly coupled and their interplay influences the physical and chemical properties of gas. In particular, modeling the radiation propagation requires calculating column densities, which can be numerically expensive in high-resolution multidimensional simulations. Aims. Developing fast methods for estimating column densities is mandatory if we are interested in the dynamical influence of the radiative transfer. In particular, we focus on the effect of the UV screening on the dynamics and on the statistical properties of molecular clouds. Methods. We have developed a tree-based method for a fast estimate of column densities, implemented in the adaptive mesh refinement code RAMSES. We performed numerical simulations using this method in order to analyze the influence of the screening on the clump formation. Results. We find that the accuracy for the extinction of the tree-based method is better than 10%, while the ...

Valdivia, Valeska

2014-01-01

319

A rapid spectrophotometric determination of persulfate anion in ISCO.  

PubMed

Due to a gradual increase in the use of persulfate as an in situ chemical oxidation (ISCO) oxidant, a simple measurement of persulfate concentration is desirable to analyze persulfate distribution at designated time intervals on/off a site. Such a distribution helps evaluate efficacy of ISCO treatment at a site. This work proposes a spectrophotometric determination of persulfate based on modification of the iodometric titration method. The analysis of absorption spectra of a yellow color solution resulting from the reaction of persulfate and iodide in the presence of sodium bicarbonate reveals an absorbance at 352 nm, without significant interferences from the reagent matrix. The calibration graph was linear in the range of persulfate solution concentration of 0-70 mM at 352 nm. The proposed method is validated by the iodometric titration method. The solution pH was at near neutral and the presence of iron activator does not interfere with the absorption measurement. Also, analysis of persulfate in a groundwater sample using the proposed method indicates a good agreement with measurements by the titration method. This proposed spectrophotometric quantification of persulfate provides a simple and rapid method for evaluation of ISCO effectiveness at a remediation site. PMID:18922560

Liang, Chenju; Huang, Chiu-Fen; Mohanty, Nihar; Kurakalva, Rama Mohan

2008-11-01

320

Catalytic-spectrophotometric determination of trace amounts of molybdenum(VI) ion  

Microsoft Academic Search

A new simple, sensitive and rapid catalytic kinetic method for the determination of trace amounts of molybdenum(VI) ion is described. The method is based on the catalytic effect of Mo(VI) on reduction reaction of Nile blue A (NBA) by hydrazine dihydrochloride (HD) in acidic media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture

M. F Mousavi; A. R Karami

2000-01-01

321

Comparison of various sensitive and selective spectrophotometric assays of environmental cyanide  

Microsoft Academic Search

A review is presented to show the advantages involved in the use of some new spectrophotometric cyanide (CN) assays, which are highly sensitive and selective, quick and affordable. Among these, the ninhydrin-based assay, the method based on CN reaction with resorcinol, as well as the Berthelot reaction were found to be highly selective. The old Aldridge 1 method, based on

Gabi Drochioiu; Karin Popa; Doina Humelnicu; Manuela Murariu; Ion Sandu; Alexandru Cecal

2008-01-01

322

A quantitative approach to the analysis of supermicron dispersions by field-flow fractionation with UV-vis detectors. The application of an absolute method  

Microsoft Academic Search

Summary  Quantitative analysis in field-flow fractionation is becoming a necessary requirement for routine applications, instrumental\\u000a optimization and scale-up to preparative separations. The use of detection systems which show complex dependence on sample\\u000a characteristics (i.e. UV spectrometry) has hindered the application of quantitative methods of analysis in field-flow fractionation.\\u000a A standardless model, shown valid in flow-through, homogeneous systems, is applied here to

P. Reschiglian; D. Melucci; G. Torsi

1997-01-01

323

UV Menace  

NSDL National Science Digital Library

UV Menace is part of an online series of modules entitled Exploring the Environment. Emphasizing an integrated approach to environmental Earth Science education through problem-based learning, this module asks students to learn about stratospheric ozone depletion and its effects, then determine future measures that will be needed to correct the current situation. Students will find extensive coverage of the Earth's hydrosphere, lithosphere, atmosphere, anthrosphere, and biosphere. They use this information to evaluate the current status of the Montreal Protocol and determine if it is adequate. If not, students must develop the changes they feel are necessary. There is an online glossary and links for further research and information, teacher resources, and a reference on problem-based learning.

324

Preparation of superhydrophobic and UV blocking cotton fabric via sol-gel method and self-assembly  

NASA Astrophysics Data System (ADS)

Superhydrophobic surface has been successfully prepared on cotton substrates with inexpensive and ordinary raw materials, Al(NO3)3 and sodium stearate (C17H35COONa). Such surfaces were obtained first by dip-coating the nano-Al sol, then the surface of the Al coating was modified with sodium stearate, to gain a thin film through self-assembly. The wettability of treated fabrics was characterized by water contact angle, spray test and hydrostatic pressure test. The results showed that the cotton fabrics treated with 1.5% Al sol and 20 mmol/L sodium stearate showed excellent hydrophobic properties and UV protection efficiency, water contact angle could reach 146.27° and the UPF value was 164.06 (UPF rating 50+). The morphology and surface roughness were characterized by SEM and AFM. The interaction between sodium stearate and Al coating was elucidated by XPS.

Pan, Chengyu; Shen, Li; Shang, Songmin; Xing, Yanjun

2012-10-01

325

Simultaneous spectrophotometric estimation of nitazoxanide and ofloxacin in tablets.  

PubMed

Two simple, accurate and precise spectrophotometric methods have been developed for simultaneous determination of nitazoxanide and ofloxacin in tablets. Method I is Q-absorbance ratio method which involves Q-absorbance at isobestic point (306.25 nm) and max (347.5 nm) of nitazoxanide, while method II is two wavelength method, where 244.6 nm and 273.0 nm were selected as 1 and 2 for determination of nitazoxanide and 294.3 nm and 388.1 nm were selected as 3 and 4 for determination of ofloxacin. Both drugs obeyed the Beer's law in the concentration range 2-30 ?g/ml,correlation coefficient (r(2)<1). Both methods were validated statistically and recovery studies were carried out to confirm the accuracy. Commercial tablet formulation was successfully analyzed using the developed methods. PMID:22131624

Game, Madhuri D; Sakarkar, D M

2011-01-01

326

Simultaneous quantitation of aspirin, amlodipine and simvastatin in a fixed dose combination of encapsulated tablet formulation by HPLC-UV method.  

PubMed

A high-pressure liquid chromatography (HPLC-UV) based simple and specific method for simultaneous quantitative determination of aspirin, amlodipine besylate and simvastatin in a capsule formulation has been developed and validated according to ICH guidelines. Chromatographic separation of the three drugs was carried out by aSpherisorbODS2 reverse phase column (4.6 x 250 mm; 5 ?m) using amobile phase, which consisted of 70: 30 (v/v) mixture of acetonitrile and triethylamine phosphate buffer (pH 3; 0.015 M) with final pH adjusted to 2.5 using dilute ortho-phosphoric acid, at a flow rate of 1mL/min. The eluents were detected at UV wavelength of 237 nm and the retention times for aspirin, amlodipine besylate and simvastatin were ~2.7 mins, ~6.1 mins and ~10.5mins, respectively. This method is suitable and specific for the three drugs and was found to be linear (R2>0.995), accurate, specific, reproducible and robust in the concentration range of 375 to 1125mcg/ml for aspirin, 25 to 75mcg/ml for amlodipine besylate and 50 to 150mcg/ml for simvastatin. This simple and convenient method could be easily utilized for the characterization and quantitation of the three drugs in a single formulation for combination therapy of cardiovascular diseases. PMID:25176250

Sultan, Faisal; Shoaib, Muhammad Harris; Yousuf, Rabia Ismail; Ahmed, Farrukh Rafiq; Salam, Faseeh A; Nasiri, Muhammad Iqbal; Khan, Muhammad Atif; Manzoor, Saeed

2014-09-01

327

Improved Spectrophotometric Analysis of Barium Styphnate.  

National Technical Information Service (NTIS)

A spectrophotometric procedure to determine the purity of barium styphnate monohydrate based upon the absorbance of the styphnate ion at 326 and 413.3 nm has been developed. The purity is determined by comparing the absorbance of the styphnate ion in bari...

J. A. Blasi, N. E. Brown

1983-01-01

328

Improved spectrophotometric analysis of barium styphnate  

Microsoft Academic Search

A spectrophotometric procedure to determine the purity of barium styphnate monohydrate based upon the absorbance of the styphnate ion at 326 and 413.3 nm has been developed. The purity is determined by comparing the absorbance of the styphnate ion in barium styphnate and in styphnic acid. Our investigation has shown that the molar absorptivity and lambda maxima of the styphnate

N. E. Brown; J. A. Blasi

1983-01-01

329

Improved spectrophotometric analysis of barium styphnate  

Microsoft Academic Search

A spectrophotometric procedure to determine the purity of barium styphnate monohydrate based upon the absorbance of the styphnate ion at 326 and 413 nm has been developed. The purity is determined by comparing the absorbance of the styphnate ion in barium styphnate and styphnic acid at pH 6.8. Our investigation has shown that the molar absorptivities and maxima of the

Norman E. Brown; Jane A. Blasi

1985-01-01

330

Spectrophotometric and tristimulus analysis of the colors of subcutaneous bleeding in living persons  

Microsoft Academic Search

In forensic activities the estimation of the age of subcutaneous bleeding is very important. The evaluation of color, however, will vary according to differences of light-source, observer, size, background and so forth. The colorimetric methods using a spectrophotometer can effectively evaluate skin discoloration. In this study, the tristimulus and spectrophotometric patterns of color changes of skin bruises were examined among

Yukihito Yajima; Masayuki Nata; Masato Funayama

2003-01-01

331

Spectrophotometric and tristimulus analysis of the colors of subcutaneous bleeding in living persons  

Microsoft Academic Search

The colorimetric patterns of color changes of skin bruises were examined in adult male Japanese volunteers wounded by a sharp pinch on the inside of the upper arm and forearm. In most cases the non-traumatic area near the bruise could be used for the control skin. By using a colorimeter, tristimulus and spectrophotometric methods were available to objectively analyze the

Yukihito Yajima; Masato Funayama

2006-01-01

332

Spectrophotometric Determination of Total Sulfite in White Wine Samples Using Crude Extracts from Flowers  

NASA Astrophysics Data System (ADS)

A didactic spectrophotometric method for determining the sulfite content in white wine samples is proposed. It is based upon a discoloring reaction between flower anthocyanins and the sulfite in basic media. Students' results obtained from iodometric data agreed well with results obtained by the proposed procedure. The use of natural dyes attracted students' interest, enhancing the learning process.

Flora Barbosa Soares, Márlon Herbert; Ramos, Luiz Antonio; Tadeu Gomes Cavalheiro, Éder

2002-09-01

333

Spectrophotometric Winkler determination of dissolved oxygen: re-examination of critical factors and reliability  

Microsoft Academic Search

The spectrophotometric iodine measurement for oxygen determination by the Winkler method is re-examined for theoretical and operational aspects. It is shown that the selection of an isobestic point for measuring the mixture of iodine and tri-iodide in the solution enhances reliability. The wavelength value of 466 nm was selected after a spectrum study. Then, performances are assessed by mean of

Thierry Labasque; Christian Chaumery; Alain Aminot; Gilles Kergoat

2004-01-01

334

Simultaneous Spectrophotometric Determination of Drotaverine Hydrochloride and Paracetamol in Tablet  

PubMed Central

Two simple, accurate and reproducible spectrophotometric methods; Q analysis and first order derivative method have been described for the simultaneous estimation of drotaverine hydrochloride and paracetamol in combined tablet dosage form. Absorption maxima of drotaverine hydrochloride and paracetamol in distilled water were found to be 303.5 nm and 243.5 nm respectively. Beer's law was obeyed in the concentration range 5-50 ?g/ml for drotaverine and 5-60 ?g/ml for paracetamol. In Q analysis method, two wavelengths were selected at isobestic point (277 nm) and ?max of paracetamol (243.5 nm). In first order derivative method, zero crossing point for drotaverine hydrochloride and paracetamol were selected at 303.5 nm and 243.5 nm, respectively. The results of two methods were validated statistically and recovery studies were found to be satisfactory. PMID:20582207

Mahaparale, Sonali; Telekone, R. S.; Raut, R. P.; Damle, S. S.; Kasture, P. V.

