Improved lossless intra coding for H.264/MPEG-4 AVC.

PubMed

Lee, Yung-Lyul; Han, Ki-Hun; Sullivan, Gary J

2006-09-01

A new lossless intra coding method based on sample-by-sample differential pulse code modulation (DPCM) is presented as an enhancement of the H.264/MPEG-4 AVC standard. The H.264/AVC design includes a multidirectional spatial prediction method to reduce spatial redundancy by using neighboring samples as a prediction for the samples in a block of data to be encoded. In the new lossless intra coding method, the spatial prediction is performed based on samplewise DPCM instead of in the block-based manner used in the current H.264/AVC standard, while the block structure is retained for the residual difference entropy coding process. We show that the new method, based on samplewise DPCM, does not have a major complexity penalty, despite its apparent pipeline dependencies. Experiments show that the new lossless intra coding method reduces the bit rate by approximately 12% in comparison with the lossless intra coding method previously included in the H.264/AVC standard. As a result, the new method is currently being adopted into the H.264/AVC standard in a new enhancement project.

Absolute method of measuring magnetic susceptibility

USGS Publications Warehouse

Thorpe, A.; Senftle, F.E.

1959-01-01

An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

Development of Gold Standard Ion-Selective Electrode-Based Methods for Fluoride Analysis

PubMed Central

Martínez-Mier, E.A.; Cury, J.A.; Heilman, J.R.; Katz, B.P.; Levy, S.M.; Li, Y.; Maguire, A.; Margineda, J.; O’Mullane, D.; Phantumvanit, P.; Soto-Rojas, A.E.; Stookey, G.K.; Villa, A.; Wefel, J.S.; Whelton, H.; Whitford, G.M.; Zero, D.T.; Zhang, W.; Zohouri, V.

2011-01-01

Background/Aims: Currently available techniques for fluoride analysis are not standardized. Therefore, this study was designed to develop standardized methods for analyzing fluoride in biological and nonbiological samples used for dental research. Methods A group of nine laboratories analyzed a set of standardized samples for fluoride concentration using their own methods. The group then reviewed existing analytical techniques for fluoride analysis, identified inconsistencies in the use of these techniques and conducted testing to resolve differences. Based on the results of the testing undertaken to define the best approaches for the analysis, the group developed recommendations for direct and microdiffusion methods using the fluoride ion-selective electrode. Results Initial results demonstrated that there was no consensus regarding the choice of analytical techniques for different types of samples. Although for several types of samples, the results of the fluoride analyses were similar among some laboratories, greater differences were observed for saliva, food and beverage samples. In spite of these initial differences, precise and true values of fluoride concentration, as well as smaller differences between laboratories, were obtained once the standardized methodologies were used. Intraclass correlation coefficients ranged from 0.90 to 0.93, for the analysis of a certified reference material, using the standardized methodologies. Conclusion The results of this study demonstrate that the development and use of standardized protocols for F analysis significantly decreased differences among laboratories and resulted in more precise and true values. PMID:21160184

A sensitive chemiluminescence enzyme immunoassay based on molecularly imprinted polymers solid-phase extraction of parathion.

PubMed

Chen, Ge; Jin, Maojun; Du, Pengfei; Zhang, Chan; Cui, Xueyan; Zhang, Yudan; She, Yongxin; Shao, Hua; Jin, Fen; Wang, Shanshan; Zheng, Lufei; Wang, Jing

2017-08-01

The chemiluminescence enzyme immunoassay (CLEIA) method responds differently to various sample matrices because of the matrix effect. In this work, the CLEIA method was coupled with molecularly imprinted polymers (MIPs) synthesized by precipitation polymerization to study the matrix effect. The sample recoveries ranged from 72.62% to 121.89%, with a relative standard deviation (RSD) of 3.74-18.14%.The ratio of the sample matrix-matched standard curve slope rate to the solvent standard curve slope was 1.21, 1.12, 1.17, and 0.85 for apple, rice, orange and cabbage in samples pretreated with the mixture of PSA and C 18 . However, the ratio of sample (apple, rice, orange, and cabbage) matrix-matched standard-MIPs curve slope rate to the solvent standard curve was 1.05, 0.92, 1.09, and 1.05 in samples pretreated with MIPs, respectively. The results demonstrated that the matrices of the samples greatly interfered with the detection of parathion residues by CLEIA. The MIPs bound specifically to the parathion in the samples and eliminated the matrix interference effect. Therefore, the CLEIA method have successfully applied MIPs in sample pretreatment to eliminate matrix interference effects and provided a new sensitive assay for agro-products. Copyright © 2017 Elsevier Inc. All rights reserved.

Evaluation of an alternate method for sampling benthic macroinvertebrates in low-gradient streams sampled as part of the National Rivers and Streams Assessment.

PubMed

Flotemersch, Joseph E; North, Sheila; Blocksom, Karen A

2014-02-01

Benthic macroinvertebrates are sampled in streams and rivers as one of the assessment elements of the US Environmental Protection Agency's National Rivers and Streams Assessment. In a 2006 report, the recommendation was made that different yet comparable methods be evaluated for different types of streams (e.g., low gradient vs. high gradient). Consequently, a research element was added to the 2008-2009 National Rivers and Streams Assessment to conduct a side-by-side comparison of the standard macroinvertebrate sampling method with an alternate method specifically designed for low-gradient wadeable streams and rivers that focused more on stream edge habitat. Samples were collected using each method at 525 sites in five of nine aggregate ecoregions located in the conterminous USA. Methods were compared using the benthic macroinvertebrate multimetric index developed for the 2006 Wadeable Streams Assessment. Statistical analysis did not reveal any trends that would suggest the overall assessment of low-gradient streams on a regional or national scale would change if the alternate method was used rather than the standard sampling method, regardless of the gradient cutoff used to define low-gradient streams. Based on these results, the National Rivers and Streams Survey should continue to use the standard field method for sampling all streams.

Evaluation of the methods for enumerating coliform bacteria from water samples using precise reference standards.

PubMed

Wohlsen, T; Bates, J; Vesey, G; Robinson, W A; Katouli, M

2006-04-01

To use BioBall cultures as a precise reference standard to evaluate methods for enumeration of Escherichia coli and other coliform bacteria in water samples. Eight methods were evaluated including membrane filtration, standard plate count (pour and spread plate methods), defined substrate technology methods (Colilert and Colisure), the most probable number method and the Petrifilm disposable plate method. Escherichia coli and Enterobacter aerogenes BioBall cultures containing 30 organisms each were used. All tests were performed using 10 replicates. The mean recovery of both bacteria varied with the different methods employed. The best and most consistent results were obtained with Petrifilm and the pour plate method. Other methods either yielded a low recovery or showed significantly high variability between replicates. The BioBall is a very suitable quality control tool for evaluating the efficiency of methods for bacterial enumeration in water samples.

Credit risk migration rates modeling as open systems: A micro-simulation approach

NASA Astrophysics Data System (ADS)

Landini, S.; Uberti, M.; Casellina, S.

2018-05-01

The last financial crisis of 2008 stimulated the development of new Regulatory Criteria (commonly known as Basel III) that pushed the banking activity to become more prudential, either in the short and the long run. As well known, in 2014 the International Accounting Standards Board (IASB) promulgated the new International Financial Reporting Standard 9 (IFRS 9) for financial instruments that will become effective in January 2018. Since the delayed recognition of credit losses on loans was identified as a weakness in existing accounting standards, the IASB has introduced an Expected Loss model that requires more timely recognition of credit losses. Specifically, new standards require entities to account both for expected losses from when the impairments are recognized for the first time and for full loan lifetime; moreover, a clear preference toward forward looking models is expressed. In this new framework, it is necessary a re-thinking of the widespread standard theoretical approach on which the well known prudential model is founded. The aim of this paper is then to define an original methodological approach to migration rates modeling for credit risk which is innovative respect to the standard method from the point of view of a bank as well as in a regulatory perspective. Accordingly, the proposed not-standard approach considers a portfolio as an open sample allowing for entries, migrations of stayers and exits as well. While being consistent with the empirical observations, this open-sample approach contrasts with the standard closed-sample method. In particular, this paper offers a methodology to integrate the outcomes of the standard closed-sample method within the open-sample perspective while removing some of the assumptions of the standard method. Three main conclusions can be drawn in terms of economic capital provision: (a) based on the Markovian hypothesis with a-priori absorbing state at default, the standard closed-sample method is to be abandoned for not to predict lenders' bankruptcy by construction; (b) to meet more reliable estimates along with the new regulatory standards, the sample to estimate migration rates matrices for credit risk should include either entries and exits; (c) the static eigen-decomposition standard procedure to forecast migration rates should be replaced with a stochastic process dynamics methodology while conditioning forecasts to macroeconomic scenarios.

Validation of a standardized extraction method for formalin-fixed paraffin-embedded tissue samples.

PubMed

Lagheden, Camilla; Eklund, Carina; Kleppe, Sara Nordqvist; Unger, Elizabeth R; Dillner, Joakim; Sundström, Karin

2016-07-01

Formalin-fixed paraffin-embedded (FFPE) samples can be DNA-extracted and used for human papillomavirus (HPV) genotyping. The xylene-based gold standard for extracting FFPE samples is laborious, suboptimal and involves health hazards for the personnel involved. To compare extraction with the standard xylene method to a xylene-free method used in an HPV LabNet Global Reference Laboratory at the Centers for Disease Control (CDC); based on a commercial method with an extra heating step. Fifty FFPE samples were randomly selected from a national audit of all cervical cancer cases diagnosed in Sweden during 10 years. For each case-block, a blank-block was sectioned, as a control for contamination. For xylene extraction, the standard WHO Laboratory Manual protocol was used. For the CDC method, the manufacturers' protocol was followed except for an extra heating step, 120°C for 20min. Samples were extracted and tested in parallel with β-globin real-time PCR, HPV16 real-time PCR and HPV typing using modified general primers (MGP)-PCR and Luminex assays. For a valid result the blank-block had to be betaglobin-negative in all tests and the case-block positive for beta-globin. Overall, detection was improved with the heating method and the amount of HPV-positive samples increased from 70% to 86% (p=0.039). For all samples where HPV type concordance could be evaluated, there was 100% type concordance. A xylene-free and robust extraction method for HPV-DNA typing in FFPE material is currently in great demand. Our proposed standardized protocol appears to be generally useful. Copyright © 2016. Published by Elsevier B.V.

Correcting for the influence of sampling conditions on biomarkers of exposure to phenols and phthalates: a 2-step standardization method based on regression residuals.

PubMed

Mortamais, Marion; Chevrier, Cécile; Philippat, Claire; Petit, Claire; Calafat, Antonia M; Ye, Xiaoyun; Silva, Manori J; Brambilla, Christian; Eijkemans, Marinus J C; Charles, Marie-Aline; Cordier, Sylvaine; Slama, Rémy

2012-04-26

Environmental epidemiology and biomonitoring studies typically rely on biological samples to assay the concentration of non-persistent exposure biomarkers. Between-participant variations in sampling conditions of these biological samples constitute a potential source of exposure misclassification. Few studies attempted to correct biomarker levels for this error. We aimed to assess the influence of sampling conditions on concentrations of urinary biomarkers of select phenols and phthalates, two widely-produced families of chemicals, and to standardize biomarker concentrations on sampling conditions. Urine samples were collected between 2002 and 2006 among 287 pregnant women from Eden and Pélagie cohorts, from which phthalates and phenols metabolites levels were assayed. We applied a 2-step standardization method based on regression residuals. First, the influence of sampling conditions (including sampling hour, duration of storage before freezing) and of creatinine levels on biomarker concentrations were characterized using adjusted linear regression models. In the second step, the model estimates were used to remove the variability in biomarker concentrations due to sampling conditions and to standardize concentrations as if all samples had been collected under the same conditions (e.g., same hour of urine collection). Sampling hour was associated with concentrations of several exposure biomarkers. After standardization for sampling conditions, median concentrations differed by--38% for 2,5-dichlorophenol to +80 % for a metabolite of diisodecyl phthalate. However, at the individual level, standardized biomarker levels were strongly correlated (correlation coefficients above 0.80) with unstandardized measures. Sampling conditions, such as sampling hour, should be systematically collected in biomarker-based studies, in particular when the biomarker half-life is short. The 2-step standardization method based on regression residuals that we proposed in order to limit the impact of heterogeneity in sampling conditions could be further tested in studies describing levels of biomarkers or their influence on health.

Quantitative Detection of Trace Explosive Vapors by Programmed Temperature Desorption Gas Chromatography-Electron Capture Detector

PubMed Central

Field, Christopher R.; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C.; Rose-Pehrsson, Susan L.

2014-01-01

The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples. PMID:25145416

Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.

PubMed

Field, Christopher R; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C; Rose-Pehrsson, Susan L

2014-07-25

The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples.

Development of a simple indocyanine green measurement method using an automated biochemical analyser.

PubMed

Sato, Yuka; Seimiya, Masanori; Yoshida, Toshihiko; Sawabe, Yuji; Hokazono, Eisaku; Osawa, Susumu; Matsushita, Kazuyuki

2017-01-01

Background The indocyanine green retention rate is important for assessing the severity of liver disorders. In the conventional method, blood needs to be collected twice. In the present study, we developed an automated indocyanine green method that does not require blood sampling before intravenous indocyanine green injections and is applicable to an automated biochemical analyser. Methods The serum samples of 471 patients collected before and after intravenous indocyanine green injections and submitted to the clinical laboratory of our hospital were used as samples. The standard procedure established by the Japan Society of Hepatology was used as the standard method. In the automated indocyanine green method, serum collected after an intravenous indocyanine green injection was mixed with the saline reagent containing a surfactant, and the indocyanine green concentration was measured at a dominant wavelength of 805 nm and a complementary wavelength of 884 nm. Results The coefficient of variations of the within- and between-run reproducibilities of this method were 2% or lower, and dilution linearity passing the origin was noted up to 10 mg/L indocyanine green. The reagent was stable for four weeks or longer. Haemoglobin, bilirubin and chyle had no impact on the results obtained. The correlation coefficient between the standard method (x) and this method (y) was r=0.995; however, slight divergence was noted in turbid samples. Conclusion Divergence in turbid samples may have corresponded to false negativity with the standard procedure. Our method may be highly practical because blood sampling before indocyanine green loading is unnecessary and measurements are simple.

Do placebo based validation standards mimic real batch products behaviour? Case studies.

PubMed

Bouabidi, A; Talbi, M; Bouklouze, A; El Karbane, M; Bourichi, H; El Guezzar, M; Ziemons, E; Hubert, Ph; Rozet, E

2011-06-01

Analytical methods validation is a mandatory step to evaluate the ability of developed methods to provide accurate results for their routine application. Validation usually involves validation standards or quality control samples that are prepared in placebo or reconstituted matrix made of a mixture of all the ingredients composing the drug product except the active substance or the analyte under investigation. However, one of the main concerns that can be made with this approach is that it may lack an important source of variability that come from the manufacturing process. The question that remains at the end of the validation step is about the transferability of the quantitative performance from validation standards to real authentic drug product samples. In this work, this topic is investigated through three case studies. Three analytical methods were validated using the commonly spiked placebo validation standards at several concentration levels as well as using samples coming from authentic batch samples (tablets and syrups). The results showed that, depending on the type of response function used as calibration curve, there were various degrees of differences in the results accuracy obtained with the two types of samples. Nonetheless the use of spiked placebo validation standards was showed to mimic relatively well the quantitative behaviour of the analytical methods with authentic batch samples. Adding these authentic batch samples into the validation design may help the analyst to select and confirm the most fit for purpose calibration curve and thus increase the accuracy and reliability of the results generated by the method in routine application. Copyright © 2011 Elsevier B.V. All rights reserved.

Validated method for quantification of genetically modified organisms in samples of maize flour.

PubMed

Kunert, Renate; Gach, Johannes S; Vorauer-Uhl, Karola; Engel, Edwin; Katinger, Hermann

2006-02-08

Sensitive and accurate testing for trace amounts of biotechnology-derived DNA from plant material is the prerequisite for detection of 1% or 0.5% genetically modified ingredients in food products or raw materials thereof. Compared to ELISA detection of expressed proteins, real-time PCR (RT-PCR) amplification has easier sample preparation and detection limits are lower. Of the different methods of DNA preparation CTAB method with high flexibility in starting material and generation of sufficient DNA with relevant quality was chosen. Previous RT-PCR data generated with the SYBR green detection method showed that the method is highly sensitive to sample matrices and genomic DNA content influencing the interpretation of results. Therefore, this paper describes a real-time DNA quantification based on the TaqMan probe method, indicating high accuracy and sensitivity with detection limits of lower than 18 copies per sample applicable and comparable to highly purified plasmid standards as well as complex matrices of genomic DNA samples. The results were evaluated with ValiData for homology of variance, linearity, accuracy of the standard curve, and standard deviation.

40 CFR 60.285 - Test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... determine compliance with the particulate matter standards in § 60.282(a) (1) and (3) as follows: (1) Method 5 shall be used to determine the particulate matter concentration. The sampling time and sample... opacity. (c) The owner or operator shall determine compliance with the particular matter standard in § 60...

40 CFR 60.285 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... determine compliance with the particulate matter standards in § 60.282(a) (1) and (3) as follows: (1) Method 5 shall be used to determine the particulate matter concentration. The sampling time and sample... opacity. (c) The owner or operator shall determine compliance with the particular matter standard in § 60...

40 CFR 60.285 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... determine compliance with the particulate matter standards in § 60.282(a) (1) and (3) as follows: (1) Method 5 shall be used to determine the particulate matter concentration. The sampling time and sample... opacity. (c) The owner or operator shall determine compliance with the particular matter standard in § 60...

40 CFR 60.285 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... determine compliance with the particulate matter standards in § 60.282(a) (1) and (3) as follows: (1) Method 5 shall be used to determine the particulate matter concentration. The sampling time and sample... opacity. (c) The owner or operator shall determine compliance with the particular matter standard in § 60...

Efficient global biopolymer sampling with end-transfer configurational bias Monte Carlo

NASA Astrophysics Data System (ADS)

Arya, Gaurav; Schlick, Tamar

2007-01-01

We develop an "end-transfer configurational bias Monte Carlo" method for efficient thermodynamic sampling of complex biopolymers and assess its performance on a mesoscale model of chromatin (oligonucleosome) at different salt conditions compared to other Monte Carlo moves. Our method extends traditional configurational bias by deleting a repeating motif (monomer) from one end of the biopolymer and regrowing it at the opposite end using the standard Rosenbluth scheme. The method's sampling efficiency compared to local moves, pivot rotations, and standard configurational bias is assessed by parameters relating to translational, rotational, and internal degrees of freedom of the oligonucleosome. Our results show that the end-transfer method is superior in sampling every degree of freedom of the oligonucleosomes over other methods at high salt concentrations (weak electrostatics) but worse than the pivot rotations in terms of sampling internal and rotational sampling at low-to-moderate salt concentrations (strong electrostatics). Under all conditions investigated, however, the end-transfer method is several orders of magnitude more efficient than the standard configurational bias approach. This is because the characteristic sampling time of the innermost oligonucleosome motif scales quadratically with the length of the oligonucleosomes for the end-transfer method while it scales exponentially for the traditional configurational-bias method. Thus, the method we propose can significantly improve performance for global biomolecular applications, especially in condensed systems with weak nonbonded interactions and may be combined with local enhancements to improve local sampling.

7 CFR 29.110 - Method of sampling.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Method of sampling. 29.110 Section 29.110 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.110 Method of sampling. In sampling tobacco...

7 CFR 29.110 - Method of sampling.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 2 2011-01-01 2011-01-01 false Method of sampling. 29.110 Section 29.110 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.110 Method of sampling. In sampling tobacco...

Neutron activation analysis of certified samples by the absolute method

NASA Astrophysics Data System (ADS)

Kadem, F.; Belouadah, N.; Idiri, Z.

2015-07-01

The nuclear reactions analysis technique is mainly based on the relative method or the use of activation cross sections. In order to validate nuclear data for the calculated cross section evaluated from systematic studies, we used the neutron activation analysis technique (NAA) to determine the various constituent concentrations of certified samples for animal blood, milk and hay. In this analysis, the absolute method is used. The neutron activation technique involves irradiating the sample and subsequently performing a measurement of the activity of the sample. The fundamental equation of the activation connects several physical parameters including the cross section that is essential for the quantitative determination of the different elements composing the sample without resorting to the use of standard sample. Called the absolute method, it allows a measurement as accurate as the relative method. The results obtained by the absolute method showed that the values are as precise as the relative method requiring the use of standard sample for each element to be quantified.

HPLC analysis and standardization of Brahmi vati – An Ayurvedic poly-herbal formulation

PubMed Central

Mishra, Amrita; Mishra, Arun K.; Tiwari, Om Prakash; Jha, Shivesh

2013-01-01

Objectives The aim of the present study was to standardize Brahmi vati (BV) by simultaneous quantitative estimation of Bacoside A3 and Piperine adopting HPLC–UV method. BV very important Ayurvedic polyherbo formulation used to treat epilepsy and mental disorders containing thirty eight ingredients including Bacopa monnieri L. and Piper longum L. Materials and methods An HPLC–UV method was developed for the standardization of BV in light of simultaneous quantitative estimation of Bacoside A3 and Piperine, the major constituents of B. monnieri L. and P. longum L. respectively. The developed method was validated on parameters including linearity, precision, accuracy and robustness. Results The HPLC analysis showed significant increase in amount of Bacoside A3 and Piperine in the in-house sample of BV when compared with all three different marketed samples of the same. Results showed variations in the amount of Bacoside A3 and Piperine in different samples which indicate non-uniformity in their quality which will lead to difference in their therapeutic effects. Conclusion The outcome of the present investigation underlines the importance of standardization of Ayurvedic formulations. The developed method may be further used to standardize other samples of BV or other formulations containing Bacoside A3 and Piperine. PMID:24396246

HPLC analysis and standardization of Brahmi vati - An Ayurvedic poly-herbal formulation.

PubMed

Mishra, Amrita; Mishra, Arun K; Tiwari, Om Prakash; Jha, Shivesh

2013-09-01

The aim of the present study was to standardize Brahmi vati (BV) by simultaneous quantitative estimation of Bacoside A3 and Piperine adopting HPLC-UV method. BV very important Ayurvedic polyherbo formulation used to treat epilepsy and mental disorders containing thirty eight ingredients including Bacopa monnieri L. and Piper longum L. An HPLC-UV method was developed for the standardization of BV in light of simultaneous quantitative estimation of Bacoside A3 and Piperine, the major constituents of B. monnieri L. and P. longum L. respectively. The developed method was validated on parameters including linearity, precision, accuracy and robustness. The HPLC analysis showed significant increase in amount of Bacoside A3 and Piperine in the in-house sample of BV when compared with all three different marketed samples of the same. Results showed variations in the amount of Bacoside A3 and Piperine in different samples which indicate non-uniformity in their quality which will lead to difference in their therapeutic effects. The outcome of the present investigation underlines the importance of standardization of Ayurvedic formulations. The developed method may be further used to standardize other samples of BV or other formulations containing Bacoside A3 and Piperine.

ISO 15859 Propellant and Fluid Specifications: A Review and Comparison with Military and NASA Specifications

NASA Technical Reports Server (NTRS)

Greene, Ben; McClure, Mark B.; Baker, David L.

2006-01-01

This work presents an overview of the International Organization for Standardization (ISO) 15859 International Standard for Space Systems Fluid Characteristics, Sampling and Test Methods Parts 1 through 13 issued in June 2004. These standards establish requirements for fluid characteristics, sampling, and test methods for 13 fluids of concern to the propellant community and propellant characterization laboratories: oxygen, hydrogen, nitrogen, helium, nitrogen tetroxide, monomethylhydrazine, hydrazine, kerosene, argon, water, ammonia, carbon dioxide, and breathing air. A comparison of the fluid characteristics, sampling, and test methods required by the ISO standards to the current military and NASA specifications, which are in use at NASA facilities and elsewhere, is presented. Many ISO standards composition limits and other content agree with those found in the applicable parts of NASA SE-S-0073, NASA SSP 30573, military performance standards and details, and Compressed Gas Association (CGA) commodity specifications. The status of a current project managed at NASA Johnson Space Center White Sands Test Facility (WSTF) to rewrite these documents is discussed.

Uniform Sampling Table Method and its Applications II--Evaluating the Uniform Sampling by Experiment.

PubMed

Chen, Yibin; Chen, Jiaxi; Chen, Xuan; Wang, Min; Wang, Wei

2015-01-01

A new method of uniform sampling is evaluated in this paper. The items and indexes were adopted to evaluate the rationality of the uniform sampling. The evaluation items included convenience of operation, uniformity of sampling site distribution, and accuracy and precision of measured results. The evaluation indexes included operational complexity, occupation rate of sampling site in a row and column, relative accuracy of pill weight, and relative deviation of pill weight. They were obtained from three kinds of drugs with different shape and size by four kinds of sampling methods. Gray correlation analysis was adopted to make the comprehensive evaluation by comparing it with the standard method. The experimental results showed that the convenience of uniform sampling method was 1 (100%), odds ratio of occupation rate in a row and column was infinity, relative accuracy was 99.50-99.89%, reproducibility RSD was 0.45-0.89%, and weighted incidence degree exceeded the standard method. Hence, the uniform sampling method was easy to operate, and the selected samples were distributed uniformly. The experimental results demonstrated that the uniform sampling method has good accuracy and reproducibility, which can be put into use in drugs analysis.

Metrological activity determination of 133Ba by sum-peak absolute method

NASA Astrophysics Data System (ADS)

da Silva, R. L.; de Almeida, M. C. M.; Delgado, J. U.; Poledna, R.; Santos, A.; de Veras, E. V.; Rangel, J.; Trindade, O. L.

2016-07-01

The National Laboratory for Metrology of Ionizing Radiation provides gamma sources of radionuclide and standardized in activity with reduced uncertainties. Relative methods require standards to determine the sample activity while the absolute methods, as sum-peak, not. The activity is obtained directly with good accuracy and low uncertainties. 133Ba is used in research laboratories and on calibration of detectors for analysis in different work areas. Classical absolute methods don't calibrate 133Ba due to its complex decay scheme. The sum-peak method using gamma spectrometry with germanium detector standardizes 133Ba samples. Uncertainties lower than 1% to activity results were obtained.

Evaluation on determination of iodine in coal by energy dispersive X-ray fluorescence

USGS Publications Warehouse

Wang, B.; Jackson, J.C.; Palmer, C.; Zheng, B.; Finkelman, R.B.

2005-01-01

A quick and inexpensive method of relative high iodine determination from coal samples was evaluated. Energy dispersive X-ray fluorescence (EDXRF) provided a detection limit of about 14 ppm (3 times of standard deviations of the blank sample), without any complex sample preparation. An analytical relative standard deviation of 16% was readily attainable for coal samples. Under optimum conditions, coal samples with iodine concentrations higher than 5 ppm can be determined using this EDXRF method. For the time being, due to the general iodine concentrations of coal samples lower than 5 ppm, except for some high iodine content coal, this method can not effectively been used for iodine determination. More work needed to meet the requirement of determination of iodine from coal samples for this method. Copyright ?? 2005 by The Geochemical Society of Japan.

Determination of total sulfur content of sedimentary rocks by a combustion method

USGS Publications Warehouse

Coller, M.E.; Leininger, R.K.

1955-01-01

Total sulfur has been determined in common sedimentary rocks by a combustion method. Sulfur contents range from 0.001 to 5.0%. Experiments show that the combustion method can be used in analyzing sedimentary rocks in which sulfur is present as sulfide, sulfate, or both. Pulverized samples from 0.100 to 0.500 gram in weight are used in this method. Each sample is placed in a No. 6 Leco combustion boat and covered with two fluxes: 0.50 gram of standard ingot iron and approximately 1.0 gram of 30-mesh granular tin. The boat with sample then is placed in the combustion tube of a Burrell Unit Package Model T29A tube furnace which is controlled at a temperature of 1310?? to 1320?? C. After the sample has been heated for 1 minute, oxygen is admitted at a rate of about 1 liter per minute. The sulfur dioxide formed is absorbed in a starch solution and is titrated with standard potassium iodate in a Leco sulfur determinator. Thirteen values obtained for National Bureau of Standards standard sample 1a, argillaceous limestone, range from 0.273 to 0.276% sulfur (certificate value 0.27% by calculation).

A STANDARDIZED ASSESSMENT METHOD (SAM) FOR RIVERINE MACROINVERTEBRATES

EPA Science Inventory

A macroinvertebrate sampling method for large rivers based on desirable characteristics of existing nonwadeable methods was developed and tested. Six sites each were sampled on the Great Miami and Kentucky Rivers, reflecting a human disturbance gradient. Samples were collected ...

CTEPP STANDARD OPERATING PROCEDURE FOR PACKING AND SHIPPING STUDY SAMPLES (SOP-3.11)

EPA Science Inventory

This SOP describes the methods for packing and shipping study samples. These methods are for packing and shipping biological and environmental samples. The methods have been tested and used in the previous pilot studies.

Evaluation of 3 dental unit waterline contamination testing methods

PubMed Central

Porteous, Nuala; Sun, Yuyu; Schoolfield, John

2015-01-01

Previous studies have found inconsistent results from testing methods used to measure heterotrophic plate count (HPC) bacteria in dental unit waterline (DUWL) samples. This study used 63 samples to compare the results obtained from an in-office chairside method and 2 currently used commercial laboratory HPC methods (Standard Methods 9215C and 9215E). The results suggest that the Standard Method 9215E is not suitable for application to DUWL quality monitoring, due to the detection of limited numbers of heterotrophic organisms at the required 35°C incubation temperature. The results also confirm that while the in-office chairside method is useful for DUWL quality monitoring, the Standard Method 9215C provided the most accurate results. PMID:25574718

New tool for getting data on the field for paleoclimate and paleoceanography data based on isotope 13C and 18O measurements

NASA Astrophysics Data System (ADS)

Mandic, M.; Stöbener, N.; Smajgl, D.

2017-12-01

For many decades different instrumental methods involving generations of the isotope ratio mass spectrometers with different periphery units for sample preparation, have provided scientifically required high precision, and high throughput of samples for varies application - from geological and hydrological to food and forensic. With this work we introduce automated measurement of δ13C and δ18O from solid carbonate samples, DIC and δ18O of water. We have demonstrated usage of a Thermo Scientific™ Delta Ray™ IRIS with URI Connect on certified reference materials and confirmed the high achievable accuracy and a precision better then <0.1‰ for both δ13C and δ18O, in the laboratory or the field with same precision and throughput of samples. With equilibration method for determination of δ18O in water samples, which we present in this work, achieved repeatability and accuracy are 0.12‰ and 0.68‰ respectively, which fulfill requirements of regulatory methods. The preparation of the samples for carbonate and DIC analysis on the Delta Ray IRIS with URI Connect is similar to the previously mentioned Gas Bench II methods. Samples are put into vials and phosphoric acid is added. The resulting sample-acid chemical reaction releases CO2 gas, which is then introduced into the Delta Ray IRIS via the Variable Volume. Three international standards of carbonate materials (NBS-18, NBS-19 and IAEA-CO-1) were analyzed. NBS-18 and NBS-19 were used as standards for calibration, and IAEA-CO-1 was treated as unknown. For water sample analysis equilibration method with 1% of CO2 in dry air was used. Test measurements and conformation of precision and accuracy of method determination δ18O in water samples were done with three lab standards, namely ANST, OCEAN 2 and HBW. All laboratory standards were previously calibrated with international reference material VSMOW2 and SLAP2 to assure accuracy of the isotopic values. The Principle of Identical Treatment was applied in sample and standard preparation, in measurement procedure, as well as in the evaluation of the results.

Rapid detection of coliforms in drinking water of Arak city using multiplex PCR method in comparison with the standard method of culture (Most Probably Number)

PubMed Central

Fatemeh, Dehghan; Reza, Zolfaghari Mohammad; Mohammad, Arjomandzadegan; Salomeh, Kalantari; Reza, Ahmari Gholam; Hossein, Sarmadian; Maryam, Sadrnia; Azam, Ahmadi; Mana, Shojapoor; Negin, Najarian; Reza, Kasravi Alii; Saeed, Falahat

2014-01-01

Objective To analyse molecular detection of coliforms and shorten the time of PCR. Methods Rapid detection of coliforms by amplification of lacZ and uidA genes in a multiplex PCR reaction was designed and performed in comparison with most probably number (MPN) method for 16 artificial and 101 field samples. The molecular method was also conducted on isolated coliforms from positive MPN samples; standard sample for verification of microbial method certificated reference material; isolated strains from certificated reference material and standard bacteria. The PCR and electrophoresis parameters were changed for reducing the operation time. Results Results of PCR for lacZ and uidA genes were similar in all of standard, operational and artificial samples and showed the 876 bp and 147 bp bands of lacZ and uidA genes by multiplex PCR. PCR results were confirmed by MPN culture method by sensitivity 86% (95% CI: 0.71-0.93). Also the total execution time, with a successful change of factors, was reduced to less than two and a half hour. Conclusions Multiplex PCR method with shortened operation time was used for the simultaneous detection of total coliforms and Escherichia coli in distribution system of Arak city. It's recommended to be used at least as an initial screening test, and then the positive samples could be randomly tested by MPN. PMID:25182727

Determination of arsenic in traditional Chinese medicine by microwave digestion with flow injection-inductively coupled plasma mass spectrometry (FI-ICP-MS).