2010-01-01

335

Simple and rapid HPLC-UV method using an ultrafine particle octadecylsilane for determination of residual fentanyl in applied Durotep MT transdermal matrix patches and its clinical application.  

PubMed

A few complicated and time-consuming methods are available for the determination of residual fentanyl in Durotep MT transdermal patches, however, their application to clinical settings is limited. The aim of this study was to develop a simple and rapid HPLC-UV method using an ultrafine particle octadecylsilane (ODS) for the determination of residual fentanyl in applied Durotep MT transdermal matrix patches. Patch extraction involved sonicating a shredded Durotep MT patch in acetonitrile for 15 min. Fentanyl separation was completed within 2 min using a 2.3-?m particle ODS column (50 × 4.6 mm i.d.) at a flow rate of 1.5 mL/min. No peaks interfering with fentanyl (1.27 min) and papaverine (0.89 min) as an internal standard were observed. The calibration curve for fentanyl was linear over the range of 0.015-9.0 mg as a Durotep MT patch. The intra- and inter-assay precisions and accuracies of each patch were within 5.3% and 103.9-110.5% and within 8.2% and 97.1-104.3%, respectively. The validated method was applied to determine residual fentanyl in Durotep MT patches used in 35 cancer patients. Although the plasma fentanyl concentration was significantly correlated with its measured absorption rate, the measured absorption rate normalized fentanyl concentration showed a large inter-individual variation. The validated simple and rapid HPLC-UV method established in the present study is helpful for evaluating the absorption rate of fentanyl in patients receiving Durotep MT patches. PMID:22223375

Naito, Takafumi; Takashina, Yoshiaki; Yagi, Tatsuya; Kawakami, Junichi

2012-01-01

336

Simple and rapid simultaneous profiling of minor components of honey by size exclusion chromatography (SEC) coupled to ultraviolet diode array detection (UV-DAD), combined with chemometric methods.  

PubMed

This paper discusses the importance of profiling UV-responsive components, properly integrated with chemometric techniques, in detecting indicative parameters for quality control of honey. The minor components in honeys of different botanical and geographical origins were investigated by size SEC-UV-DAD. We diluted honey with mobile phase before injection into the chromatographic apparatus and a single chromatographic run gave a fast profile of high- (proteins and enzymes), intermediate- (e.g. terpenoid glycosides in lime tree honey) and low-molecular-weight components (secondary metabolites, e.g. kynurenic acid in chestnut honey). The analysis of a total number of 32 honey samples from different regions (Italy, Western Balkan countries, Brazil, Cameroon, Kenya) and of different botanical origins (herbal flower and arboreal flower nectars/honeydews) showed peculiar and characteristic distribution of these markers, which were basically related to their floral origin. Chemometric examination carried out using principal component analysis (PCA) and hierarchical cluster analysis (HCA) of the chromatograms (RT vs. absorption) detected four main clusters in which the groups of (i) chestnut honeys, (ii) honeys from rain forests and (iii) counterfeit/adulterated honeys were clearly separated from the main group of flower nectar honeys. The method is fast, requiring minimal sample handling, and the chromatographic data can be analyzed by multivariate statistical techniques to obtain descriptive information about the honey's quality and composition. PMID:21962760

Beretta, Giangiacomo; Fermo, Paola; Maffei Facino, Roberto

2012-01-25

337

[Spectrophotometric determination of trace cadmium in polyferric sulphate flocculent].  

PubMed

A new sensitive method for determining trace cadmium in polyferric sulphate flocculent is proposed in the paper. The new sensitive method is spectrophotometric method. The color reagents are the butylrhodamin B and potassium iodide. The surfactant is the polyvingl alcohol(PVA). The maximum absorbency wavelength is 607 nm. The molar absorptivity is 4.99 x 10(5) L.mol-1.cm-1. The sandell sensitivity is 2.25 x 10(-4) micrograms Cd2+.cm-2. The Beer's law is obeyed for Cd(II) in the range of 0-1.5 micrograms.25 mL-1. The recovery is 96%-105% and the sample processing procedure is simple. This method has been applied to determination of trace Cd(II) in polyferric sulphate flocculent. The determining results are satisfactory. PMID:12945384

Zheng, H; Gao, J; Yu, Z

2000-08-01

338

A novel method for the thermal analysis of GaN/AlGaN back-illuminated high power UV LEDs  

NASA Astrophysics Data System (ADS)

We report a novel method for the thermal analysis of high-power multi-quantum well GaN/AlGaN UV LEDs of ? ˜ 330 nm. 3D modeling and simulations of chip-on-plate (COP) have been investigated for the packaging of UV LEDs. Steady state thermal analysis of COP packaged devices were carried out using finite element method (FEM). Different heat sinks’ designs such as plate-fins, and pin-fins were modeled to determine device junction temperatures (T j). We also employed thermal resistance circuit (TRC) model to determine the T j considering both conductive and convective methods of heat transfer. Results were in good agreement both for the FEM and TRC models. For the fine plate-fin dense and the less-dense large-fins heat sinks, calculated T j values were ˜37 °C, and ˜46 °C for a corresponding operating power of ˜1.5 W, respectively. On other hand, similar power level junction temperatures of 33 °C and 41 °C were determined respectively for high- and low-density pin-fins heat sinks. Furthermore, thermal flux analysis of these heat sinks was also performed. A comparative study of on-substrate un-packaged and two different (COP) packaged devices was also performed. It was found that our COP based packaged devices are thermally more stable with improved photoluminescence (PL) intensity. As much as around 30% enhancement in the PL intensity of the packaged devices along with a noticeable decrease in the red-shift (about 7 nm) of the spectrum was determined.

Kudsieh, N.; Khizar, M.; Raja, M. Y. A.

2014-04-01

339

Preconcentration of Sn (II) using the methylene blue on the activated carbon and its determination by spectrophotometry method.  

PubMed

A simple and accurate spectrophotometric method for determination of trace amounts of Sn (II) ion in soil sample was developed by using the methylene blue (MB) in the presence of activated carbon (AC) as the adsorbent Solid Phase Extraction (SPE) of Sn (II) and then determined by UV-Vis. The Beer's law is obeyed over the concentration range of 1-80ngmL(-1) of Sn (II) with the detection limits of 0.34ngmL(-1). The influence of type and volume of eluent, concentration of MB, pH, and amount of AC on sensitivity of spectrophotometric method were optimized. The method has been successfully applied for Sn (II) ion determination in soil sample. PMID:24394524

Khodadoust, Saeid; Cham Kouri, Narges

2014-04-01

340

Spectrophotometric determination of anilines based on charge-transfer reaction  

NASA Astrophysics Data System (ADS)

The molecular interactions between aniline, p-toluidines, benzidine and p-phenylenediamine as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as acceptor have been investigated by spectrophotometric method. Different variables affecting the reaction were studies and optimized. At the optimum reaction conditions Beer's law was obeyed in a concentration limit of 0.6-3.0, 0.3-3.0, 0.3-3.0 and 0.3-2.7 ?g ml -1 for aniline, p-toluidines, benzidine and p-phenylenediamine. The developed methods were applied successfully for the determination of the studied compounds in waste water and relative standard deviation of the methods were 0.8-3.0%. Percentage recoveries ranged from 97.22% to 102.78%.

Wu, Hao; Du, Li Ming

2007-07-01

341

Spectrophotometric determination of anilines based on charge-transfer reaction.  

PubMed

The molecular interactions between aniline, p-toluidines, benzidine and p-phenylenediamine as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as acceptor have been investigated by spectrophotometric method. Different variables affecting the reaction were studies and optimized. At the optimum reaction conditions Beer's law was obeyed in a concentration limit of 0.6-3.0, 0.3-3.0, 0.3-3.0 and 0.3-2.7 microg ml(-1) for aniline, p-toluidines, benzidine and p-phenylenediamine. The developed methods were applied successfully for the determination of the studied compounds in waste water and relative standard deviation of the methods were 0.8-3.0%. Percentage recoveries ranged from 97.22% to 102.78%. PMID:17267269

Wu, Hao; Du, Li Ming

2007-07-01

342

Flow injection spectrophotometric determination of ofloxacin in pharmaceuticals and urine.  

PubMed

A sensitive and fast flow-injection spectrophotometric method for the determination of ofloxacin is proposed. The method is based on the formation of a yellow complex between ofloxacin and Fe (III), in sulphuric medium. The influence of FI and chemical variables were studied. The calibration graph resulting from measuring the absorbance at 420 nm is linear over the range 5.0 x 10(-6)8.0 x 10(-4)M (1.8-289 mg l(-1)) with a detection limit of 2.0 x 10(-6)M (0.72 mg l(-1)). The method is applied to the routine analysis of ofloxacin in pharmaceuticals and human urine. PMID:16005199

Soledad García, M; Isabel Albero, M; Sánchez-Pedreño, Concepción; Salem Abuherba, Mustafa

2005-09-01

343

A fast tree-based method for estimating column densities in adaptive mesh refinement codes. Influence of UV radiation field on the structure of molecular clouds  

NASA Astrophysics Data System (ADS)

Context. Ultraviolet radiation plays a crucial role in molecular clouds. Radiation and matter are tightly coupled and their interplay influences the physical and chemical properties of gas. In particular, modeling the radiation propagation requires calculating column densities, which can be numerically expensive in high-resolution multidimensional simulations. Aims: Developing fast methods for estimating column densities is mandatory if we are interested in the dynamical influence of the radiative transfer. In particular, we focus on the effect of the UV screening on the dynamics and on the statistical properties of molecular clouds. Methods: We have developed a tree-based method for a fast estimate of column densities, implemented in the adaptive mesh refinement code RAMSES. We performed numerical simulations using this method in order to analyze the influence of the screening on the clump formation. Results: We find that the accuracy for the extinction of the tree-based method is better than 10%, while the relative error for the column density can be much more. We describe the implementation of a method based on precalculating the geometrical terms that noticeably reduces the calculation time. To study the influence of the screening on the statistical properties of molecular clouds we present the probability distribution function of gas and the associated temperature per density bin and the mass spectra for different density thresholds. Conclusions: The tree-based method is fast and accurate enough to be used during numerical simulations since no communication is needed between CPUs when using a fully threaded tree. It is then suitable to parallel computing. We show that the screening for far UV radiation mainly affects the dense gas, thereby favoring low temperatures and affecting the fragmentation. We show that when we include the screening, more structures are formed with higher densities in comparison to the case that does not include this effect. We interpret this as the result of the shielding effect of dust, which protects the interiors of clumps from the incoming radiation, thus diminishing the temperature and changing locally the Jeans mass.