PubMed

Ong, E S; Yong, Y L; Woo, S O

1999-01-01

A simple, rapid, and sensitive method with high sample throughput was developed for determining arsenic in traditional Chinese medicine (TCM) in the form of uncoated tablets, sugar-coated tablets, black pills, capsules, powders, and syrups. The method involves microwave digestion with flow injection-inductively coupled plasma mass spectrometry (FI-ICP-MS). Method precision was 2.7-10.1% (relative standard deviation, n = 6) for different concentrations of arsenic in different TCM samples analyzed by different analysts on different days. Method accuracy was checked with a certified reference material (sea lettuce, Ulva lactuca, BCR CRM 279) for external calibration and by spiking arsenic standard into different TCMs. Recoveries of 89-92% were obtained for the certified reference material and higher than 95% for spiked TCMs. Matrix interference was insignificant for samples analyzed by the method of standard addition. Hence, no correction equation was used in the analysis of arsenic in the samples studied. Sample preparation using microwave digestion gave results that were very similar to those obtained by conventional wet acid digestion using nitric acid.

Standardization of 237Np by the CIEMAT/NIST LSC tracer method

PubMed

Gunther

2000-03-01

The standardization of 237Np presents some difficulties: several groups of alpha, beta and gamma radiation, chemical problems with the daughter nuclide 233Pa, an incomplete radioactive equilibrium after sample preparation, high conversion of some gamma transitions. To solve the chemical problems, a sample composition involving the Ultima Gold AB scintillator and a high concentration of HCl is used. Standardization by the CIEMAT/NIST method and by pulse shape discrimination is described. The results agree within 0.1% with those obtained by two other methods.

7 CFR 51.308 - Methods of sampling and calculation of percentages.

Code of Federal Regulations, 2012 CFR

2012-01-01

..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Methods of Sampling and Calculation... where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be calculated on the basis of count. (b) In all other...

7 CFR 51.308 - Methods of sampling and calculation of percentages.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Methods of Sampling and Calculation... where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be calculated on the basis of count. (b) In all other...

7 CFR 51.308 - Methods of sampling and calculation of percentages.

Code of Federal Regulations, 2010 CFR

2010-01-01

..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Methods of Sampling and Calculation... where the minimum diameter of the smallest apple does not vary more than 1/2 inch from the minimum diameter of the largest apple, percentages shall be calculated on the basis of count. (b) In all other...

29 CFR 1926.752 - Site layout, site-specific erection plan and construction sequence.

Code of Federal Regulations, 2011 CFR

2011-07-01

... standard test method of field-cured samples, either 75 percent of the intended minimum compressive design... the basis of an appropriate ASTM standard test method of field-cured samples, either 75 percent of the intended minimum compressive design strength or sufficient strength to support the loads imposed during...

29 CFR 1926.752 - Site layout, site-specific erection plan and construction sequence.

Code of Federal Regulations, 2013 CFR

2013-07-01

... standard test method of field-cured samples, either 75 percent of the intended minimum compressive design... the basis of an appropriate ASTM standard test method of field-cured samples, either 75 percent of the intended minimum compressive design strength or sufficient strength to support the loads imposed during...

29 CFR 1926.752 - Site layout, site-specific erection plan and construction sequence.

Code of Federal Regulations, 2012 CFR

2012-07-01

... standard test method of field-cured samples, either 75 percent of the intended minimum compressive design... the basis of an appropriate ASTM standard test method of field-cured samples, either 75 percent of the intended minimum compressive design strength or sufficient strength to support the loads imposed during...

29 CFR 1926.752 - Site layout, site-specific erection plan and construction sequence.

Code of Federal Regulations, 2010 CFR

2010-07-01

... standard test method of field-cured samples, either 75 percent of the intended minimum compressive design... the basis of an appropriate ASTM standard test method of field-cured samples, either 75 percent of the intended minimum compressive design strength or sufficient strength to support the loads imposed during...

29 CFR 1926.752 - Site layout, site-specific erection plan and construction sequence.

Code of Federal Regulations, 2014 CFR

2014-07-01

... standard test method of field-cured samples, either 75 percent of the intended minimum compressive design... the basis of an appropriate ASTM standard test method of field-cured samples, either 75 percent of the intended minimum compressive design strength or sufficient strength to support the loads imposed during...

Daily sodium and potassium excretion can be estimated by scheduled spot urine collections.

PubMed

Doenyas-Barak, Keren; Beberashvili, Ilia; Bar-Chaim, Adina; Averbukh, Zhan; Vogel, Ofir; Efrati, Shai

2015-01-01

The evaluation of sodium and potassium intake is part of the optimal management of hypertension, metabolic syndrome, renal stones, and other conditions. To date, no convenient method for its evaluation exists, as the gold standard method of 24-hour urine collection is cumbersome and often incorrectly performed, and methods that use spot or shorter collections are not accurate enough to replace the gold standard. The aim of this study was to evaluate the correlation and agreement between a new method that uses multiple-scheduled spot urine collection and the gold standard method of 24-hour urine collection. The urine sodium or potassium to creatinine ratios were determined for four scheduled spot urine samples. The mean ratios of the four spot samples and the ratios of each of the single spot samples were corrected for estimated creatinine excretion and compared to the gold standard. A significant linear correlation was demonstrated between the 24-hour urinary solute excretions and estimated excretion evaluated by any of the scheduled spot urine samples. The correlation of the mean of the four spots was better than for any of the single spots. Bland-Altman plots showed that the differences between these measurements were within the limits of agreement. Four scheduled spot urine samples can be used as a convenient method for estimation of 24-hour sodium or potassium excretion. © 2015 S. Karger AG, Basel.

Novel methodology to isolate microplastics from vegetal-rich samples.

PubMed

Herrera, Alicia; Garrido-Amador, Paloma; Martínez, Ico; Samper, María Dolores; López-Martínez, Juan; Gómez, May; Packard, Theodore T

2018-04-01

Microplastics are small plastic particles, globally distributed throughout the oceans. To properly study them, all the methodologies for their sampling, extraction, and measurement should be standardized. For heterogeneous samples containing sediments, animal tissues and zooplankton, several procedures have been described. However, definitive methodologies for samples, rich in algae and plant material, have not yet been developed. The aim of this study was to find the best extraction protocol for vegetal-rich samples by comparing the efficacies of five previously described digestion methods, and a novel density separation method. A protocol using 96% ethanol for density separation was better than the five digestion methods tested, even better than using H 2 O 2 digestion. As it was the most efficient, simple, safe and inexpensive method for isolating microplastics from vegetal rich samples, we recommend it as a standard separation method. Copyright © 2018 Elsevier Ltd. All rights reserved.

Evaluation of a new automated instrument for pretransfusion testing.

PubMed

Morelati, F; Revelli, N; Maffei, L M; Poretti, M; Santoro, C; Parravicini, A; Rebulla, P; Cole, R; Sirchia, G

1998-10-01

A number of automated devices for pretransfusion testing have recently become available. This study evaluated a fully automated device based on column agglutination technology (AutoVue System, Ortho, Raritan, NJ). Some 6747 tests including forward and reverse ABO group, Rh type and phenotype, antibody screen, autocontrol, and crossmatch were performed on random samples from 1069 blood donors, 2063 patients, and 98 newborns and cord blood. Also tested were samples from 168 immunized patients and 53 donors expressing weak or variant A and D antigens. Test results and technician times required for their performance were compared with those obtained by standard methods (manual column agglutination technology, slide, semiautomatic handler). No erroneous conclusions were found in regard to the 5028 ABO group and Rh type or phenotype determinations carried out with the device. The device rejected 1.53 percent of tests for sample inadequacy. Of the remaining 18 tests with discrepant results found with the device and not confirmed with the standard methods, 6 gave such results because of mixed-field reactions, 10 gave negative results with A2 RBCs in reverse ABO grouping, and 2 gave very weak positive reactions in antibody screening and crossmatching. In the samples from immunized patients, the device missed one weak anti-K, whereas standard methods missed five weak antibodies. In addition, 48, 34, and 31 of the 53 weak or variant antigens were detected by the device, the slide method, and the semiautomated handler, respectively. Technician time with the standard methods was 1.6 to 7 times higher than that with the device. The technical performance of the device compared favorably with that of standard methods, with a number of advantages, including in particular the saving of technician time. Sample inadequacy was the most common cause of discrepancy, which suggests that standardization of sample collection can further improve the performance of the device.

A method for direct, semi-quantitative analysis of gas phase samples using gas chromatography-inductively coupled plasma-mass spectrometry

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

Carter, Kimberly E; Gerdes, Kirk

2013-07-01

A new and complete GC–ICP-MS method is described for direct analysis of trace metals in a gas phase process stream. The proposed method is derived from standard analytical procedures developed for ICP-MS, which are regularly exercised in standard ICP-MS laboratories. In order to implement the method, a series of empirical factors were generated to calibrate detector response with respect to a known concentration of an internal standard analyte. Calibrated responses are ultimately used to determine the concentration of metal analytes in a gas stream using a semi-quantitative algorithm. The method was verified using a traditional gas injection from a GCmore » sampling valve and a standard gas mixture containing either a 1 ppm Xe + Kr mix with helium balance or 100 ppm Xe with helium balance. Data collected for Xe and Kr gas analytes revealed that agreement of 6–20% with the actual concentration can be expected for various experimental conditions. To demonstrate the method using a relevant “unknown” gas mixture, experiments were performed for continuous 4 and 7 hour periods using a Hg-containing sample gas that was co-introduced into the GC sample loop with the xenon gas standard. System performance and detector response to the dilute concentration of the internal standard were pre-determined, which allowed semi-quantitative evaluation of the analyte. The calculated analyte concentrations varied during the course of the 4 hour experiment, particularly during the first hour of the analysis where the actual Hg concentration was under predicted by up to 72%. Calculated concentration improved to within 30–60% for data collected after the first hour of the experiment. Similar results were seen during the 7 hour test with the deviation from the actual concentration being 11–81% during the first hour and then decreasing for the remaining period. The method detection limit (MDL) was determined for the mercury by injecting the sample gas into the system following a period of equilibration. The MDL for Hg was calculated as 6.8 μg · m -3. This work describes the first complete GC–ICP-MS method to directly analyze gas phase samples, and detailed sample calculations and comparisons to conventional ICP-MS methods are provided.« less

CTEPP STANDARD OPERATING PROCEDURE FOR HANDLING SAMPLE AND DATA CUSTODY (SOP-2.26)

EPA Science Inventory

This SOP describes the method for handling sample custody. A standardized Chain-of-Custody (CoC) Record is used to document the sample/data custody. Each participant is assigned one CoC Record for the samples/data collected at their home and/or day care center.

Simultaneous Spectrophotometric Determination of Rifampicin, Isoniazid and Pyrazinamide in a Single Step

PubMed Central

Asadpour-Zeynali, Karim; Saeb, Elhameh

2016-01-01

Three antituberculosis medications are investigated in this work consist of rifampicin, isoniazid and pyrazinamide. The ultra violet (UV) spectra of these compounds are overlapped, thus use of suitable chemometric methods are helpful for simultaneous spectrophotometric determination of them. A generalized version of net analyte signal standard addition method (GNASSAM) was used for determination of three antituberculosis medications as a model system. In generalized net analyte signal standard addition method only one standard solution was prepared for all analytes. This standard solution contains a mixture of all analytes of interest, and the addition of such solution to sample, causes increases in net analyte signal of each analyte which are proportional to the concentrations of analytes in added standards solution. For determination of concentration of each analyte in some synthetic mixtures, the UV spectra of pure analytes and each sample were recorded in the range of 210 nm-550 nm. The standard addition procedure was performed for each sample and the UV spectrum was recorded after each addition and finally the results were analyzed by net analyte signal method. Obtained concentrations show acceptable performance of GNASSAM in these cases. PMID:28243267

Solid matrix transformation and tracer addition using molten ammonium bifluoride salt as a sample preparation method for laser ablation inductively coupled plasma mass spectrometry.

PubMed

Grate, Jay W; Gonzalez, Jhanis J; O'Hara, Matthew J; Kellogg, Cynthia M; Morrison, Samuel S; Koppenaal, David W; Chan, George C-Y; Mao, Xianglei; Zorba, Vassilia; Russo, Richard E

2017-09-08

Solid sampling and analysis methods, such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), are challenged by matrix effects and calibration difficulties. Matrix-matched standards for external calibration are seldom available and it is difficult to distribute spikes evenly into a solid matrix as internal standards. While isotopic ratios of the same element can be measured to high precision, matrix-dependent effects in the sampling and analysis process frustrate accurate quantification and elemental ratio determinations. Here we introduce a potentially general solid matrix transformation approach entailing chemical reactions in molten ammonium bifluoride (ABF) salt that enables the introduction of spikes as tracers or internal standards. Proof of principle experiments show that the decomposition of uranium ore in sealed PFA fluoropolymer vials at 230 °C yields, after cooling, new solids suitable for direct solid sampling by LA. When spikes are included in the molten salt reaction, subsequent LA-ICP-MS sampling at several spots indicate that the spikes are evenly distributed, and that U-235 tracer dramatically improves reproducibility in U-238 analysis. Precisions improved from 17% relative standard deviation for U-238 signals to 0.1% for the ratio of sample U-238 to spiked U-235, a factor of over two orders of magnitude. These results introduce the concept of solid matrix transformation (SMT) using ABF, and provide proof of principle for a new method of incorporating internal standards into a solid for LA-ICP-MS. This new approach, SMT-LA-ICP-MS, provides opportunities to improve calibration and quantification in solids based analysis. Looking forward, tracer addition to transformed solids opens up LA-based methods to analytical methodologies such as standard addition, isotope dilution, preparation of matrix-matched solid standards, external calibration, and monitoring instrument drift against external calibration standards.

40 CFR 761.243 - Standard wipe sample method and size.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., AND USE PROHIBITIONS Determining a PCB Concentration for Purposes of Abandonment or Disposal of Natural Gas Pipeline: Selecting Sample Sites, Collecting Surface Samples, and Analyzing Standard PCB Wipe.../Rinse Cleanup as Recommended by the Environmental Protection Agency PCB Spill Cleanup Policy,” dated...

Confidence intervals for the population mean tailored to small sample sizes, with applications to survey sampling.

PubMed

Rosenblum, Michael A; Laan, Mark J van der

2009-01-07

The validity of standard confidence intervals constructed in survey sampling is based on the central limit theorem. For small sample sizes, the central limit theorem may give a poor approximation, resulting in confidence intervals that are misleading. We discuss this issue and propose methods for constructing confidence intervals for the population mean tailored to small sample sizes. We present a simple approach for constructing confidence intervals for the population mean based on tail bounds for the sample mean that are correct for all sample sizes. Bernstein's inequality provides one such tail bound. The resulting confidence intervals have guaranteed coverage probability under much weaker assumptions than are required for standard methods. A drawback of this approach, as we show, is that these confidence intervals are often quite wide. In response to this, we present a method for constructing much narrower confidence intervals, which are better suited for practical applications, and that are still more robust than confidence intervals based on standard methods, when dealing with small sample sizes. We show how to extend our approaches to much more general estimation problems than estimating the sample mean. We describe how these methods can be used to obtain more reliable confidence intervals in survey sampling. As a concrete example, we construct confidence intervals using our methods for the number of violent deaths between March 2003 and July 2006 in Iraq, based on data from the study "Mortality after the 2003 invasion of Iraq: A cross sectional cluster sample survey," by Burnham et al. (2006).

Spectrophotometric methods for the determination of urea in real samples using silver nanoparticles by standard addition and 2nd order derivative methods

NASA Astrophysics Data System (ADS)

Ali, Nauman; Ismail, Muhammad; Khan, Adnan; Khan, Hamayun; Haider, Sajjad; Kamal, Tahseen

2018-01-01

In this work, we have developed simple, sensitive and inexpensive methods for the spectrophotometric determination of urea in urine samples using silver nanoparticles (AgNPs). The standard addition and 2nd order derivative methods were adopted for this purpose. AgNPs were prepared by chemical reduction of AgNO3 with hydrazine using 1,3-di-(1H-imidazol-1-yl)-2-propanol (DIPO) as a stabilizing agent in aqueous medium. The proposed methods were based on the complexation of AgNPs with urea. Using this concept, urea in the urine samples was successfully determined spectrophotometric methods. The results showed high percent recovery with ± RSD. The recoveries of urea in the three urine samples by spectrophotometric standard addition were 99.2% ± 5.37, 96.3% ± 4.49, 104.88% ± 4.99 and that of spectrophotometric 2nd order derivative method were 115.3% ± 5.2, 103.4% ± 2.6, 105.93% ± 0.76. The results show that these methods can open doors for a potential role of AgNPs in the clinical determination of urea in urine, blood, biological, non-biological fluids.

Standard-less analysis of Zircaloy clad samples by an instrumental neutron activation method

NASA Astrophysics Data System (ADS)

Acharya, R.; Nair, A. G. C.; Reddy, A. V. R.; Goswami, A.

2004-03-01

A non-destructive method for analysis of irregular shape and size samples of Zircaloy has been developed using the recently standardized k0-based internal mono standard instrumental neutron activation analysis (INAA). The samples of Zircaloy-2 and -4 tubes, used as fuel cladding in Indian boiling water reactors (BWR) and pressurized heavy water reactors (PHWR), respectively, have been analyzed. Samples weighing in the range of a few tens of grams were irradiated in the thermal column of Apsara reactor to minimize neutron flux perturbations and high radiation dose. The method utilizes in situ relative detection efficiency using the γ-rays of selected activation products in the sample for overcoming γ-ray self-attenuation. Since the major and minor constituents (Zr, Sn, Fe, Cr and/or Ni) in these samples were amenable to NAA, the absolute concentrations of all the elements were determined using mass balance instead of using the concentration of the internal mono standard. Concentrations were also determined in a smaller size Zircaloy-4 sample by irradiating in the core position of the reactor to validate the present methodology. The results were compared with literature specifications and were found to be satisfactory. Values of sensitivities and detection limits have been evaluated for the elements analyzed.

Identification and quantification of nitrofurazone metabolites by ultraperformance liquid chromatography-quadrupole time-of-flight high-resolution mass spectrometry with precolumn derivatization.

PubMed

Zhang, Shuai; Li, PeiPei; Yan, Zhongyong; Long, Ju; Zhang, Xiaojun

2017-03-01

An ultraperformance liquid chromatography-quadrupole time-of-flight high-resolution mass spectrometry method was developed and validated for the determination of nitrofurazone metabolites. Precolumn derivatization with 2,4-dinitrophenylhydrazine and p-dimethylaminobenzaldehyde as an internal standard was used successfully to determine the biomarker 5-nitro-2-furaldehyde. In negative electrospray ionization mode, the precise molecular weights of the derivatives were 320.0372 for the biomarker and 328.1060 for the internal standard (relative error 1.08 ppm). The matrix effect was evaluated and the analytical characteristics of the method and derivatization reaction conditions were validated. For comparison purposes, spiked samples were tested by both internal and external standard methods. The results show high precision can be obtained with p-dimethylaminobenzaldehyde as an internal standard for the identification and quantification of nitrofurazone metabolites in complex biological samples. Graphical Abstract A simplified preparation strategy for biological samples.

Comparison of two filtration-elution procedures to improve the standard methods ISO 10705-1 & 2 for bacteriophage detection in groundwater, surface water and finished water samples.

PubMed

Helmi, K; Jacob, P; Charni-Ben-Tabassi, N; Delabre, K; Arnal, C

2011-09-01

To select a reliable method for bacteriophage concentration prior detection by culture from surface water, groundwater and drinking water to enhance the sensitivity of the standard methods ISO 10705-1 & 2. Artificially contaminated (groundwater and drinking water) and naturally contaminated (surface water) 1-litre samples were processed for bacteriophages detection. The spiked samples were inoculated with about 150 PFU of F-specific RNA bacteriophages and somatic coliphages using wastewater. Bacteriophage detection in the water samples was achieved using the standard method without and with a concentration step (electropositive Anodisc membrane or a pretreated electronegative Micro Filtration membrane, MF). For artificially contaminated matrices (drinking and ground waters), recovery rates using the concentration step were superior to 70% whilst analyses without concentration step mainly led to false negative results. Besides, the MF membrane presented higher performances compared with the Anodisc membrane. The concentration of a large volume of water (up to one litre) on a filter membrane avoids false negative results obtained by direct analysis as it allows detecting low number of bacteriophages in water samples. The addition of concentration step before applying the standard method could be useful to enhance the reliability of bacteriophages monitoring in water samples as bio-indicators to highlight faecal pollution. © No claim to French Government works. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

Point-of-Care Quantitative Measure of Glucose-6-Phosphate Dehydrogenase Enzyme Deficiency.

PubMed

Bhutani, Vinod K; Kaplan, Michael; Glader, Bertil; Cotten, Michael; Kleinert, Jairus; Pamula, Vamsee

2015-11-01

Widespread newborn screening on a point-of-care basis could prevent bilirubin neurotoxicity in newborns with glucose-6-phosphate dehydrogenase (G6PD) deficiency. We evaluated a quantitative G6PD assay on a digital microfluidic platform by comparing its performance with standard clinical methods. G6PD activity was measured quantitatively by using digital microfluidic fluorescence and the gold standard fluorescence biochemical test on a convenience sample of 98 discarded blood samples. Twenty-four samples were designated as G6PD deficient. Mean ± SD G6PD activity for normal samples using the digital microfluidic method and the standard method, respectively, was 9.7 ± 2.8 and 11.1 ± 3.0 U/g hemoglobin (Hb), respectively; for G6PD-deficient samples, it was 0.8 ± 0.7 and 1.4 ± 0.9 U/g Hb. Bland-Altman analysis determined a mean difference of -0.96 ± 1.8 U/g Hb between the digital microfluidic fluorescence results and the standard biochemical test results. The lower and upper limits for the digital microfluidic platform were 4.5 to 19.5 U/g Hb for normal samples and 0.2 to 3.7 U/g Hb for G6PD-deficient samples. The lower and upper limits for the Stanford method were 5.5 to 20.7 U/g Hb for normal samples and 0.1 to 2.8 U/g Hb for G6PD-deficient samples. The measured activity discriminated between G6PD-deficient samples and normal samples with no overlap. Pending further validation, a digital microfluidics platform could be an accurate point-of-care screening tool for rapid newborn G6PD screening. Copyright © 2015 by the American Academy of Pediatrics.

Minerals and Trace Elements in Milk, Milk Products, Infant Formula, and Adult/Pediatric Nutritional Formula, ICP-MS Method: Collaborative Study, AOAC Final Action 2015.06, ISO/DIS 21424, IDF 243.

PubMed

Pacquette, Lawrence H; Thompson, Joseph J; Malaviole, I; Zywicki, R; Woltjes, F; Ding, Y; Mittal, A; Ikeuchi, Y; Sadipiralla, B; Kimura, S; Veltman, H; Miura, A

2018-03-01

AOAC Final Action Official MethodSM 2015.06 "Minerals and Trace Elements in Milk, Milk Products, Infant Formula and Adult/Pediatric Nutritional Formula, ICP-MS Method" was collaboratively studied. Note that "milk, milk products" has now been added to the title of the Final Action method because whole milk and several dairy ingredients were successfully incorporated into the collaborative study for the purpose of developing an International Organization for Standardization/International Dairy Federation standard (ISO/DIS 21424; in progress). The method determines sodium, magnesium, phosphorus, potassium, calcium, iron, manganese, zinc, copper, chromium, molybdenum, and selenium by inductively coupled plasma (ICP)-MS after microwave digestion. Ten laboratories participated in the study, and data from five different model ICP-MS units were represented. Thirteen products, five placebo products, and six dairy samples were tested as blind duplicates in this study, along with a standard reference material, for a total 50 samples. The overall repeatability and reproducibility for all samples met Standard Method Performance Requirements put forth by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals, with a few exceptions. Comparisons are made to ICP-atomic emission data from a collaborative study of AOAC Official Method 2011.14 carried out concurrently on these same samples.

Feasibility of zero tolerance for Salmonella on raw poultry

USDA-ARS?s Scientific Manuscript database

Ideally, poultry producing countries around the globe should use internationally standardized sampling methods for Salmonella. It is difficult to compare prevalence data from country-to-country when sample plan, sample type, sample frequency and laboratory media along with methods differ. The Europe...

Evaluation of timing of re-appearance of VBNC Legionella for risk assessment in hospital water distribution systems.

PubMed

Marinelli, L; Cottarelli, A; Solimini, A G; Del Cimmuto, A; De Giusti, M

2017-01-01

In this study we estimated the presence of Legionella species, viable but non-culturable (VBNC), in hospital water networks. We also evaluated the time and load of Legionella appearance in samples found negative using the standard culture method. A total of 42 samples was obtained from the tap water of five hospital buildings. The samples were tested for Legionella by the standard culture method and were monitored for up to 12 months for the appearance of VBNC Legionella. All the 42 samples were negative at the time of collection. Seven of the 42 samples (17.0%) became positive for Legionella at different times of monitoring. The time to the appearance of VBNC Legionella was extremely variable, from 15 days to 9 months from sampling. The most frequent Legionella species observed were Legionella spp and L. anisa and only in one sample L. pneumophila srg.1. Our study confirms the presence of VBNC Legionella in samples resulting negative using the standard culture method and highlights the different time to its appearance that can occur several months after sampling. The results are important for risk assessment and risk management of engineered water systems.

Coding of DNA samples and data in the pharmaceutical industry: current practices and future directions--perspective of the I-PWG.

PubMed

Franc, M A; Cohen, N; Warner, A W; Shaw, P M; Groenen, P; Snapir, A

2011-04-01

DNA samples collected in clinical trials and stored for future research are valuable to pharmaceutical drug development. Given the perceived higher risk associated with genetic research, industry has implemented complex coding methods for DNA. Following years of experience with these methods and with addressing questions from institutional review boards (IRBs), ethics committees (ECs) and health authorities, the industry has started reexamining the extent of the added value offered by these methods. With the goal of harmonization, the Industry Pharmacogenomics Working Group (I-PWG) conducted a survey to gain an understanding of company practices for DNA coding and to solicit opinions on their effectiveness at protecting privacy. The results of the survey and the limitations of the coding methods are described. The I-PWG recommends dialogue with key stakeholders regarding coding practices such that equal standards are applied to DNA and non-DNA samples. The I-PWG believes that industry standards for privacy protection should provide adequate safeguards for DNA and non-DNA samples/data and suggests a need for more universal standards for samples stored for future research.

Evaluation of a Wipe Surface Sample Method for Collection of Bacillus Spores from Nonporous Surfaces▿

PubMed Central

Brown, Gary S.; Betty, Rita G.; Brockmann, John E.; Lucero, Daniel A.; Souza, Caroline A.; Walsh, Kathryn S.; Boucher, Raymond M.; Tezak, Mathew; Wilson, Mollye C.; Rudolph, Todd

2007-01-01

Polyester-rayon blend wipes were evaluated for efficiency of extraction and recovery of powdered Bacillus atrophaeus spores from stainless steel and painted wallboard surfaces. Method limits of detection were also estimated for both surfaces. The observed mean efficiency of polyester-rayon blend wipe recovery from stainless steel was 0.35 with a standard deviation of ±0.12, and for painted wallboard it was 0.29 with a standard deviation of ±0.15. Evaluation of a sonication extraction method for the polyester-rayon blend wipes produced a mean extraction efficiency of 0.93 with a standard deviation of ±0.09. Wipe recovery quantitative limits of detection were estimated at 90 CFU per unit of stainless steel sample area and 105 CFU per unit of painted wallboard sample area. The method recovery efficiency and limits of detection established in this work provide useful guidance for the planning of incident response environmental sampling following the release of a biological agent such as Bacillus anthracis. PMID:17122390

Evaluation of a wipe surface sample method for collection of Bacillus spores from nonporous surfaces.

PubMed

Brown, Gary S; Betty, Rita G; Brockmann, John E; Lucero, Daniel A; Souza, Caroline A; Walsh, Kathryn S; Boucher, Raymond M; Tezak, Mathew; Wilson, Mollye C; Rudolph, Todd

2007-02-01

Polyester-rayon blend wipes were evaluated for efficiency of extraction and recovery of powdered Bacillus atrophaeus spores from stainless steel and painted wallboard surfaces. Method limits of detection were also estimated for both surfaces. The observed mean efficiency of polyester-rayon blend wipe recovery from stainless steel was 0.35 with a standard deviation of +/-0.12, and for painted wallboard it was 0.29 with a standard deviation of +/-0.15. Evaluation of a sonication extraction method for the polyester-rayon blend wipes produced a mean extraction efficiency of 0.93 with a standard deviation of +/-0.09. Wipe recovery quantitative limits of detection were estimated at 90 CFU per unit of stainless steel sample area and 105 CFU per unit of painted wallboard sample area. The method recovery efficiency and limits of detection established in this work provide useful guidance for the planning of incident response environmental sampling following the release of a biological agent such as Bacillus anthracis.

Limitation in the detection of Listeria monocytogenes in food in the presence of competing Listeria innocua.

PubMed

Oravcová, K; Trncíková, T; Kuchta, T; Kaclíková, E

2008-02-01

Detectability of Listeria monocytogenes at 10(0) CFU per food sample in the presence of Listeria innocua using standard microbiological detection was evaluated and compared with the real-time PCR-based method. Enrichment in half-Fraser broth followed by subculture in Fraser broth according to EN ISO 11290-1 was used. False-negative detection of 10(0) CFU L. monocytogenes was obtained in the presence of 10(1) CFU L. innocua per sample using the standard detection method in contrast to more than 10(5) CFU L. innocua per sample using real-time PCR. Identification of L. monocytogenes on the chromogenic medium by the standard procedure was impossible if L. innocua was able to overgrow L. monocytogenes by more than three orders of magnitude after the enrichment in model samples. These results were confirmed using naturally contaminated food samples. Standard microbiological method was insufficient for the reliable detection of 10(0) CFU L. monocytogenes in the presence of more than 10(0) CFU of L. innocua per sample. On the other hand, if the growth of L. monocytogenes was sufficient to reach the concentration equal to the detection limit of PCR, the amount of the other microflora present in the food sample including L. innocua was not relevant for success of the PCR detection of L. monocytogenes. After the enrichment, the PCR detection is more convenient than the standard one as PCR detection is not compromised by other present microflora.

Distribution of the two-sample t-test statistic following blinded sample size re-estimation.

PubMed

Lu, Kaifeng

2016-05-01

We consider the blinded sample size re-estimation based on the simple one-sample variance estimator at an interim analysis. We characterize the exact distribution of the standard two-sample t-test statistic at the final analysis. We describe a simulation algorithm for the evaluation of the probability of rejecting the null hypothesis at given treatment effect. We compare the blinded sample size re-estimation method with two unblinded methods with respect to the empirical type I error, the empirical power, and the empirical distribution of the standard deviation estimator and final sample size. We characterize the type I error inflation across the range of standardized non-inferiority margin for non-inferiority trials, and derive the adjusted significance level to ensure type I error control for given sample size of the internal pilot study. We show that the adjusted significance level increases as the sample size of the internal pilot study increases. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Sampling bee communities using pan traps: alternative methods increase sample size

USDA-ARS?s Scientific Manuscript database

Monitoring of the status of bee populations and inventories of bee faunas require systematic sampling. Efficiency and ease of implementation has encouraged the use of pan traps to sample bees. Efforts to find an optimal standardized sampling method for pan traps have focused on pan trap color. Th...

Method for measuring recovery of catalytic elements from fuel cells

DOEpatents

Shore, Lawrence [Edison, NJ; Matlin, Ramail [Berkeley, NJ

2011-03-08

A method is provided for measuring the concentration of a catalytic clement in a fuel cell powder. The method includes depositing on a porous substrate at least one layer of a powder mixture comprising the fuel cell powder and an internal standard material, ablating a sample of the powder mixture using a laser, and vaporizing the sample using an inductively coupled plasma. A normalized concentration of catalytic element in the sample is determined by quantifying the intensity of a first signal correlated to the amount of catalytic element in the sample, quantifying the intensity of a second signal correlated to the amount of internal standard material in the sample, and using a ratio of the first signal intensity to the second signal intensity to cancel out the effects of sample size.

Measurement of trace elements in tree rings using the PIXE method

NASA Astrophysics Data System (ADS)

Aoki, Toru; Katayama, Yukio; Kagawa, Akira; Koh, Susumu; Yoshida, Kohji

1998-03-01

Standard materials were prepared in order to calculate element concentrations in tree samples using the particle induced X-ray emission (PIXE) method. Five standard solutions (1) Ti, Fe, Cu, As, Rb, Sr; (2) Ca, V, Co, Zn, As, Rb; (3) Ti, Mn, Ni, As, Sr; (4) K, Mn, Co, As, Rb, Sr; and (5) Ca, Mn, Cu, As, Rb, Sr, were added to filter papers. The dried filter papers were used as standard samples. Pellets of Pepperbush leaves (National Institute for Environmental Studies (NIES)) and Peach leaves (National Institute of Standards and Technology (NIST)) were used as references. The peak counts of Ca, Mn, Cu, Zn, Rb, and Sr in samples taken from a kaki ( Diospros kaki Thunb.) were measured and the concentrations (ppm) of the elements were calculated using the yield curve obtained from the standard filter papers. The concentrations of Mn, Zn, Rb, and Ca were compared with the data obtained from a separate INAA analysis. Concentrations of Mn, Zn, and Ca obtained by both methods were almost the same, but the concentrations of Rb differed slightly. The amounts of trace elements in samples taken from a sugi ( Cryptomeria japonica D. Don) were also measured.

The Effect of Cluster Sampling Design in Survey Research on the Standard Error Statistic.

ERIC Educational Resources Information Center

Wang, Lin; Fan, Xitao

Standard statistical methods are used to analyze data that is assumed to be collected using a simple random sampling scheme. These methods, however, tend to underestimate variance when the data is collected with a cluster design, which is often found in educational survey research. The purposes of this paper are to demonstrate how a cluster design…

A standardized method for sampling and extraction methods for quantifying microplastics in beach sand.

PubMed

Besley, Aiken; Vijver, Martina G; Behrens, Paul; Bosker, Thijs

2017-01-15

Microplastics are ubiquitous in the environment, are frequently ingested by organisms, and may potentially cause harm. A range of studies have found significant levels of microplastics in beach sand. However, there is a considerable amount of methodological variability among these studies. Methodological variation currently limits comparisons as there is no standard procedure for sampling or extraction of microplastics. We identify key sampling and extraction procedures across the literature through a detailed review. We find that sampling depth, sampling location, number of repeat extractions, and settling times are the critical parameters of variation. Next, using a case-study we determine whether and to what extent these differences impact study outcomes. By investigating the common practices identified in the literature with the case-study, we provide a standard operating procedure for sampling and extracting microplastics from beach sand. Copyright © 2016 Elsevier Ltd. All rights reserved.

[An attempt for standardization of serum CA19-9 levels, in order to dissolve the gap between three different methods].

PubMed

Hayashi, Kuniki; Hoshino, Tadashi; Yanai, Mitsuru; Tsuchiya, Tatsuyuki; Kumasaka, Kazunari; Kawano, Kinya

2004-06-01

It is well known that serious method-related differences exist in results of serum CA19-9, and the necessity of standardization has been pointed out. In this study, differences of serum tumor marker CA19-9 levels obtained by various immunoassay kits (CLEIA, FEIA, LPIA and RIA) were evaluated in sixty-seven clinical samples and five calibrators and the possibility to improve the inter-methodological differences were observed not only for clinical samples but also for calibrators. We supposed an assumed standard material using by a calibrator. We calculated the serum levels of CA19-9 when using the assumed standard material for three different measurement methods. We approximate the CA19-9 values using by this method. It is suggested that the obtained CA19-9 values could be approximated by recalculation with the assumed standard material would be able to correct between-method and between-laboratory discrepancies in particular systematic errors.

Sulfuric acid/hydrogen peroxide digestion and colorimetric a collaborative study.

PubMed

Christians, D K; Aspelund, T G; Brayton, S V; Roberts, L L

1991-01-01

Seven laboratories participated in a collaborative study of a method for determination of phosphorus in meat and meat products. Samples are digested in sulfuric acid and hydrogen peroxide; digestion is complete in approximately 10 min. Phosphorus is determined by colorimetric analysis of a dilute aliquot of the sample digest. The collaborators analyzed 3 sets of blind duplicate samples from each of 6 classes of meat (U.S. Department of Agriculture classifications): smoked ham, water-added ham, canned ham, pork sausage, cooked sausage, and hamburger. The calibration curve was linear over the range of standard solutions prepared (phosphorus levels from 0.05 to 1.00%); levels in the collaborative study samples ranged from 0.10 to 0.30%. Standard deviations for repeatability (sr) and reproducibility (SR) ranged from 0.004 to 0.012 and 0.007 to 0.014, respectively. Corresponding relative standard deviations (RSDr and RSDR, respectively) ranged from 1.70 to 7.28% and 3.50 to 9.87%. Six laboratories analyzed samples by both the proposed method and AOAC method 24.016 (14th Ed.). One laboratory reported results by the proposed method only. Statistical evaluations indicated no significant difference between the 2 methods. The method has been adopted official first action by AOAC.

Quantitative Analysis of Ca, Mg, and K in the Roots of Angelica pubescens f. biserrata by Laser-Induced Breakdown Spectroscopy Combined with Artificial Neural Networks

NASA Astrophysics Data System (ADS)

Wang, J.; Shi, M.; Zheng, P.; Xue, Sh.; Peng, R.

2018-03-01

Laser-induced breakdown spectroscopy has been applied for the quantitative analysis of Ca, Mg, and K in the roots of Angelica pubescens Maxim. f. biserrata Shan et Yuan used in traditional Chinese medicine. Ca II 317.993 nm, Mg I 517.268 nm, and K I 769.896 nm spectral lines have been chosen to set up calibration models for the analysis using the external standard and artificial neural network methods. The linear correlation coefficients of the predicted concentrations versus the standard concentrations of six samples determined by the artificial neural network method are 0.9896, 0.9945, and 0.9911 for Ca, Mg, and K, respectively, which are better than for the external standard method. The artificial neural network method also gives better performance comparing with the external standard method for the average and maximum relative errors, average relative standard deviations, and most maximum relative standard deviations of the predicted concentrations of Ca, Mg, and K in the six samples. Finally, it is proved that the artificial neural network method gives better performance compared to the external standard method for the quantitative analysis of Ca, Mg, and K in the roots of Angelica pubescens.

A simple web-based tool to compare freshwater fish data collected using AFS standard methods

USGS Publications Warehouse

Bonar, Scott A.; Mercado-Silva, Norman; Rahr, Matt; Torrey, Yuta T.; Cate, Averill

2016-01-01

The American Fisheries Society (AFS) recently published Standard Methods for Sampling North American Freshwater Fishes. Enlisting the expertise of 284 scientists from 107 organizations throughout Canada, Mexico, and the United States, this text was developed to facilitate comparisons of fish data across regions or time. Here we describe a user-friendly web tool that automates among-sample comparisons in individual fish condition, population length-frequency distributions, and catch per unit effort (CPUE) data collected using AFS standard methods. Currently, the web tool (1) provides instantaneous summaries of almost 4,000 data sets of condition, length frequency, and CPUE of common freshwater fishes collected using standard gears in 43 states and provinces; (2) is easily appended with new standardized field data to update subsequent queries and summaries; (3) compares fish data from a particular water body with continent, ecoregion, and state data summaries; and (4) provides additional information about AFS standard fish sampling including benefits, ongoing validation studies, and opportunities to comment on specific methods. The web tool—programmed in a PHP-based Drupal framework—was supported by several AFS Sections, agencies, and universities and is freely available from the AFS website and fisheriesstandardsampling.org. With widespread use, the online tool could become an important resource for fisheries biologists.

[Assessment comparison between area sampling and personal sampling noise measurement in new thermal power plant].

PubMed

Zhang, Hua; Chen, Qing-song; Li, Nan; Hua, Yan; Zeng, Lin; Xu, Guo-yang; Tao, Li-yuan; Zhao, Yi-ming

2013-05-01

To compare the results of noise hazard evaluations based on area sampling and personal sampling in a new thermal power plant and to analyze the similarities and differences between the two measurement methods. According to Measurement of Physical agents in Workplace Part 8: Noise(GBZff 189.8-2007), area sampling was performed at various operating points for noise measurement, and meanwhile the workers under different types of work wore noise dosimeters for personal noise exposure measurement. The two measurement methods were used to evaluate the level of noise hazards in the enterprise according to the corresponding occupational health standards, and the evaluation results were compared. Area sampling was performed at 99 operating points, the mean noise level was 88.9 ± 11.1 dB (A)(range, 51.3-107.0 dB (A)), with an over-standard rate of 75.8%. Personal sampling was performed (73 person times),and the mean noise level was 79.3 ± 6.3 dB (A), with an over-standard rate of 6.6% ( 16/241 ). There was a statistically significant difference in the over-standard rate between the evaluation results of the two measurement methods ( x2=53.869, ?<0.001 ). Because of the characteristics of the work in new thermal power plants, the noise hazard evaluation based on area sampling cannot be used instead of personal noise exposure measurement among workers. Personal sampling should be used in the noise measurement in new thermal power plant.

Sample handling for mass spectrometric proteomic investigations of human sera.

PubMed

West-Nielsen, Mikkel; Høgdall, Estrid V; Marchiori, Elena; Høgdall, Claus K; Schou, Christian; Heegaard, Niels H H

2005-08-15

Proteomic investigations of sera are potentially of value for diagnosis, prognosis, choice of therapy, and disease activity assessment by virtue of discovering new biomarkers and biomarker patterns. Much debate focuses on the biological relevance and the need for identification of such biomarkers while less effort has been invested in devising standard procedures for sample preparation and storage in relation to model building based on complex sets of mass spectrometric (MS) data. Thus, development of standardized methods for collection and storage of patient samples together with standards for transportation and handling of samples are needed. This requires knowledge about how sample processing affects MS-based proteome analyses and thereby how nonbiological biased classification errors are avoided. In this study, we characterize the effects of sample handling, including clotting conditions, storage temperature, storage time, and freeze/thaw cycles, on MS-based proteomics of human serum by using principal components analysis, support vector machine learning, and clustering methods based on genetic algorithms as class modeling and prediction methods. Using spiking to artificially create differentiable sample groups, this integrated approach yields data that--even when working with sample groups that differ more than may be expected in biological studies--clearly demonstrate the need for comparable sampling conditions for samples used for modeling and for the samples that are going into the test set group. Also, the study emphasizes the difference between class prediction and class comparison studies as well as the advantages and disadvantages of different modeling methods.

Interlaboratory evaluation of a standardized inductively coupled plasma mass spectrometry method for the determination of trace beryllium in air filter samples.

PubMed

Ashley, Kevin; Brisson, Michael J; Howe, Alan M; Bartley, David L

2009-12-01

A collaborative interlaboratory evaluation of a newly standardized inductively coupled plasma mass spectrometry (ICP-MS) method for determining trace beryllium in workplace air samples was carried out toward fulfillment of method validation requirements for ASTM International voluntary consensus standard test methods. The interlaboratory study (ILS) was performed in accordance with an applicable ASTM International standard practice, ASTM E691, which describes statistical procedures for investigating interlaboratory precision. Uncertainty was also estimated in accordance with ASTM D7440, which applies the International Organization for Standardization Guide to the Expression of Uncertainty in Measurement to air quality measurements. Performance evaluation materials (PEMs) used consisted of 37 mm diameter mixed cellulose ester filters that were spiked with beryllium at levels of 0.025 (low loading), 0.5 (medium loading), and 10 (high loading) microg Be/filter; these spiked filters were prepared by a contract laboratory. Participating laboratories were recruited from a pool of over 50 invitees; ultimately, 20 laboratories from Europe, North America, and Asia submitted ILS results. Triplicates of each PEM (blanks plus the three different loading levels) were conveyed to each volunteer laboratory, along with a copy of the draft standard test method that each participant was asked to follow; spiking levels were unknown to the participants. The laboratories were requested to prepare the PEMs by one of three sample preparation procedures (hotplate or microwave digestion or hotblock extraction) that were described in the draft standard. Participants were then asked to analyze aliquots of the prepared samples by ICP-MS and to report their data in units of mu g Be/filter sample. Interlaboratory precision estimates from participating laboratories, computed in accordance with ASTM E691, were 0.165, 0.108, and 0.151 (relative standard deviation) for the PEMs spiked at 0.025, 0.5, and 10 microg Be/filter, respectively. Overall recoveries were 93.2%, 102%, and 80.6% for the low, medium, and high beryllium loadings, respectively. Expanded uncertainty estimates for interlaboratory analysis of low, medium, and high beryllium loadings, calculated in accordance with ASTM D7440, were 18.8%, 19.8%, and 24.4%, respectively. These figures of merit support promulgation of the analytical procedure as an ASTM International standard test method, ASTM D7439.

Importance sampling with imperfect cloning for the computation of generalized Lyapunov exponents

NASA Astrophysics Data System (ADS)

Anteneodo, Celia; Camargo, Sabrina; Vallejos, Raúl O.

2017-12-01

We revisit the numerical calculation of generalized Lyapunov exponents, L (q ) , in deterministic dynamical systems. The standard method consists of adding noise to the dynamics in order to use importance sampling algorithms. Then L (q ) is obtained by taking the limit noise-amplitude → 0 after the calculation. We focus on a particular method that involves periodic cloning and pruning of a set of trajectories. However, instead of considering a noisy dynamics, we implement an imperfect (noisy) cloning. This alternative method is compared with the standard one and, when possible, with analytical results. As a workbench we use the asymmetric tent map, the standard map, and a system of coupled symplectic maps. The general conclusion of this study is that the imperfect-cloning method performs as well as the standard one, with the advantage of preserving the deterministic dynamics.

Comparison of a New Cobinamide-Based Method to a Standard Laboratory Method for Measuring Cyanide in Human Blood

PubMed Central

Swezey, Robert; Shinn, Walter; Green, Carol; Drover, David R.; Hammer, Gregory B.; Schulman, Scott R.; Zajicek, Anne; Jett, David A.; Boss, Gerry R.

2013-01-01

Most hospital laboratories do not measure blood cyanide concentrations, and samples must be sent to reference laboratories. A simple method is needed for measuring cyanide in hospitals. The authors previously developed a method to quantify cyanide based on the high binding affinity of the vitamin B12 analog, cobinamide, for cyanide and a major spectral change observed for cyanide-bound cobinamide. This method is now validated in human blood, and the findings include a mean inter-assay accuracy of 99.1%, precision of 8.75% and a lower limit of quantification of 3.27 µM cyanide. The method was applied to blood samples from children treated with sodium nitroprusside and it yielded measurable results in 88 of 172 samples (51%), whereas the reference laboratory yielded results in only 19 samples (11%). In all 19 samples, the cobinamide-based method also yielded measurable results. The two methods showed reasonable agreement when analyzed by linear regression, but not when analyzed by a standard error of the estimate or paired t-test. Differences in results between the two methods may be because samples were assayed at different times on different sample types. The cobinamide-based method is applicable to human blood, and can be used in hospital laboratories and emergency rooms. PMID:23653045

Data-optimized source modeling with the Backwards Liouville Test–Kinetic method

DOE PAGES

Woodroffe, J. R.; Brito, T. V.; Jordanova, V. K.; ...

2017-09-14

In the standard practice of neutron multiplicity counting , the first three sampled factorial moments of the event triggered neutron count distribution were used to quantify the three main neutron source terms: the spontaneous fissile material effective mass, the relative (α,n) production and the induced fission source responsible for multiplication. Our study compares three methods to quantify the statistical uncertainty of the estimated mass: the bootstrap method, propagation of variance through moments, and statistical analysis of cycle data method. Each of the three methods was implemented on a set of four different NMC measurements, held at the JRC-laboratory in Ispra,more » Italy, sampling four different Pu samples in a standard Plutonium Scrap Multiplicity Counter (PSMC) well counter.« less

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

Woodroffe, J. R.; Brito, T. V.; Jordanova, V. K.

In the standard practice of neutron multiplicity counting , the first three sampled factorial moments of the event triggered neutron count distribution were used to quantify the three main neutron source terms: the spontaneous fissile material effective mass, the relative (α,n) production and the induced fission source responsible for multiplication. Our study compares three methods to quantify the statistical uncertainty of the estimated mass: the bootstrap method, propagation of variance through moments, and statistical analysis of cycle data method. Each of the three methods was implemented on a set of four different NMC measurements, held at the JRC-laboratory in Ispra,more » Italy, sampling four different Pu samples in a standard Plutonium Scrap Multiplicity Counter (PSMC) well counter.« less

A rapid and high-precision method for sulfur isotope δ(34)S determination with a multiple-collector inductively coupled plasma mass spectrometer: matrix effect correction and applications for water samples without chemical purification.

PubMed

Lin, An-Jun; Yang, Tao; Jiang, Shao-Yong

2014-04-15

Previous studies have indicated that prior chemical purification of samples, although complex and time-consuming, is essential in obtaining precise and accurate results for sulfur isotope ratios using multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). In this study, we introduce a new, rapid and precise MC-ICP-MS method for sulfur isotope determination from water samples without chemical purification. The analytical work was performed on an MC-ICP-MS instrument with medium mass resolution (m/Δm ~ 3000). Standard-sample bracketing (SSB) was used to correct samples throughout the analytical sessions. Reference materials included an Alfa-S (ammonium sulfate) standard solution, ammonium sulfate provided by the lab of the authors and fresh seawater from the South China Sea. A range of matrix-matched Alfa-S standard solutions and ammonium sulfate solutions was used to investigate the matrix (salinity) effect (matrix was added in the form of NaCl). A seawater sample was used to confirm the reliability of the method. Using matrix-matched (salinity-matched) Alfa-S as the working standard, the measured δ(34)S value of AS (-6.73 ± 0.09‰) was consistent with the reference value (-6.78 ± 0.07‰) within the uncertainty, suggesting that this method could be recommended for the measurement of water samples without prior chemical purification. The δ(34)S value determination for the unpurified seawater also yielded excellent results (21.03 ± 0.18‰) that are consistent with the reference value (20.99‰), thus confirming the feasibility of the technique. The data and the results indicate that it is feasible to use MC-ICP-MS and matrix-matched working standards to measure the sulfur isotopic compositions of water samples directly without chemical purification. In comparison with the existing MC-ICP-MS techniques, the new method is better for directly measuring δ(34)S values in water samples with complex matrices; therefore, it can significantly accelerate analytical turnover. Copyright © 2014 John Wiley & Sons, Ltd.

Comparing interval estimates for small sample ordinal CFA models

PubMed Central

Natesan, Prathiba

2015-01-01

Robust maximum likelihood (RML) and asymptotically generalized least squares (AGLS) methods have been recommended for fitting ordinal structural equation models. Studies show that some of these methods underestimate standard errors. However, these studies have not investigated the coverage and bias of interval estimates. An estimate with a reasonable standard error could still be severely biased. This can only be known by systematically investigating the interval estimates. The present study compares Bayesian, RML, and AGLS interval estimates of factor correlations in ordinal confirmatory factor analysis models (CFA) for small sample data. Six sample sizes, 3 factor correlations, and 2 factor score distributions (multivariate normal and multivariate mildly skewed) were studied. Two Bayesian prior specifications, informative and relatively less informative were studied. Undercoverage of confidence intervals and underestimation of standard errors was common in non-Bayesian methods. Underestimated standard errors may lead to inflated Type-I error rates. Non-Bayesian intervals were more positive biased than negatively biased, that is, most intervals that did not contain the true value were greater than the true value. Some non-Bayesian methods had non-converging and inadmissible solutions for small samples and non-normal data. Bayesian empirical standard error estimates for informative and relatively less informative priors were closer to the average standard errors of the estimates. The coverage of Bayesian credibility intervals was closer to what was expected with overcoverage in a few cases. Although some Bayesian credibility intervals were wider, they reflected the nature of statistical uncertainty that comes with the data (e.g., small sample). Bayesian point estimates were also more accurate than non-Bayesian estimates. The results illustrate the importance of analyzing coverage and bias of interval estimates, and how ignoring interval estimates can be misleading. Therefore, editors and policymakers should continue to emphasize the inclusion of interval estimates in research. PMID:26579002

Comparing interval estimates for small sample ordinal CFA models.

PubMed

Natesan, Prathiba

2015-01-01

Robust maximum likelihood (RML) and asymptotically generalized least squares (AGLS) methods have been recommended for fitting ordinal structural equation models. Studies show that some of these methods underestimate standard errors. However, these studies have not investigated the coverage and bias of interval estimates. An estimate with a reasonable standard error could still be severely biased. This can only be known by systematically investigating the interval estimates. The present study compares Bayesian, RML, and AGLS interval estimates of factor correlations in ordinal confirmatory factor analysis models (CFA) for small sample data. Six sample sizes, 3 factor correlations, and 2 factor score distributions (multivariate normal and multivariate mildly skewed) were studied. Two Bayesian prior specifications, informative and relatively less informative were studied. Undercoverage of confidence intervals and underestimation of standard errors was common in non-Bayesian methods. Underestimated standard errors may lead to inflated Type-I error rates. Non-Bayesian intervals were more positive biased than negatively biased, that is, most intervals that did not contain the true value were greater than the true value. Some non-Bayesian methods had non-converging and inadmissible solutions for small samples and non-normal data. Bayesian empirical standard error estimates for informative and relatively less informative priors were closer to the average standard errors of the estimates. The coverage of Bayesian credibility intervals was closer to what was expected with overcoverage in a few cases. Although some Bayesian credibility intervals were wider, they reflected the nature of statistical uncertainty that comes with the data (e.g., small sample). Bayesian point estimates were also more accurate than non-Bayesian estimates. The results illustrate the importance of analyzing coverage and bias of interval estimates, and how ignoring interval estimates can be misleading. Therefore, editors and policymakers should continue to emphasize the inclusion of interval estimates in research.

Acid Rain Analysis by Standard Addition Titration.

ERIC Educational Resources Information Center

Ophardt, Charles E.

1985-01-01

The standard addition titration is a precise and rapid method for the determination of the acidity in rain or snow samples. The method requires use of a standard buret, a pH meter, and Gran's plot to determine the equivalence point. Experimental procedures used and typical results obtained are presented. (JN)

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of low-level silver by graphite furnace atomic absorption spectrophotometry

USGS Publications Warehouse

Damrau, D.L.

1993-01-01

Increased awareness of the quality of water in the United States has led to the development of a method for determining low levels (0.2-5.0 microg/L) of silver in water samples. Use of graphite furnace atomic absorption spectrophotometry provides a sensitive, precise, and accurate method for determining low-level silver in samples of low ionic-strength water, precipitation water, and natural water. The minimum detection limit determined for low-level silver is 0.2 microg/L. Precision data were collected on natural-water samples and SRWS (Standard Reference Water Samples). The overall percent relative standard deviation for natural-water samples with silver concentrations more than 0.2 microg/L was less than 40 percent throughout the analytical range. For the SRWS with concentrations more than 0.2 microg/L, the overall percent relative standard deviation was less than 25 percent throughout the analytical range. The accuracy of the results was determined by spiking 6 natural-water samples with different known concentrations of the silver standard. The recoveries ranged from 61 to 119 percent at the 0.5-microg/L spike level. At the 1.25-microg/L spike level, the recoveries ranged from 92 to 106 percent. For the high spike level at 3.0 microg/L, the recoveries ranged from 65 to 113 percent. The measured concentrations of silver obtained from known samples were within the Branch of Quality Assurance accepted limits of 1 1/2 standard deviations on the basis of the SRWS program for Inter-Laboratory studies.

Simple and accurate quantification of BTEX in ambient air by SPME and GC-MS.

PubMed

Baimatova, Nassiba; Kenessov, Bulat; Koziel, Jacek A; Carlsen, Lars; Bektassov, Marat; Demyanenko, Olga P

2016-07-01

Benzene, toluene, ethylbenzene and xylenes (BTEX) comprise one of the most ubiquitous and hazardous groups of ambient air pollutants of concern. Application of standard analytical methods for quantification of BTEX is limited by the complexity of sampling and sample preparation equipment, and budget requirements. Methods based on SPME represent simpler alternative, but still require complex calibration procedures. The objective of this research was to develop a simpler, low-budget, and accurate method for quantification of BTEX in ambient air based on SPME and GC-MS. Standard 20-mL headspace vials were used for field air sampling and calibration. To avoid challenges with obtaining and working with 'zero' air, slope factors of external standard calibration were determined using standard addition and inherently polluted lab air. For polydimethylsiloxane (PDMS) fiber, differences between the slope factors of calibration plots obtained using lab and outdoor air were below 14%. PDMS fiber provided higher precision during calibration while the use of Carboxen/PDMS fiber resulted in lower detection limits for benzene and toluene. To provide sufficient accuracy, the use of 20mL vials requires triplicate sampling and analysis. The method was successfully applied for analysis of 108 ambient air samples from Almaty, Kazakhstan. Average concentrations of benzene, toluene, ethylbenzene and o-xylene were 53, 57, 11 and 14µgm(-3), respectively. The developed method can be modified for further quantification of a wider range of volatile organic compounds in air. In addition, the new method is amenable to automation. Copyright © 2016 Elsevier B.V. All rights reserved.

Sparse feature learning for instrument identification: Effects of sampling and pooling methods.

PubMed

Han, Yoonchang; Lee, Subin; Nam, Juhan; Lee, Kyogu

2016-05-01

Feature learning for music applications has recently received considerable attention from many researchers. This paper reports on the sparse feature learning algorithm for musical instrument identification, and in particular, focuses on the effects of the frame sampling techniques for dictionary learning and the pooling methods for feature aggregation. To this end, two frame sampling techniques are examined that are fixed and proportional random sampling. Furthermore, the effect of using onset frame was analyzed for both of proposed sampling methods. Regarding summarization of the feature activation, a standard deviation pooling method is used and compared with the commonly used max- and average-pooling techniques. Using more than 47 000 recordings of 24 instruments from various performers, playing styles, and dynamics, a number of tuning parameters are experimented including the analysis frame size, the dictionary size, and the type of frequency scaling as well as the different sampling and pooling methods. The results show that the combination of proportional sampling and standard deviation pooling achieve the best overall performance of 95.62% while the optimal parameter set varies among the instrument classes.

Counting at low concentrations: the statistical challenges of verifying ballast water discharge standards

USGS Publications Warehouse

Frazier, Melanie; Miller, A. Whitman; Lee, Henry; Reusser, Deborah A.

2013-01-01

Discharge from the ballast tanks of ships is one of the primary vectors of nonindigenous species in marine environments. To mitigate this environmental and economic threat, international, national, and state entities are establishing regulations to limit the concentration of living organisms that may be discharged from the ballast tanks of ships. The proposed discharge standards have ranged from zero detectable organisms to 3. If standard sampling methods are used, verifying whether ballast discharge complies with these stringent standards will be challenging due to the inherent stochasticity of sampling. Furthermore, at low concentrations, very large volumes of water must be sampled to find enough organisms to accurately estimate concentration. Despite these challenges, adequate sampling protocols comprise a critical aspect of establishing standards because they help define the actual risk level associated with a standard. A standard that appears very stringent may be effectively lax if it is paired with an inadequate sampling protocol. We describe some of the statistical issues associated with sampling at low concentrations to help regulators understand the uncertainties of sampling as well as to inform the development of sampling protocols that ensure discharge standards are adequately implemented.

Methodological integrative review of the work sampling technique used in nursing workload research.

PubMed

Blay, Nicole; Duffield, Christine M; Gallagher, Robyn; Roche, Michael

2014-11-01

To critically review the work sampling technique used in nursing workload research. Work sampling is a technique frequently used by researchers and managers to explore and measure nursing activities. However, work sampling methods used are diverse making comparisons of results between studies difficult. Methodological integrative review. Four electronic databases were systematically searched for peer-reviewed articles published between 2002-2012. Manual scanning of reference lists and Rich Site Summary feeds from contemporary nursing journals were other sources of data. Articles published in the English language between 2002-2012 reporting on research which used work sampling to examine nursing workload. Eighteen articles were reviewed. The review identified that the work sampling technique lacks a standardized approach, which may have an impact on the sharing or comparison of results. Specific areas needing a shared understanding included the training of observers and subjects who self-report, standardization of the techniques used to assess observer inter-rater reliability, sampling methods and reporting of outcomes. Work sampling is a technique that can be used to explore the many facets of nursing work. Standardized reporting measures would enable greater comparison between studies and contribute to knowledge more effectively. Author suggestions for the reporting of results may act as guidelines for researchers considering work sampling as a research method. © 2014 John Wiley & Sons Ltd.

Comparing generalized ensemble methods for sampling of systems with many degrees of freedom

DOE PAGES

Lincoff, James; Sasmal, Sukanya; Head-Gordon, Teresa

2016-11-03

Here, we compare two standard replica exchange methods using temperature and dielectric constant as the scaling variables for independent replicas against two new corresponding enhanced sampling methods based on non-equilibrium statistical cooling (temperature) or descreening (dielectric). We test the four methods on a rough 1D potential as well as for alanine dipeptide in water, for which their relatively small phase space allows for the ability to define quantitative convergence metrics. We show that both dielectric methods are inferior to the temperature enhanced sampling methods, and in turn show that temperature cool walking (TCW) systematically outperforms the standard temperature replica exchangemore » (TREx) method. We extend our comparisons of the TCW and TREx methods to the 5 residue met-enkephalin peptide, in which we evaluate the Kullback-Leibler divergence metric to show that the rate of convergence between two independent trajectories is faster for TCW compared to TREx. Finally we apply the temperature methods to the 42 residue amyloid-β peptide in which we find non-negligible differences in the disordered ensemble using TCW compared to the standard TREx. All four methods have been made available as software through the OpenMM Omnia software consortium.« less

Comparing generalized ensemble methods for sampling of systems with many degrees of freedom.

PubMed

Lincoff, James; Sasmal, Sukanya; Head-Gordon, Teresa

2016-11-07

We compare two standard replica exchange methods using temperature and dielectric constant as the scaling variables for independent replicas against two new corresponding enhanced sampling methods based on non-equilibrium statistical cooling (temperature) or descreening (dielectric). We test the four methods on a rough 1D potential as well as for alanine dipeptide in water, for which their relatively small phase space allows for the ability to define quantitative convergence metrics. We show that both dielectric methods are inferior to the temperature enhanced sampling methods, and in turn show that temperature cool walking (TCW) systematically outperforms the standard temperature replica exchange (TREx) method. We extend our comparisons of the TCW and TREx methods to the 5 residue met-enkephalin peptide, in which we evaluate the Kullback-Leibler divergence metric to show that the rate of convergence between two independent trajectories is faster for TCW compared to TREx. Finally we apply the temperature methods to the 42 residue amyloid-β peptide in which we find non-negligible differences in the disordered ensemble using TCW compared to the standard TREx. All four methods have been made available as software through the OpenMM Omnia software consortium (http://www.omnia.md/).

Accurate determination of arsenic in arsenobetaine standard solutions of BCR-626 and NMIJ CRM 7901-a by neutron activation analysis coupled with internal standard method.

PubMed

Miura, Tsutomu; Chiba, Koichi; Kuroiwa, Takayoshi; Narukawa, Tomohiro; Hioki, Akiharu; Matsue, Hideaki

2010-09-15

Neutron activation analysis (NAA) coupled with an internal standard method was applied for the determination of As in the certified reference material (CRM) of arsenobetaine (AB) standard solutions to verify their certified values. Gold was used as an internal standard to compensate for the difference of the neutron exposure in an irradiation capsule and to improve the sample-to-sample repeatability. Application of the internal standard method significantly improved linearity of the calibration curve up to 1 microg of As, too. The analytical reliability of the proposed method was evaluated by k(0)-standardization NAA. The analytical results of As in AB standard solutions of BCR-626 and NMIJ CRM 7901-a were (499+/-55)mgkg(-1) (k=2) and (10.16+/-0.15)mgkg(-1) (k=2), respectively. These values were found to be 15-20% higher than the certified values. The between-bottle variation of BCR-626 was much larger than the expanded uncertainty of the certified value, although that of NMIJ CRM 7901-a was almost negligible. Copyright (c) 2010 Elsevier B.V. All rights reserved.

CTEPP STANDARD OPERATING PROCEDURE FOR EXTRACTING AND PREPARING DERMAL WIPE AND SURFACE WIPE SAMPLES FOR ANALYSIS OF POLAR ORGANIC POLLUTANTS (SOP-5.27)

EPA Science Inventory

The method for extracting and preparing a dermal or surface wipe sample for analysis of acidic persistent organic pollutants is summarized in this standard operating procedure. It covers the extraction and concentration of samples that are to be analyzed by gas chromatography/mas...