Valdivia, Valeska; Hennebelle, Patrick

2014-11-01

344

Screening method for the detection of artificial colours in saffron using derivative UV-Vis spectrometry after precipitation of crocetin  

Microsoft Academic Search

A screening method for the detection of artificial colours (naphthol yellow, tartrazine, quinoline yellow, Sunset yellow, Allura red, amaranth, azorubine, Ponceau 4R and Red 2G) in saffron is described. The method involves removal of crocins by precipitation of crocetin (pH 0.1, 90°C) before adsorption of the artificial colours on polyamide SPE cartridges (pH 2). After washing with methanol, acetone and

A. Zalacain; S. A. Ordoudi; I. Blázquez; E. M. Díaz-Plaza; M. Carmona; M. Z. Tsimidou; G. L. Alonso

2005-01-01

345

The absolute spectrophotometric catalog by Anita Cochran  

NASA Astrophysics Data System (ADS)

The absolute spectrophotometric catalog by Anita Cochran is presented in a machine-readable form. The catalog systematizes observations acquired at the McDonald Observatory in 1977-1978. The data are compared with other sources, in particular, the calculated broadband stellar magnitudes are compared with photometric observations by other authors, to show that the observational data given in the catalog are reliable and suitable for a variety of applications. Observations of variable stars of different types make Cochran's catalog especially valuable.

Burnashev, V. I.; Burnasheva, B. A.; Ruban, E. V.; Hagen-Torn, E. I.

2014-06-01

346

A method to derive long-term time series and trends of UV-B radiation (1968-1997) from observations at Hohenpeissenberg (Bavaria)  

Microsoft Academic Search

The aim of this study is to estimate the solar ultraviolet (UV) radiation reaching the ground during the last 30 years. Solar UV-B irradiance (290-320 nm) measured by the Brewer spectrophotometer 10 at Hohenpeissenberg, Germany (48°N, 11°E), was compared with other ground-based measurements at Hohenpeissenberg. Eight years (1990-1997) of operationally measured UV were used to establish statistical relations between spectral

Leonhard Gantner; Peter Winkler; Ulf Köhler

2000-01-01

347

Determination of cmc of imidazolium based surface active ionic liquids through probe-less UV-vis spectrophotometry.  

PubMed

In the first of its kind we herein report the results of our studies undertaken on the micellization behaviour of imidazolium based surface active ionic liquids (SAILs) to prove that their critical micelle concentration (cmc) can be estimated through ultraviolet-visible (UV-vis) spectroscopy without using any external probe. Tensiometric and spectrophotometric investigations of a series of freshly prepared SAILs viz. 1-octyl-3-methylimidazolium chloride ([OMIM][Cl]), 1-octyl-3-methylimidazolium dodecylsulphate ([OMIM][DS]), 1-octyl-3-methylimidazolium benzoate ([OMIM][Bz]), 1-octyl-3-methylimidazolium salicylate ([OMIM][Sc]), 1-octyl-3-methylimidazolium acetate ([OMIM][Ac]) are presented as a case study in support of the said claim. The cmcs estimated through spectrophotometric method were found to be close to the values estimated through tensiometry for the said SAILs. The cmcs for the investigated SAILS were found to vary in order of [OMIM][Cl]>[OMIM][Ac]>[OMIM][Bz]>[OMIM][Sc]>[OMIM][DS]. To the best of our knowledge the present communication will be the first report about the synthesis, characterization and micellization behaviour of [OMIM][Bz] and [OMIM][Sc]. PMID:25281072

Rather, Mudasir Ahmad; Rather, Ghulam Mohammad; Pandit, Sarwar Ahmad; Bhat, Sajad Ahmad; Bhat, Mohsin Ahmad

2015-01-01

348

Rapid and simplified HPLC-UV method with on-line wavelengths switching for determination of capecitabine in human plasma.  

PubMed

Capecitabine is an important oral fluoropyrimidine anticancer drug. The purpose of this study was to overcome limitations of previously reported methods and propose an optimized and widely available tool for analysis of capecitabine in human plasma. The simplification of the liquid-liquid extraction procedure involved elimination of unnecessary addition of phosphoric acid and reduction of the extraction solvent volume. The use of voriconazole as the internal standard, combined with gradient elution and on-line wavelength switching, assured very high within- and between-run precision of results (relative standard deviation < 7.1% for lower limit of quantification) and enabled the reduction of the total chromatographic run time to 8 min. The calibration curve was linear within the range of 0.05-10.00 microg/mL and the method selectivity was confirmed in the presence of capecitabine metabolites. All validation parameters met the acceptance criteria set by international regulatory guidances, which proves that the method leads to reliable results. The method may be applied in human pharmacokinetic studies, for the regulatory purposes and therapeutic drug monitoring. PMID:25073394

Piórkowska, E; Kaza, M; Fitatiuk, J; Szlaska, I; Pawi?ski, T; Rudzki, P J

2014-07-01

349

Spectrophotometric determination of triclosan in personal care products  

NASA Astrophysics Data System (ADS)

A spectrophotometric method for the determination of triclosan in personal care products was proposed. It was based on the reaction of sodium nitrite with p-sulfanilic acid in an acidic medium to form diazonium ion, with which triclosan further formed an azo compound in an alkaline medium. The resulting yellow colored product has a maximum absorption at 452 nm. A good linear relationship ( r = 0.9999) was obtained in the range of 0-30 mg L -1 triclosan. A detection limit of 0.079 g L -1 was achieved and the relative standard deviation was 0.24% ( n = 11) at 14 mg L -1 triclosan. The proposed method has been applied to the analyses of triclosan in several personal care products and the results were in good agreement with those obtained by high-performance liquid chromatography.

Lu, Huihui; Ma, Hongbing; Tao, Guanhong

2009-09-01

350

Flow-injection spectrophotometric determination of methyldopa in pharmaceutical formulations.  

PubMed

A flow-injection spectrophotometric procedure is proposed for methyldopa determination in pharmaceutical preparations. The determination is based on formation of a yellow product (measured at 410nm) after complexation of methyldopa with molybdate. Under optimal conditions, Beer's law is obeyed in a concentration range of 50-200mgl(-1) methyldopa. Typical correlation between absorbance and analyte concentration was 0.9999. Usual excipients used as additives in pharmaceuticals do not interfere with the proposed method. The analytical frequency was 210h(-1) and the relative standard deviation (R.S.D.) was method were in good agreement with labeled values and those obtained by the Brazilian Pharmacopoeia procedure at 95% confidence level. PMID:18970162

Ribeiro, P R S; Neto, J A Gomes; Pezza, L; Pezza, H R

2005-07-15

351

UV-based therapy.  

PubMed

UV phototherapy has a long history of use for the treatment of select diseases in dermatology. Its use has evolved into more effective and targeted modalities, including psoralen + UV-A photochemotherapy, narrowband UV-B, excimer laser, and UV-A1 phototherapy. With its proven record of efficacy and safety, UV phototherapy is an excellent option in the treatment of an ever-growing number of skin conditions. PMID:24891061

Totonchy, Mariam B; Chiu, Melvin W

2014-07-01

352

Simple and validated UHPLC method coupled to UV detection for determination of daptomycin in human plasma and urine.  

PubMed

Daptomycin, a lipopeptide antibiotic with excellent activity against Gram-positive bacteria, is excreted primarily by the kidneys. Development of effective chromatographic methodologies for the determination of daptomycin in human specimens is necessary for clinical use. This study developed a simple and validated ultra-high-performance liquid chromatography method coupled to ultraviolet detection for determination of daptomycin in human plasma and urine. After the pretreatments involving protein precipitation, the supernatants were separated using a 2.3?µm particle size octadecylsilyl column, and the run time was 1?min. The calibration curves were linear over the concentration ranges of 2-200?mg/L for plasma and 25-300?mg/L for urine. Intra- and inter-assay precision and accuracy values of plasma were within 13.5 and 92-100% and within 10.7 and 100-107%, respectively. Those of urine were within 5.0 and 101-104% and within 3.7 and 100-101%, respectively. The validated method was applied to the determination of plasma and urine samples in patients receiving 4-6?mg/kg of intravenous daptomycin, resulting in sufficient sensitivity for evaluating the plasma exposure and urinary excretion. In conclusion, the present method with acceptable analytical performance can be helpful for evaluating the pharmacokinetic disposition of daptomycin in clinical settings. PMID:24037956

Naito, Takafumi; Yamada, Takahiro; Yagi, Tatsuya; Kawakami, Junichi

2014-03-01

353

Multiresidue chromatographic method for the determination of macrolide residues in muscle by high-performance liquid chromatography with UV detection.  

PubMed

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of tilmicosin, tylosin, spiramycin, and its major metabolite neospiramycin was developed that is suitable for porcine, bovine, and poultry muscles. Macrolide residues were extracted from muscle with acetonitrile, fat was removed by liquid-liquid extraction with isooctane, and the extract was then cleaned on Bond Elut C18 cartridges. The HPLC separation was performed on an Inertsil ODS3 C18 column (150 x 4 mm) with 0.05% trifluoroacetic acid-acetonitrile in a gradient mode. Two different chromatographic gradients were used for tilmicosin-tylosin and spiramycin-neospiramycin, and the detection wavelengths were 287 and 232 nm, respectively. The method was validated from 1/2 the maximum residue limit (MRL) to 4 times the MRL with pork muscle samples. Mean recoveries were 60, 63.5, 51, and 42% for tilmicosin, tylosin, spiramycin, and neospiramycin, respectively. The detection limits are 15 micrograms/kg for tilmicosin and tylosin, 30 micrograms/kg for spiramycin, and 25 micrograms/kg for neospiramycin. Linearity, precision, and accuracy of the method were also tested. PMID:10513006

Juhel-Gaugain, M; Anger, B; Laurentie, M

1999-01-01

354

Comparative Analysis of Lycorine in Wild Plant and Callus Culture Samples of Hymenocallis littoralis by HPLC-UV Method  

PubMed Central

The Hymenocallis littoralis, an ornamental and medicinal plant, had been traditionally used for wound healing. In the present study, an analytical method using HPLC with ultraviolet detection was developed for the quantification of lycorine in the extracts of different parts of wild plant and tissue culture samples of H. littoralis. The separation was achieved using a reversed-phase column. The method was found to be accurate, repeatable, and sensitive for the quantification of minute amount of lycorine present in the samples. The highest lycorine content was found in the bulb extract (2.54 ± 0.02??g/mg) whereas the least was in the root extract (0.71 ± 0.02??g/mg) of the wild plants. Few callus culture samples had high content of lycorine, comparable to that of wild plants. The results showed that plant growth regulators, 2,4-dichlorophenoxyacetic acid (2,4-D) alone at 4.5??M (2.58 ± 0.38??g/mg) or a combination of 2,4-D at 9.00??M with 4.5??M of 6-benzylaminopurine (BAP), were the optimum concentrations for the production of high lycorine (2.45 ± 0.15??g/mg) content in callus culture. The present analytical method could be of value for routine quantification of lycorine in the tissue culture production and standardization of the raw material or extracts of H. littoralis. PMID:24895650

Sahgal, Geethaa; Murugaiyah, Vikneswaran

2014-01-01

355

HPLC method with UV detection for evaluation of digoxin tablet dissolution in acidic medium after solid-phase extraction.  

PubMed

A simple and reliable method for the evaluation of dissolution of digoxin tablets in 0.01 M hydrochloric acid was developed. Digoxin and its degradation products after solid-phase extraction using C18 Sep-Pak cartridges were evaluated. Analyses were performed on C18 column (LiChrospher RP-18e, 5 microm, 125 x 4.0 mm), as mobile phase water and acetonitrile (72:28, v/v) were used. Detection wavelength was 218 nm. Identity of digoxin degradation products was confirmed by HPLC-MS. PMID:12946537

Jedlicka, A; Grafnetterová, T; Miller, V

2003-09-15

356

A comparative study of progressive versus successive spectrophotometric resolution techniques applied for pharmaceutical ternary mixtures  

NASA Astrophysics Data System (ADS)

This work represents a comparative study of a novel progressive spectrophotometric resolution technique namely, amplitude center method (ACM), versus the well-established successive spectrophotometric resolution techniques namely; successive derivative subtraction (SDS); successive derivative of ratio spectra (SDR) and mean centering of ratio spectra (MCR). All the proposed spectrophotometric techniques consist of several consecutive steps utilizing ratio and/or derivative spectra. The novel amplitude center method (ACM) can be used for the determination of ternary mixtures using single divisor where the concentrations of the components are determined through progressive manipulation performed on the same ratio spectrum. Those methods were applied for the analysis of the ternary mixture of chloramphenicol (CHL), dexamethasone sodium phosphate (DXM) and tetryzoline hydrochloride (TZH) in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the official BP methods, showing no significant difference with respect to accuracy and precision.