30 CFR 870.18 - General rules for calculating excess moisture.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Collection of Coal Samples from Core; and, D1412-93, Standard Test Method for Equilibrium Moisture of Coal at... shipment or use. (5) Core sample means a cylindrical sample of coal that represents the thickness of a coal seam penetrated by drilling according to ASTM standard D5192-91. (6) Correction factor means the...

30 CFR 870.18 - General rules for calculating excess moisture.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Collection of Coal Samples from Core; and, D1412-93, Standard Test Method for Equilibrium Moisture of Coal at... shipment or use. (5) Core sample means a cylindrical sample of coal that represents the thickness of a coal seam penetrated by drilling according to ASTM standard D5192-91. (6) Correction factor means the...

30 CFR 870.18 - General rules for calculating excess moisture.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Collection of Coal Samples from Core; and, D1412-93, Standard Test Method for Equilibrium Moisture of Coal at... shipment or use. (5) Core sample means a cylindrical sample of coal that represents the thickness of a coal seam penetrated by drilling according to ASTM standard D5192-91. (6) Correction factor means the...

30 CFR 870.18 - General rules for calculating excess moisture.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Collection of Coal Samples from Core; and, D1412-93, Standard Test Method for Equilibrium Moisture of Coal at... shipment or use. (5) Core sample means a cylindrical sample of coal that represents the thickness of a coal seam penetrated by drilling according to ASTM standard D5192-91. (6) Correction factor means the...

CTEPP STANDARD OPERATING PROCEDURE FOR DETECTION AND QUANTIFICATION OF TARGET ANALYTES BY GAS CHROMATOGRAPHY/MASS SPECTROMETRY (GC/MS) (SOP-5.24)

EPA Science Inventory

This standard operating procedure describes the method used for the determination of target analytes in sample extracts and related quality assurance/quality control sample extracts generated in the CTEPP study.

Efficiency of snake sampling methods in the Brazilian semiarid region.

PubMed

Mesquita, Paula C M D; Passos, Daniel C; Cechin, Sonia Z

2013-09-01

The choice of sampling methods is a crucial step in every field survey in herpetology. In countries where time and financial support are limited, the choice of the methods is critical. The methods used to sample snakes often lack objective criteria, and the traditional methods have apparently been more important when making the choice. Consequently researches using not-standardized methods are frequently found in the literature. We have compared four commonly used methods for sampling snake assemblages in a semiarid area in Brazil. We compared the efficacy of each method based on the cost-benefit regarding the number of individuals and species captured, time, and financial investment. We found that pitfall traps were the less effective method in all aspects that were evaluated and it was not complementary to the other methods in terms of abundance of species and assemblage structure. We conclude that methods can only be considered complementary if they are standardized to the objectives of the study. The use of pitfall traps in short-term surveys of the snake fauna in areas with shrubby vegetation and stony soil is not recommended.

7 CFR 28.179 - Methods of cotton classification and comparison.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 2 2013-01-01 2013-01-01 false Methods of cotton classification and comparison. 28... STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Classification for Foreign Growth Cotton § 28.179 Methods of cotton classification and comparison. The classification of samples from...

7 CFR 28.179 - Methods of cotton classification and comparison.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Methods of cotton classification and comparison. 28... STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Classification for Foreign Growth Cotton § 28.179 Methods of cotton classification and comparison. The classification of samples from...

7 CFR 28.179 - Methods of cotton classification and comparison.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 2 2012-01-01 2012-01-01 false Methods of cotton classification and comparison. 28... STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Classification for Foreign Growth Cotton § 28.179 Methods of cotton classification and comparison. The classification of samples from...

7 CFR 28.179 - Methods of cotton classification and comparison.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 2 2011-01-01 2011-01-01 false Methods of cotton classification and comparison. 28... STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Classification for Foreign Growth Cotton § 28.179 Methods of cotton classification and comparison. The classification of samples from...

7 CFR 28.179 - Methods of cotton classification and comparison.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 2 2014-01-01 2014-01-01 false Methods of cotton classification and comparison. 28... STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Classification for Foreign Growth Cotton § 28.179 Methods of cotton classification and comparison. The classification of samples from...

Method performance and multi-laboratory assessment of a normal phase high pressure liquid chromatography-fluorescence detection method for the quantitation of flavanols and procyanidins in cocoa and chocolate containing samples.

PubMed

Robbins, Rebecca J; Leonczak, Jadwiga; Johnson, J Christopher; Li, Julia; Kwik-Uribe, Catherine; Prior, Ronald L; Gu, Liwei

2009-06-12

The quantitative parameters and method performance for a normal-phase HPLC separation of flavanols and procyanidins in chocolate and cocoa-containing food products were optimized and assessed. Single laboratory method performance was examined over three months using three separate secondary standards. RSD(r) ranged from 1.9%, 4.5% to 9.0% for cocoa powder, liquor and chocolate samples containing 74.39, 15.47 and 1.87 mg/g flavanols and procyanidins, respectively. Accuracy was determined by comparison to the NIST Standard Reference Material 2384. Inter-lab assessment indicated that variability was quite low for seven different cocoa-containing samples, with a RSD(R) of less than 10% for the range of samples analyzed.

Application of a spectrum standardization method for carbon analysis in coal using laser-induced breakdown spectroscopy (LIBS).

PubMed

Li, Xiongwei; Wang, Zhe; Fu, Yangting; Li, Zheng; Liu, Jianmin; Ni, Weidou

2014-01-01

Measurement of coal carbon content using laser-induced breakdown spectroscopy (LIBS) is limited by its low precision and accuracy. A modified spectrum standardization method was proposed to achieve both reproducible and accurate results for the quantitative analysis of carbon content in coal using LIBS. The proposed method used the molecular emissions of diatomic carbon (C2) and cyanide (CN) to compensate for the diminution of atomic carbon emissions in high volatile content coal samples caused by matrix effect. The compensated carbon line intensities were further converted into an assumed standard state with standard plasma temperature, electron number density, and total number density of carbon, under which the carbon line intensity is proportional to its concentration in the coal samples. To obtain better compensation for fluctuations of total carbon number density, the segmental spectral area was used and an iterative algorithm was applied that is different from our previous spectrum standardization calculations. The modified spectrum standardization model was applied to the measurement of carbon content in 24 bituminous coal samples. The results demonstrate that the proposed method has superior performance over the generally applied normalization methods. The average relative standard deviation was 3.21%, the coefficient of determination was 0.90, the root mean square error of prediction was 2.24%, and the average maximum relative error for the modified model was 12.18%, showing an overall improvement over the corresponding values for the normalization with segmental spectrum area, 6.00%, 0.75, 3.77%, and 15.40%, respectively.

40 CFR 63.1385 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... applicable emission limits: (1) Method 1 (40 CFR part 60, appendix A) for the selection of the sampling port location and number of sampling ports; (2) Method 2 (40 CFR part 60, appendix A) for volumetric flow rate.... Each run shall consist of a minimum run time of 2 hours and a minimum sample volume of 60 dry standard...

Estimating the mass variance in neutron multiplicity counting-A comparison of approaches

NASA Astrophysics Data System (ADS)

Dubi, C.; Croft, S.; Favalli, A.; Ocherashvili, A.; Pedersen, B.

2017-12-01

In the standard practice of neutron multiplicity counting , the first three sampled factorial moments of the event triggered neutron count distribution are used to quantify the three main neutron source terms: the spontaneous fissile material effective mass, the relative (α , n) production and the induced fission source responsible for multiplication. This study compares three methods to quantify the statistical uncertainty of the estimated mass: the bootstrap method, propagation of variance through moments, and statistical analysis of cycle data method. Each of the three methods was implemented on a set of four different NMC measurements, held at the JRC-laboratory in Ispra, Italy, sampling four different Pu samples in a standard Plutonium Scrap Multiplicity Counter (PSMC) well counter.

Estimating the mass variance in neutron multiplicity counting $-$ A comparison of approaches

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

Dubi, C.; Croft, S.; Favalli, A.

In the standard practice of neutron multiplicity counting, the first three sampled factorial moments of the event triggered neutron count distribution are used to quantify the three main neutron source terms: the spontaneous fissile material effective mass, the relative (α,n) production and the induced fission source responsible for multiplication. This study compares three methods to quantify the statistical uncertainty of the estimated mass: the bootstrap method, propagation of variance through moments, and statistical analysis of cycle data method. Each of the three methods was implemented on a set of four different NMC measurements, held at the JRC-laboratory in Ispra, Italy,more » sampling four different Pu samples in a standard Plutonium Scrap Multiplicity Counter (PSMC) well counter.« less

Estimating the mass variance in neutron multiplicity counting $-$ A comparison of approaches

DOE PAGES

Dubi, C.; Croft, S.; Favalli, A.; ...

2017-09-14

In the standard practice of neutron multiplicity counting, the first three sampled factorial moments of the event triggered neutron count distribution are used to quantify the three main neutron source terms: the spontaneous fissile material effective mass, the relative (α,n) production and the induced fission source responsible for multiplication. This study compares three methods to quantify the statistical uncertainty of the estimated mass: the bootstrap method, propagation of variance through moments, and statistical analysis of cycle data method. Each of the three methods was implemented on a set of four different NMC measurements, held at the JRC-laboratory in Ispra, Italy,more » sampling four different Pu samples in a standard Plutonium Scrap Multiplicity Counter (PSMC) well counter.« less

An Improved Quantitative Real-Time PCR Assay for the Enumeration of Heterosigma akashiwo (Raphidophyceae) Cysts Using a DNA Debris Removal Method and a Cyst-Based Standard Curve.

PubMed

Kim, Joo-Hwan; Kim, Jin Ho; Wang, Pengbin; Park, Bum Soo; Han, Myung-Soo

2016-01-01

The identification and quantification of Heterosigma akashiwo cysts in sediments by light microscopy can be difficult due to the small size and morphology of the cysts, which are often indistinguishable from those of other types of algae. Quantitative real-time PCR (qPCR) based assays represent a potentially efficient method for quantifying the abundance of H. akashiwo cysts, although standard curves must be based on cyst DNA rather than on vegetative cell DNA due to differences in gene copy number and DNA extraction yield between these two cell types. Furthermore, qPCR on sediment samples can be complicated by the presence of extracellular DNA debris. To solve these problems, we constructed a cyst-based standard curve and developed a simple method for removing DNA debris from sediment samples. This cyst-based standard curve was compared with a standard curve based on vegetative cells, as vegetative cells may have twice the gene copy number of cysts. To remove DNA debris from the sediment, we developed a simple method involving dilution with distilled water and heating at 75°C. A total of 18 sediment samples were used to evaluate this method. Cyst abundance determined using the qPCR assay without DNA debris removal yielded results up to 51-fold greater than with direct counting. By contrast, a highly significant correlation was observed between cyst abundance determined by direct counting and the qPCR assay in conjunction with DNA debris removal (r2 = 0.72, slope = 1.07, p < 0.001). Therefore, this improved qPCR method should be a powerful tool for the accurate quantification of H. akashiwo cysts in sediment samples.

Computation of Standard Errors

PubMed Central

Dowd, Bryan E; Greene, William H; Norton, Edward C

2014-01-01

Objectives We discuss the problem of computing the standard errors of functions involving estimated parameters and provide the relevant computer code for three different computational approaches using two popular computer packages. Study Design We show how to compute the standard errors of several functions of interest: the predicted value of the dependent variable for a particular subject, and the effect of a change in an explanatory variable on the predicted value of the dependent variable for an individual subject and average effect for a sample of subjects. Empirical Application Using a publicly available dataset, we explain three different methods of computing standard errors: the delta method, Krinsky–Robb, and bootstrapping. We provide computer code for Stata 12 and LIMDEP 10/NLOGIT 5. Conclusions In most applications, choice of the computational method for standard errors of functions of estimated parameters is a matter of convenience. However, when computing standard errors of the sample average of functions that involve both estimated parameters and nonstochastic explanatory variables, it is important to consider the sources of variation in the function's values. PMID:24800304

Rapid extraction and assay of uranium from environmental surface samples

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

Barrett, Christopher A.; Chouyyok, Wilaiwan; Speakman, Robert J.

Extraction methods enabling faster removal and concentration of uranium compounds for improved trace and low-level assay are demonstrated for standard surface sampling material in support of nuclear safeguards efforts, health monitoring, and other nuclear analysis applications. A key problem with the existing surface sampling swipes is the requirement for complete digestion of sample and sampling matrix. This is a time-consuming and labour-intensive process that limits laboratory throughput, elevates costs, and increases background levels. Various extraction methods are explored for their potential to quickly and efficiently remove different chemical forms of uranium from standard surface sampling material. A combination of carbonatemore » and peroxide solutions is shown to give the most rapid and complete form of uranyl compound extraction and dissolution. This rapid extraction process is demonstrated to be compatible with standard inductive coupled plasma mass spectrometry methods for uranium isotopic assay as well as screening techniques such as x-ray fluorescence. The general approach described has application beyond uranium to other analytes of nuclear forensic interest (e.g., rare earth elements and plutonium) as well as heavy metals for environmental and industrial hygiene monitoring.« less

Standard test method for grindability of coal by the hardgrove-machine method

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

Not Available

1975-01-01

This method is used to determine the relative grindability or ease of pulverization of coals in comparison with coals chosen as standards. A prepared sample receives a definite amount of grinding energy in a miniature pulverizer, and the change in size consist is determined by sieving.

Validation of a method for the determination of zolpidem in human plasma using LC with fluorescence detection.

PubMed

Ring, P R; Bostick, J M

2000-04-01

A sensitive and selective high-performance liquid chromatography (HPLC) method was developed for the determination of zolpidem in human plasma. Zolpidem and the internal standard (trazodone) were extracted from human plasma that had been made basic. The basic sample was loaded onto a conditioned Bond Elut C18 cartridge, rinsed with water and eluted with methanol. Forty microliters were then injected onto the LC system. Separation was achieved on a C18 column (150 x 4.6 mm, 5 microm) with a mobile phase composed of acetonitrile:50 mM potassium phosphate monobasic at pH 6.0 (4:6, v/v). Detection was by fluorescence, with excitation at 254 nm and emission at 400 nm. The retention times of zolpidem and internal standard were approximately 4.7 and 5.3 min, respectively. The LC run time was 8 min. The assay was linear in concentration range 1-400 ng/ml for zolpidem in human plasma. The analysis of quality control samples for zolpidem (3, 30, and 300 ng/ml) demonstrated excellent precision with relative standard deviations (RSD) of 3.7, 4.6, and 3.0%, respectively (n = 18). The method was accurate with all intraday (n = 6) and overall (n = 18) mean concentrations within 5.8% from nominal at all quality control sample concentrations. This method was also performed using a Gilson Aspec XL automated sample processor and autoinjector. The samples were manually fortified with internal standard and made basic. The aspec then performed the solid phase extraction and made injections of the samples onto the LC system. Using the automated procedure for analysis, quality control samples for zolpidem (3, 30, and 300 ng/ml) demonstrated acceptable precision with RSD values of 9.0, 4.9, and 5.1%, respectively (n = 12). The method was accurate with all intracurve (n = 4) and overall (n = 12) mean values being less than 10.8% from nominal at all quality control sample concentrations.

Surface microbial contamination in hospitals: A pilot study on methods of sampling and the use of proposed microbiologic standards.

PubMed

Claro, Tânia; O'Reilly, Marese; Daniels, Stephen; Humphreys, Hilary

2015-09-01

Contamination of hospital surfaces by bacteria is increasingly recognized. We assessed commonly touched surfaces using contact plates and Petrifilms (3M, St. Paul, MN) and compared the results against proposed microbiology standards. Toilet door handles were the most heavily contaminated (7.97 ± 0.68 colony forming units [CFU]/cm(2)) and exceeded proposed standards on 74% of occasions. Petrifilms detected statistically higher CFU from bedside lockers. Further research is required on the use of standards and methods of sampling. Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

40 CFR 61.32 - Emission standard.

Code of Federal Regulations, 2010 CFR

2010-07-01

... frequency of calibration. (b) Method of sample analysis. (c) Averaging technique for determining 30-day...) Plant and sampling area plots showing emission points and sampling sites. Topographic features...

Residual antibiotics in decontaminated human cardiovascular tissues intended for transplantation and risk of falsely negative microbiological analyses.

PubMed

Buzzi, Marina; Guarino, Anna; Gatto, Claudio; Manara, Sabrina; Dainese, Luca; Polvani, Gianluca; Tóthová, Jana D'Amato

2014-01-01

We investigated the presence of antibiotics in cryopreserved cardiovascular tissues and cryopreservation media, after tissue decontamination with antibiotic cocktails, and the impact of antibiotic residues on standard tissue bank microbiological analyses. Sixteen cardiovascular tissues were decontaminated with bank-prepared cocktails and cryopreserved by two different tissue banks according to their standard operating procedures. Before and after decontamination, samples underwent microbiological analysis by standard tissue bank methods. Cryopreserved samples were tested again with and without the removal of antibiotic residues using a RESEP tube, after thawing. Presence of antibiotics in tissue homogenates and processing liquids was determined by a modified agar diffusion test. All cryopreserved tissue homogenates and cryopreservation media induced important inhibition zones on both Staphylococcus aureus- and Pseudomonas aeruginosa-seeded plates, immediately after thawing and at the end of the sterility test. The RESEP tube treatment markedly reduced or totally eliminated the antimicrobial activity of tested tissues and media. Based on standard tissue bank analysis, 50% of tissues were found positive for bacteria and/or fungi, before decontamination and 2 out of 16 tested samples (13%) still contained microorganisms after decontamination. After thawing, none of the 16 cryopreserved samples resulted positive with direct inoculum method. When the same samples were tested after removal of antibiotic residues, 8 out of 16 (50%) were contaminated. Antibiotic residues present in tissue allografts and processing liquids after decontamination may mask microbial contamination during microbiological analysis performed with standard tissue bank methods, thus resulting in false negatives.

Residual Antibiotics in Decontaminated Human Cardiovascular Tissues Intended for Transplantation and Risk of Falsely Negative Microbiological Analyses

PubMed Central

Gatto, Claudio; Manara, Sabrina; Dainese, Luca; Polvani, Gianluca; Tóthová, Jana D'Amato

2014-01-01

We investigated the presence of antibiotics in cryopreserved cardiovascular tissues and cryopreservation media, after tissue decontamination with antibiotic cocktails, and the impact of antibiotic residues on standard tissue bank microbiological analyses. Sixteen cardiovascular tissues were decontaminated with bank-prepared cocktails and cryopreserved by two different tissue banks according to their standard operating procedures. Before and after decontamination, samples underwent microbiological analysis by standard tissue bank methods. Cryopreserved samples were tested again with and without the removal of antibiotic residues using a RESEP tube, after thawing. Presence of antibiotics in tissue homogenates and processing liquids was determined by a modified agar diffusion test. All cryopreserved tissue homogenates and cryopreservation media induced important inhibition zones on both Staphylococcus aureus- and Pseudomonas aeruginosa-seeded plates, immediately after thawing and at the end of the sterility test. The RESEP tube treatment markedly reduced or totally eliminated the antimicrobial activity of tested tissues and media. Based on standard tissue bank analysis, 50% of tissues were found positive for bacteria and/or fungi, before decontamination and 2 out of 16 tested samples (13%) still contained microorganisms after decontamination. After thawing, none of the 16 cryopreserved samples resulted positive with direct inoculum method. When the same samples were tested after removal of antibiotic residues, 8 out of 16 (50%) were contaminated. Antibiotic residues present in tissue allografts and processing liquids after decontamination may mask microbial contamination during microbiological analysis performed with standard tissue bank methods, thus resulting in false negatives. PMID:25397402

A quick method based on SIMPLISMA-KPLS for simultaneously selecting outlier samples and informative samples for model standardization in near infrared spectroscopy

NASA Astrophysics Data System (ADS)

Li, Li-Na; Ma, Chang-Ming; Chang, Ming; Zhang, Ren-Cheng

2017-12-01

A novel method based on SIMPLe-to-use Interactive Self-modeling Mixture Analysis (SIMPLISMA) and Kernel Partial Least Square (KPLS), named as SIMPLISMA-KPLS, is proposed in this paper for selection of outlier samples and informative samples simultaneously. It is a quick algorithm used to model standardization (or named as model transfer) in near infrared (NIR) spectroscopy. The NIR experiment data of the corn for analysis of the protein content is introduced to evaluate the proposed method. Piecewise direct standardization (PDS) is employed in model transfer. And the comparison of SIMPLISMA-PDS-KPLS and KS-PDS-KPLS is given in this research by discussion of the prediction accuracy of protein content and calculation speed of each algorithm. The conclusions include that SIMPLISMA-KPLS can be utilized as an alternative sample selection method for model transfer. Although it has similar accuracy to Kennard-Stone (KS), it is different from KS as it employs concentration information in selection program. This means that it ensures analyte information is involved in analysis, and the spectra (X) of the selected samples is interrelated with concentration (y). And it can be used for outlier sample elimination simultaneously by validation of calibration. According to the statistical data results of running time, it is clear that the sample selection process is more rapid when using KPLS. The quick algorithm of SIMPLISMA-KPLS is beneficial to improve the speed of online measurement using NIR spectroscopy.

Determination of arsenic and cadmium in crude oil by direct sampling graphite furnace atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

de Jesus, Alexandre; Zmozinski, Ariane Vanessa; Damin, Isabel Cristina Ferreira; Silva, Márcia Messias; Vale, Maria Goreti Rodrigues

2012-05-01

In this work, a direct sampling graphite furnace atomic absorption spectrometry method has been developed for the determination of arsenic and cadmium in crude oil samples. The samples were weighed directly on the solid sampling platforms and introduced into the graphite tube for analysis. The chemical modifier used for both analytes was a mixture of 0.1% Pd + 0.06% Mg + 0.06% Triton X-100. Pyrolysis and atomization curves were obtained for both analytes using standards and samples. Calibration curves with aqueous standards could be used for both analytes. The limits of detection obtained were 5.1 μg kg- 1 for arsenic and 0.2 μg kg- 1 for cadmium, calculated for the maximum amount of sample that can be analyzed (8 mg and 10 mg) for arsenic and cadmium, respectively. Relative standard deviations lower than 20% were obtained. For validation purposes, a calibration curve was constructed with the SRM 1634c and aqueous standards for arsenic and the results obtained for several crude oil samples were in agreement according to paired t-test. The result obtained for the determination of arsenic in the SRM against aqueous standards was also in agreement with the certificate value. As there is no crude oil or similar reference material available with a certified value for cadmium, a digestion in an open vessel under reflux using a "cold finger" was adopted for validation purposes. The use of paired t-test showed that the results obtained by direct sampling and digestion were in agreement at a 95% confidence level. Recovery tests were carried out with inorganic and organic standards and the results were between 88% and 109%. The proposed method is simple, fast and reliable, being appropriated for routine analysis.

Investigating a Drop-on-Demand Microdispenser for Standardized Sample Preparation

DTIC Science & Technology

2012-09-01

Demand Microdispenser for Standardized Sample Preparation Ellen L. Holthoff, Mikella E. Farrell, and Paul M. Pellegrino Sensors and Electron Devices...instrument. The use of a gravimetric method, such as a quartz crystal microbalance4 ( QCM ) or a sensitive microbalance as discussed in this report, is

A SIMPLE METHOD FOR EVALUATING DATA FROM AN INTERLABORATORY STUDY

EPA Science Inventory

Large-scale laboratory-and method-performance studies involving more than about 30 laboratories may be evaluated by calculating the HORRAT ratio for each test sample (HORRAT=[experimentally found among-laboratories relative standard deviation] divided by [relative standard deviat...

40 CFR 61.207 - Radium-226 sampling and measurement procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... B, Method 114. (3) Calculate the mean, x 1, and the standard deviation, s 1, of the n 1 radium-226... owner or operator of a phosphogypsum stack shall report the mean, standard deviation, 95th percentile..., Method 114. (4) Recalculate the mean and standard deviation of the entire set of n 2 radium-226...

Microprobe Analysis of Pu-Ga Standards

DOE PAGES

Wall, Angélique D.; Romero, Joseph P.; Schwartz, Daniel

2017-08-04

In order to obtain quantitative analysis using an Electron Scanning Microprobe it is essential to have a standard of known composition. Most elemental and multi-elemental standards can be easily obtained from places like Elemental Scientific or other standards organizations that are NIST (National Institute of Standards and Technology) traceable. It is, however, more challenging to find standards for plutonium. Past work performed in our group has typically involved using the plutonium sample to be analysed as its own standard as long as all other known components of the sample have standards to be compared to [1,2,3]. Finally, this method worksmore » well enough, but this experiment was performed in order to develop a more reliable standard for plutonium using five samples of known chemistry of a plutonium gallium mix that could then be used as the main plutonium and gallium standards for future experiments.« less

Microprobe Analysis of Pu-Ga Standards

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

Wall, Angélique D.; Romero, Joseph P.; Schwartz, Daniel

In order to obtain quantitative analysis using an Electron Scanning Microprobe it is essential to have a standard of known composition. Most elemental and multi-elemental standards can be easily obtained from places like Elemental Scientific or other standards organizations that are NIST (National Institute of Standards and Technology) traceable. It is, however, more challenging to find standards for plutonium. Past work performed in our group has typically involved using the plutonium sample to be analysed as its own standard as long as all other known components of the sample have standards to be compared to [1,2,3]. Finally, this method worksmore » well enough, but this experiment was performed in order to develop a more reliable standard for plutonium using five samples of known chemistry of a plutonium gallium mix that could then be used as the main plutonium and gallium standards for future experiments.« less

A rapid method for estimation of Pu-isotopes in urine samples using high volume centrifuge.

PubMed

Kumar, Ranjeet; Rao, D D; Dubla, Rupali; Yadav, J R

2017-07-01

The conventional radio-analytical technique used for estimation of Pu-isotopes in urine samples involves anion exchange/TEVA column separation followed by alpha spectrometry. This sequence of analysis consumes nearly 3-4 days for completion. Many a times excreta analysis results are required urgently, particularly under repeat and incidental/emergency situations. Therefore, there is need to reduce the analysis time for the estimation of Pu-isotopes in bioassay samples. This paper gives the details of standardization of a rapid method for estimation of Pu-isotopes in urine samples using multi-purpose centrifuge, TEVA resin followed by alpha spectrometry. The rapid method involves oxidation of urine samples, co-precipitation of plutonium along with calcium phosphate followed by sample preparation using high volume centrifuge and separation of Pu using TEVA resin. Pu-fraction was electrodeposited and activity estimated using 236 Pu tracer recovery by alpha spectrometry. Ten routine urine samples of radiation workers were analyzed and consistent radiochemical tracer recovery was obtained in the range 47-88% with a mean and standard deviation of 64.4% and 11.3% respectively. With this newly standardized technique, the whole analytical procedure is completed within 9h (one working day hour). Copyright © 2017 Elsevier Ltd. All rights reserved.

X-ray Fluorescence Spectroscopy Study of Coating Thickness and Base Metal Composition

NASA Technical Reports Server (NTRS)

Rolin, T. D.; Leszczuk, Y.

2008-01-01

For electrical, electronic, and electromechanical (EEE) parts to be approved for space use, they must be able to meet safety standards approved by NASA. A fast, reliable, and precise method is needed to make sure these standards are met. Many EEE parts are coated in gold (Au) and nickel (Ni), and the thickness coating is crucial to a part s performance. A nondestructive method that is efficient in measuring coating thickness is x-ray fluorescence (XRF) spectroscopy. The XRF spectrometer is a machine designed to measure layer thickness and composition of single or multilayered samples. By understanding the limitations in the collection of the data by this method, accurate composition and thickness measurements can be obtained for samples with Au and Ni coatings. To understand the limitations of data found, measurements were taken with the XRF spectrometer and compared to true values of standard reference materials (SRM) that were National Institute of Standards and Technology (NIST) traceable. For every sample, six different parameters were varied to understand measurement error: coating/substrate combination, number of layers, counting interval, collimator size, coating thickness, and test area location. Each measurement was taken in accordance with standards set by the American Society for Testing and Materials (ASTM) International Standard B 568.

Estimating the probability that the sample mean is within a desired fraction of the standard deviation of the true mean.

PubMed

Schillaci, Michael A; Schillaci, Mario E

2009-02-01

The use of small sample sizes in human and primate evolutionary research is commonplace. Estimating how well small samples represent the underlying population, however, is not commonplace. Because the accuracy of determinations of taxonomy, phylogeny, and evolutionary process are dependant upon how well the study sample represents the population of interest, characterizing the uncertainty, or potential error, associated with analyses of small sample sizes is essential. We present a method for estimating the probability that the sample mean is within a desired fraction of the standard deviation of the true mean using small (n<10) or very small (n < or = 5) sample sizes. This method can be used by researchers to determine post hoc the probability that their sample is a meaningful approximation of the population parameter. We tested the method using a large craniometric data set commonly used by researchers in the field. Given our results, we suggest that sample estimates of the population mean can be reasonable and meaningful even when based on small, and perhaps even very small, sample sizes.

A method for the analysis of perfluorinated compounds in environmental and drinking waters and the determination of their lowest concentration minimal reporting levels.

PubMed

Boone, J Scott; Guan, Bing; Vigo, Craig; Boone, Tripp; Byrne, Christian; Ferrario, Joseph

2014-06-06

A trace analytical method was developed for the determination of seventeen specific perfluorinated chemicals (PFCs) in environmental and drinking waters. The objectives were to optimize an isotope-dilution method to increase the precision and accuracy of the analysis of the PFCs and to eliminate the need for matrix-matched standards. A 250 mL sample of environmental or drinking water was buffered to a pH of 4, spiked with labeled surrogate standards, extracted through solid phase extraction cartridges, and eluted with ammonium hydroxide in methyl tert-butyl ether: methanol solution. The sample eluents were concentrated to volume and analyzed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). The lowest concentration minimal reporting levels (LCMRLs) for the seventeen PFCs were calculated and ranged from 0.034 to 0.600 ng/L for surface water and from 0.033 to 0.640 ng/L for drinking water. The relative standard deviations (RSDs) for all compounds were <20% for all concentrations above the LCMRL. The method proved effective and cost efficient and addressed the problems with the recovery of perfluorobutanoic acid (PFBA) and other short chain PFCs. Various surface water and drinking water samples were used during method development to optimize this method. The method was used to evaluate samples from the Mississippi River at New Orleans and drinking water samples from a private residence in that same city. The method was also used to determine PFC contamination in well water samples from a fire training area where perfluorinated foams were used in training to extinguish fires. Published by Elsevier B.V.

Trace element analysis of extraterrestrial metal samples by inductively coupled plasma mass spectrometry: the standard solutions and digesting acids.

PubMed

Wang, Guiqin; Wu, Yangsiqian; Lin, Yangting

2016-02-28

Nearly 99% of the total content of extraterrestrial metals is composed of Fe and Ni, but with greatly variable trace element contents. The accuracy obtained in the inductively coupled plasma mass spectrometry (ICP-MS) analysis of solutions of these samples can be significantly influenced by matrix contents, polyatomic ion interference, and the concentrations of external standard solutions. An ICP-MS instrument (X Series 2) was used to determine 30 standard solutions with different concentrations of trace elements, and different matrix contents. Based on these measurements, the matrix effects were determined. Three iron meteorites were dissolved separately in aqua regia and HNO3. Deviations due to variation of matrix contents in the external standard solutions were evaluated and the analysis results of the two digestion methods for iron meteorites were assessed. Our results show obvious deviations due to unmatched matrix contents in the external standard solutions. Furthermore, discrepancy in the measurement of some elements was found between the sample solutions prepared with aqua regia and HNO3, due to loss of chloride during sample preparation and/or incomplete digestion of highly siderophile elements in iron meteorites. An accurate ICP-MS analysis method for extraterrestrial metal samples has been established using external standard solutions with matched matrix contents and digesting the samples with HNO3 and aqua regia. Using the data from this work, the Mundrabilla iron meteorite previously classified as IAB-ung is reclassified as IAB-MG. Copyright © 2016 John Wiley & Sons, Ltd.

Natural chlorate in the environment: Application of a new IC-ESI/MS/MS method with a Cl18O3- internal standard

USGS Publications Warehouse

Rao, Balaji; Hatzinger, Paul B.; Böhlke, John Karl; Sturchio, Neil C.; Andraski, Brian J.; Eckardt, Frank D.; Jackson, W. Andrew

2010-01-01

A new ion chromatography electrospray tandem mass spectrometry (IC-ESI/MS/MS) method has been developed for quantification and confirmation of chlorate (ClO3−) in environmental samples. The method involves the electro-chemical generation of isotopically labeled chlorate internal standard (Cl18O3−) using 18O water (H218O). The standard was added to all samples prior to analysis thereby minimizing the matrix effects that are associated with common ions without the need for expensive sample pretreatments. The method detection limit (MDL) for ClO3− was 2 ng L−1 for a 1 mL volume sample injection. The proposed method was successfully applied to analyze ClO3− in difficult environmental samples including soil and plant leachates. The IC-ESI/MS/MS method described here was also compared to established EPA method 317.0 for ClO3− analysis. Samples collected from a variety of environments previously shown to contain natural perchlorate (ClO4−) occurrence were analyzed using the proposed method and ClO3− was found to co-occur with ClO4− at concentrations ranging from <2 ng L−1 in precipitation from Texas and Puerto Rico to >500 mg kg−1 in caliche salt deposits from the Atacama Desert in Chile. Relatively low concentrations of ClO3− in some natural groundwater samples (<0.1 μg L−1) analyzed in this work may indicate lower stability when compared to ClO4− in the subsurface. The high concentrations of ClO3− in caliches and soils (3−6 orders of magnitude greater) as compared to precipitation samples indicate that ClO3−, like ClO4−, may be atmospherically produced and deposited, then concentrated in dry soils, and is possibly a minor component in the biogeochemical cycle of chlorine.

Natural chlorate in the environment: application of a new IC-ESI/MS/MS method with a Cl¹⁸O₃-internal standard.

PubMed

Balaji Rao, Balaji Rao; Hatzinger, Paul B; Böhlke, John Karl; Sturchio, Neil C; Andraski, Brian J; Eckardt, Frank D; Jackson, W Andrew

2010-11-15

A new ion chromatography electrospray tandem mass spectrometry (IC-ESI/MS/MS) method has been developed for quantification and confirmation of chlorate (ClO₃⁻) in environmental samples. The method involves the electrochemical generation of isotopically labeled chlorate internal standard (Cl¹⁸O₃⁻) using ¹⁸O water (H₂¹⁸O) he standard was added to all samples prior to analysis thereby minimizing the matrix effects that are associated with common ions without the need for expensive sample pretreatments. The method detection limit (MDL) for ClO₃⁻ was 2 ng L⁻¹ for a 1 mL volume sample injection. The proposed method was successfully applied to analyze ClO₃⁻ in difficult environmental samples including soil and plant leachates. The IC-ESI/MS/MS method described here was also compared to established EPA method 317.0 for ClO₃⁻ analysis. Samples collected from a variety of environments previously shown to contain natural perchlorate (ClO₄⁻) occurrence were analyzed using the proposed method and ClO₃⁻ was found to co-occur with ClO₄⁻ at concentrations ranging from < 2 ng L⁻¹ in precipitation from Texas and Puerto Rico to >500 mg kg⁻¹ in caliche salt deposits from the Atacama Desert in Chile. Relatively low concentrations of ClO₃⁻ in some natural groundwater samples (0.1 µg L⁻¹) analyzed in this work may indicate lower stability when compared to ClO₄⁻ in the subsurface. The high concentrations ClO₃⁻ in caliches and soils (3-6 orders of magnitude greater) as compared to precipitation samples indicate that ClO₃⁻, like ClO₄⁻, may be atmospherically produced and deposited, then concentrated in dry soils, and is possibly a minor component in the biogeochemical cycle of chlorine.

PIXE analysis of Nigerian flour and bread samples

NASA Astrophysics Data System (ADS)

Olise, Felix S.; Fernandes, Adriana M.; Cristina Chaves, P.; Taborda, Ana; Reis, Miguel A.

2014-01-01

The alleged use of potassium bromate (KBrO3) in bread baking led a few authors to report on the chemical methods for the determination of KBrO3 levels in bread. In order to examine the potentials of a non chemical particle induced X-ray emission (PIXE) method for this purpose, six sets of samples, each composed of flour, dough and bread from a production batch were analysed. The samples were obtained from six different bakers of bread at Ile-Ife, Nigeria. The flour samples were air-dried while others were freeze dried at about -16 °C. The samples were homogenised in an agate mortar and then pelletised. Samples were analysed at the CTN standard PIXE setup and standard procedures for thick target samples analysis were followed. In some samples significant concentrations of bromine were found. In the present work we present possible explanations for the presence of this potentially dangerous contaminant in the samples.

A method for quantitative analysis of standard and high-throughput qPCR expression data based on input sample quantity.

PubMed

Adamski, Mateusz G; Gumann, Patryk; Baird, Alison E

2014-01-01

Over the past decade rapid advances have occurred in the understanding of RNA expression and its regulation. Quantitative polymerase chain reactions (qPCR) have become the gold standard for quantifying gene expression. Microfluidic next generation, high throughput qPCR now permits the detection of transcript copy number in thousands of reactions simultaneously, dramatically increasing the sensitivity over standard qPCR. Here we present a gene expression analysis method applicable to both standard polymerase chain reactions (qPCR) and high throughput qPCR. This technique is adjusted to the input sample quantity (e.g., the number of cells) and is independent of control gene expression. It is efficiency-corrected and with the use of a universal reference sample (commercial complementary DNA (cDNA)) permits the normalization of results between different batches and between different instruments--regardless of potential differences in transcript amplification efficiency. Modifications of the input quantity method include (1) the achievement of absolute quantification and (2) a non-efficiency corrected analysis. When compared to other commonly used algorithms the input quantity method proved to be valid. This method is of particular value for clinical studies of whole blood and circulating leukocytes where cell counts are readily available.

Development of a Methodology for Assessing Aircrew Workloads.

DTIC Science & Technology

1981-11-01

Workload Feasibility Study. .. ...... 52 Subjects. .. .............. ........ 53 Equipment .. ............... ....... 53 Date Analysis ... analysis ; simulation; standard time systems; switching synthetic time systems; task activities; task interference; time study; tracking; workload; work sampl...standard data systems, information content analysis , work sampling and job evaluation. Con- ventional methods were found to be deficient in accounting

Fast, Exact Bootstrap Principal Component Analysis for p > 1 million

PubMed Central

Fisher, Aaron; Caffo, Brian; Schwartz, Brian; Zipunnikov, Vadim

2015-01-01

Many have suggested a bootstrap procedure for estimating the sampling variability of principal component analysis (PCA) results. However, when the number of measurements per subject (p) is much larger than the number of subjects (n), calculating and storing the leading principal components from each bootstrap sample can be computationally infeasible. To address this, we outline methods for fast, exact calculation of bootstrap principal components, eigenvalues, and scores. Our methods leverage the fact that all bootstrap samples occupy the same n-dimensional subspace as the original sample. As a result, all bootstrap principal components are limited to the same n-dimensional subspace and can be efficiently represented by their low dimensional coordinates in that subspace. Several uncertainty metrics can be computed solely based on the bootstrap distribution of these low dimensional coordinates, without calculating or storing the p-dimensional bootstrap components. Fast bootstrap PCA is applied to a dataset of sleep electroencephalogram recordings (p = 900, n = 392), and to a dataset of brain magnetic resonance images (MRIs) (p ≈ 3 million, n = 352). For the MRI dataset, our method allows for standard errors for the first 3 principal components based on 1000 bootstrap samples to be calculated on a standard laptop in 47 minutes, as opposed to approximately 4 days with standard methods. PMID:27616801

Emission spectrographic determination of volatile trace elements in geologic materials by a carrier distillation technique

USGS Publications Warehouse

Barton, H.N.

1986-01-01

Trace levels of chalcophile elements that form volatile sulfide minerals are determined in stream sediments and in the nonmagnetic fraction of a heavy-mineral concentrate of stream sediments by a carrier distillation emission spectrographic method. Photographically recorded spectra of samples are visually compared with those of synthetic standards for the two sample types. Rock and soil samples may also be analyzed by comparison with the stream-sediment standards. A gallium oxide spectrochemical carrier/buffer enhances the early emission of the volatile elements. Detection limits in parts per million attained are: Sb 5, As 20, Bi 0.1, Cd 1, Cu 1, Pb 2, Ag 0.1, Zn 2, and Sn 0.1. A comparison with other methods of analysis, total-burn emission and atomic absorption spectroscopy, shows good correlation for standard reference for materials and samples from a variety of geologic terranes. ?? 1986.

UPLC-MS/MS determination of ptaquiloside and pterosin B in preserved natural water.

PubMed

Clauson-Kaas, Frederik; Hansen, Hans Christian Bruun; Strobel, Bjarne W

2016-11-01

The naturally occurring carcinogen ptaquiloside and its degradation product pterosin B are found in water leaching from bracken stands. The objective of this work is to present a new sample preservation method and a fast UPLC-MS/MS method for quantification of ptaquiloside and pterosin B in environmental water samples, employing a novel internal standard. A faster, reliable, and efficient method was developed for isolation of high purity ptaquiloside and pterosin B from plant material for use as analytical standards, with purity verified by 1 H-NMR. The chemical analysis was performed by cleanup and preconcentration of samples with solid phase extraction, before analyte quantification with UPLC-MS/MS. By including gradient elution and optimizing the liquid chromatography mobile phase buffer system, a total run cycle of 5 min was achieved, with method detection limits, including preconcentration, of 8 and 4 ng/L for ptaquiloside and pterosin B, respectively. The use of loganin as internal standard improved repeatability of the determination of both analytes, though it could not be employed for sample preparation. Buffering raw water samples in situ with ammonium acetate to pH ∼5.5 decisively increased sample integrity at realistic transportation and storing conditions prior to extraction. Groundwater samples collected in November 2015 at the shallow water table below a Danish bracken stand were preserved and analyzed using the above methods, and PTA concentrations of 3.8 ± 0.24 μg/L (±sd, n = 3) were found, much higher than previously reported. Graphical abstract Workflow overview of ptaquiloside determination.

Gross Motor Development in Children Aged 3-5 Years, United States 2012.

PubMed

Kit, Brian K; Akinbami, Lara J; Isfahani, Neda Sarafrazi; Ulrich, Dale A

2017-07-01

Objective Gross motor development in early childhood is important in fostering greater interaction with the environment. The purpose of this study is to describe gross motor skills among US children aged 3-5 years using the Test of Gross Motor Development (TGMD-2). Methods We used 2012 NHANES National Youth Fitness Survey (NNYFS) data, which included TGMD-2 scores obtained according to an established protocol. Outcome measures included locomotor and object control raw and age-standardized scores. Means and standard errors were calculated for demographic and weight status with SUDAAN using sample weights to calculate nationally representative estimates, and survey design variables to account for the complex sampling methods. Results The sample included 339 children aged 3-5 years. As expected, locomotor and object control raw scores increased with age. Overall mean standardized scores for locomotor and object control were similar to the mean value previously determined using a normative sample. Girls had a higher mean locomotor, but not mean object control, standardized score than boys (p < 0.05). However, the mean locomotor standardized scores for both boys and girls fell into the range categorized as "average." There were no other differences by age, race/Hispanic origin, weight status, or income in either of the subtest standardized scores (p > 0.05). Conclusions In a nationally representative sample of US children aged 3-5 years, TGMD-2 mean locomotor and object control standardized scores were similar to the established mean. These results suggest that standardized gross motor development among young children generally did not differ by demographic or weight status.

Comparison of American Fisheries Society (AFS) standard fish sampling techniques and environmental DNA for characterizing fish communities in a large reservoir

USGS Publications Warehouse

Perez, Christina R.; Bonar, Scott A.; Amberg, Jon J.; Ladell, Bridget; Rees, Christopher B.; Stewart, William T.; Gill, Curtis J.; Cantrell, Chris; Robinson, Anthony

2017-01-01

Recently, methods involving examination of environmental DNA (eDNA) have shown promise for characterizing fish species presence and distribution in waterbodies. We evaluated the use of eDNA for standard fish monitoring surveys in a large reservoir. Specifically, we compared the presence, relative abundance, biomass, and relative percent composition of Largemouth Bass Micropterus salmoides and Gizzard Shad Dorosoma cepedianum measured through eDNA methods and established American Fisheries Society standard sampling methods for Theodore Roosevelt Lake, Arizona. Catches at electrofishing and gillnetting sites were compared with eDNA water samples at sites, within spatial strata, and over the entire reservoir. Gizzard Shad were detected at a higher percentage of sites with eDNA methods than with boat electrofishing in both spring and fall. In contrast, spring and fall gillnetting detected Gizzard Shad at more sites than eDNA. Boat electrofishing and gillnetting detected Largemouth Bass at more sites than eDNA; the exception was fall gillnetting, for which the number of sites of Largemouth Bass detection was equal to that for eDNA. We observed no relationship between relative abundance and biomass of Largemouth Bass and Gizzard Shad measured by established methods and eDNA copies at individual sites or lake sections. Reservoirwide catch composition for Largemouth Bass and Gizzard Shad (numbers and total weight [g] of fish) as determined through a combination of gear types (boat electrofishing plus gillnetting) was similar to the proportion of total eDNA copies from each species in spring and fall field sampling. However, no similarity existed between proportions of fish caught via spring and fall boat electrofishing and the proportion of total eDNA copies from each species. Our study suggests that eDNA field sampling protocols, filtration, DNA extraction, primer design, and DNA sequencing methods need further refinement and testing before incorporation into standard fish sampling surveys.

Quantification of integrated HIV DNA by repetitive-sampling Alu-HIV PCR on the basis of poisson statistics.

PubMed

De Spiegelaere, Ward; Malatinkova, Eva; Lynch, Lindsay; Van Nieuwerburgh, Filip; Messiaen, Peter; O'Doherty, Una; Vandekerckhove, Linos

2014-06-01

Quantification of integrated proviral HIV DNA by repetitive-sampling Alu-HIV PCR is a candidate virological tool to monitor the HIV reservoir in patients. However, the experimental procedures and data analysis of the assay are complex and hinder its widespread use. Here, we provide an improved and simplified data analysis method by adopting binomial and Poisson statistics. A modified analysis method on the basis of Poisson statistics was used to analyze the binomial data of positive and negative reactions from a 42-replicate Alu-HIV PCR by use of dilutions of an integration standard and on samples of 57 HIV-infected patients. Results were compared with the quantitative output of the previously described Alu-HIV PCR method. Poisson-based quantification of the Alu-HIV PCR was linearly correlated with the standard dilution series, indicating that absolute quantification with the Poisson method is a valid alternative for data analysis of repetitive-sampling Alu-HIV PCR data. Quantitative outputs of patient samples assessed by the Poisson method correlated with the previously described Alu-HIV PCR analysis, indicating that this method is a valid alternative for quantifying integrated HIV DNA. Poisson-based analysis of the Alu-HIV PCR data enables absolute quantification without the need of a standard dilution curve. Implementation of the CI estimation permits improved qualitative analysis of the data and provides a statistical basis for the required minimal number of technical replicates. © 2014 The American Association for Clinical Chemistry.

Determination of Wastewater Compounds in Whole Water by Continuous Liquid-Liquid Extraction and Capillary-Column Gas Chromatography/Mass Spectrometry

USGS Publications Warehouse

Zaugg, Steven D.; Smith, Steven G.; Schroeder, Michael P.

2006-01-01

A method for the determination of 69 compounds typically found in domestic and industrial wastewater is described. The method was developed in response to increasing concern over the impact of endocrine-disrupting chemicals on aquatic organisms in wastewater. This method also is useful for evaluating the effects of combined sanitary and storm-sewer overflow on the water quality of urban streams. The method focuses on the determination of compounds that are indicators of wastewater or have endocrine-disrupting potential. These compounds include the alkylphenol ethoxylate nonionic surfactants, food additives, fragrances, antioxidants, flame retardants, plasticizers, industrial solvents, disinfectants, fecal sterols, polycyclic aromatic hydrocarbons, and high-use domestic pesticides. Wastewater compounds in whole-water samples were extracted using continuous liquid-liquid extractors and methylene chloride solvent, and then determined by capillary-column gas chromatography/mass spectrometry. Recoveries in reagent-water samples fortified at 0.5 microgram per liter averaged 72 percent ? 8 percent relative standard deviation. The concentration of 21 compounds is always reported as estimated because method recovery was less than 60 percent, variability was greater than 25 percent relative standard deviation, or standard reference compounds were prepared from technical mixtures. Initial method detection limits averaged 0.18 microgram per liter. Samples were preserved by adding 60 grams of sodium chloride and stored at 4 degrees Celsius. The laboratory established a sample holding-time limit prior to sample extraction of 14 days from the date of collection.

Determination of Labeled Fatty Acids Content in Milk Products, Infant Formula, and Adult/Pediatric Nutritional Formula by Capillary Gas Chromatography: Collaborative Study, Final Action 2012.13.

PubMed

Golay, Pierre-Alain; Moulin, Julie

2016-01-01

A collaborative study was conducted on AOAC First Action Method 2012.13 "Determination of Labeled Fatty Acids Content in Milk Products and Infant Formula by Capillary Gas Chromatography," which is based on an initial International Organization for Standardization (ISO)-International Dairy Federation (IDF) New Work Item that has been moved forward to ISO 16958:2015|IDF 231:2015 in November 2015. It was decided to merge the two activities after the agreement signed between ISO and AOAC in June 2012 to develop common standards and to avoid duplicate work. The collaborative study was performed after having provided highly satisfactory single-laboratory validation results [Golay, P.A., & Dong, Y. (2015) J. AOAC Int. 98, 1679-1696] that exceeded the performance criteria defined in AOAC Standard Method Performance Requirement (SMPR(®)) 2012.011 (September 29, 2012) on 12 products selected by the AOAC Stakeholder Panel on Infant Formula (SPIFAN). After a qualification period of 1 month, 18 laboratories participated in the fatty acids analysis of 12 different samples in duplicate. Six samples were selected to meet AOAC SPIFAN requirements (i.e., infant formula and adult nutritionals in powder and liquid formats), and the other Six samples were selected to meet ISO-IDF requirements (i.e., dairy products such as milk powder, liquid milk, cream, butter, infant formula with milk, and cheese). The fatty acids were analyzed directly in all samples without preliminary fat extraction, except in one sample (cheese). Powdered samples were analyzed after dissolution (i.e., reconstitution) in water, whereas liquid samples (or extracted fat) were analyzed directly. After addition of the internal standards solution [C11:0 fatty acid methyl ester (FAME) and C13:0 triacylglycerols (TAG)] to the samples, fatty acids attached to lipids were transformed into FAMEs by direct transesterification using methanolic sodium methoxide. FAMEs were separated using highly polar capillary GLC and were identified by comparison with the retention times of pure analytical standards. Quantification of fatty acids was done relative to C11:0 FAME as internal standard and to instrument response factors (determined separately using calibration standards mixture). The performance of the method (i.e., transesterification) was monitored in all samples using the second internal standard, C13:0 TAG. RSDR values were summarized separately for labeled fatty acids in SPIFAN materials and ISO-IDF materials due to different expression of results. This method was applied to representative dairy, infant formula, and adult/pediatric nutritional products and demonstrated global acceptable reproducibility precision for all fatty acids analyzed (i.e., 46 individuals and/or groups) for these categories of products.

Quantitative determination of amorphous cyclosporine in crystalline cyclosporine samples by Fourier transform infrared spectroscopy.

PubMed

Bertacche, Vittorio; Pini, Elena; Stradi, Riccardo; Stratta, Fabio

2006-01-01

The purpose of this study is the development of a quantification method to detect the amount of amorphous cyclosporine using Fourier transform infrared (FTIR) spectroscopy. The mixing of different percentages of crystalline cyclosporine with amorphous cyclosporine was used to obtain a set of standards, composed of cyclosporine samples characterized by different percentages of amorphous cyclosporine. Using a wavelength range of 450-4,000 cm(-1), FTIR spectra were obtained from samples in potassium bromide pellets and then a partial least squares (PLS) model was exploited to correlate the features of the FTIR spectra with the percentage of amorphous cyclosporine in the samples. This model gave a standard error of estimate (SEE) of 0.3562, with an r value of 0.9971 and a standard error of prediction (SEP) of 0.4168, which derives from the cross validation function used to check the precision of the model. Statistical values reveal the applicability of the method to the quantitative determination of amorphous cyclosporine in crystalline cyclosporine samples.

Extraction of organic contaminants from marine sediments and tissues using microwave energy.

PubMed

Jayaraman, S; Pruell, R J; McKinney, R

2001-07-01

In this study, we compared microwave solvent extraction (MSE) to conventional methods for extracting organic contaminants from marine sediments and tissues with high and varying moisture content. The organic contaminants measured were polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, and polycyclic aromatic hydrocarbons (PAHs). Initial experiments were conducted on dry standard reference materials (SRMs) and field collected marine sediments. Moisture content in samples greatly influenced the recovery of the analytes of interest. When wet sediments were included in a sample batch, low recoveries were often encountered in other samples in the batch, including the dry SRM. Experiments were conducted to test the effect of standardizing the moisture content in all samples in a batch prior to extraction. SRM1941a (marine sediment). SRM1974a (mussel tissue), as well as QA96SED6 (marine sediment), and QA96TIS7 (marine tissue), both from 1996 NIST Intercalibration Exercise were extracted using microwave and conventional methods. Moisture levels were adjusted in SRMs to match those of marine sediment and tissue samples before microwave extraction. The results demonstrated that it is crucial to standardize the moisture content in all samples, including dry reference material to ensure good recovery of organic contaminants. MSE yielded equivalent or superior recoveries compared to conventional methods for the majority of the compounds evaluated. The advantages of MSE over conventional methods are reduced solvent usage, higher sample throughput and the elimination of halogenated solvent usage.

Optical Methods for Identifying Hard Clay Core Samples During Petrophysical Studies

NASA Astrophysics Data System (ADS)

Morev, A. V.; Solovyeva, A. V.; Morev, V. A.

2018-01-01

X-ray phase analysis of the general mineralogical composition of core samples from one of the West Siberian fields was performed. Electronic absorption spectra of the clay core samples with an added indicator were studied. The speed and availability of applying the two methods in petrophysical laboratories during sample preparation for standard and special studies were estimated.

Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of Cr, Cd and Pb in plastics.

PubMed

Li, Po-Chien; Jiang, Shiuh-Jen

2006-07-01

Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cell inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) for the determination of Cr, Cd and Pb in several plastic samples, using NH4NO3 as the modifier, is described. The influences of the instrumental operating conditions and the slurry preparation technique on the ion signals are investigated. A reduction in the intensity of the background at signals corresponding to chromium masses (arising from matrix elements) was achieved by using NH3 as the reaction cell gas in the DRC. The method was applied to determine Cr, Cd and Pb in two polystyrene (PS) samples and a polyvinyl chloride (PVC) sample using two different calibration methods, namely standard addition and isotope dilution. The results were in good agreement with those for digested samples analyzed by ultrasonic nebulization DRC-ICP-MS. The precision between sample replicates was better than 17% with the USS-ETV-DRC-ICP-MS method. The method detection limits, estimated from standard addition curves, were about 6-9, 1-2 and 8-11 ng g(-1) for Cr, Cd and Pb, respectively, in the original plastic samples.

Quantitative LIBS analysis of vanadium in samples of hexagonal mesoporous silica catalysts.

PubMed

Pouzar, Miloslav; Kratochvíl, Tomás; Capek, Libor; Smoláková, Lucie; Cernohorský, Tomás; Krejcová, Anna; Hromádko, Ludek

2011-02-15

The method for the analysis of vanadium in hexagonal mesoporous silica (V-HMS) catalysts using Laser Induced Breakdown Spectrometry (LIBS) was suggested. Commercially available LIBS spectrometer was calibrated with the aid of authentic V-HMS samples previously analyzed by ICP OES after microwave digestion. Deposition of the sample on the surface of adhesive tape was adopted as a sample preparation method. Strong matrix effect connected with the catalyst preparation technique (1st vanadium added in the process of HMS synthesis, 2nd already synthesised silica matrix was impregnated by vanadium) was observed. The concentration range of V in the set of nine calibration standards was 1.3-4.5% (w/w). Limit of detection was 0.13% (w/w) and it was calculated as a triple standard deviation from five replicated determinations of vanadium in the real sample with a very low vanadium concentration. Comparable results of LIBS and ED XRF were obtained if the same set of standards was used for calibration of both methods and vanadium was measured in the same type of real samples. LIBS calibration constructed using V-HMS-impregnated samples failed for measuring of V-HMS-synthesized samples. LIBS measurements seem to be strongly influenced with different chemical forms of vanadium in impregnated and synthesised samples. The combination of LIBS and ED XRF is able to provide new information about measured samples (in our case for example about procedure of catalyst preparation). Copyright © 2010 Elsevier B.V. All rights reserved.

EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. I. Collection of Virus Samples

PubMed Central

Fout, G. Shay; Cashdollar, Jennifer L.; Varughese, Eunice A.; Parshionikar, Sandhya U.; Grimm, Ann C.

2015-01-01

EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. The standardized sampling component of the method concentrates viruses that may be present in water by passage of a minimum specified volume of water through an electropositive cartridge filter. The minimum specified volumes for surface and finished/ground water are 300 L and 1,500 L, respectively. A major method limitation is the tendency for the filters to clog before meeting the sample volume requirement. Studies using two different, but equivalent, cartridge filter options showed that filter clogging was a problem with 10% of the samples with one of the filter types compared to 6% with the other filter type. Clogging tends to increase with turbidity, but cannot be predicted based on turbidity measurements only. From a cost standpoint one of the filter options is preferable over the other, but the water quality and experience with the water system to be sampled should be taken into consideration in making filter selections. PMID:25867928

Comparison of Efficiency of Jackknife and Variance Component Estimators of Standard Errors. Program Statistics Research. Technical Report.

ERIC Educational Resources Information Center

Longford, Nicholas T.

Large scale surveys usually employ a complex sampling design and as a consequence, no standard methods for estimation of the standard errors associated with the estimates of population means are available. Resampling methods, such as jackknife or bootstrap, are often used, with reference to their properties of robustness and reduction of bias. A…

Comparison of the acetyl bromide spectrophotometric method with other analytical lignin methods for determining lignin concentration in forage samples.

PubMed

Fukushima, Romualdo S; Hatfield, Ronald D

2004-06-16

Present analytical methods to quantify lignin in herbaceous plants are not totally satisfactory. A spectrophotometric method, acetyl bromide soluble lignin (ABSL), has been employed to determine lignin concentration in a range of plant materials. In this work, lignin extracted with acidic dioxane was used to develop standard curves and to calculate the derived linear regression equation (slope equals absorptivity value or extinction coefficient) for determining the lignin concentration of respective cell wall samples. This procedure yielded lignin values that were different from those obtained with Klason lignin, acid detergent acid insoluble lignin, or permanganate lignin procedures. Correlations with in vitro dry matter or cell wall digestibility of samples were highest with data from the spectrophotometric technique. The ABSL method employing as standard lignin extracted with acidic dioxane has the potential to be employed as an analytical method to determine lignin concentration in a range of forage materials. It may be useful in developing a quick and easy method to predict in vitro digestibility on the basis of the total lignin content of a sample.

Determination of Porosity in Shale by Double Headspace Extraction GC Analysis.

PubMed

Zhang, Chun-Yun; Li, Teng-Fei; Chai, Xin-Sheng; Xiao, Xian-Ming; Barnes, Donald

2015-11-03

This paper reports on a novel method for the rapid determination of the shale porosity by double headspace extraction gas chromatography (DHE-GC). Ground core samples of shale were placed into headspace vials and DHE-GC measurements of released methane gas were performed at a given time interval. A linear correlation between shale porosity and the ratio of consecutive GC signals was established both theoretically and experimentally by comparing with the results from the standard helium pycnometry method. The results showed that (a) the porosity of ground core samples of shale can be measured within 30 min; (b) the new method is not significantly affected by particle size of the sample; (c) the uncertainties of measured porosities of nine shale samples by the present method range from 0.31 to 0.46 p.u.; and (d) the results obtained by the DHE-GC method are in a good agreement with those from the standard helium pycnometry method. In short, the new DHE-GC method is simple, rapid, and accurate, making it a valuable tool for shale gas-related research and applications.

EVALUATION OF ANALYTICAL REPORTING ERRORS GENERATED AS DESCRIBED IN SW-846 METHOD 8261A

EPA Science Inventory

SW-846 Method 8261A incorporates the vacuum distillation of analytes from samples, and their recoveries are characterized by internal standards. The internal standards measure recoveries with confidence intervals as functions of physical properties. The frequency the calculate...

Verification of three-microphone impedance tube method for measurement of transmission loss in aerogels

NASA Astrophysics Data System (ADS)

Connick, Robert J.

Accurate measurement of normal incident transmission loss is essential for the acoustic characterization of building materials. In this research, a method of measuring normal incidence sound transmission loss proposed by Salissou et al. as a complement to standard E2611-09 of the American Society for Testing and Materials [Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method (American Society for Testing and Materials, New York, 2009)] is verified. Two sam- ples from the original literature are used to verify the method as well as a Filtros RTM sample. Following the verification, several nano-material Aerogel samples are measured.

The performance of diphoton primary vertex reconstruction methods in H → γγ+Met channel of ATLAS experiment

NASA Astrophysics Data System (ADS)

Tomiwa, K. G.

2017-09-01

The search for new physics in the H → γγ+met relies on how well the missing transverse energy is reconstructed. The Met algorithm used by the ATLAS experiment in turns uses input variables like photon and jets which depend on the reconstruction of the primary vertex. This document presents the performance of di-photon vertex reconstruction algorithms (hardest vertex method and Neural Network method). Comparing the performance of these algorithms for the nominal Standard Model sample and the Beyond Standard Model sample, we see the overall performance of the Neural Network method of primary vertex selection performed better than the Hardest vertex method.

Evaluating a novel application of optical fibre evanescent field absorbance: rapid measurement of red colour in winegrape homogenates

NASA Astrophysics Data System (ADS)

Lye, Peter G.; Bradbury, Ronald; Lamb, David W.

Silica optical fibres were used to measure colour (mg anthocyanin/g fresh berry weight) in samples of red wine grape homogenates via optical Fibre Evanescent Field Absorbance (FEFA). Colour measurements from 126 samples of grape homogenate were compared against the standard industry spectrophotometric reference method that involves chemical extraction and subsequent optical absorption measurements of clarified samples at 520 nm. FEFA absorbance on homogenates at 520 nm (FEFA520h) was correlated with the industry reference method measurements of colour (R2 = 0.46, n = 126). Using a simple regression equation colour could be predicted with a standard error of cross-validation (SECV) of 0.21 mg/g, with a range of 0.6 to 2.2 mg anthocyanin/g and a standard deviation of 0.33 mg/g. With a Ratio of Performance Deviation (RPD) of 1.6, the technique when utilizing only a single detection wavelength, is not robust enough to apply in a diagnostic sense, however the results do demonstrate the potential of the FEFA method as a fast and low-cost assay of colour in homogenized samples.

Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples.

PubMed

Taher, Mohammad Ali; Pourmohammad, Fatemeh; Fazelirad, Hamid

2015-12-01

In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A comparative study between different alternatives to prepare gaseous standards for calibrating UV-Ion Mobility Spectrometers.

PubMed

Criado-García, Laura; Garrido-Delgado, Rocío; Arce, Lourdes; Valcárcel, Miguel

2013-07-15

An UV-Ion Mobility Spectrometer is a simple, rapid, inexpensive instrument widely used in environmental analysis among other fields. The advantageous features of its underlying technology can be of great help towards developing reliable, economical methods for determining gaseous compounds from gaseous, liquid and solid samples. Developing an effective method using UV-Ion Mobility Spectrometry (UV-IMS) to determine volatile analytes entails using appropriate gaseous standards for calibrating the spectrometer. In this work, two home-made sample introduction systems (SISs) and a commercial gas generator were used to obtain such gaseous standards. The first home-made SIS used was a static head-space to measure compounds present in liquid samples and the other home-made system was an exponential dilution set-up to measure compounds present in gaseous samples. Gaseous compounds generated by each method were determined on-line by UV-IMS. Target analytes chosen for this comparative study were ethanol, acetone, benzene, toluene, ethylbenzene and xylene isomers. The different alternatives were acceptable in terms of sensitivity, precision and selectivity. Copyright © 2013 Elsevier B.V. All rights reserved.

An isotope-dilution standard GC/MS/MS method for steroid hormones in water

USGS Publications Warehouse

Foreman, William T.; Gray, James L.; ReVello, Rhiannon C.; Lindley, Chris E.; Losche, Scott A.