Saleh, Sarah S.; Lotfy, Hayam M.; Hassan, Nagiba Y.; Salem, Hesham

2014-11-01

357

Gravimetric and spectrophotometric determination of hexafluoroantimonate with tetraphenylarsonium chloride, nitron and ferroin.  

PubMed

Two methods are described for the gravimetric determination of the hexafluoroantimonate anion with tetraphenylarsonium chloride and nitron as precipitants. In addition, a spectrophotometric method for this anion with ferroin as reagent is described. Hydrolysis of the anion is avoided by using stock solutions of KSbF(6) in N,N-dimethylformanude and adding these directly to concentrated aqueous solutions of the analytical reagent. Interference studies are included on a number of anions. PMID:18960258

Archer, V S; Twelves, R B

1968-01-01

358

Spectrophotometric Determination of Nitrogen Dioxide in Air and Nitrite in Water And Soil Samples  

Microsoft Academic Search

A sensitive spectrophotometric method for the determination of nitrogen dioxide in air and nitrite in water and soil samples is described. Nitrogen dioxide in air is fixed as nitrite ion in alkaline sodium arsenite or in triethanolamine absorber solutions. The method is based on the diazo coupling reaction between p-nitro aniline and 1-hydroxy-2-naphthoic acid. The azo dye formed under aqueous

M. Pandurangappa; N. Balasubramanian

1995-01-01

359

Solid phase extraction–spectrophotometric determination of fluoride in water samples using magnetic iron oxide nanoparticles  

Microsoft Academic Search

A new, sensitive, fast and simple method using magnetic iron oxide nanoparticles (MIONs), as an adsorbent has been developed for extraction, preconcentration and determination of traces of fluoride ions. The determination method is based on the discoloration of Fe(III)–SCN complex with extracted fluoride ions which was subsequently monitored spectrophotometrically at ?max=458nm. Various parameters affecting the adsorption of fluoride by the

H. Parham; N. Rahbar

2009-01-01

360

Simultaneous kinetic spectrophotometric analysis of five synthetic food colorants with the aid of chemometrics  

Microsoft Academic Search

This paper describes a simple and sensitive kinetic spectrophotometric method for the simultaneous determination of Amaranth, Ponceau 4R, Sunset Yellow, Tartrazine and Brilliant Blue in mixtures with the aid of chemometrics. The method involved two coupled reactions, viz. the reduction of iron(III) by the analytes to iron(II) in sodium acetate\\/hydrochloric acid solution (pH 1.71) and the chromogenic reaction between iron(II)

Yongnian Ni; Yong Wang; Serge Kokot

2009-01-01

361

Apparatus for continuous-flow underway spectrophotometric measurement of surface water pH  

Microsoft Academic Search

A continuous-flow method for spectrophotometric measurement of seawater pH providing high temporal resolution has been developed incorporating a CCD-based spectrophotometer and dual pumps for seawater and indicator dye solution. The method showed good laboratory precision (±0.0007 pH units). The accuracy of the measurement system was assessed by comparing in situ measured pCO2 values calculated from measured pH and alkalinity. An

Melissa Tapp; Keith Hunter; Kim Currie; Burns Mackaskill

2000-01-01

362

Optimization and Validation of RP-HPLC-UV/Vis Method for Determination Phenolic Compounds in Several Personal Care Products  

PubMed Central

An HPLC method with ultraviolet-visible spectrophotometry detection has been optimized and validated for the simultaneous determination of phenolic compounds, such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) as antioxidants, and octyl methyl cinnamate (OMC) as UVB-filter in several personal care products. The dynamic range was between 1 to 250?mg/L with relative standard deviation less than 0.25% (n = 4). Limits of detection for BHA, BHT, and OMC were 0.196, 0.170, and 0.478?mg/L, respectively. While limits of quantification for BHA, BHT, and OMC were 0.593, 0.515, and 1.448?mg/L, respectively. The recovery for BHA, BHT, and OMC was ranged from 92.1–105.9%, 83.2–108.9%, and 87.3–103.7%, respectively. The concentration ranges of BHA, BHT, and OMC in 12 commercial personal care samples were 0.13–4.85, 0.16–2.30, and 0.12–65.5?mg/g, respectively. The concentrations of phenolic compounds in these personal care samples were below than maximum allowable concentration in personal care formulation, that is, 0.0004–10?mg/g, 0.002–5?mg/g, and up to 100?mg/g for BHA, BHT, and OMC, respectively. PMID:21760792

Akkbik, Mohammed; Assim, Zaini Bin; Ahmad, Fasihuddin Badruddin

2011-01-01

363

Thin layer chromatography-spray mass spectrometry: a method for easy identification of synthesis products and UV filters from TLC aluminum foils.  

PubMed

A straightforward procedure for direct mass spectrometric (MS) analysis of spots from thin layer chromatography (TLC) plates, without the need of an external ion source, was developed using the aluminum plate backing as spray tip. The spots were cut out shaped as a tip with a 60° angle, mounted in front of the MS orifice, and after addition of a spray solvent spectra were obtained immediately. A high-resolution time-of-flight MS was used since the method is of particular interest for rapid identification or confirmation of spots from TLC plates. The practical benefits of this technique were demonstrated by detection of by-products of organic reactions, by identification of degradation products, and by accurate confirmation of spots when UV filters in sunscreens were analyzed by TLC. Employing the described method TLC spots can be evaluated fast without the need of an external ion source or devices for analyte transfer from TLC to MS, only a basic MS instrument and a high-voltage power supply is required. PMID:24500757

Himmelsbach, Markus; Waser, Mario; Klampfl, Christian W

2014-06-01

364

Development of HPLC method by UV-VIS detection for the quantification of phenolic acids in different Ocimum sanctum Linn. extracts.  

PubMed

A simple and rapid chromatographic method has been developed for the simultaneous determination of five phenolic acids including Gallic acid, Chloroganic acid, Syringic acid, Benzoic acid and Vanillic acid by HPLC with UV-VIS detector. These Phenolic acids were separated by analytical column Intersil ODS-3 C18, a gradient elution system of ACN and acidified water solution with 1ml/min flow rate and quantified in a total run of 30 minutes at 210nm wavelength. In the quantitative analysis of these compounds showed good regression (0.995-0.999). The limit of detection [LOD] and limit of quantification [LOQ] of these compounds were in the range of 0.15-0.46 and 0.42-2.47 ?g/mL. The average recoveries were between 95.8-103.1% and their RSD values were less than 3.34%. By the proposed method Gallic acid, Chloroganic acid and Syringic acid were found and quantified in Methanolic, Ethanolic and Acetonic extract of Ocimum sanctum Linn. leaves. While the two other phenolic acids benzoic acid and vanillic acid was not found in the extracts of Ocimum sanctum Linn. leaves. PMID:25176382

Shafqatullah; Khan, Rasool; Hassan, Waseem; Hussain, Arshad; Asadullah; Rehman, Khaliqur; Ali, Javid

2014-09-01

365

Ab initio calculation of UV-absorption spectra of chlorophyll a: Comparison study between RHF/CIS, TDDFT, and semi-empirical methods  

E-print Network

Chlorophyll a is one the most abundant pigment on Earth, which is responsible for trapping the light energy to perform the photosynthesis process in green plants. This molecule is a metal-complex compound that consists of a porphyrins ring with high symmetry that acts as ligands with magnesium as the central ion. Chlorophyll a has been studied for many years from different point of views for both experimental and theoretical interests. In this study, the restricted Hartree-Fock configuration interaction single (RHF/CIS), time-dependent density functional theory (TDDFT) and some semi-empirical methods (CNDO/s and ZINDO) calculations were carried out and compared to reconstruct the UV-Vis absorption spectra of chlorophyll a. In some extend, the calculation results based on a single molecule calculation were succeeded to reconstruct the absorption spectra but required to be scaling and broaden to match the experimental one. Different computational methods (ab initio and semi-empirical) exhibits the differences i...

Suendo, Veinardi

2011-01-01

366

Kinetic spectrophotometric determination of low levels of nitrite by catalytic reaction between pyrogallol red and bromate.  

PubMed

A kinetic spectrophotometric method for the determination of trace nitrite (0.003-1.000 microg/ml) based on its catalytic effect on the reaction between potassium bromate and pyrogallol red in acidic media is described. The reaction is monitored spectrophotometrically by measuring the decreasing colour of pyrogallol red at 467 nm by the fixed-time method. At a given time of 3.0 min at 30 degrees, the detection limit is 0.001 microg/ml and the relative standard deviation for 0.010 microg/ml nitrite is 1.8% (n = 8). The method is free from most interferences, especially from large amounts of nitrate and ammonium. The procedure was successfully applied to the determination of trace nitrite in natural water without preconcentration. PMID:18965793

Ensafi, A A; Samimifar, M

1993-09-01

367

Spectrophotometric determination of enoxacin as ion-pairs with bromophenol blue and bromocresol purple in bulk and pharmaceutical dosage form  

Microsoft Academic Search

Three simple, accurate and sensitive spectrophotometric methods were developed for determination of enoxacin. The methods based on extraction of this drug into chloroform as ion pairs with sulphonphthalein dyes as bromophenol blue and bromocresol purple. The optimum conditions of the reactions were studied and optimized. The absorbance of yellow products was measured at 412 nm for enoxacin–bromophenol blue and 410

?ncilay Süslü; Ayla Tamer

2002-01-01

368

Development of an HPLC-UV Method for the Analysis of Drugs Used for Combined Hypertension Therapy in Pharmaceutical Preparations and Human Plasma.  

PubMed

A simple, rapid, and selective HPLC-UV method was developed for the determination of antihypertensive drug substances: amlodipine besilat (AML), olmesartan medoxomil (OLM), valsartan (VAL), and hydrochlorothiazide (HCT) in pharmaceuticals and plasma. These substances are mostly used as combinations. The combinations are found in various forms, especially in current pharmaceuticals as threesome components: OLM, AML, and HCT (combination I) and AML, VAL, and HCT (combination II). The separation was achieved by using an RP-CN column, and acetonitrile-methanol-10?mmol orthophosphoric acid pH 2.5 (7?:?13?:?80, v/v/v) was used as a mobile phase; the detector wavelength was set at 235?nm. The linear ranges were found as 0.1-18.5? ? g/mL, 0.4-25.6? ? g/mL, 0.3-15.5? ? g/mL, and 0.3-22? ? g/mL for AML, OLM, VAL, and HCT, respectively. In order to check the selectivity of the method for pharmaceutical preparations, forced degradation studies were carried out. According to the validation studies, the developed method was found to be reproducible and accurate as shown by RSD ?6.1%, 5.7%, 6.9%, and 4.6% and relative mean error (RME) ?10.6%, 5.8%, 6.5%, and 6.8% for AML, OLM, VAL, and HCT, respectively. Consequently, the method was applied to the analysis of tablets and plasma of the patients using drugs including those substances. PMID:23634320

Kepekci Tekkeli, Serife Evrim

2013-01-01

369

Spectrophotometric determination of ofloxacin in pharmaceuticals by redox reaction  

NASA Astrophysics Data System (ADS)

Two simple spectrophotometric methods have been developed to analyze ofloxacin (OFX) in pharmaceuticals. The methods are based on the oxidation of OFX by a measured excess of cerium(IV) sulfate in H2SO4 medium. This was followed by the determination of the unreacted oxidant by reacting it with either p-toluidine ( p-TD) and measuring the absorbance at 525 nm (method A) or o-dianisidine ( o-DA) and measuring the absorbance at 470 nm (method B). In both methods, the amount of cerium(IV) sulfate reacted corresponds to the amount of OFX. Calibration graphs were linear over the ranges of 0-120 and 0-4 g/ml OFX for methods A and B, respectively. The calculated molar absorptivity (2.34?103 and 5.99?104), Sandell sensitivity, and limit of quantification for the methods are reported. The intra-day precision (%RSD) and accuracy (%RE) were < 8.0 and ? 4.0%, respectively, and the inter-day RSD and RE values were within 5 and 4.0%, respectively. The applicability of the methods was demonstrated by determining OFX in tablets with an accuracy (%RE) of < 3% and precision (%RSD) of ?2.65%. The accuracy of the methods was further ascertained by recovery experiments via a standard-addition procedure.