2013-01-01

An isotope-dilution quantification method was developed for 20 natural and synthetic steroid hormones and additional compounds in filtered and unfiltered water. Deuterium- or carbon-13-labeled isotope-dilution standards (IDSs) are added to the water sample, which is passed through an octadecylsilyl solid-phase extraction (SPE) disk. Following extract cleanup using Florisil SPE, method compounds are converted to trimethylsilyl derivatives and analyzed by gas chromatography with tandem mass spectrometry. Validation matrices included reagent water, wastewater-affected surface water, and primary (no biological treatment) and secondary wastewater effluent. Overall method recovery for all analytes in these matrices averaged 100%; with overall relative standard deviation of 28%. Mean recoveries of the 20 individual analytes for spiked reagent-water samples prepared along with field samples analyzed in 2009–2010 ranged from 84–104%, with relative standard deviations of 6–36%. Detection levels estimated using ASTM International’s D6091–07 procedure range from 0.4 to 4 ng/L for 17 analytes. Higher censoring levels of 100 ng/L for bisphenol A and 200 ng/L for cholesterol and 3-beta-coprostanol are used to prevent bias and false positives associated with the presence of these analytes in blanks. Absolute method recoveries of the IDSs provide sample-specific performance information and guide data reporting. Careful selection of labeled compounds for use as IDSs is important because both inexact IDS-analyte matches and deuterium label loss affect an IDS’s ability to emulate analyte performance. Six IDS compounds initially tested and applied in this method exhibited deuterium loss and are not used in the final method.

Performance evaluation of direct saline stool microscopy, Formol ether concentration and Kato Katz diagnostic methods for intestinal parasitosis in the absence of gold standard methods.

PubMed

Hailu, Tadesse; Abera, Bayeh

2015-07-01

The parasite load within the sample and the amount of sample taken during examination greatly compromise the sensitivity of direct saline stool microscopy. A cross-sectional study was conducted in March 2011 in Bahir Dar city among 778 fresh single stool samples to evaluate the performance of direct saline (DS), Kato Katz (KK) and Formol ether concentration (FEC) methods against the 'Gold' standard. Among 778 stool samples from school age children, the highest prevalence of intestinal parasites was recorded by FEC (55.1%). The sensitivity of DS, FEC and KK were 61.1%, 92.3% and 58.7%, respectively. FEC is more sensitive than DS and KK. Hence, use of the latter is preferred. © The Author(s) 2015.

Alternative Confidence Interval Methods Used in the Diagnostic Accuracy Studies

PubMed Central

Gülhan, Orekıcı Temel

2016-01-01

Background/Aim. It is necessary to decide whether the newly improved methods are better than the standard or reference test or not. To decide whether the new diagnostics test is better than the gold standard test/imperfect standard test, the differences of estimated sensitivity/specificity are calculated with the help of information obtained from samples. However, to generalize this value to the population, it should be given with the confidence intervals. The aim of this study is to evaluate the confidence interval methods developed for the differences between the two dependent sensitivity/specificity values on a clinical application. Materials and Methods. In this study, confidence interval methods like Asymptotic Intervals, Conditional Intervals, Unconditional Interval, Score Intervals, and Nonparametric Methods Based on Relative Effects Intervals are used. Besides, as clinical application, data used in diagnostics study by Dickel et al. (2010) has been taken as a sample. Results. The results belonging to the alternative confidence interval methods for Nickel Sulfate, Potassium Dichromate, and Lanolin Alcohol are given as a table. Conclusion. While preferring the confidence interval methods, the researchers have to consider whether the case to be compared is single ratio or dependent binary ratio differences, the correlation coefficient between the rates in two dependent ratios and the sample sizes. PMID:27478491

Alternative Confidence Interval Methods Used in the Diagnostic Accuracy Studies.

PubMed

Erdoğan, Semra; Gülhan, Orekıcı Temel

2016-01-01

Background/Aim. It is necessary to decide whether the newly improved methods are better than the standard or reference test or not. To decide whether the new diagnostics test is better than the gold standard test/imperfect standard test, the differences of estimated sensitivity/specificity are calculated with the help of information obtained from samples. However, to generalize this value to the population, it should be given with the confidence intervals. The aim of this study is to evaluate the confidence interval methods developed for the differences between the two dependent sensitivity/specificity values on a clinical application. Materials and Methods. In this study, confidence interval methods like Asymptotic Intervals, Conditional Intervals, Unconditional Interval, Score Intervals, and Nonparametric Methods Based on Relative Effects Intervals are used. Besides, as clinical application, data used in diagnostics study by Dickel et al. (2010) has been taken as a sample. Results. The results belonging to the alternative confidence interval methods for Nickel Sulfate, Potassium Dichromate, and Lanolin Alcohol are given as a table. Conclusion. While preferring the confidence interval methods, the researchers have to consider whether the case to be compared is single ratio or dependent binary ratio differences, the correlation coefficient between the rates in two dependent ratios and the sample sizes.

[Detection of KRAS mutation in colorectal cancer patients' cfDNA with droplet digital PCR].

PubMed

Luo, Yuwen; Li, Yao

2018-03-25

This study aims to develop a new method for the detection of KRAS mutations related to colorectal cancer in cfDNA, and to evaluate the sensitivity and accuracy of the detection. We designed a method of cfDNA based KRAS detection by droplets digital PCR (ddPCR). The theoretical performance of the method is evaluated by reference standard and compared to the ARMS PCR method. Two methods, ddPCR and qPCR, were successfully established to detect KRAS wild type and 7 mutants. Both methods were validated using plasmid standards and actual samples. The results were evaluated by false positive rate, linearity, and limit of detection. Finally, 52 plasma cfDNA samples from patients and 20 samples from healthy people were tested, the clinical sensitivity is 97.64%, clinical specificity is 81.43%. ddPCR method shows higher performance than qPCR. The LOD of ddPCR method reached single digits of cfDNA copies, it can detect as low as 0.01% to 0.04% mutation abundance.

Solid-phase extraction and GC-MS analysis of THC-COOH method optimized for a high-throughput forensic drug-testing laboratory.

PubMed

Stout, P R; Horn, C K; Klette, K L

2001-10-01

In order to facilitate the confirmation analysis of large numbers of urine samples previously screened positive for delta9-tetrahydrocannabinol (THC), an extraction, derivitization, and GC-MS analysis method was developed. This method utilized a positive pressure manifold anion-exchange polymer-based solid-phase extraction followed by elution directly into the automated liquid sampling (ALS) vials. Rapid derivitization was accomplished using pentafluoropropionic anhydride/pentafluoropropanol (PFPA/PFPOH). Recoveries averaged 95% with a limit of detection of 0.875 ng/mL with a 3-mL sample volume. Performance of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH)-d3 and THC-COOH-d9 internal standards were evaluated. The method was linear to 900 ng/mL THC-COOH using THC-COOH-d9 with negligible contribution from the internal standard to very weak samples. Excellent agreement was seen with previous quantitations of human urine samples. More than 1000 human urine samples were analyzed using the method with 300 samples analyzed using an alternate qualifier ion (m/z 622) after some interference was observed with a qualifier ion (m/z 489). The 622 ion did not exhibit any interference even in samples with interfering peaks present in the 489 ion. The method resulted in dramatic reductions in processing time, waste production, and exposure hazards to laboratory personnel.

Extraction method based on emulsion breaking for the determination of Cu, Fe and Pb in Brazilian automotive gasoline samples by high-resolution continuum source flame atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Leite, Clarice C.; de Jesus, Alexandre; Kolling, Leandro; Ferrão, Marco F.; Samios, Dimitrios; Silva, Márcia M.

2018-04-01

This work reports a new method for extraction of Cu, Fe and Pb from Brazilian automotive gasoline and their determination by high-resolution continuous source flame atomic absorption spectrometry (HR-CS FAAS). The method was based on the formation of water-in-oil emulsion by mixing 2.0 mL of extraction solution constituted by 12% (w/v) Triton X-100 and 5% (v/v) HNO3 with 10 mL of sample. After heating at 90 °C for 10 min, two well-defined phases were formed. The bottom phase (approximately 3.5 mL), composed of acidified water and part of the ethanol originally present in the gasoline sample, containing the extracted analytes was analyzed. The surfactant and HNO3 concentrations and the heating temperature employed in the process were optimized by Doehlert design, using a Brazilian gasoline sample spiked with Cu, Fe and Pb (organometallic compounds). The efficiency of extraction was investigated and it ranged from 80 to 89%. The calibration was accomplished by using matrix matching method. For this, the standards were obtained performing the same extraction procedure used for the sample, using emulsions obtained with a gasoline sample free of analytes and the addition of inorganic standards. Limits of detection obtained were 3.0, 5.0 and 14.0 μg L-1 for Cu, Fe and Pb, respectively. These limits were estimated for the original sample taking into account the preconcentration factor obtained. The accuracy of the proposed method was assured by recovery tests spiking the samples with organometallic standards and the obtained values ranged from 98 to 105%. Ten gasoline samples were analyzed and Fe was found in four samples (0.04-0.35 mg L-1) while Cu (0.28 mg L-1) and Pb (0.60 mg L-1) was found in just one sample.

A Tool for Estimating Variability in Wood Preservative Treatment Retention

Treesearch

Patricia K. Lebow; Adam M. Taylor; Timothy M. Young

2015-01-01

Composite sampling is standard practice for evaluation of preservative retention levels in preservative-treated wood. Current protocols provide an average retention value but no estimate of uncertainty. Here we describe a statistical method for calculating uncertainty estimates using the standard sampling regime with minimal additional chemical analysis. This tool can...

Cross-Validation of FITNESSGRAM® Health-Related Fitness Standards in Hungarian Youth

ERIC Educational Resources Information Center

Laurson, Kelly R.; Saint-Maurice, Pedro F.; Karsai, István; Csányi, Tamás

2015-01-01

Purpose: The purpose of this study was to cross-validate FITNESSGRAM® aerobic and body composition standards in a representative sample of Hungarian youth. Method: A nationally representative sample (N = 405) of Hungarian adolescents from the Hungarian National Youth Fitness Study (ages 12-18.9 years) participated in an aerobic capacity assessment…

Comparison of matrix effects in HPLC-MS/MS and UPLC-MS/MS analysis of nine basic pharmaceuticals in surface waters.

PubMed

Van De Steene, Jet C; Lambert, Willy E

2008-05-01

When developing an LC-MS/MS-method matrix effects are a major issue. The effect of co-eluting compounds arising from the matrix can result in signal enhancement or suppression. During method development much attention should be paid to diminishing matrix effects as much as possible. The present work evaluates matrix effects from aqueous environmental samples in the simultaneous analysis of a group of 9 specific pharmaceuticals with HPLC-ESI/MS/MS and UPLC-ESI/MS/MS: flubendazole, propiconazole, pipamperone, cinnarizine, ketoconazole, miconazole, rabeprazole, itraconazole and domperidone. When HPLC-MS/MS is used, matrix effects are substantial and can not be compensated for with analogue internal standards. For different surface water samples different matrix effects are found. For accurate quantification the standard addition approach is necessary. Due to the better resolution and more narrow peaks in UPLC, analytes will co-elute less with interferences during ionisation, so matrix effects could be lower, or even eliminated. If matrix effects are eliminated with this technique, the standard addition method for quantification can be omitted and the overall method will be simplified. Results show that matrix effects are almost eliminated if internal standards (structural analogues) are used. Instead of the time-consuming and labour-intensive standard addition method, with UPLC the internal standardization can be used for quantification and the overall method is substantially simplified.

One-calibrant kinetic calibration for on-site water sampling with solid-phase microextraction.

PubMed

Ouyang, Gangfeng; Cui, Shufen; Qin, Zhipei; Pawliszyn, Janusz

2009-07-15

The existing solid-phase microextraction (SPME) kinetic calibration technique, using the desorption of the preloaded standards to calibrate the extraction of the analytes, requires that the physicochemical properties of the standard should be similar to those of the analyte, which limited the application of the technique. In this study, a new method, termed the one-calibrant kinetic calibration technique, which can use the desorption of a single standard to calibrate all extracted analytes, was proposed. The theoretical considerations were validated by passive water sampling in laboratory and rapid water sampling in the field. To mimic the variety of the environment, such as temperature, turbulence, and the concentration of the analytes, the flow-through system for the generation of standard aqueous polycyclic aromatic hydrocarbons (PAHs) solution was modified. The experimental results of the passive samplings in the flow-through system illustrated that the effect of the environmental variables was successfully compensated with the kinetic calibration technique, and all extracted analytes can be calibrated through the desorption of a single calibrant. On-site water sampling with rotated SPME fibers also illustrated the feasibility of the new technique for rapid on-site sampling of hydrophobic organic pollutants in water. This technique will accelerate the application of the kinetic calibration method and also will be useful for other microextraction techniques.

Determination of fluoride in oxides with the fluoride-ion activity electrode.

PubMed

Peters, M A; Ladd, D M

1971-07-01

The application of the fluoride-ion activity electrode to the determination of fluoride in various samples has been studied. Samples are decomposed by fusion and the fluoride concentration is determined by a standard-addition or a direct method. The standard-addition method is unsuitable, owing to a positive bias. The direct method, however, is rapid, accurate and precise. The fluoride content of exploration ores, fluorspar, opal glass, phosphate rock and various production samples, has been successfully determined. The success of the direct method depends on the effectiveness of the system used to buffer pH and ionic strength and complex possible interferences (Al(3+), Ca(2+), Fe(3+)). The effect of interferences has been studied and found to be minimal. The procedures are rapid and accurate and may be substituted for the traditional Willard and Winter or pyro hydrolysis methods, with considerable saving of time.

A systematic study on the influencing parameters and improvement of quantitative analysis of multi-component with single marker method using notoginseng as research subject.

PubMed

Wang, Chao-Qun; Jia, Xiu-Hong; Zhu, Shu; Komatsu, Katsuko; Wang, Xuan; Cai, Shao-Qing

2015-03-01

A new quantitative analysis of multi-component with single marker (QAMS) method for 11 saponins (ginsenosides Rg1, Rb1, Rg2, Rh1, Rf, Re and Rd; notoginsenosides R1, R4, Fa and K) in notoginseng was established, when 6 of these saponins were individually used as internal referring substances to investigate the influences of chemical structure, concentrations of quantitative components, and purities of the standard substances on the accuracy of the QAMS method. The results showed that the concentration of the analyte in sample solution was the major influencing parameter, whereas the other parameters had minimal influence on the accuracy of the QAMS method. A new method for calculating the relative correction factors by linear regression was established (linear regression method), which demonstrated to decrease standard method differences of the QAMS method from 1.20%±0.02% - 23.29%±3.23% to 0.10%±0.09% - 8.84%±2.85% in comparison with the previous method. And the differences between external standard method and the QAMS method using relative correction factors calculated by linear regression method were below 5% in the quantitative determination of Rg1, Re, R1, Rd and Fa in 24 notoginseng samples and Rb1 in 21 notoginseng samples. And the differences were mostly below 10% in the quantitative determination of Rf, Rg2, R4 and N-K (the differences of these 4 constituents bigger because their contents lower) in all the 24 notoginseng samples. The results indicated that the contents assayed by the new QAMS method could be considered as accurate as those assayed by external standard method. In addition, a method for determining applicable concentration ranges of the quantitative components assayed by QAMS method was established for the first time, which could ensure its high accuracy and could be applied to QAMS methods of other TCMs. The present study demonstrated the practicability of the application of the QAMS method for the quantitative analysis of multi-component and the quality control of TCMs and TCM prescriptions. Copyright © 2014 Elsevier B.V. All rights reserved.

H-point standard additions method for simultaneous determination of sulfamethoxazole and trimethoprim in pharmaceutical formulations and biological fluids with simultaneous addition of two analytes

NASA Astrophysics Data System (ADS)

Givianrad, M. H.; Saber-Tehrani, M.; Aberoomand-Azar, P.; Mohagheghian, M.

2011-03-01

The applicability of H-point standard additions method (HPSAM) to the resolving of overlapping spectra corresponding to the sulfamethoxazole and trimethoprim is verified by UV-vis spectrophotometry. The results show that the H-point standard additions method with simultaneous addition of both analytes is suitable for the simultaneous determination of sulfamethoxazole and trimethoprim in aqueous media. The results of applying the H-point standard additions method showed that the two drugs could be determined simultaneously with the concentration ratios of sulfamethoxazole to trimethoprim varying from 1:18 to 16:1 in the mixed samples. Also, the limits of detections were 0.58 and 0.37 μmol L -1 for sulfamethoxazole and trimethoprim, respectively. In addition the means of the calculated RSD (%) were 1.63 and 2.01 for SMX and TMP, respectively in synthetic mixtures. The proposed method has been successfully applied to the simultaneous determination of sulfamethoxazole and trimethoprim in some synthetic, pharmaceutical formulation and biological fluid samples.

H-point standard additions method for simultaneous determination of sulfamethoxazole and trimethoprim in pharmaceutical formulations and biological fluids with simultaneous addition of two analytes.

PubMed

Givianrad, M H; Saber-Tehrani, M; Aberoomand-Azar, P; Mohagheghian, M

2011-03-01

The applicability of H-point standard additions method (HPSAM) to the resolving of overlapping spectra corresponding to the sulfamethoxazole and trimethoprim is verified by UV-vis spectrophotometry. The results show that the H-point standard additions method with simultaneous addition of both analytes is suitable for the simultaneous determination of sulfamethoxazole and trimethoprim in aqueous media. The results of applying the H-point standard additions method showed that the two drugs could be determined simultaneously with the concentration ratios of sulfamethoxazole to trimethoprim varying from 1:18 to 16:1 in the mixed samples. Also, the limits of detections were 0.58 and 0.37 μmol L(-1) for sulfamethoxazole and trimethoprim, respectively. In addition the means of the calculated RSD (%) were 1.63 and 2.01 for SMX and TMP, respectively in synthetic mixtures. The proposed method has been successfully applied to the simultaneous determination of sulfamethoxazole and trimethoprim in some synthetic, pharmaceutical formulation and biological fluid samples. Copyright © 2011 Elsevier B.V. All rights reserved.

International Council for Standardization in Haematology (ICSH) Recommendations for Laboratory Measurement of Direct Oral Anticoagulants.

PubMed

Gosselin, Robert C; Adcock, Dorothy M; Bates, Shannon M; Douxfils, Jonathan; Favaloro, Emmanuel J; Gouin-Thibault, Isabelle; Guillermo, Cecilia; Kawai, Yohko; Lindhoff-Last, Edelgard; Kitchen, Steve

2018-03-01

This guidance document was prepared on behalf of the International Council for Standardization in Haematology (ICSH) for providing haemostasis-related guidance documents for clinical laboratories. This inaugural coagulation ICSH document was developed by an ad hoc committee, comprised of international clinical and laboratory direct acting oral anticoagulant (DOAC) experts. The committee developed consensus recommendations for laboratory measurement of DOACs (dabigatran, rivaroxaban, apixaban and edoxaban), which would be germane for laboratories assessing DOAC anticoagulation. This guidance document addresses all phases of laboratory DOAC measurements, including pre-analytical (e.g. preferred time sample collection, preferred sample type, sample stability), analytical (gold standard method, screening and quantifying methods) and post analytical (e.g. reporting units, quality assurance). The committee addressed the use and limitations of screening tests such as prothrombin time, activated partial thromboplastin time as well as viscoelastic measurements of clotting blood and point of care methods. Additionally, the committee provided recommendations for the proper validation or verification of performance of laboratory assays prior to implementation for clinical use, and external quality assurance to provide continuous assessment of testing and reporting method. Schattauer GmbH Stuttgart.

[Validation of measurement methods and estimation of uncertainty of measurement of chemical agents in the air at workstations].

PubMed

Dobecki, Marek

2012-01-01

This paper reviews the requirements for measurement methods of chemical agents in the air at workstations. European standards, which have a status of Polish standards, comprise some requirements and information on sampling strategy, measuring techniques, type of samplers, sampling pumps and methods of occupational exposure evaluation at a given technological process. Measurement methods, including air sampling and analytical procedure in a laboratory, should be appropriately validated before intended use. In the validation process, selected methods are tested and budget of uncertainty is set up. The validation procedure that should be implemented in the laboratory together with suitable statistical tools and major components of uncertainity to be taken into consideration, were presented in this paper. Methods of quality control, including sampling and laboratory analyses were discussed. Relative expanded uncertainty for each measurement expressed as a percentage, should not exceed the limit of values set depending on the type of occupational exposure (short-term or long-term) and the magnitude of exposure to chemical agents in the work environment.

Evaluation of sodium hydroxide-N-acetyl-l-cysteine and 0.7% chlorhexidine decontamination methods for recovering Mycobacterium tuberculosis from sputum samples: A comparative analysis (The Gambia Experience).

PubMed

Gitteh, Ensa; Kweku Otu, Jacob; Jobarteh, Tijan; Mendy, Francis; Faal-Jawara, Isatou Tutty; Ofori-Anyinam, Nana Boatema; Ayorinde, Abigail; Secka, Ousman; Gehre, Florian

2016-12-01

To determine the culture yield and time to detection of mycobacterial growth between samples decontaminated using 0.7% chlorhexidine and sodium hydroxide-N-acetyl-l-cysteine (NaOH-NALC) and cultured on the Löwenstein-Jensen (LJ) medium. We also aimed to determine the contamination rate between the 0.7% chlorhexidine and NaOH-NALC decontamination methods. The study was carried out on 68 sputa samples (42 smear positives and 26 smear negatives). Of these 68 samples, 46 were collected from men and 26 from women with an approximate average age of 27years. All the sputum samples were decontaminated using the standard NaOH-NALC and 0.7% chlorhexidine methods. The concentrates were cultured in parallel on LJ media in which reading of the slope for mycobacterial growth was obtained daily for the first 2weeks and then weekly until week 8. The mycobacterial recovery rate, time to detection, and contamination rate were then compared. The overall recovery rate of mycobacterial growth on samples treated with both decontamination methods inoculated on LJ media is 51.5% (35/68). Specifically, mycobacterial growth rates on samples treated with 0.7% chlorhexidine and standard NaOH-NALC on LJ media were 61.8% (42/68) and 54.4% (37/68), respectively. However, the growth of Mycobacterium tuberculosis complex was faster on samples treated with 0.7% chlorhexidine than those treated with NaOH-NALC (average, 32±5days vs. 33±5.2days, respectively). The contamination rate on samples treated with 0.7% chlorhexidine was 1.5% (1/68), whereas on those treated with NaOH-NALC, the rate was 4.4% (3/68). The 0.7% chlorhexidine decontamination method is rapid and has less contamination rate in terms of mycobacterial recovery compared with the standard NaOH-NALC method. Therefore, the 0.7% chlorhexidine decontamination method would be an ideal alternative option for decontamination of sputum samples and recovery/isolation of M. tuberculosis in resource-poor countries. Copyright © 2016.

Analysis of volatile organic compounds. [trace amounts of organic volatiles in gas samples

NASA Technical Reports Server (NTRS)

Zlatkis, A. (Inventor)

1977-01-01

An apparatus and method are described for reproducibly analyzing trace amounts of a large number of organic volatiles existing in a gas sample. Direct injection of the trapped volatiles into a cryogenic percolum provides a sharply defined plug. Applications of the method include: (1) analyzing the headspace gas of body fluids and comparing a profile of the organic volatiles with standard profiles for the detection and monitoring of disease; (2) analyzing the headspace gas of foods and beverages and comparing the profile with standard profiles to monitor and control flavor and aroma; and (3) analyses for determining the organic pollutants in air or water samples.

Lectin-Magnetic Separation (LMS) for isolation of Toxoplasma gondii oocysts from concentrated water samples prior to detection by microscopy or qPCR

USDA-ARS?s Scientific Manuscript database

Although standard methods for analyzing water samples for the protozoan parasites Cryptosporidium spp. and Giardia duodenalis are available and widely used, equivalent methods for analyzing water samples for Toxoplasma oocysts are lacking. This is partly due to the lack of a readily available, relia...

Application of quantitative 1H NMR for the calibration of protoberberine alkaloid reference standards.

PubMed

Wu, Yan; He, Yi; He, Wenyi; Zhang, Yumei; Lu, Jing; Dai, Zhong; Ma, Shuangcheng; Lin, Ruichao

2014-03-01

Quantitative nuclear magnetic resonance spectroscopy (qNMR) has been developed into an important tool in the drug analysis, biomacromolecule detection, and metabolism study. Compared with mass balance method, qNMR method bears some advantages in the calibration of reference standard (RS): it determines the absolute amount of a sample; other chemical compound and its certified reference material (CRM) can be used as internal standard (IS) to obtain the purity of the sample. Protoberberine alkaloids have many biological activities and have been used as reference standards for the control of many herbal drugs. In present study, the qNMR methods were developed for the calibration of berberine hydrochloride, palmatine hydrochloride, tetrahydropalmatine, and phellodendrine hydrochloride with potassium hydrogen phthalate as IS. Method validation was carried out according to the guidelines for the method validation of Chinese Pharmacopoeia. The results of qNMR were compared with those of mass balance method and the differences between the results of two methods were acceptable based on the analysis of estimated measurement uncertainties. Therefore, qNMR is an effective and reliable analysis method for the calibration of RS and can be used as a good complementarity to the mass balance method. Copyright © 2013 Elsevier B.V. All rights reserved.

[Study on the method for the determination of trace boron, molybdenum, silver, tin and lead in geochemical samples by direct current arc full spectrum direct reading atomic emission spectroscopy (DC-Arc-AES)].

PubMed

Hao, Zhi-hong; Yao, Jian-zhen; Tang, Rui-ling; Zhang, Xue-mei; Li, Wen-ge; Zhang, Qin

2015-02-01

The method for the determmation of trace boron, molybdenum, silver, tin and lead in geochemical samples by direct current are full spectrum direct reading atomic emission spectroscopy (DC-Arc-AES) was established. Direct current are full spectrum direct reading atomic emission spectrometer with a large area of solid-state detectors has functions of full spectrum direct reading and real-time background correction. The new electrodes and new buffer recipe were proposed in this paper, and have applied for national patent. Suitable analytical line pairs, back ground correcting points of elements and the internal standard method were selected, and Ge was used as internal standard. Multistage currents were selected in the research on current program, and each current set different holding time to ensure that each element has a good signal to noise ratio. Continuous rising current mode selected can effectively eliminate the splash of the sample. Argon as shielding gas can eliminate CN band generating and reduce spectral background, also plays a role in stabilizing the are, and argon flow 3.5 L x min(-1) was selected. Evaporation curve of each element was made, and it was concluded that the evaporation behavior of each element is consistent, and combined with the effects of different spectrographic times on the intensity and background, the spectrographic time of 35s was selected. In this paper, national standards substances were selected as a standard series, and the standard series includes different nature and different content of standard substances which meet the determination of trace boron, molybdenum, silver, tin and lead in geochemical samples. In the optimum experimental conditions, the detection limits for B, Mo, Ag, Sn and Pb are 1.1, 0.09, 0.01, 0.41, and 0.56 microg x g(-1) respectively, and the precisions (RSD, n=12) for B, Mo, Ag, Sn and Pb are 4.57%-7.63%, 5.14%-7.75%, 5.48%-12.30%, 3.97%-10.46%, and 4.26%-9.21% respectively. The analytical accuracy was validated by national standards and the results are in agreement with certified values. The method is simple, rapid, is an advanced analytical method for the determination of trace amounts of geochemical samples' boron, molybdenum, silver, tin and lead, and has a certain practicality.

Comparison of methods for the measurement of mist and vapor from light mineral oil-based metalworking fluids.

PubMed

Simpson, Andrew T

2003-11-01

The measurement of oil mist derived from metalworking fluids formulated with light mineral oils can be highly inaccurate when using traditional filter sampling. This is due to evaporation of oil from the filter. In this work the practicability of an alternative approach measuring total oil mist and vapor was investigated. Combinations of inhalable particle samplers with backup sorbent vapor traps and standard vapor sampling on pumped and diffusive sorbent tubes were evaluated with gravimetric, infrared spectroscopic, and gas chromatographic analytical methods against the performance requirements of European Standard EN 482. An artificial aerosol was used to compare the methods against a reference method of filter sampler in series with three impingers. Multi-orifice samplers were used with standard 8-mm diameter charcoal tubes at 2 L/min without any signs of channelling or significant breakthrough, as were conical inhalable samplers with XAD-2 tubes at 1 L/min. Most combinations of samplers had a bias of less than 3 percent, but solitary pumped charcoal tubes underestimated total oil by 13 percent. Diffusive sampling was affected by impaction of mist particles and condensation of oil vapor. Gravimetric analysis of filters revealed significant potential sample loss during storage, with 4 percent being lost after one day when stored at room temperature and 2 percent when refrigerated. Samples left overnight in the balance room to equilibrate lost 24 percent. Infrared spectroscopy gave more precise results for vapor than gas chromatography (p = 0.002). Gas chromatography was less susceptible to bias from contaminating solvent vapors than infrared spectroscopy, but was still vulnerable to petroleum distillates. Under the specific test conditions (one oil type and mist particle size), all combinations of methods examined complied with the requirements of European Standard EN 484. Total airborne oil can be measured accurately; however, care must be taken to avoid contamination by hydrocarbon solvent vapors during sampling.

Workshop on standards in biomass for energy and chemicals: proceedings

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

Milne, T.A.

1984-11-01

In the course of reviewing standards literature, visiting prominent laboratories and research groups, attending biomass meetings and corresponding widely, a whole set of standards needs was identified, the most prominent of which were: biomass standard reference materials, research materials and sample banks; special collections of microorganisms, clonal material, algae, etc.; standard methods of characterization of substrates and biomass fuels; standard tests and methods for the conversion and end-use of biomass; standard protocols for the description, harvesting, preparation, storage, and measurement of productivity of biomass materials in the energy context; glossaries of terms; development of special tests for assay of enzymaticmore » activity and related processes. There was also a recognition of the need for government, professional and industry support of concensus standards development and the dissemination of information on standards. Some 45 biomass researchers and managers met with key NBS staff to identify and prioritize standards needs. This was done through three working panels: the Panel on Standard Reference Materials (SRM's), Research Materials (RM's), and Sample Banks; the Panel on Production and Characterization; and the Panel on Tests and Methods for Conversion and End Use. This report gives a summary of the action items in standards development recommended unanimously by the workshop attendees. The proceedings of the workshop, and an appendix, contain an extensive written record of the findings of the workshop panelists and others regarding presently existing standards and standards issues and needs. Separate abstracts have been prepared for selected papers for inclusion in the Energy Database.« less

[Determination of heavy metals in four traditional Chinese medicines by ICP-MS].

PubMed

Wen, Hui-Min; Chen, Xiao-Hui; Dong, Ting-Xia; Zhan, Hua-Qiang; Bi, Kai-Shun

2006-08-01

To establish a ICP-MS method for the determination of heavy metals, including As, Hg, Pb, Cd, in four traditional Chinese medicines. The samples were digested by closed-versel microwave. The four heavy metals were directly analyzed by ICP-MS. Select internal standard element in for the method by which the analyse signal drife is corrected by the signal of another element (internal standard elements) added to both the standard solution and sample. For all of the analyzed heary methals, the correlative coefficient of the calibration curves was over 0.999 2. The recovery rates of the procedure were 97.5%-108.0%, and its RSD was lower than 11.6%. This method was convenient, quick-acquired, accurate and highly sensitive. The method can be used for the quality control of trace elements in traditional Chinese medicines and for the contents determination of traditional Chinese medicines from different habitats and species.

Optimization of Sample Preparation for the Identification and Quantification of Saxitoxin in Proficiency Test Mussel Sample using Liquid Chromatography-Tandem Mass Spectrometry

PubMed Central

Harju, Kirsi; Rapinoja, Marja-Leena; Avondet, Marc-André; Arnold, Werner; Schär, Martin; Burrell, Stephen; Luginbühl, Werner; Vanninen, Paula

2015-01-01

Saxitoxin (STX) and some selected paralytic shellfish poisoning (PSP) analogues in mussel samples were identified and quantified with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sample extraction and purification methods of mussel sample were optimized for LC-MS/MS analysis. The developed method was applied to the analysis of the homogenized mussel samples in the proficiency test (PT) within the EQuATox project (Establishment of Quality Assurance for the Detection of Biological Toxins of Potential Bioterrorism Risk). Ten laboratories from eight countries participated in the STX PT. Identification of PSP toxins in naturally contaminated mussel samples was performed by comparison of product ion spectra and retention times with those of reference standards. The quantitative results were obtained with LC-MS/MS by spiking reference standards in toxic mussel extracts. The results were within the z-score of ±1 when compared to the results measured with the official AOAC (Association of Official Analytical Chemists) method 2005.06, pre-column oxidation high-performance liquid chromatography with fluorescence detection (HPLC-FLD). PMID:26610567

Determination of free sulfites (SO3-2) in dried fruits processed with sulfur dioxide by ion chromatography through anion exchange column and conductivity detection.