Ramesh, P. J.; Basavaiah, K.; Rajendraprasad, N.; Devi, O. Zenita; Vinay, K. B.

2011-07-01

370

A spectrophotometric catalogue of HII galaxies  

E-print Network

We present a spectrophotometric catalogue of 90 emission-line galaxies (ELGs) discovered during an objective - prism survey that aimed to search for dwarf galaxies within the voids (Popescu et al. 1996, 1998). The paper presents line ratios, equivalent widths and absolute fluxes for the emission-lines seen in the spectra of the galaxies. A list of newly discovered Wolf-Rayet galaxies is presented. Many objects included in the catalogue have low metallicity and the extreme cases are proposed as candidates for very low metallicity galaxies.

Cristina C. Popescu; Ulrich Hopp

1999-12-23

371

Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent  

NASA Astrophysics Data System (ADS)

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80-400 ?g mL -1 for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.

Saleh, Gamal A.; El-Shaboury, Salwa R.; Mohamed, Fardous A.; Rageh, Azza H.

2009-09-01

372

UV opportunities at ESO  

NASA Astrophysics Data System (ADS)

After summarizing the UV capabilities available at the Paranal observatory, the perspectives for additional UV instruments are discussed. When considering that most likely the E-ELT will not be optimized for UV, and that HST operations will be soon discontinued, UV instruments at the VLT may represent the best capabilities for the ESO community for a few years. In particular the cases of spectroscopy close to the atmospheric cutoff and Blue diffraction limited imaging show a great scientific potential.

Pasquini, Luca

2014-11-01

373

Self-referencing spectrophotometric measurements  

DOEpatents

A method is described for measuring the concentration of a chemical substance by spectrophotometry comprising the steps of placing a sample of a photoreactive substance between the light source and a spectrophotometer, obtaining an absorption spectrum of the substance using a fixed amount of light from the light source, obtaining a second absorption spectrum after a short interval, comparing the two to determine the concentration of the chemical substance from the difference in the spectra. If the chemical substance is not photoreactive, a photoreactive mixture can be made with a photoreactive dye that has photoreactive properties unique to the mixture. Alternatively, an optically transparent substrate can absorb the substance or the dye/substance mixture. 3 figures.

O'Rourke, P.E.; Van Hare, D.R.

1994-03-29

374

Potential fingerprints detection using UV spectral imaging  

NASA Astrophysics Data System (ADS)

Spectral imaging technology research is becoming more extensive in the field of examination of material evidence. UV spectral imaging technology is an important part of the full spectrum of imaging technology. This paper summarizes the application of the results of UV imaging technology in the field of evidence examination, explores the common object of potential fingerprints of UV spectra characteristic for the research objectives, which shows the potential traces of criminal using the ultraviolet spectrum imaging method.

Huang, Wei; Yang, Zhichao; Xu, Xiaojing; Guo, Jingjing

2012-11-01

375

UV-Visible Spectroscopy  

NSDL National Science Digital Library

This webpage, part of a larger project "Understanding Chemistry", provides an introduction to UV-visible spectroscopy suitable for use in introductory chemistry and introductory analytical chemistry courses. The pages discuss UV-visible light, absorption, Beer's law, the double-beam spectrometer, and introduce some standard applications of UV-vis spectroscopy.

Clark, Jim

2012-09-20

376

Microfluidic Analysis of Serine Levels Using Seryl-tRNA Synthetase Coupled with Spectrophotometric Detection.  

PubMed

The measurement of amino acid content is useful for the diagnosis of several types of diseases, including cancer and diabetes. In this study, a microfluidic method for the analysis of serine using enzymatic reactions coupled with spectrophotometric detection was developed. The assay system has some advantages in the analytical field, such as the ability to detect small amounts of analyte and reaction solution and a rapid and efficient reaction. For the specific detection of serine, seryl-tRNA synthetase was coupled with the generation of hydrogen peroxide, which was then detected by the Trinder reagent spectrophotometric method. Seryl- and other aminoacyl-tRNA synthetases are involved in the biosynthesis of peptides and proteins in the human body and should allow precise recognition of the corresponding amino acids. This approach provided selective quantitation of up to 250 ?M serine in 100 mM Tris-HCl buffer (pH 8.0) in a semiautomatic system. PMID:25190303

Kugimiya, Akimitsu; Matsuzaki, Emi

2014-12-01

377

Determination of Nitrites, Nitrates, and Their Mixtures Using Flow Injection Analysis with Spectrophotometric Detection  

Microsoft Academic Search

A new flow injection analysis (FIA) method has been developed for determination of nitrites, nitrates, and their mixtures, based on the reaction of nitrites with rivanol (2-ethoxy-6,9-diaminoacridinium lactate) in HCl medium; the concentration of the diazonium salt formed is evaluated spectrophotometrically (? = 520 nm). Flow-through determination of nitrates can be carried out by using the same reaction following prior reduction in a

M. Brabcová; P. Rychlovský; I. N?mcová

2003-01-01

378

Spectrophotometric determination of rosmarinic acid in plant cell cultures by complexation with Fe 2+ ions  

Microsoft Academic Search

A spectrophotometric method for determining rosmarinic acid (a-O-caffeoyl-3,4-dihydroxyphenyllactic acid) in unpurified methanolic extracts from Lavandula cell cultures is reported. It is based on a complexation reaction of rosmarinic acid with Fe2+ to give a blue-dark product with ?max=572 nm and ?573=3.82×103 l mol-1 cm-1. The stoichiometry of the reaction and the optimal conditions for colour development are checked. The sensitivity

T. López-Arnaldos; M. López-Serrano; A. Ros Barceló; A. A. Calderón; J. M. Zapata

1995-01-01

379

Spectrophotometric Determination of Iron In Wines, Vegetables, Pharmaceutical Compounds and Minerals With Mandelohydroxamic Acid (Mha)  

Microsoft Academic Search

A new reagent, mandelohydroxamic acid (MHA), which has an easy synthesis and an high water solubility (64.48 gL) is proposed for a simple, rapid, selective and sensitive method for the spectrophotometric determination of iron based upon the formation of the MHA-Fe(III) complex and its extraction into n-butanol under optimum operating conditions. A yellow color is formed when the complex is

F. Salinas; A. R. Fernandez-alba; J. L. Martinez-vidal

1989-01-01

380

Development of HPLC-UV method for rapid and sensitive analysis of topically applied tetracaine: its comparison with a CZE method.  

PubMed

Topically applied tetracaine is a local anaesthetic. A novel HPLC method for the rapid and sensitive analysis of tetracaine was developed and compared with a short end direction capillary zone electrophoresis (CZE) method. The method was developed and validated for the separation and quantification of tetracaine in skin samples removed by 'tape-stripping'. Tetracaine was extracted from tape with 100% methanol, which was then diluted to 50% with water for injection. Tetracaine and the internal standard, procaine, were separated on a reversed-phase Luna PFP(2), 3 µm, 150 × 4.6 mm column at ambient temperature using isocratic elution with KH2 PO4 buffer (pH 2.5) and methanol (35:65, v/v). The flow rate was 1 mL/min, with detection at 312 nm. The limit of quantification for tetracaine was 0.03 µg/mL. Calibration lines were linear with r(2) values >0.99. The within- and between-assay imprecision and the percentage of inaccuracy for the QC samples including lower and upper limits of quantitation were <6 and <10%. The absolute mean recovery of tetracaine was >92%. Compared with CZE, the mean percentage error and the absolute mean percentage error were 0.62 and 6.29, respectively. The two methods were compared in a number of pharmacokinetic studies. PMID:24861750

Al-Otaibi, Faisal; Ghazaly, Essam; Johnston, Atholl; Perrett, David

2014-06-01

381

Development and validation of a discriminative dissolution method for atorvastatin calcium tablets using in vivo data by LC and UV methods.  

PubMed

A dissolution method to analyze atorvastatin tablets using in vivo data for RP and test pilot (PB) was developed and validated. The appropriate conditions were determined after solubility tests using different media, and sink conditions were established. The conditions used were equipment paddle at 50 rpm and 900 mL of potassium phosphate buffer pH 6.0 as dissolution medium. In vivo release profiles were obtained from the bioequivalence study of RP and the generic candidate PB. The fraction of dose absorbed was calculated using the Loo-Riegelman method. It was necessary to use a scale factor of time similar to 6.0, to associate the values of absorbed fraction and dissolved fraction, obtaining an in vivo-in vitro correlation level A. The dissolution method to quantify the amount of drug dissolved was validated using high-performance liquid chromatography and ultraviolet spectrophotometry, and validated according to the USP protocol. The discriminative power of dissolution conditions was assessed using two different pilot batches of atorvastatin tablets (PA and PB) and RP. The dissolution test was validated and may be used as a discriminating method in quality control and in the development of the new formulations. PMID:24265014

Machado, J C; Lange, A D; Todeschini, V; Volpato, N M

2014-02-01

382

UV Curable Polyimides  

NASA Technical Reports Server (NTRS)

The development of UV curable polyimides for high-temperature applications is a growing area of research activity. The objective of this technology is an attempt to bypass many of the issues associated with "typical" high-temperature polymers. For example, the use of toxic or mutagenic monomers (i.e., many aromatic diamines) can be prevented. Also, it proves to be a viable means in circumventing the problems associated with high-processing temperature of polymers, which cause thermally induced processing stresses (i.e., microcracking). The approach that we have been pursuing is Diels-Alder Polymerization. In this approach, we are generating dienes with light instead of heat. This process is called photoenolization. Several bismaleimides and bisacrylates are used as the dienophiles. The method is fairly general and a wide variety of diketones and bismaleimides can be used. UV curability processes are advantageous due to the following: (1) With such a wide variety of monomers, it allows for the use of nontoxic/nonmutagenic monomers; (2) Polyimides cure at room temperature, which reduces thermally induced stresses; (3) It reduces processing and tooling cost; (4) There are many potential applications for this technology, i.e., thin films as alignment layers for LC displays, photoresists, and photonic material as well as a potential market for use as adhesives.

Meador, Michael; Oliver, Thomas

2001-01-01

383

Development of an extractive spectrophotometric method for estimation of uranium in ore leach solutions using 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A) and tri-n-octyl phosphine oxide (TOPO) mixture as extractant and 2-(5-bromo-2-pyridylozo)-5-diethyl aminophenol (Br-PADAP) as chromophore  

NASA Astrophysics Data System (ADS)

An extractive spectrophotometric analytical method has been developed for the determination of uranium in ore leach solution. This technique is based on the selective extraction of uranium from multielement system using a synergistic mixture of 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A) and tri-n-octyl phosphine oxide (TOPO) in cyclohexane and color development from the organic phase aliquot using 2-(5-Bromo-2-pyridylazo)-5-diethyl aminophenol (Br-PADAP) as chromogenic reagent. The absorption maximum (?max) for UO22+-Br-PADAP complex in organic phase samples, in 64% (v/v) ethanol containing buffer solution (pH 7.8) and 1,2-cyclohexylenedinitrilotetraacetic acid (CyDTA) complexing agent, has been found to be at 576 nm (molar extinction coefficient, ?: 36,750 ± 240 L mol-1 cm-1). Effects of various parameters like stability of complex, ethanol volume, ore matrix, interfering ions etc. on the determination of uranium have also been evaluated. Absorbance measurements as a function of time showed that colored complex is stable up to >24 h. Presence of increased amount of ethanol in colored solution suppresses the absorption of a standard UO22+-Br-PADAP solution. Analyses of synthetic standard as well as ore leach a solution show that for 10 determination relative standard deviation (RSD) is <2%. The accuracy of the developed method has been checked by determining uranium using standard addition method and was found to be accurate with a 98-105% recovery rate. The developed method has been applied for the analysis of a number of uranium samples generated from uranium ore leach solutions and results were compared with standard methods like inductively coupled plasma emission spectrometry (ICPAES). The determined values of uranium concentrations by these methods are within ±2%. This method can be used to determine 2.5-250 ?g mL-1 uranium in ore leach solutions with high accuracy and precision.

Biswas, Sujoy; Pathak, P. N.; Roy, S. B.

2012-06-01

384

Spectrophotometric simultaneous determination of nitrophenol isomers by orthogonal signal correction and partial least squares.  

PubMed

A simple, novel and sensitive spectrophotometric method was described for simultaneous determination of nitrophenol isomers mixtures. All factors affecting on the sensitivity were optimized and the linear dynamic range for determination of nitrophenol isomers were found. The simultaneous determination of nitrophenol mixtures by using spectrophotometric methods is a difficult problem, due to the spectral interferences. The partial least squares modeling was used for the multivariate calibration of the spectrophotometric data. The orthogonal signal correction was used for preprocessing of data matrices and the prediction results of model, with and without using orthogonal signal correction, were statistically compared. The experimental calibration matrix was designed by measuring the absorbance over the range 300-520 nm for 21 samples of 1-20, 1-20 and 1-10 microg ml(-1) of m-nitrophenol, o-nitrophenol and p-nitrophenol, respectively. The RMSEP for m-nitrophenol, o-nitrophenol and p-nitrophenol with and without OSC were 0.3682, 0.5965, 0.3408 and 0.7351, 0.9962, 1.0055, respectively. The proposed method was successfully applied for the determination of m-nitrophenol, o-nitrophenol and p-nitrophenol in synthetic and real matrix samples such as water. PMID:17445981

Niazi, Ali; Yazdanipour, Ateesa

2007-07-19

385

Precision and accuracy of spectrophotometric pH measurements at environmental conditions in the Baltic Sea  

NASA Astrophysics Data System (ADS)

The increasing uptake of anthropogenic CO2 by the oceans has raised an interest in precise and accurate pH measurement in order to assess the impact on the marine CO2-system. Spectrophotometric pH measurements were refined during the last decade yielding a precision and accuracy that cannot be achieved with the conventional potentiometric method. However, until now the method was only tested in oceanic systems with a relative stable and high salinity and a small pH range. This paper describes the first application of such a pH measurement system at conditions in the Baltic Sea which is characterized by a wide salinity and pH range. The performance of the spectrophotometric system at pH values as low as 7.0 (“total” scale) and salinities between 0 and 35 was examined using TRIS-buffer solutions, certified reference materials, and tests of consistency with measurements of other parameters of the marine CO2 system. Using m-cresol purple as indicator dye and a spectrophotometric measurement system designed at Scripps Institution of Oceanography (B. Carter, A. Dickson), a precision better than ±0.001 and an accuracy between ±0.01 and ±0.02 was achieved within the observed pH and salinity ranges in the Baltic Sea. The influence of the indicator dye on the pH of the sample was determined theoretically and is presented as a pH correction term for the different alkalinity regimes in the Baltic Sea. Because of the encouraging tests, the ease of operation and the fact that the measurements refer to the internationally accepted “total” pH scale, it is recommended to use the spectrophotometric method also for pH monitoring and trend detection in the Baltic Sea.

Hammer, Karoline; Schneider, Bernd; Kuli?ski, Karol; Schulz-Bull, Detlef E.

2014-06-01

386

Ultraviolet spectrophotometric determination of nitrate: detecting nitrification rates and inhibition.  

PubMed

Simple methods that rapidly detect nitrification inhibition are needed to enforce pretreatment programs and prevent upsets. The objective of this study was to demonstrate a rapid method for measuring nitrification inhibition by using nitrate generation rates (NGRs) coupled with direct UV detection of nitrate. The NGRs were measured with UV spectrophotometry at wavelengths between 225 and 240 nm, without chemical manipulation, and verified against ion chromatography. The method was shown to quickly and accurately measure nitrate concentrations after correcting for nitrite interference. Cadmium, hypochlorite and 1-chloro-2,4-dintrobenzene (CDNB) were tested for their ability to cause nitrification inhibition using this method. The CDNB was found to cause a correctable interference with the test, while hypochlorite provided an uncorrectable interference. Used as a batch method coupled with biotic and abiotic controls, this approach can be deployed at full-scale treatment plants as a relatively rapid (1.5 hours) means of identifying nitrification-inhibiting wastewaters. PMID:17710926

Kelly, Richard T; Love, Nancy G

2007-07-01

387

Deoxyribonucleic Acid Relatedness Among Mycobacterium leprae, Mycobacterium lepraernuriurn, and Selected Bacteria by Dot Blot and Spectrophotometric Deoxyribonucleic Acid Hybridization Assays  

Microsoft Academic Search

Deoxyribonucleic acid relatedness between Mycobacterium leprae or Mycobacterium lepraemurium and other selected bacteria was studied by both dot blot and spectrophotometric deoxyribonucleic acid hybridization assays. The results obtained by the two methods were similar, except for the relatedness values between M. leprae and two corynebacterial strains. Among the mycobacterial species examined, acid-fast organisms isolated from armadillos and a mangabey monkey

R. S. ATHWAL; S. S. DEO; T. IMAEDA

388

Simultaneous determination of cefdinir and cefixime in human plasma by RP-HPLC/UV detection method: Method development, optimization, validation, and its application to a pharmacokinetic study.  

PubMed

A novel isocratic reversed-phase high performance liquid-chromatography/ultraviolet detection method for simultaneous determination of cefdinir and cefixime in human plasma was developed and validated after optimization of various chromatographic conditions and other experimental parameters. Sample preparation based on a simple extraction procedure consisting of deproteination and extraction with 3 parts of 6% trichloroacetic acid aqueous solution followed by volume make up with the aqueous component of the mobile phase obtained best recoveries of the two analytes. Samples were separated on a Supelco Discovery HS C(18) (150 mm × 4.6 mm, 5 ?m) analytical column protected by a Perkin Elmer C(18) (30 mm × 4.6 mm, 10 ?m) guard cartridge. The mobile phase, methanol/acetonitrile (50/50, v/v):0.05% trifluoroacetic acid (19:81, v/v), operated at 50°C column oven temperature was pumped at a flow rate of 2.0 mL min(-1) and the column eluents were monitored at a wavelength of 285 nm. When Sample was injected into the Perkin Elmer high performance liquid-chromatography system through Rheodyne manual (or auto-sampler) injector equipped with 20 ?L loop, separation was achieved within 4 min. The present method demonstrated acceptable values for selectivity, linearity within the expected concentration range (0.004-5.0 ?g mL(-1); r(2)>0.999 for both analytes), recovery (>95% for cefdinir and >96% for cefixime), precision (%RSD<2.0 for cefdinir and <2.2 for cefixime), sensitivity (limit of detection: 1 ng mL(-1) and lower limit of quantification: 4 ng mL(-1) for both analytes), stability of solutions, and robustness. The method was efficiently applied to a pharmacokinetic study in healthy volunteers. PMID:21782531

Khan, Abbas; Iqbal, Zafar; Khan, Muhammad Imran; Javed, Khalid; Khan, Abad; Ahmad, Lateef; Shah, Yasar; Nasir, Fazli

2011-08-15

389

Selective spectrophotometric determination of phenolic beta-lactam antibiotics.  

PubMed

Two simple and selective spectrophotometric methods were developed for the quantitative determination of cefoperazone sodium, cefadroxil monohydrate, cefprozil anhydrous and amoxicillin trihydrate in pure forms as well as in their pharmaceutical formulations. The methods are based on the selective oxidation of these drugs with either Ce (IV) or Fe (III) in acid medium to give an intense yellow coloured product (lambda(max)=397 nm). The reaction conditions were studied and optimized. Beer's plots were obeyed in a general concentration range of 5-30 microg ml(-1) with correlation coefficients not less than 0.9979 for the four drugs with the two reagents. The methods are successfully applied to the analysis of pharmaceutical formulations containing amoxicillin, either alone or in combination with potassium clavulanate, flucloxacillin or dicloxacillin. They were also applied to the analysis of the other three studied drugs in vials, capsules, tablets and suspensions with good recovery; percent ranged from 99.7 (+/-0.46) to 100.32 (+/-1.05) in the Ce (IV) method and 99.6 (+/-0.50) to 100.3 (+/-1.32) in the Fe (III) method. Interferences from other antibiotics and additives products were investigated. PMID:12049985

Salem, Hesham; Saleh, Gamal A

2002-06-15

390

Spectrophotometric Assay of Mebendazole in Dosage Forms Using Sodium Hypochlorite  

NASA Astrophysics Data System (ADS)

A simple, selective and sensitive spectrophotometric method is described for the determination of mebendazole (MBD) in bulk drug and dosage forms. The method is based on the reaction of MBD with hypochlorite in the presence of sodium bicarbonate to form the chloro derivative of MBD, followed by the destruction of the excess hypochlorite by nitrite ion. The color was formed by the oxidation of iodide with the chloro derivative of MBD to iodine in the presence of starch and forming the blue colored product, which was measured at 570 nm. The optimum conditions that affect the reaction were ascertained and, under these conditions, a linear relationship was obtained in the concentration range of 1.25-25.0·g/ml MBD. The calculated molar absorptivity and Sandell sensitivity values are 9.56·103 l·mol-1·cm-1 and 0.031 ?g/cm2, respectively. The limits of detection and quantification are 0.11 and 0.33 ?g/ml, respectively. The proposed method was applied successfully to the determination of MBD in bulk drug and dosage forms, and no interference was observed from excipients present in the dosage forms. The reliability of the proposed method was further checked by parallel determination by the reference method and also by recovery studies.

Swamy, N.; Prashanth, K. N.; Basavaiah, K.

2014-07-01

391

Volumetric and spectrophotometric determination of oxcarbazepine in tablets.  