PubMed

Liao, Benjamin S; Sram, Jacqueline C; Files, Darin J

2013-01-01

A simple and effective anion ion chromatography (IC) method with anion exchange column and conductivity detector has been developed to determine free sulfites (SO3-2) in dried fruits processed with sulfur dioxide. No oxidation agent, such as hydrogen peroxide, is used to convert sulfites to sulfates for IC analysis. In addition, no stabilizing agent, such as formaldehyde, fructose or EDTA, is required during the sample extraction. This method uses aqueous 0.2 N NaOH as the solvent for standard preparation and sample extraction. The sulfites, either prepared from standard sodium sulfite powder or extracted from food samples, are presumed to be unbound SO3-2 in aqueous 0.2 N NaOH (pH > 13), because the bound sulfites in the sample matrix are released at pH > 10. In this study, sulfites in the standard solutions were stable at room temperature (i.e., 15-25 degrees C) for up to 12 days. The lowest standard of the linear calibration curve is set at 1.59 microg/mL SO3-2 (equivalent to 6.36 microg/g sample with no dilution) for analysis of processed dried fruits that would contain high levels (>1000 microg/g) of sulfites. As a consequence, this method typically requires significant dilution of the sample extract. Samples are prepared with a simple procedure of sample compositing, extraction with aqueous 0.2 N NaOH, centrifugation, dilution as needed, and filtration prior to IC. The sulfites in these sample extracts are stable at room temperature for up to 20 h. Using anion IC, the sulfites are eluted under isocratic conditions with 10 mM aqueous sodium carbonate solution as the mobile phase passing through an anion exchange column. The sulfites are easily separated, with an analysis run time of 18 min, regardless of the dried fruit matrix. Recoveries from samples spiked with sodium sulfites were demonstrated to be between 81 and 105% for five different fruit matrixes (apricot, golden grape, white peach, fig, and mango). Overall, this method is simple to perform and effective for the determination of high levels of sulfites in dried fruits.

New Cost-Effective Method for Long-Term Groundwater Monitoring Programs

DTIC Science & Technology

2013-05-01

with a small-volume, gas -tight syringe (< 1 mL) and injected directly into the field-portable GC. Alternatively, the well headspace sample can be...according to manufacturers’ protocols. Isobutylene was used as the calibration standard for the PID. The standard gas mixtures were used for 3-point...monitoring wells are being evaluated: 1) direct headspace sampling, 2) sampling tube with gas permeable membrane, and 3) gas -filled passive vapor

Atmospheric Transformation of Volatile Organic Compounds

DTIC Science & Technology

2008-03-01

Study Analysis Reactant mixtures and standards from product identification experiments were sampled by exposing a 100% polydimethylsiloxane solid...later using the DNPH derivatization method described above and confirmed against a commercial standard. HPLC analysis of the DNPH cartridges also...reaction mixture for a combined total photolysis time ofapproximately 50 seconds. 2.3. Kinetic Study Analysis Samples from kinetic studies were

STANDARDIZED ASSESSMENT METHOD (SAM) FOR RIVERINE MACROINVERTEBRATES

EPA Science Inventory

During the summer of 2001, twelve sites were sampled for macroinvertebrates, six each on the Great Miami and Kentucky Rivers. Sites were chosen in each river from those sampled in the 1999 methods comparison study to reflect a disturbance gradient. At each site, a total distanc...

CTEPP STANDARD OPERATING PROCEDURE FOR COLLECTION OF URINE SAMPLES (SOP-2.14)

EPA Science Inventory

This SOP describes the method for collecting urine samples from the study participants (children and their primary caregivers). Urine samples will be approximate 48-hr collections, collected as spot urine samples accumulated over the 48-hr sampling period. If the household or da...

A thioacidolysis method tailored for higher‐throughput quantitative analysis of lignin monomers

PubMed Central

Foster, Cliff; Happs, Renee M.; Doeppke, Crissa; Meunier, Kristoffer; Gehan, Jackson; Yue, Fengxia; Lu, Fachuang; Davis, Mark F.

2016-01-01

Abstract Thioacidolysis is a method used to measure the relative content of lignin monomers bound by β‐O‐4 linkages. Current thioacidolysis methods are low‐throughput as they require tedious steps for reaction product concentration prior to analysis using standard GC methods. A quantitative thioacidolysis method that is accessible with general laboratory equipment and uses a non‐chlorinated organic solvent and is tailored for higher‐throughput analysis is reported. The method utilizes lignin arylglycerol monomer standards for calibration, requires 1–2 mg of biomass per assay and has been quantified using fast‐GC techniques including a Low Thermal Mass Modular Accelerated Column Heater (LTM MACH). Cumbersome steps, including standard purification, sample concentrating and drying have been eliminated to help aid in consecutive day‐to‐day analyses needed to sustain a high sample throughput for large screening experiments without the loss of quantitation accuracy. The method reported in this manuscript has been quantitatively validated against a commonly used thioacidolysis method and across two different research sites with three common biomass varieties to represent hardwoods, softwoods, and grasses. PMID:27534715

A thioacidolysis method tailored for higher-throughput quantitative analysis of lignin monomers

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

Harman-Ware, Anne E.; Foster, Cliff; Happs, Renee M.

Thioacidolysis is a method used to measure the relative content of lignin monomers bound by β-O-4 linkages. Current thioacidolysis methods are low-throughput as they require tedious steps for reaction product concentration prior to analysis using standard GC methods. A quantitative thioacidolysis method that is accessible with general laboratory equipment and uses a non-chlorinated organic solvent and is tailored for higher-throughput analysis is reported. The method utilizes lignin arylglycerol monomer standards for calibration, requires 1-2 mg of biomass per assay and has been quantified using fast-GC techniques including a Low Thermal Mass Modular Accelerated Column Heater (LTM MACH). Cumbersome steps, includingmore » standard purification, sample concentrating and drying have been eliminated to help aid in consecutive day-to-day analyses needed to sustain a high sample throughput for large screening experiments without the loss of quantitation accuracy. As a result, the method reported in this manuscript has been quantitatively validated against a commonly used thioacidolysis method and across two different research sites with three common biomass varieties to represent hardwoods, softwoods, and grasses.« less

A thioacidolysis method tailored for higher-throughput quantitative analysis of lignin monomers

DOE PAGES

Harman-Ware, Anne E.; Foster, Cliff; Happs, Renee M.; ...

2016-09-14

Thioacidolysis is a method used to measure the relative content of lignin monomers bound by β-O-4 linkages. Current thioacidolysis methods are low-throughput as they require tedious steps for reaction product concentration prior to analysis using standard GC methods. A quantitative thioacidolysis method that is accessible with general laboratory equipment and uses a non-chlorinated organic solvent and is tailored for higher-throughput analysis is reported. The method utilizes lignin arylglycerol monomer standards for calibration, requires 1-2 mg of biomass per assay and has been quantified using fast-GC techniques including a Low Thermal Mass Modular Accelerated Column Heater (LTM MACH). Cumbersome steps, includingmore » standard purification, sample concentrating and drying have been eliminated to help aid in consecutive day-to-day analyses needed to sustain a high sample throughput for large screening experiments without the loss of quantitation accuracy. As a result, the method reported in this manuscript has been quantitatively validated against a commonly used thioacidolysis method and across two different research sites with three common biomass varieties to represent hardwoods, softwoods, and grasses.« less

Validation and long-term evaluation of a modified on-line chiral analytical method for therapeutic drug monitoring of (R,S)-methadone in clinical samples.

PubMed

Ansermot, Nicolas; Rudaz, Serge; Brawand-Amey, Marlyse; Fleury-Souverain, Sandrine; Veuthey, Jean-Luc; Eap, Chin B

2009-08-01

Matrix effects, which represent an important issue in liquid chromatography coupled to mass spectrometry or tandem mass spectrometry detection, should be closely assessed during method development. In the case of quantitative analysis, the use of stable isotope-labelled internal standard with physico-chemical properties and ionization behaviour similar to the analyte is recommended. In this paper, an example of the choice of a co-eluting deuterated internal standard to compensate for short-term and long-term matrix effect in the case of chiral (R,S)-methadone plasma quantification is reported. The method was fully validated over a concentration range of 5-800 ng/mL for each methadone enantiomer with satisfactory relative bias (-1.0 to 1.0%), repeatability (0.9-4.9%) and intermediate precision (1.4-12.0%). From the results obtained during validation, a control chart process during 52 series of routine analysis was established using both intermediate precision standard deviation and FDA acceptance criteria. The results of routine quality control samples were generally included in the +/-15% variability around the target value and mainly in the two standard deviation interval illustrating the long-term stability of the method. The intermediate precision variability estimated in method validation was found to be coherent with the routine use of the method. During this period, 257 trough concentration and 54 peak concentration plasma samples of patients undergoing (R,S)-methadone treatment were successfully analysed for routine therapeutic drug monitoring.

Salmonella detection in poultry samples. Comparison of two commercial real-time PCR systems with culture methods for the detection of Salmonella spp. in environmental and fecal samples of poultry.

PubMed

Sommer, D; Enderlein, D; Antakli, A; Schönenbrücher, H; Slaghuis, J; Redmann, T; Lierz, M

2012-01-01

The efficiency of two commercial PCR methods based on real-time technology, the foodproof® Salmonella detection system and the BAX® PCR Assay Salmonella system was compared to standardized culture methods (EN ISO 6579:2002 - Annex D) for the detection of Salmonella spp. in poultry samples. Four sample matrices (feed, dust, boot swabs, feces) obtained directly from poultry flocks, as well as artificially spiked samples of the same matrices, were used. All samples were tested for Salmonella spp. using culture methods first as the gold standard. In addition samples spiked with Salmonella Enteridis were tested to evaluate the sensitivity of both PCR methods. Furthermore all methods were evaluated in an annual ring-trial of the National Salmonella Reference Laboratory of Germany. Salmonella detection in the matrices feed, dust and boot swabs were comparable in both PCR systems whereas the results from feces differed markedly. The quality, especially the freshness, of the fecal samples had an influence on the sensitivity of the real-time PCR and the results of the culture methods. In fresh fecal samples an initial spiking level of 100cfu/25g Salmonella Enteritidis was detected. Two-days-dried fecal samples allowed the detection of 14cfu/25g. Both real- time PCR protocols appear to be suitable for the detection of Salmonella spp. in all four matrices. The foodproof® system detected eight samples more to be positive compared to the BAX® system, but had a potential false positive result in one case. In 7-days-dried samples none of the methods was able to detect Salmonella likely through letal cell damage. In general the advantage of PCR analyses over the culture method is the reduction of working time from 4-5 days to only 2 days. However, especially for the analysis of fecal samples official validation should be conducted according to the requirement of EN ISO6579:2002 - Annex D.

Direct determination of chromium in infant formulas employing high-resolution continuum source electrothermal atomic absorption spectrometry and solid sample analysis.

PubMed

Silva, Arlene S; Brandao, Geovani C; Matos, Geraldo D; Ferreira, Sergio L C

2015-11-01

The present work proposed an analytical method for the direct determination of chromium in infant formulas employing the high-resolution continuum source electrothermal atomic absorption spectrometry combined with the solid sample analysis (SS-HR-CS ET AAS). Sample masses up to 2.0mg were directly weighted on a solid sampling platform and introduced into the graphite tube. In order to minimize the formation of carbonaceous residues and to improve the contact of the modifier solution with the solid sample, a volume of 10 µL of a solution containing 6% (v/v) H2O2, 20% (v/v) ethanol and 1% (v/v) HNO3 was added. The pyrolysis and atomization temperatures established were 1600 and 2400 °C, respectively, using magnesium as chemical modifier. The calibration technique was evaluated by comparing the slopes of calibration curves established using aqueous and solid standards. This test revealed that chromium can be determined employing the external calibration technique using aqueous standards. Under these conditions, the method developed allows the direct determination of chromium with limit of quantification of 11.5 ng g(-1), precision expressed as relative standard deviation (RSD) in the range of 4.0-17.9% (n=3) and a characteristic mass of 1.2 pg of chromium. The accuracy was confirmed by analysis of a certified reference material of tomato leaves furnished by National Institute of Standards and Technology. The method proposed was applied for the determination of chromium in five different infant formula samples. The chromium content found varied in the range of 33.9-58.1 ng g(-1) (n=3). These samples were also analyzed employing ICP-MS. A statistical test demonstrated that there is no significant difference between the results found by two methods. The chromium concentrations achieved are lower than the maximum limit permissible for chromium in foods by Brazilian Legislation. Copyright © 2015. Published by Elsevier B.V.

Matrix effect and correction by standard addition in quantitative liquid chromatographic-mass spectrometric analysis of diarrhetic shellfish poisoning toxins.

PubMed

Ito, Shinya; Tsukada, Katsuo

2002-01-11

An evaluation of the feasibility of liquid chromatography-mass spectrometry (LC-MS) with atmospheric pressure ionization was made for quantitation of four diarrhetic shellfish poisoning toxins, okadaic acid, dinophysistoxin-1, pectenotoxin-6 and yessotoxin in scallops. When LC-MS was applied to the analysis of scallop extracts, large signal suppressions were observed due to coeluting substances from the column. To compensate for these matrix signal suppressions, the standard addition method was applied. First, the sample was analyzed and then the sample involving the addition of calibration standards is analyzed. Although this method requires two LC-MS runs per analysis, effective correction of quantitative errors was found.

Method of analysis at the U.S. Geological Survey California Water Science Center, Sacramento Laboratory - determination of haloacetic acid formation potential, method validation, and quality-control practices

USGS Publications Warehouse

Zazzi, Barbara C.; Crepeau, Kathryn L.; Fram, Miranda S.; Bergamaschi, Brian A.

2005-01-01

An analytical method for the determination of haloacetic acid formation potential of water samples has been developed by the U.S. Geological Survey California Water Science Center Sacramento Laboratory. The haloacetic acid formation potential is measured by dosing water samples with chlorine under specified conditions of pH, temperature, incubation time, darkness, and residual-free chlorine. The haloacetic acids formed are bromochloroacetic acid, bromodichloroacetic acid, dibromochloroacetic acid, dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, tribromoacetic acid, and trichloroacetic acid. They are extracted, methylated, and then analyzed using a gas chromatograph equipped with an electron capture detector. Method validation experiments were performed to determine the method accuracy, precision, and detection limit for each of the compounds. Method detection limits for these nine haloacetic acids ranged from 0.11 to 0.45 microgram per liter. Quality-control practices include the use of blanks, quality-control samples, calibration verification standards, surrogate recovery, internal standard, matrix spikes, and duplicates.

Comparison of Standard Culture-Based Method to Culture-Independent Method for Evaluation of Hygiene Effects on the Hand Microbiome

PubMed Central

Leff, J.; Henley, J.; Tittl, J.; De Nardo, E.; Butler, M.; Griggs, R.; Fierer, N.

2017-01-01

ABSTRACT Hands play a critical role in the transmission of microbiota on one’s own body, between individuals, and on environmental surfaces. Effectively measuring the composition of the hand microbiome is important to hand hygiene science, which has implications for human health. Hand hygiene products are evaluated using standard culture-based methods, but standard test methods for culture-independent microbiome characterization are lacking. We sampled the hands of 50 participants using swab-based and glove-based methods prior to and following four hand hygiene treatments (using a nonantimicrobial hand wash, alcohol-based hand sanitizer [ABHS], a 70% ethanol solution, or tap water). We compared results among culture plate counts, 16S rRNA gene sequencing of DNA extracted directly from hands, and sequencing of DNA extracted from culture plates. Glove-based sampling yielded higher numbers of unique operational taxonomic units (OTUs) but had less diversity in bacterial community composition than swab-based sampling. We detected treatment-induced changes in diversity only by using swab-based samples (P < 0.001); we were unable to detect changes with glove-based samples. Bacterial cell counts significantly decreased with use of the ABHS (P < 0.05) and ethanol control (P < 0.05). Skin hydration at baseline correlated with bacterial abundances, bacterial community composition, pH, and redness across subjects. The importance of the method choice was substantial. These findings are important to ensure improvement of hand hygiene industry methods and for future hand microbiome studies. On the basis of our results and previously published studies, we propose recommendations for best practices in hand microbiome research. PMID:28351915

Comparison of Collection Methods for Fecal Samples for Discovery Metabolomics in Epidemiologic Studies.

PubMed

Loftfield, Erikka; Vogtmann, Emily; Sampson, Joshua N; Moore, Steven C; Nelson, Heidi; Knight, Rob; Chia, Nicholas; Sinha, Rashmi

2016-11-01

The gut metabolome may be associated with the incidence and progression of numerous diseases. The composition of the gut metabolome can be captured by measuring metabolite levels in the feces. However, there are little data describing the effect of fecal sample collection methods on metabolomic measures. We collected fecal samples from 18 volunteers using four methods: no solution, 95% ethanol, fecal occult blood test (FOBT) cards, and fecal immunochemical test (FIT). One set of samples was frozen after collection (day 0), and for 95% ethanol, FOBT, and FIT, a second set was frozen after 96 hours at room temperature. We evaluated (i) technical reproducibility within sample replicates, (ii) stability after 96 hours at room temperature for 95% ethanol, FOBT, and FIT, and (iii) concordance of metabolite measures with the putative "gold standard," day 0 samples without solution. Intraclass correlation coefficients (ICC) estimating technical reproducibility were high for replicate samples for each collection method. ICCs estimating stability at room temperature were high for 95% ethanol and FOBT (median ICC > 0.87) but not FIT (median ICC = 0.52). Similarly, Spearman correlation coefficients (r s ) estimating metabolite concordance with the "gold standard" were higher for 95% ethanol (median r s = 0.82) and FOBT (median r s = 0.70) than for FIT (median r s = 0.40). Metabolomic measurements appear reproducible and stable in fecal samples collected with 95% ethanol or FOBT. Concordance with the "gold standard" is highest with 95% ethanol and acceptable with FOBT. Future epidemiologic studies should collect feces using 95% ethanol or FOBT if interested in studying fecal metabolomics. Cancer Epidemiol Biomarkers Prev; 25(11); 1483-90. ©2016 AACR. ©2016 American Association for Cancer Research.

Cultural and Molecular Evidence of Legionella spp. Colonization in Dental Unit Waterlines: Which Is the Best Method for Risk Assessment?

PubMed

Ditommaso, Savina; Giacomuzzi, Monica; Ricciardi, Elisa; Zotti, Carla M

2016-02-06

Legionella spp. are ubiquitous in aquatic habitats and water distribution systems, including dental unit waterlines (DUWLs). The aim of the present study was to determine the prevalence of Legionella in DUWLs and tap water samples using PMA-qPCR and standard culture methods. The total viable counts (TVCs) of aerobic heterotrophic bacteria in the samples were also determined. Legionella spp. were detected and quantified using the modified ISO 11731 culture method. Extracted genomic DNA was analysed using the iQ-Check Quanti Legionella spp. kit, and the TVCs were determined according to the ISO protocol 6222. Legionella spp. were detected in 100% of the samples using the PMA-qPCR method, whereas these bacteria were detected in only 7% of the samples using the culture method. The number of colony forming units (CFUs) of the TVCs in the DUWL and tap water samples differed, with the bacterial load being significantly lower in the tap water samples (p-value = 0). The counts obtained were within the Italian standard range established for potable water in only 5% of the DUWL water samples and in 77% of the tap water samples. Our results show that the level of Legionella spp. contamination determined using the culture method does not reflect the true scale of the problem, and consequently we recommend testing for the presence of aerobic heterotrophic bacteria based on the assumption that Legionella spp. are components of biofilms.

Cultural and Molecular Evidence of Legionella spp. Colonization in Dental Unit Waterlines: Which Is the Best Method for Risk Assessment?

PubMed Central

Ditommaso, Savina; Giacomuzzi, Monica; Ricciardi, Elisa; Zotti, Carla M.

2016-01-01

Legionella spp. are ubiquitous in aquatic habitats and water distribution systems, including dental unit waterlines (DUWLs). The aim of the present study was to determine the prevalence of Legionella in DUWLs and tap water samples using PMA-qPCR and standard culture methods. The total viable counts (TVCs) of aerobic heterotrophic bacteria in the samples were also determined. Legionella spp. were detected and quantified using the modified ISO 11731 culture method. Extracted genomic DNA was analysed using the iQ-Check Quanti Legionella spp. kit, and the TVCs were determined according to the ISO protocol 6222. Legionella spp. were detected in 100% of the samples using the PMA-qPCR method, whereas these bacteria were detected in only 7% of the samples using the culture method. The number of colony forming units (CFUs) of the TVCs in the DUWL and tap water samples differed, with the bacterial load being significantly lower in the tap water samples (p-value = 0). The counts obtained were within the Italian standard range established for potable water in only 5% of the DUWL water samples and in 77% of the tap water samples. Our results show that the level of Legionella spp. contamination determined using the culture method does not reflect the true scale of the problem, and consequently we recommend testing for the presence of aerobic heterotrophic bacteria based on the assumption that Legionella spp. are components of biofilms. PMID:26861373

Semi-Supervised Tripled Dictionary Learning for Standard-dose PET Image Prediction using Low-dose PET and Multimodal MRI

PubMed Central

Wang, Yan; Ma, Guangkai; An, Le; Shi, Feng; Zhang, Pei; Lalush, David S.; Wu, Xi; Pu, Yifei; Zhou, Jiliu; Shen, Dinggang

2017-01-01

Objective To obtain high-quality positron emission tomography (PET) image with low-dose tracer injection, this study attempts to predict the standard-dose PET (S-PET) image from both its low-dose PET (L-PET) counterpart and corresponding magnetic resonance imaging (MRI). Methods It was achieved by patch-based sparse representation (SR), using the training samples with a complete set of MRI, L-PET and S-PET modalities for dictionary construction. However, the number of training samples with complete modalities is often limited. In practice, many samples generally have incomplete modalities (i.e., with one or two missing modalities) that thus cannot be used in the prediction process. In light of this, we develop a semi-supervised tripled dictionary learning (SSTDL) method for S-PET image prediction, which can utilize not only the samples with complete modalities (called complete samples) but also the samples with incomplete modalities (called incomplete samples), to take advantage of the large number of available training samples and thus further improve the prediction performance. Results Validation was done on a real human brain dataset consisting of 18 subjects, and the results show that our method is superior to the SR and other baseline methods. Conclusion This work proposed a new S-PET prediction method, which can significantly improve the PET image quality with low-dose injection. Significance The proposed method is favorable in clinical application since it can decrease the potential radiation risk for patients. PMID:27187939

Comparison of gel column, card, and cartridge techniques for dog erythrocyte antigen 1.1 blood typing

PubMed Central

Seth, Mayank; Jackson, Karen V.; Winzelberg, Sarah; Giger, Urs

2012-01-01

Objective To compare accuracy and ease of use of a card agglutination assay, an immunochromatographic cartridge method, and a gel-based method for canine blood typing. Sample Blood samples from 52 healthy blood donor dogs, 10 dogs with immune-mediated hemolytic anemia (IMHA), and 29 dogs with other diseases. Procedures Blood samples were tested in accordance with manufacturer guidelines. Samples with low PCVs were created by the addition of autologous plasma to separately assess the effects of anemia on test results. Results Compared with a composite reference standard of agreement between 2 methods, the gel-based method was found to be 100% accurate. The card agglutination assay was 89% to 91% accurate, depending on test interpretation, and the immunochromatographic cartridge method was 93% accurate but 100% specific. Errors were observed more frequently in samples from diseased dogs, particularly those with IMHA. In the presence of persistent autoagglutination, dog erythrocyte antigen (DEA) 1.1 typing was not possible, except with the immunochromatographic cartridge method. Conclusions and Clinical Relevance The card agglutination assay and immunochromatographic cartridge method, performed by trained personnel, were suitable for in-clinic emergency DEA 1.1 blood typing. There may be errors, particularly for samples from dogs with IMHA, and the immunochromatographic cartridge method may have an advantage of allowing typing of samples with persistent autoagglutination. The laboratory gel-based method would be preferred for routine DEA 1.1 typing of donors and patients if it is available and time permits. Current DEA 1.1 typing techniques appear to be appropriately standardized and easy to use. PMID:22280380

New method for determination of ten pesticides in human blood.

PubMed

García-Repetto, R; Giménez, M P; Repetto, M

2001-01-01

An analytical method was developed for precise identification and quantitation of 10 pesticides in human blood. The pesticides studied, which have appeared frequently in actual cases, were endosulfan, lindane, parathion, ethyl-azinphos, diazinon, malathion, alachlor, tetradifon, fenthion and dicofol (o-p' and p-p' isomers). The current method replaces an earlier method which involved liquid-liquid extraction with a mixture of n-hexane-benzene (1 + 1). The extraction is performed by solid-phase extraction, with C18 cartridges and 2 internal standards, perthane and triphenylphosphate. Eluates were analyzed by gas chromatography (GC) with nitrogen-phosphorus and electrochemical detectors. Results were confirmed by GC-mass spectrometry in the electron impact mode. Blood blank samples spiked with 2 standard mixtures and an internal standard were used for quantitation. Mean recoveries ranged from 71.83 to 97.10%. Detection and quantitation limits are reported for each pesticide. Examples are provided to show the application of the present method to actual samples.

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of chromium in water by graphite furnace atomic absorption spectrophotometry

USGS Publications Warehouse

McLain, B.J.

1993-01-01

Graphite furnace atomic absorption spectrophotometry is a sensitive, precise, and accurate method for the determination of chromium in natural water samples. The detection limit for this analytical method is 0.4 microg/L with a working linear limit of 25.0 microg/L. The precision at the detection limit ranges from 20 to 57 percent relative standard deviation (RSD) with an improvement to 4.6 percent RSD for concentrations more than 3 microg/L. Accuracy of this method was determined for a variety of reference standards that was representative of the analytical range. The results were within the established standard deviations. Samples were spiked with known concentrations of chromium with recoveries ranging from 84 to 122 percent. In addition, a comparison of data between graphite furnace atomic absorption spectrophotometry and direct-current plasma atomic emission spectrometry resulted in suitable agreement between the two methods, with an average deviation of +/- 2.0 microg/L throughout the analytical range.

Verification of spectrophotometric method for nitrate analysis in water samples

NASA Astrophysics Data System (ADS)

Kurniawati, Puji; Gusrianti, Reny; Dwisiwi, Bledug Bernanti; Purbaningtias, Tri Esti; Wiyantoko, Bayu

2017-12-01

The aim of this research was to verify the spectrophotometric method to analyze nitrate in water samples using APHA 2012 Section 4500 NO3-B method. The verification parameters used were: linearity, method detection limit, level of quantitation, level of linearity, accuracy and precision. Linearity was obtained by using 0 to 50 mg/L nitrate standard solution and the correlation coefficient of standard calibration linear regression equation was 0.9981. The method detection limit (MDL) was defined as 0,1294 mg/L and limit of quantitation (LOQ) was 0,4117 mg/L. The result of a level of linearity (LOL) was 50 mg/L and nitrate concentration 10 to 50 mg/L was linear with a level of confidence was 99%. The accuracy was determined through recovery value was 109.1907%. The precision value was observed using % relative standard deviation (%RSD) from repeatability and its result was 1.0886%. The tested performance criteria showed that the methodology was verified under the laboratory conditions.

CTEPP STANDARD OPERATING PROCEDURE FOR HANDLING MISSING SAMPLES AND DATA (SOP-2.24)

EPA Science Inventory

This SOP describes the method for handling missing samples or data. Missing samples or data will be identified as soon as possible during field sampling. It provides guidance to collect the missing sample or data and document the reason for the missing sample or data.

A cryopreservation method for Pasteurella multocida from wetland samples

USGS Publications Warehouse

Moore, Melody K.; Shadduck, D.J.; Goldberg, Diana R.; Samuel, M.D.

1998-01-01

A cryopreservation method and improved isolation techniques for detection of Pasteurella multocida from wetland samples were developed. Wetland water samples were collected in the field, diluted in dimethyl sulfoxide (DMSO, final concentration 10%), and frozen at -180 C in a liquid nitrogen vapor shipper. Frozen samples were transported to the laboratory where they were subsequently thawed and processed in Pasteurella multocida selective broth (PMSB) to isolate P. multocida. This method allowed for consistent isolation of 2 to 18 organisms/ml from water seeded with known concentrations of P. multocida. The method compared favorably with the standard mouse inoculation method and allowed for preservation of the samples until they could be processed in the laboratory.

Performing skin microbiome research: A method to the madness

PubMed Central

Kong, Heidi H.; Andersson, Björn; Clavel, Thomas; Common, John E.; Jackson, Scott A.; Olson, Nathan D.; Segre, Julia A.; Traidl-Hoffmann, Claudia

2017-01-01

Growing interest in microbial contributions to human health and disease has increasingly led investigators to examine the microbiome in both healthy skin and cutaneous disorders, including acne, psoriasis and atopic dermatitis. The need for common language, effective study design, and validated methods are critical for high-quality, standardized research. Features, unique to skin, pose particular challenges when conducting microbiome research. This review discusses microbiome research standards and highlights important factors to consider, including clinical study design, skin sampling, sample processing, DNA sequencing, control inclusion, and data analysis. PMID:28063650

Determination of vitamin A (retinol) in infant formula and adult nutritionals by liquid chromatography: First Action 2011.15.

PubMed

DeVries, Jonathan W; Silvera, Karlene R; McSherry, Elliot; Dowell, Dawn

2012-01-01

During the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting," held on June 29, 2011, an Expert Review Panel (ERP) reviewed the method for the "Determination of Vitamins A (Retinol) and E (alpha-Tocopherol) in Foods by Liquid Chromatography: Collaborative Study," published by Jonathan W. DeVries and Karlene R. Silvera in J. AOAC Int. in 2002. After evaluation of the original validation data, an ERP agreed in June 2011 that the method meets standard method performance requirements (SMPRs) for vitamin A, as articulated by the Stakeholder Panel on Infant Formula and Adult Nutritionals. The ERP granted the method First Action status, applicable to determining vitamin A in ready-to-eat infant and adult nutritional formula. In an effort to achieve Final Action status, it was recommended that additional information be generated for different types of infant and adult nutritional formula matrixes at varied concentration levels as indicated in the vitamin A (retinol) SMPR. Existing AOAC LC methods are suited for specific vitamin A analytical applications. The original method differs from existing methods in that it can be used to assay samples in all nine sectors of the food matrix. One sector of the food matrix was powdered infant formula and gave support for the First Action approval for vitamin A in infant and adult nutritional formula. In this method, standards and test samples are saponified in basic ethanol-water solution, neutralized, and diluted, converting fats to fatty acids and retinol esters to retinol. Retinol is quantitated by an LC method, using UV detection at 313 or 328 nm for retinol. Vitamin concentration is calculated by comparison of the peak heights or peak areas of retinol in test samples with those of standards.

Evaluation of alternative model selection criteria in the analysis of unimodal response curves using CART

USGS Publications Warehouse

Ribic, C.A.; Miller, T.W.

1998-01-01

We investigated CART performance with a unimodal response curve for one continuous response and four continuous explanatory variables, where two variables were important (ie directly related to the response) and the other two were not. We explored performance under three relationship strengths and two explanatory variable conditions: equal importance and one variable four times as important as the other. We compared CART variable selection performance using three tree-selection rules ('minimum risk', 'minimum risk complexity', 'one standard error') to stepwise polynomial ordinary least squares (OLS) under four sample size conditions. The one-standard-error and minimum-risk-complexity methods performed about as well as stepwise OLS with large sample sizes when the relationship was strong. With weaker relationships, equally important explanatory variables and larger sample sizes, the one-standard-error and minimum-risk-complexity rules performed better than stepwise OLS. With weaker relationships and explanatory variables of unequal importance, tree-structured methods did not perform as well as stepwise OLS. Comparing performance within tree-structured methods, with a strong relationship and equally important explanatory variables, the one-standard-error-rule was more likely to choose the correct model than were the other tree-selection rules 1) with weaker relationships and equally important explanatory variables; and 2) under all relationship strengths when explanatory variables were of unequal importance and sample sizes were lower.

Nonclinical dose formulation analysis method validation and sample analysis.

PubMed

Whitmire, Monica Lee; Bryan, Peter; Henry, Teresa R; Holbrook, John; Lehmann, Paul; Mollitor, Thomas; Ohorodnik, Susan; Reed, David; Wietgrefe, Holly D

2010-12-01

Nonclinical dose formulation analysis methods are used to confirm test article concentration and homogeneity in formulations and determine formulation stability in support of regulated nonclinical studies. There is currently no regulatory guidance for nonclinical dose formulation analysis method validation or sample analysis. Regulatory guidance for the validation of analytical procedures has been developed for drug product/formulation testing; however, verification of the formulation concentrations falls under the framework of GLP regulations (not GMP). The only current related regulatory guidance is the bioanalytical guidance for method validation. The fundamental parameters for bioanalysis and formulation analysis validations that overlap include: recovery, accuracy, precision, specificity, selectivity, carryover, sensitivity, and stability. Divergence in bioanalytical and drug product validations typically center around the acceptance criteria used. As the dose formulation samples are not true "unknowns", the concept of quality control samples that cover the entire range of the standard curve serving as the indication for the confidence in the data generated from the "unknown" study samples may not always be necessary. Also, the standard bioanalytical acceptance criteria may not be directly applicable, especially when the determined concentration does not match the target concentration. This paper attempts to reconcile the different practices being performed in the community and to provide recommendations of best practices and proposed acceptance criteria for nonclinical dose formulation method validation and sample analysis.