PubMed

Two cerimetric procedures are described for the assay of oxcarbazepine (OXC) in bulk drug and in tablets. Titrimetry (method A) is based on the reaction of OXC by a measured excess cerium(IV) sulphate in sulphuric acid medium and the determination of the unreacted oxidant by titration with iron(II) solution using ferroin as indicator. Spectrophotometry (method B) is based on oxidation of OXC by cerium(IV) in perchloric acid (HClO4) medium and the determination of the unreacted oxidant using a colour reaction with p-dimethylaminobenzaldehyde (p-DMAB) having an absorption maximum of 460 nm. The titrimetric method is applicable in the range of 2.0-20.0 mg OXC with a 1:2 reaction stoichiometry [OXC:Ce(IV)]. In the spectrophotometric method a rectilinear relationship is obtained over the concentration range of 0.3-6.0 µg mL-1 OXC. The linear regression equation of the calibration graph is A = 0.9820-0.1477 C with a regression coefficient (r) of -0.9967 (n = 6). The molar absorptivity is calculated to be 3.76 × 104 L mol-1 cm-1 and the Sandell sensitivity is 0.0067 µg cm-2. The limits of detection (LOD) and quantification (LOQ) values are calculated according to ICH guidelines. The methods are successfully applied to the determination of OXC in tablets. PMID:24062127

Rajendraprasad, Nagaraju; Basavaiah, Kanakapura; Vinay, Kanakapura Basavaiah

2011-09-01

392

Development of UV stable LED encapsulants  

Microsoft Academic Search

In recent years, high power white LED devices (LEDs) have been developed and widely used in display, display backlight module and general lightings. UV LED pumped RGB phosphors is one of the methods to generate white light. It shows some advantages, such as: excellent color rendering index (CRI), tolerant to LED variation, etc. However, the high energy of UV or

Chih-Hau Lin; Hsun-Tien Li; Shu-Chen Huang; Chia-Wen Hsu; Kai-Chi Chen; Wen-Bin Chen

2009-01-01

393

Proceedings of the Workshop on the Spectrophotometric Dating of Stars and Galaxies  

NASA Technical Reports Server (NTRS)

In the past decade, we have seen an avalanche of new observational results from space observatories and ground-based observatories. These observations have revealed young globular clusters in the cores of merger galaxies, elliptical galaxies at redshifts up to z=1.5, and starburst galaxies at high redshift. Analyses of the detailed spectra or color- magnitude diagrams of these systems promise to give a new understanding of evolutionary processes and to provide a check on cosmological ages. At the same time, these new spectro-photometric data present new challenges to current methods of spectral analysis and modeling.At the Workshop, we will discuss these new opportunities and challenges on spectro-photometric dating of stars and galaxies.

Hubeny, Ivan; Heap, Sara; Cornett, Robert

1999-01-01

394

nanophosphors prepared by citrate-gel combustion method: a potential red-emitting phosphor for near-UV light-emitting diodes  

NASA Astrophysics Data System (ADS)

In the present work, red-emitting Ca2V2O7: xEu3+ ( x = 0.5-6.0 mol%) nanophosphors, in the form of powders, were synthesized by the citrate-gel combustion method using metal nitrates as precursors and citric acid as fuel. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy, photoluminescence (PL) and cathodoluminescence (CL) spectroscopy were used to study the structure, morphology and spectral properties of the samples. The chemical compositions and electronic states of the powders were analyzed with X-ray photoelectron spectroscopy. The average crystallite sizes estimated using the XRD data were found to be in the range of 30-45 nm, and were cross verified by TEM. The lattice parameters determined by the POWD program were approximated as a = 7.242 Å, b = 6.674 Å, c = 6.932 Å and V = 291.24 Å3, respectively. Under UV (395 nm) (PL) and electron (CL) excitation, the nanophosphors show characteristic emission from the Eu3+ ion (5D0 ? 7Fj, j = 1-5) with the main peaks at 612 and 616 nm. The maximum emission intensity was recorded from the sample with an Eu3+ concentration of 4 mol% and a critical energy distance of 19.084 Å between the donor and the acceptor. Above this concentration, there was a reduction in the intensity due to dipole-dipole induced concentration quenching effects. The potential applications of this phosphor as a high color-purity phosphor in light-emitting diodes are evaluated.

Kumar, Vinay; Bedyal, A. K.; Sharma, J.; Kumar, V.; Ntwaeaborwa, O. M.; Swart, H. C.

2014-09-01

395

Spectrophotometric determination of trace levels of nickel in water samples after dispersive liquid liquid microextraction using 2,2'-furildioxime as the complexing agent.  

PubMed

A new method of dispersive liquid-liquid microextraction (DLLME) combined with UV-Vis spectrophotometry was proposed for the determination of trace nickel using 2,2'-Furildioxime as chelating and spectrophotometric reagent. In the proposed approach chloroform and ethanol were used as extraction and dispersive solvents, respectively. Some factors influencing the extraction efficiency of nickel and its subsequent determination were studied and optimized, such as the extraction and dispersive solvent type and volume, pH of the sample solution, extraction time and ionic strength. Under the optimal conditions, the calibration curve was linear within the range of 5-180 µg L-1 of nickel with R2 = 0.9960. Limit of detection (3Sb/m) was 0.6 µg L-1 in the original solution and the relative standard deviation for ten replicate determination of 100 µg L-1 nickel was 2.9%. The proposed method has been applied for the determination of nickel in various water samples with satisfactory results. PMID:24061321

Rahnama, Reyhaneh; Jojadeh, Zeynab Chamani; Jamali, Mohammad Reza

2012-09-01

396

Oxygen radical production in bluegill sunfish liver microsomes exposed to anthracene and UV radiation  

SciTech Connect

Many polycyclic aromatic hydrocarbons (PAHs) are acutely toxic to fish in the presence of ultraviolet radiation. Oxygen radicals are very reactive and are responsible for many cellular injuries including membrane peroxidation and DNA fragmentation. In this research increased oxygen radical production was hypothesized for the mechanism of UV-PAH acute toxicity. In order to test this hypothesis Bluegill sunfish (Lepomis machrochirus) liver microsomes were exposed to anthracene and UV radiation in four different combinations: (No UV + No Ant), (No UV + Ant), (UV + No Ant), (UV + Ant). The production of superoxide anion was quantified by measuring the spectrophotometric absorbance of acetylated cytochrome c, which is reduced by superoxide anion. 1 ml of reaction solution contained 1 mg of microsomes and, for Ant treatments, 7.7 {micro}g of anthracene. After 3 hours preincubation, acetylated cytochrome c solution was added. The UV treatment groups were exposed to UV-A for 20 minutes at 37 C. The highest mean concentration of reduced acetylated cytochrome c was found in the UV + Ant treatment group and it was significantly different from all other treatment groups. No significant differences were observed among the other three treatment groups. This result coincides with previous studies revealing that anthracene is acutely toxic to fish only under UV radiation, and it implies that the photoinduced toxicity of anthracene, as well as other PAHs, is manifested by the action of oxygen radicals.

Choi, J.; Oris, J. [Miami Univ., Oxford, OH (United States). Dept. of Zoology

1995-12-31

397

Improved spectrophotometric analysis of barium styphnate  

SciTech Connect

A spectrophotometric procedure to determine the purity of barium styphnate monohydrate based upon the absorbance of the styphnate ion at 326 and 413.3 nm has been developed. The purity is determined by comparing the absorbance of the styphnate ion in barium styphnate and in styphnic acid. Our investigation has shown that the molar absorptivity and lambda maxima of the styphnate ion are quite pH dependent; therefore, the pH is buffered to 6.8 to 7.0 with ammonium acetate. Under these conditions the molar absorptivity is 1.6 x 10/sup 4/ L/mol-cm. Analyses following the procedure in the Navy specification WS13444A using water were found to give low molar absorptivities (1.3 x 10/sup 4/ L/mol-cm) for the styphnic acid calibration resulting in erroneous values for barium styphnate purity.

Brown, N E; Blasi, J A

1983-01-01

398

A simple spectrophotometric determination of meptyldinocap by its hydrolysis.  

PubMed

A simple spectrophotometric method is proposed for the determination of meptyldinocap (2,4-dinitro-6-octylphenyl crotonate). The method is based on the hydrolysis of meptyldinocap by hydroxylamine solution in alkaline medium to give 2,4-dinitro-6-octylphenol (2,4-DNOP), having maximum absorption at 380 nm. The reaction is found to be instantaneous in presence of ethanol. Beer's law is valid over the concentration range of 1.2-13 microg mL(-1) with molar absorptivity and Sandell's sensitivity of 3.22 x 10(6) L mol(-1) cm(-1) and 0.0001 microg cm(-2) respectively. The limit of detection and quantification were 0.0892 and 0.2703 microg mL(-1), respectively. The tolerance limits of interfering ions are discussed. All variables were studied in order to optimize the reaction conditions. The validity of the method was checked by its simultaneous determination in fruits and water samples and the results were statistically compared with those of a reference method by applying the Student's t-test and F-test. PMID:23841335

Kurup, Sunita; Pillai, Ajai Kumar

2013-01-01

399

Direct spectrophotometric determination of alkylphenol polyethoxylate nonionic surfactants in wastewater.  

PubMed

A new spectrophotometric method is proposed for direct determination of alkylphenol polyethoxylate, RO(CH(2)CH(2)O)(n)H (where R is alkylphenyl and n is the degree of polymerization), in wastewater. The method is based on the formation of ternary complex, Pb(II)-meso-tetra-(3,5-dibromo-4-hydrooxyphenyl)-Porphyrin (T(DBHP)P)-alkylphenol polyethoxylate (APE). Under optimum reaction conditions, T(DBHP)P reacts with lead(II) and APE to form a yellow ternary complex with the maximum absorption peak at 479 nm. The color reaction is rapidly completed and the absorbance remains stable for at least 24h under room temperature. The apparent molar absorption coefficients were 0.4-4.3 x 10(4) L mol(-1) cm(-1) for n=5-50. As little as 0.02 microg mL(-1) of APE can be detected. The effects of various substances on the determination of APE were also investigated in detail. It was found that all the studied co-existing substances, especially cationic and anionic surfactants, which always seriously interfere in some reported methods, could be tolerated in considerable amounts. The method offered the advantages of simplicity, rapidity, sensitivity and selectivity without any prior separation or extraction. PMID:14511721

Zhu, Zhenzhong; Li, Zaijun; Hao, Zhuoli; Chen, Jian

2003-11-01

400

Simpler spectrophotometric assay of paracetamol in tablets and urine samples  

NASA Astrophysics Data System (ADS)

A very fast, economical and simpler direct spectrophotometric method was investigated for paracetamol (PC) determination in aqueous medium without using any chemical reagents. The method is based on the photo-absorption of the analyte at 243 nm after dissolution in water. The change in structure of PC after addition of water was studied by comparing the corresponding FTIR spectra. Optimization studies were conducted by using a 5 ?g ml -1 standard solution of the analyte. Various parameters studied include, time for stability and measurement of spectra, effect of HCl, NaOH, CH 3COOH and NH 3 for change in absorbance and shift in spectra, interference by some analgesic drugs and some polar solvents and temperature effect. After optimization, Beer's law was obeyed in the range of 0.3-20 ?g ml -1 PC solution with a correlation coefficient of 0.9999 and detection limit of 0.1 ?g ml -1. The newly developed method was successfully applied for PC determination in some locally available tablets and urine samples. The proposed method is very useful for quick analysis of various types of solid and liquid samples containing PC.

Sirajuddin; Khaskheli, Abdul Rauf; Shah, Afzal; Bhanger, Muhammad Iqbal; Niaz, Abdul; Mahesar, Sarfaraz

2007-11-01

401

Titrimetric and spectrophotometric assay of oxcarbazepine in pharmaceuticals using N-bromosuccinimide and bromopyrogallol red.  

PubMed

Titrimetric and spectrophotometric methods are described for the determination of oxcarbazepine (OXC) in bulk drug and in tablets. The methods use N-bromosuccinimide (NBS) and bromopyrogallol red (BPR) as reagents. In titrimetry (method A), an acidified solution of OXC is titrated directly with NBS using methyl orange as indicator. Spectrophotometry (method B) involves the addition of known excess of NBS to an acidified solution of OXC followed by the determination of the unreacted NBS by reacting with BPR and measuring the absorbance of the unreacted dye at 460?nm. Titrimetry allows the determination of 6-18?mg of OXC and follows a reaction stoichiometry of 1?:?1 (OXC?:?NBS), whereas spectrophotometry is applicable over the concentration range of 0.8-8.0??g?mL(-1). Method B with a calculated molar absorptivity of 2.52 × 10(4)?L?mol(-1)?cm(-1) is the most sensitive spectrophotometric method ever developed for OXC. The optical characteristics such as limits of detection (LOD), quantification (LOQ), and Sandell's sensitivity values are also reported for the spectrophotometric method. The accuracy and precision of the methods were studied on intraday and interday basis. The methods described could usefully be applied to routine quality control of tablets containing OXC. No interference was observed from common pharmaceutical adjuvants. Statistical comparison of the results with a reference method shows an excellent agreement and indicates no significant difference in accuracy and precision. The reliability of the methods was further ascertained by recovery studies in standard addition procedure. PMID:21785594

Rajendraprasad, Nagaraju; Basavaiah, Kanakapura; Vinay, Kanakapura B

2011-01-01

402

TOMS UV Algorithm: Problems and Enhancements. 2  

NASA Technical Reports Server (NTRS)

Satellite instruments provide global maps of surface ultraviolet (UV) irradiance by combining backscattered radiance measurements with radiative transfer models. The models are limited by uncertainties in input parameters of the atmosphere and the surface. We evaluate the effects of possible enhancements of the current Total Ozone Mapping Spectrometer (TOMS) surface UV irradiance algorithm focusing on effects of diurnal variation of cloudiness and improved treatment of snow/ice. The emphasis is on comparison between the results of the current (version 1) TOMS UV algorithm and each of the changes proposed. We evaluate different approaches for improved treatment of pixel average cloud attenuation, with and without snow/ice on the ground. In addition to treating clouds based only on the measurements at the local time of the TOMS observations, the results from other satellites and weather assimilation models can be used to estimate attenuation of the incident UV irradiance throughout the day. A new method is proposed to obtain a more realistic treatment of snow covered terrain. The method is based on a statistical relation between UV reflectivity and snow depth. The new method reduced the bias between the TOMS UV estimations and ground-based UV measurements for snow periods. The improved (version 2) algorithm will be applied to re-process the existing TOMS UV data record (since 1978) and to the future satellite sensors (e.g., Quik/TOMS, GOME, OMI on EOS/Aura and Triana/EPIC).

Krotkov, Nickolay; Herman, Jay; Bhartia, P. K.; Seftor, Colin; Arola, Antti; Kaurola, Jussi; Kroskinen, Lasse; Kalliskota, S.; Taalas, Petteri; Geogdzhaev, I.

2002-01-01

403

Filling the gap --near UV, optical and near IR extinction  

NASA Astrophysics Data System (ADS)

We propose a SNAP program to obtain STIS low resolution near-UV, optical and near-IR (G430L and G750L) spectra for a set of O7-B7 class III-V stars in the Galaxy and Magellanic Clouds with available IUE or HST/STIS UV spectropotometry, optical photometry and 2MASS IR photometry. Together with the existing data, the new observations will provide complete photometric and spectrophotometric coverage from 1150 to 10000 A and enable us to produce complete extinction curves from the far-UV to the near-IR, with well-determined values of R(V). The proposed set of 150 program sight lines includes the full range of interstellar extinction curve types from both the Galaxy and the Magellanic Clouds. The new data will allow us to examine variability in the near-UV through near-IR spectral regions, including the UV-optical "knee", and the "Very Broad Structure" and to verify the applicability of the near IR extinction law recently derived by Fitzpatrick and Massa (2009). We will examine the response of these features to different interstellar environments and their relationship to other curve features. These are largely unexplored aspects of the extinction curves which will provide additional constraints on the properties of interstellar grains. The curves will be derived using model atmospheres for the program stars, eliminating the need for standard stars.

Massa, Derck

2014-10-01

404

Utility of N-bromosuccinimide for the titrimetric and spectrophotometric determination of famotidine in pharmaceutical formulations.  

PubMed

Two titrimetric and two spectrophotometric methods are described for the assay of famotidine (FMT) in tablets using N-bromosuccinimide (NBS). The first titrimetric method is direct in which FMT is titrated directly with NBS in HCl medium using methyl orange as indicator (method A). The remaining three methods are indirect in which the unreacted NBS is determined after the complete reaction between FMT and NBS by iodometric back titration (method B) or by reacting with a fixed amount of either indigo carmine (method C) or neutral red (method D). The method A and method B are applicable over the range of 2-9?mg and 1-7?mg, respectively. In spectrophotometric methods, Beer's law is obeyed over the concentration ranges of 0.75-6.0??g?mL(-1) (method C) and 0.3-3.0??g?mL(-1) (method D). The applicability of the developed methods was demonstrated by the determination of FMT in pure drug as well as in tablets. PMID:21760785

Zenita, O; Basavaiah, K

2011-01-01

405

Solar UV variability  

NASA Technical Reports Server (NTRS)

Measurements from the Solar Backscatter Ultraviolet (SBUV) provide solar UV flux in the 160 to 400 nm wavelength range, backed up by independent measurement in the 115 to 305 nm range from the Solar Mesosphere Explorer (SME). The full disc UV flux from spatially resolved measurements of solar activity was modeled, which provides a better understanding of why the UV variations have their observed temporal and wavelength dependencies. Long term, intermediate term, and short term variations are briefly examined.

Donnelly, Richard F.

1989-01-01

406

CORONA-INDUCED PHOTOXIDATION OF ALCOHOLS AND HYDROCARBONS OVER TIO2 IN THE ABSENCE OF A UV LIGHT SOURCE - A NOVEL AND ENVIRONMENTALLY FRIENDLY METHOD FOR OXIDATION  

EPA Science Inventory

Corona-induced photooxidation is a novel oxidation methodology for the efficient oxidation of alcohols and hydrocarbons utilizing the advantage of both the high oxidizing power of ozone formed in the reactor as well as the photooxidation capability of the UV light generated durin...

407

Direct spectrophotometric determination of hesperidin in pharmaceutical preparations.  

PubMed

A simple, rapid and reliable direct spectrophotometric method for the determination of hesperidin is proposed and validated. The influence of wavelength, solvent, the ionic strength, pH and temperature on hesperidin determination were investigated. Under the optimum conditions, ? = 283 nm, 60% methanol as the solvent, ionic strength, I = 2.5 × 10-5 mol L-1, pH = 6.4 and T = 37.0 °C, the Beer's law is obeyed in the concentration range 1.83-24.5 µg mL-1. The molar absorptivity and Sandells sensitivity were found to be 1.8 × 104 L mol-1 cm-1 and 0.03 µg cm-2, respectively. The sensitivity of the proposed method was 0.9 µg mL-1 (as limit of detection) and 3.2 µg mL-1 (as limit of quantification). Applicability of the proposed method to the direct determination of total flavonoids as hesperidin equivalents in pharmaceutical formulation (Vitamin C with citrus bioflavonoids & Rose Hips) was demonstrated. Although the presence of ascorbic acid may cause problem in identification and measurements, hesperidin has been determined successfully. PMID:24061264

Kunti?, Vesna; Peji?, Nataša; Mi?i?, Svetlana

2012-06-01

408

Spectrophotometric determination of paracetamol with microwave assisted alkaline hydrolysis  

NASA Astrophysics Data System (ADS)

A novel and rapid spectrophotometric method for the determination of paracetamol is proposed in this paper. The proposed method is based on the microwave assisted alkaline hydrolysis of paracetamol to p-aminophenol that reacts with S 2- in the presence of Fe 3+ as oxidant to produce a methylene blue-like dye having an absorptivity maximum at 540 nm. The experiment showed that paracetamol could be hydrolysed quantitatively to p-aminophenol in only 1.5 min under radiation power 640 W using a microwave in NaOH medium. The system obeys Beer's law in the range of 0-3.0×10 -4 mol l -1 paracetamol. The molar absorptivity and Sandell's sensitivity were found to be 3.2×10 3 l mol -1 cm -1 and 0.047 ?g cm -2, respectively. The relative standard deviation ( n=11) was 1.7% for 8.0×10 -5 mol l -1 paracetamol. The method has been applied successfully to analysis of paracetamol in pharmaceutical preparation.

Xu, Chunli; Li, Baoxin

2004-07-01

409

An optimized and validated RP-HPLC\\/UV detection method for simultaneous determination of all-trans-Retinol (Vitamin A) and ?-Tocopherol (Vitamin E) in human serum: Comparison of different particulate reversed-phase HPLC columns  

Microsoft Academic Search

A novel, simple and fast reversed-phase HPLC\\/UV method was developed, optimized for various chromatographic conditions, and validated according to international guidelines for simultaneous determination of all-trans-retinol and ?-tocopherol in human serum using retinyl acetate as internal standard in the concentration of 0.5?g\\/ml. A liquid-phase extraction was applied to the 250?l of serum with n-hexane–dichloromethane mixture (70:30, v\\/v), in two steps,

Abad Khan; Muhammad I. Khan; Zafar Iqbal; Yasar Shah; Lateef Ahmad; David G. Watson

2010-01-01

410

p-Dimethylaminocinnamaldehyde Derivatization for Colorimetric Detection and HPLC-UV/Vis-MS/MS Identification of Indoles  

PubMed Central

Cytochrome P450 2A13 is a lung specific enzyme known to activate the potent tobacco procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) into two carcinogenic metabolites. CYP2A13 has been crystallized and X-ray diffraction experiments illuminated the structure of this enzyme, but with an unknown ligand present in the enzyme active site. This unknown ligand was suspected to be indole but a selective method had to be developed to differentiate among indole and its metabolites in the protein sample. We successfully modified a microbiological colorimetric assay to spectrophotometrically differentiate between indole and a number of possible indole metabolites in nanomolar concentrations by derivatization with p-dimethylaminocinnamaldehyde (DMACA). Further differentiation of indoles was made by mass spectrometry (HPLC-UV/Vis-MS/MS) utilizing the chromophore generated in the DMACA conjugation as a UV signature for HPLC detection. The ligand in the crystallized protein was identified as unsubstituted indole, which facilitated refinement of two alternate conformations in the CYP2A13 crystal structure active site. PMID:18423367

Porubsky, Patrick R.; Scott, Emily E.; Williams, Todd D.

2008-01-01

411

p-dimethylaminocinnamaldehyde derivatization for colorimetric detection and HPLC-UV/vis-MS/MS identification of indoles.  

PubMed

Cytochrome P450 2A13 (CYP2A13) is a lung specific enzyme known to activate the potent tobacco procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) into two carcinogenic metabolites. CYP2A13 has been crystallized and X-ray diffraction experiments illuminated the structure of this enzyme, but with an unknown ligand present in the enzyme active site. This unknown ligand was suspected to be indole but a selective method had to be developed to differentiate among indole and its metabolites in the protein sample. We successfully modified a microbiological colorimetric assay to spectrophotometrically differentiate between indole and a number of possible indole metabolites in nanomolar concentrations by derivatization with p-dimethylaminocinnamaldehyde (DMACA). Further differentiation of indoles was made by mass spectrometry (HPLC-UV/vis-MS/MS) utilizing the chromophore generated in the DMACA conjugation as a UV signature for HPLC detection. The ligand in the crystallized protein was identified as unsubstituted indole, which facilitated refinement of two alternate conformations in the CYP2A13 crystal structure active site. PMID:18423367

Porubsky, Patrick R; Scott, Emily E; Williams, Todd D

2008-07-01