Sensitive diagnosis of cutaneous leishmaniasis by lesion swab sampling coupled to qPCR

PubMed Central

ADAMS, EMILY R.; GOMEZ, MARIA ADELAIDA; SCHESKE, LAURA; RIOS, RUBY; MARQUEZ, RICARDO; COSSIO, ALEXANDRA; ALBERTINI, AUDREY; SCHALLIG, HENK; SARAVIA, NANCY GORE

2015-01-01

SUMMARY Variation in clinical accuracy of molecular diagnostic methods for cutaneous leishmaniasis (CL) is commonly observed depending on the sample source, the method of DNA recovery and the molecular test. Few attempts have been made to compare these variables. Two swab and aspirate samples from lesions of patients with suspected CL (n = 105) were evaluated alongside standard diagnosis by microscopic detection of amastigotes or culture of parasites from lesion material. Three DNA extraction methods were compared: Qiagen on swab and aspirate specimens, Isohelix on swabs and Boil/Spin of lesion aspirates. Recovery of Leishmania DNA was evaluated for each sample type by real-time polymerase chain reaction detection of parasitic 18S rDNA, and the diagnostic accuracy of the molecular method determined. Swab sampling combined with Qiagen DNA extraction was the most efficient recovery method for Leishmania DNA, and was the most sensitive (98%; 95% CI: 91–100%) and specific (84%; 95% CI: 64–95%) approach. Aspirated material was less sensitive at 80% (95% CI: 70–88%) and 61% (95% CI: 50–72%) when coupled to Qiagen or Boil-Spin DNA extraction, respectively. Swab sampling of lesions was painless, simple to perform and coupled with standardized DNA extraction enhances the feasibility of molecular diagnosis of CL. PMID:25111885

Random vs. systematic sampling from administrative databases involving human subjects.

PubMed

Hagino, C; Lo, R J

1998-09-01

Two sampling techniques, simple random sampling (SRS) and systematic sampling (SS), were compared to determine whether they yield similar and accurate distributions for the following four factors: age, gender, geographic location and years in practice. Any point estimate within 7 yr or 7 percentage points of its reference standard (SRS or the entire data set, i.e., the target population) was considered "acceptably similar" to the reference standard. The sampling frame was from the entire membership database of the Canadian Chiropractic Association. The two sampling methods were tested using eight different sample sizes of n (50, 100, 150, 200, 250, 300, 500, 800). From the profile/characteristics, summaries of four known factors [gender, average age, number (%) of chiropractors in each province and years in practice], between- and within-methods chi 2 tests and unpaired t tests were performed to determine whether any of the differences [descriptively greater than 7% or 7 yr] were also statistically significant. The strengths of the agreements between the provincial distributions were quantified by calculating the percent agreements for each (provincial pairwise-comparison methods). Any percent agreement less than 70% was judged to be unacceptable. Our assessments of the two sampling methods (SRS and SS) for the different sample sizes tested suggest that SRS and SS yielded acceptably similar results. Both methods started to yield "correct" sample profiles at approximately the same sample size (n > 200). SS is not only convenient, it can be recommended for sampling from large databases in which the data are listed without any inherent order biases other than alphabetical listing by surname.

Development of methodologies for identification and quantification of hazardous air pollutants from turbine engine emissions.

PubMed

Anneken, David; Striebich, Richard; DeWitt, Matthew J; Klingshirn, Christopher; Corporan, Edwin

2015-03-01

Aircraft turbine engines are a significant source of particulate matter (PM) and gaseous emissions in the vicinity of airports and military installations. Hazardous air pollutants (HAPs) (e.g., formaldehyde, benzene, naphthalene and other compounds) associated with aircraft emissions are an environmental concern both in flight and at ground level. Therefore, effective sampling, identification, and accurate measurement of these trace species are important to assess their environmental impact. This effort evaluates two established ambient air sampling and analysis methods, U.S. Environmental Protection Agency (EPA) Method TO-11A and National Institute for Occupational Safety and Health (NIOSH) Method 1501, for potential use to quantify HAPs from aircraft turbine engines. The techniques were used to perform analysis of the exhaust from a T63 turboshaft engine, and were examined using certified gas standards transferred through the heated sampling systems used for engine exhaust gaseous emissions measurements. Test results show that the EPA Method TO-11A (for aldehydes) and NIOSH Method 1501 (for semivolatile hydrocarbons) were effective techniques for the sampling and analysis of most HAPs of interest. Both methods showed reasonable extraction efficiencies of HAP species from the sorbent tubes, with the exception of acrolein, styrene, and phenol, which were not well quantified. Formaldehyde measurements using dinitrophenylhydrazine (DNPH) tubes (EPA method TO-11A) were accurate for gas-phase standards, and compared favorably to measurements using gas-phase Fourier-transform infrared (FTIR) spectroscopy. In general, these two standard methodologies proved to be suitable techniques for field measurement of turbine engine HAPs within a reasonable (5-10 minutes) sampling period. Details of the tests, the analysis methods, calibration procedures, and results from the gas standards and T63 engine tested using a conventional JP-8 jet fuel are provided. HAPs from aviation-related sources are important because of their adverse health and environmental impacts in and around airports and flight lines. Simpler, more convenient techniques to measure the important HAPs, especially aldehydes and volatile organic HAPs, are needed to provide information about their occurrence and assist in the development of engines that emit fewer harmful emissions.

40 CFR 80.582 - What are the sampling and testing methods for the fuel marker?

Code of Federal Regulations, 2010 CFR

2010-07-01

... developed by a Voluntary Consensus-Based Standards Body, such as the American Society for Testing and... test method documentation, including a description of the technology and/or instrumentation that makes... this standard from the American Society for Testing and Materials, 100 Barr Harbor Dr., West...

40 CFR 80.582 - What are the sampling and testing methods for the fuel marker?

Code of Federal Regulations, 2011 CFR

2011-07-01

... developed by a Voluntary Consensus-Based Standards Body, such as the American Society for Testing and... test method documentation, including a description of the technology and/or instrumentation that makes... this standard from the American Society for Testing and Materials, 100 Barr Harbor Dr., West...

Simultaneous spectrophotometric determination of valsartan and hydrochlorothiazide by H-point standard addition method and partial least squares regression.

PubMed

Lakshmi, Karunanidhi Santhana; Lakshmi, Sivasubramanian

2011-03-01

Simultaneous determination of valsartan and hydrochlorothiazide by the H-point standard additions method (HPSAM) and partial least squares (PLS) calibration is described. Absorbances at a pair of wavelengths, 216 and 228 nm, were monitored with the addition of standard solutions of valsartan. Results of applying HPSAM showed that valsartan and hydrochlorothiazide can be determined simultaneously at concentration ratios varying from 20:1 to 1:15 in a mixed sample. The proposed PLS method does not require chemical separation and spectral graphical procedures for quantitative resolution of mixtures containing the titled compounds. The calibration model was based on absorption spectra in the 200-350 nm range for 25 different mixtures of valsartan and hydrochlorothiazide. Calibration matrices contained 0.5-3 μg mL-1 of both valsartan and hydrochlorothiazide. The standard error of prediction (SEP) for valsartan and hydrochlorothiazide was 0.020 and 0.038 μg mL-1, respectively. Both proposed methods were successfully applied to the determination of valsartan and hydrochlorothiazide in several synthetic and real matrix samples.

Passive Sampling in Regulatory Chemical Monitoring of Nonpolar Organic Compounds in the Aquatic Environment.

PubMed

Booij, Kees; Robinson, Craig D; Burgess, Robert M; Mayer, Philipp; Roberts, Cindy A; Ahrens, Lutz; Allan, Ian J; Brant, Jan; Jones, Lisa; Kraus, Uta R; Larsen, Martin M; Lepom, Peter; Petersen, Jördis; Pröfrock, Daniel; Roose, Patrick; Schäfer, Sabine; Smedes, Foppe; Tixier, Céline; Vorkamp, Katrin; Whitehouse, Paul

2016-01-05

We reviewed compliance monitoring requirements in the European Union, the United States, and the Oslo-Paris Convention for the protection of the marine environment of the North-East Atlantic, and evaluated if these are met by passive sampling methods for nonpolar compounds. The strengths and shortcomings of passive sampling are assessed for water, sediments, and biota. Passive water sampling is a suitable technique for measuring concentrations of freely dissolved compounds. This method yields results that are incompatible with the EU's quality standard definition in terms of total concentrations in water, but this definition has little scientific basis. Insufficient quality control is a present weakness of passive sampling in water. Laboratory performance studies and the development of standardized methods are needed to improve data quality and to encourage the use of passive sampling by commercial laboratories and monitoring agencies. Successful prediction of bioaccumulation based on passive sampling is well documented for organisms at the lower trophic levels, but requires more research for higher levels. Despite the existence of several knowledge gaps, passive sampling presently is the best available technology for chemical monitoring of nonpolar organic compounds. Key issues to be addressed by scientists and environmental managers are outlined.

Brief communication: the relation between standard error of the estimate and sample size of histomorphometric aging methods.

PubMed

Hennig, Cheryl; Cooper, David

2011-08-01

Histomorphometric aging methods report varying degrees of precision, measured through Standard Error of the Estimate (SEE). These techniques have been developed from variable samples sizes (n) and the impact of n on reported aging precision has not been rigorously examined in the anthropological literature. This brief communication explores the relation between n and SEE through a review of the literature (abstracts, articles, book chapters, theses, and dissertations), predictions based upon sampling theory and a simulation. Published SEE values for age prediction, derived from 40 studies, range from 1.51 to 16.48 years (mean 8.63; sd: 3.81 years). In general, these values are widely distributed for smaller samples and the distribution narrows as n increases--a pattern expected from sampling theory. For the two studies that have samples in excess of 200 individuals, the SEE values are very similar (10.08 and 11.10 years) with a mean of 10.59 years. Assuming this mean value is a 'true' characterization of the error at the population level, the 95% confidence intervals for SEE values from samples of 10, 50, and 150 individuals are on the order of ± 4.2, 1.7, and 1.0 years, respectively. While numerous sources of variation potentially affect the precision of different methods, the impact of sample size cannot be overlooked. The uncertainty associated with SEE values derived from smaller samples complicates the comparison of approaches based upon different methodology and/or skeletal elements. Meaningful comparisons require larger samples than have frequently been used and should ideally be based upon standardized samples. Copyright © 2011 Wiley-Liss, Inc.

BACTERIOLOGICAL ANALYSIS WITH SAMPLING AND SAMPLE PRESERVATION SPECIFICS

EPA Science Inventory

Current federal regulations (40CFR 503) specify that under certain conditions treated municipal biosolids must be analyzed for fecal coliform or salmonellae. The regulations state that representative samples of biosolids must be collected and analyzed using standard methods. Th...

Optimizing fish sampling for fish - mercury bioaccumulation factors

USGS Publications Warehouse

Scudder Eikenberry, Barbara C.; Riva-Murray, Karen; Knightes, Christopher D.; Journey, Celeste A.; Chasar, Lia C.; Brigham, Mark E.; Bradley, Paul M.

2015-01-01

Fish Bioaccumulation Factors (BAFs; ratios of mercury (Hg) in fish (Hgfish) and water (Hgwater)) are used to develop Total Maximum Daily Load and water quality criteria for Hg-impaired waters. Both applications require representative Hgfish estimates and, thus, are sensitive to sampling and data-treatment methods. Data collected by fixed protocol from 11 streams in 5 states distributed across the US were used to assess the effects of Hgfish normalization/standardization methods and fish sample numbers on BAF estimates. Fish length, followed by weight, was most correlated to adult top-predator Hgfish. Site-specific BAFs based on length-normalized and standardized Hgfish estimates demonstrated up to 50% less variability than those based on non-normalized Hgfish. Permutation analysis indicated that length-normalized and standardized Hgfish estimates based on at least 8 trout or 5 bass resulted in mean Hgfish coefficients of variation less than 20%. These results are intended to support regulatory mercury monitoring and load-reduction program improvements.

Gear and seasonal bias associated with abundance and size structure estimates for lentic freshwater fishes

USGS Publications Warehouse

Fischer, Jesse R.; Quist, Michael C.

2014-01-01

All freshwater fish sampling methods are biased toward particular species, sizes, and sexes and are further influenced by season, habitat, and fish behavior changes over time. However, little is known about gear-specific biases for many common fish species because few multiple-gear comparison studies exist that have incorporated seasonal dynamics. We sampled six lakes and impoundments representing a diversity of trophic and physical conditions in Iowa, USA, using multiple gear types (i.e., standard modified fyke net, mini-modified fyke net, sinking experimental gill net, bag seine, benthic trawl, boat-mounted electrofisher used diurnally and nocturnally) to determine the influence of sampling methodology and season on fisheries assessments. Specifically, we describe the influence of season on catch per unit effort, proportional size distribution, and the number of samples required to obtain 125 stock-length individuals for 12 species of recreational and ecological importance. Mean catch per unit effort generally peaked in the spring and fall as a result of increased sampling effectiveness in shallow areas and seasonal changes in habitat use (e.g., movement offshore during summer). Mean proportional size distribution decreased from spring to fall for white bass Morone chrysops, largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and black crappie Pomoxis nigromaculatus, suggesting selectivity for large and presumably sexually mature individuals in the spring and summer. Overall, the mean number of samples required to sample 125 stock-length individuals was minimized in the fall with sinking experimental gill nets, a boat-mounted electrofisher used at night, and standard modified nets for 11 of the 12 species evaluated. Our results provide fisheries scientists with relative comparisons between several recommended standard sampling methods and illustrate the effects of seasonal variation on estimates of population indices that will be critical to the future development of standardized sampling methods for freshwater fish in lentic ecosystems.

Agreement and Diagnostic Performance of FITNESSGRAM®, International Obesity Task Force, and Hungarian National BMI Standards

ERIC Educational Resources Information Center

Laurson, Kelly R.; Welk, Gregory J.; Marton, Orsolya; Kaj, Mónika; Csányi, Tamás

2015-01-01

Purpose: This study examined agreement between all 3 standards (as well as relative diagnostic associations with metabolic syndrome) using a representative sample of youth from the Hungarian National Youth Fitness Study. Method: Body mass index (BMI) was assessed in a field sample of 2,352 adolescents (ages 10-18.5 years) and metabolic syndrome…

Detailed description of oil shale organic and mineralogical heterogeneity via fourier transform infrared mircoscopy

USGS Publications Warehouse

Washburn, Kathryn E.; Birdwell, Justin E.; Foster, Michael; Gutierrez, Fernando

2015-01-01

Mineralogical and geochemical information on reservoir and source rocks is necessary to assess and produce from petroleum systems. The standard methods in the petroleum industry for obtaining these properties are bulk measurements on homogenized, generally crushed, and pulverized rock samples and can take from hours to days to perform. New methods using Fourier transform infrared (FTIR) spectroscopy have been developed to more rapidly obtain information on mineralogy and geochemistry. However, these methods are also typically performed on bulk, homogenized samples. We present a new approach to rock sample characterization incorporating multivariate analysis and FTIR microscopy to provide non-destructive, spatially resolved mineralogy and geochemistry on whole rock samples. We are able to predict bulk mineralogy and organic carbon content within the same margin of error as standard characterization techniques, including X-ray diffraction (XRD) and total organic carbon (TOC) analysis. Validation of the method was performed using two oil shale samples from the Green River Formation in the Piceance Basin with differing sedimentary structures. One sample represents laminated Green River oil shales, and the other is representative of oil shale breccia. The FTIR microscopy results on the oil shales agree with XRD and LECO TOC data from the homogenized samples but also give additional detail regarding sample heterogeneity by providing information on the distribution of mineral phases and organic content. While measurements for this study were performed on oil shales, the method could also be applied to other geological samples, such as other mudrocks, complex carbonates, and soils.

Improvements in the gaseous hydrogen-water equilibration technique for hydrogen isotope ratio analysis

USGS Publications Warehouse

Coplen, T.B.; Wildman, J.D.; Chen, J.

1991-01-01

Improved precision in the H2-H2O equilibration method for ??D analysis has been achieved in an automated system. Reduction in 1-?? standard deviation of a single mass-spectrometer analysis to 1.3??? is achieved by (1) bonding catalyst to glass rods and assigning use to specific equilibration chambers to monitor performance of catalyst, (2) improving the apparatus design, and (3) reducing the H3+ contribution of the mass-spectrometer ion source. For replicate analysis of a water sample, the standard deviation improved to 0.8???. H2S-bearing samples and samples as small as 0.1 mL can be analyzed routinely with this method.

Airborne environmental endotoxin: a cross-validation of sampling and analysis techniques.

PubMed Central

Walters, M; Milton, D; Larsson, L; Ford, T

1994-01-01

A standard method for measurement of airborne environmental endotoxin was developed and field tested in a fiberglass insulation-manufacturing facility. This method involved sampling with a capillary-pore membrane filter, extraction in buffer using a sonication bath, and analysis by the kinetic-Limulus assay with resistant-parallel-line estimation (KLARE). Cross-validation of the extraction and assay method was performed by comparison with methanolysis of samples followed by 3-hydroxy fatty acid (3-OHFA) analysis by gas chromatography-mass spectrometry. Direct methanolysis of filter samples and methanolysis of buffer extracts of the filters yielded similar 3-OHFA content (P = 0.72); the average difference was 2.1%. Analysis of buffer extracts for endotoxin content by the KLARE method and by gas chromatography-mass spectrometry for 3-OHFA content produced similar results (P = 0.23); the average difference was 0.88%. The source of endotoxin was gram-negative bacteria growing in recycled washwater used to clean the insulation-manufacturing equipment. The endotoxin and bacteria become airborne during spray cleaning operations. The types of 3-OHFAs in bacteria cultured from the washwater, present in the washwater and in the air, were similar. Virtually all of the bacteria cultured from air and water were gram negative composed mostly of two species, Deleya aesta and Acinetobacter johnsonii. Airborne countable bacteria correlated well with endotoxin (r2 = 0.64). Replicate sampling showed that results with the standard sampling, extraction, and Limulus assay by the KLARE method were highly reproducible (95% confidence interval for endotoxin measurement +/- 0.28 log10). These results demonstrate the accuracy, precision, and sensitivity of the standard procedure proposed for airborne environmental endotoxin. PMID:8161191

Sampling methods for the study of pneumococcal carriage: a systematic review.

PubMed

Gladstone, R A; Jefferies, J M; Faust, S N; Clarke, S C

2012-11-06

Streptococcus pneumoniae is an important pathogen worldwide. Accurate sampling of S. pneumoniae carriage is central to surveillance studies before and following conjugate vaccination programmes to combat pneumococcal disease. Any bias introduced during sampling will affect downstream recovery and typing. Many variables exist for the method of collection and initial processing, which can make inter-laboratory or international comparisons of data complex. In February 2003, a World Health Organisation working group published a standard method for the detection of pneumococcal carriage for vaccine trials to reduce or eliminate variability. We sought to describe the variables associated with the sampling of S. pneumoniae from collection to storage in the context of the methods recommended by the WHO and those used in pneumococcal carriage studies since its publication. A search of published literature in the online PubMed database was performed on the 1st June 2012, to identify published studies that collected pneumococcal carriage isolates, conducted after the publication of the WHO standard method. After undertaking a systematic analysis of the literature, we show that a number of differences in pneumococcal sampling protocol continue to exist between studies since the WHO publication. The majority of studies sample from the nasopharynx, but the choice of swab and swab transport media is more variable between studies. At present there is insufficient experimental data that supports the optimal sensitivity of any standard method. This may have contributed to incomplete adoption of the primary stages of the WHO detection protocol, alongside pragmatic or logistical issues associated with study design. Consequently studies may not provide a true estimate of pneumococcal carriage. Optimal sampling of carriage could lead to improvements in downstream analysis and the evaluation of pneumococcal vaccine impact and extrapolation to pneumococcal disease control therefore further in depth comparisons would be of value. Copyright © 2012 Elsevier Ltd. All rights reserved.

\\tLaboratory Environmental Sample Disposal Information Document - Companion to Standardized Analytical Methods for Environmental Restoration Following Homeland Security Events (SAM) – Revision 5.0

EPA Pesticide Factsheets

Document is intended to provide general guidelines for use byEPA and EPA-contracted laboratories when disposing of samples and associated analytical waste following use of the analytical methods listed in SAM.

21 CFR 177.1950 - Vinyl chloride-ethylene copolymers.

Code of Federal Regulations, 2013 CFR

2013-04-01

... deciliter per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution... vinyl chloride-ethylene copol-ymer per 100 grams of sample tested as determined from the organic... using duplicate blanks. Approximately 400 grams of sample (accurately weighed) shall be placed in a 2...

21 CFR 177.1950 - Vinyl chloride-ethylene copolymers.

Code of Federal Regulations, 2012 CFR

2012-04-01

... deciliter per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution... vinyl chloride-ethylene copol-ymer per 100 grams of sample tested as determined from the organic... using duplicate blanks. Approximately 400 grams of sample (accurately weighed) shall be placed in a 2...

Laser based water equilibration method for d18O determination of water samples

NASA Astrophysics Data System (ADS)

Mandic, Magda; Smajgl, Danijela; Stoebener, Nils

2017-04-01

Determination of d18O with water equilibration method using mass spectrometers equipped with equilibration unit or Gas Bench is known already for many years. Now, with development of laser spectrometers this extends methods and possibilities to apply different technologies in laboratory but also in the field. The Thermo Scientific™ Delta Ray™ Isotope Ratio Infrared Spectrometer (IRIS) analyzer with the Universal Reference Interface (URI) Connect and Teledyne Cetac ASX-7100 offers high precision and throughput of samples. It employs optical spectroscopy for continuous measurement of isotope ratio values and concentration of carbon dioxide in ambient air, and also for analysis of discrete samples from vials, syringes, bags, or other user-provided sample containers. Test measurements and conformation of precision and accuracy of method determination d18O in water samples were done in Thermo Fisher application laboratory with three lab standards, namely ANST, Ocean II and HBW. All laboratory standards were previously calibrated with international reference material VSMOW2 and SLAP2 to assure accuracy of the isotopic values of the water. With method that we present in this work achieved repeatability and accuracy are 0.16‰ and 0.71‰, respectively, which fulfill requirements of regulatory method for wine and must after equilibration with CO2.

40 CFR 60.46 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Fossil-Fuel... the results of the four pairs of samples. (c) When combinations of fossil fuels or fossil fuel and...

40 CFR 60.46 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Fossil-Fuel... the results of the four pairs of samples. (c) When combinations of fossil fuels or fossil fuel and...

Hypothesis Testing Using Factor Score Regression

PubMed Central

Devlieger, Ines; Mayer, Axel; Rosseel, Yves

2015-01-01

In this article, an overview is given of four methods to perform factor score regression (FSR), namely regression FSR, Bartlett FSR, the bias avoiding method of Skrondal and Laake, and the bias correcting method of Croon. The bias correcting method is extended to include a reliable standard error. The four methods are compared with each other and with structural equation modeling (SEM) by using analytic calculations and two Monte Carlo simulation studies to examine their finite sample characteristics. Several performance criteria are used, such as the bias using the unstandardized and standardized parameterization, efficiency, mean square error, standard error bias, type I error rate, and power. The results show that the bias correcting method, with the newly developed standard error, is the only suitable alternative for SEM. While it has a higher standard error bias than SEM, it has a comparable bias, efficiency, mean square error, power, and type I error rate. PMID:29795886

Evaluation of the furosine and homoarginine methods for determining reactive lysine in rumen-undegraded protein.

PubMed

Boucher, S E; Pedersen, C; Stein, H H; Schwab, C G

2009-08-01

Three samples of soybean meal (SBM), 3 samples of expeller SBM (SoyPlus, West Central Cooperative, Ralston, IA), 5 samples of distillers dried grains with solubles (DDGS), and 5 samples of fish meal were used to evaluate the furosine and homoarginine procedures to estimate reactive Lys in the rumen-undegraded protein fraction (RUP-Lys). One sample each of SBM, expeller SBM, and DDGS were subjected to additional heat treatment in the lab to ensure there was a wide range in reactive RUP-Lys content among the samples. Furosine is a secondary product of the initial stages of the Maillard reaction and can be used to calculate blocked Lys. Homoarginine is formed via the reaction of reactive Lys with O-methylisourea and can be used to calculate the concentration of reactive Lys. In previous experiments, each sample was ruminally incubated in situ for 16 h, and standardized RUP-Lys digestibility of the samples was determined in cecectomized roosters. All rumen-undegraded residue (RUR) samples were analyzed for furosine and Lys; however, only 9 of the 16 samples contained furosine, and only the 4 unheated DDGS samples contained appreciable amounts of furosine. Blocked RUP-Lys was calculated from the furosine and Lys concentrations of the RUR. Both the intact feed and RUR samples were evaluated using the homoarginine method. All samples were incubated with an O-methylisourea/BaOH solution for 72 h and analyzed for Lys and homoarginine concentrations. Reactive Lys concentrations of the intact feeds and RUR were calculated. Results of the experiment indicate that blocked RUP-Lys determined via the furosine method was negatively correlated with standardized RUP-Lys digestibility, and reactive RUP-Lys determined via the guanidination method was positively correlated with standardized RUP-Lys digestibility. Reactive Lys concentrations of the intact samples were also highly correlated with RUP-Lys digestibility. In conclusion, the furosine assay is useful in predicting RUP-Lys digestibility of DDGS samples, and the guanidination procedure can be used to predict RUP-Lys digestibility of SBM, expeller SBM, DDGS, and fish meal samples.

Comparative evaluation of chromogenic agar CM1046 and mFC agar for detection of E. coli and thermotolerant coliform bacteria from water samples.

PubMed

Wohlsen, T D

2011-08-01

The equivalence of Oxoid (CM 1046) Brilliance((TM)) E. coli/coliform selective agar to mFC agar, as used in the Australian/New Zealand Standard Method to detect thermotolerant coliforms and Escherichia coli in water samples, was assessed. A total of 244 water samples were analysed in parallel over a 5-month period. Sewage effluent samples (n = 131, sites = 43), freshwater (n = 62, sites = 18) and marine/brackish water samples (n = 51, sites = 23) were analysed. The Wilcoxon matched-pairs signed-ranks test showed a varying degree of statistical difference between the two methods. All matrices had a higher recovery in the trial method. Enterococci faecalis, Aeromonas spp. and Vibrio spp. did not grow on the CM1046 agar, and Pseudomonas aeruginosa and Enterobacter aerogenes were inhibited. The use of CM 1046 for the detection and enumeration of E. coli and thermotolerant coliforms in water samples is a suitable alternative to the AS/NZS Standard Method. The use of CM1046 agar was less labour intensive and time consuming, as no secondary confirmation steps were required. Confirmed results could be reported within 24 h of sample analysis, as compared to 48 h with the reference method. Public health concerns can be addressed in a more efficient manner. © 2011 Unitywater. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

The Infinitesimal Jackknife with Exploratory Factor Analysis

ERIC Educational Resources Information Center

Zhang, Guangjian; Preacher, Kristopher J.; Jennrich, Robert I.

2012-01-01

The infinitesimal jackknife, a nonparametric method for estimating standard errors, has been used to obtain standard error estimates in covariance structure analysis. In this article, we adapt it for obtaining standard errors for rotated factor loadings and factor correlations in exploratory factor analysis with sample correlation matrices. Both…

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory : determination of polycyclic aromatic hydrocarbon compounds in sediment by gas chromatography/mass spectrometry

USGS Publications Warehouse

Olson, Mary C.; Iverson, Jana L.; Furlong, Edward T.; Schroeder, Michael P.

2004-01-01

A method for the determination of 28 polycyclic aromatic hydrocarbons (PAHs) and 25 alkylated PAH homolog groups in sediment samples is described. The compounds are extracted from sediment by solvent extraction, followed by partial isolation using high-performance gel permeation chromatography. The compounds are identified and uantitated using capillary-column gas chromatography/mass spectrometry. The report presents performance data for full-scan ion monitoring. Method detection limits in laboratory reagent matrix samples range from 1.3 to 5.1 micrograms per kilogram for the 28 PAHs. The 25 groups of alkylated PAHs are homologs of five groups of isomeric parent PAHs. Because of the lack of authentic standards, these homologs are reported semiquantitatively using a response factor from a parent PAH or a specific alkylated PAH. Precision data for the alkylated PAH homologs are presented using two different standard reference manuals produced by the National Institute of Standards and Technology: SRM 1941b and SRM 1944. The percent relative standard deviations for identified alkylated PAH homolog groups ranged from 1.55 to 6.98 for SRM 1941b and from 6.11 to 12.0 for SRM 1944. Homolog group concentrations reported under this method include the concentrations of individually identified compounds that are members of the group. Organochlorine (OC) pesticides--including toxaphene, polychlorinated biphenyls (PCBs), and organophosphate (OP) pesticides--can be isolated simultaneously using this method. In brief, sediment samples are centrifuged to remove excess water and extracted overnight with dichloromethan (95 percent) and methanol (5 percent). The extract is concentrated and then filtered through a 0.2-micrometer polytetrafluoroethylene syringe filter. The PAH fraction is isolated by quantitatively injecting an aliquot of sample onto two polystyrene-divinylbenzene gel-permeation chromatographic columns connected in series. The compounds are eluted with dichloromethane, a PAH fraction is collected, and a portion of the coextracted interferences, including elemental sulfur, is separated and discarded. The extract is solvent exchanged, the volume is reduced, and internal standard is added. Sample analysis is completed using a gas chromatograph/mass spectrometer and full-scan acquisition.

Quantitative analysis of concrete using portable x-ray fluorescence: Method development and validation

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

Washington, Aaron L.; Narrows, William; Christian, Jonathan H.

During Decommissioning and Demolition (D&D) activities at SRS, it is important that the building be screened for radionuclides and heavy metals to ensure that the proper safety and disposal metrics are in place. A major source of contamination at DOE facilities is the accumulation of mercury contamination, from nuclear material processing and Liquid Waste System (LWS). This buildup of mercury could possibly cause harm to any demolition crew or the environment should this material be released. The current standard method is to take core samples in various places in the facility and use X-ray fluorescence (XRF) to detect the contamination.more » This standard method comes with a high financial value due to the security levels of these sample facilities with unknown contamination levels. Here in we propose the use of portable XRF units to detect for this contamination on-site. To validate this method, the instrument has to be calibrated to detect the heavy metal contamination, be both precise with the known elemental concentrations and consistent with its actual results of a sample concrete and pristine contaminant, and be able to detect changes in the sample concrete’s composition. After receiving the various concrete samples with their compositions found by a XRF wave-dispersive method, the calibration factor’s linear regressions were adjusted to give the baseline concentration of the concrete with no contamination. Samples of both concrete and concrete/flyash were evaluated; their standard deviations revealed that the measurements were consistent with the known composition. Finally, the samples were contaminated with different concentrations of sodium tungsten dihydrate, allowed to air dry, and measured. When the contaminated samples were analyzed, the heavy metal contamination was seen within the spectrum of the instrument, but there was not a trend of quantification based on the concentration of the solution.« less

[Fast determination of induction period of motor gasoline using Fourier transform attenuated total reflection infrared spectroscopy].

PubMed

Liu, Ya-Fei; Yuan, Hong-Fu; Song, Chun-Feng; Xie, Jin-Chun; Li, Xiao-Yu; Yan, De-Lin

2014-11-01

A new method is proposed for the fast determination of the induction period of gasoline using Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR). A dedicated analysis system with the function of spectral measurement, data processing, display and storage was designed and integrated using a Fourier transform infrared spectrometer module and chemometric software. The sample presentation accessory designed which has advantages of constant optical path, convenient sample injection and cleaning is composed of a nine times reflection attenuated total reflectance (ATR) crystal of zinc selenide (ZnSe) coated with a diamond film and a stainless steel lid with sealing device. The influence of spectral scanning number and repeated sample loading times on the spectral signal-to-noise ratio was studied. The optimum spectral scanning number is 15 times and the optimum sample loading number is 4 times. Sixty four different gasoline samples were collected from the Beijing-Tianjin area and the induction period values were determined as reference data by standard method GB/T 8018-87. The infrared spectra of these samples were collected in the operating condition mentioned above using the dedicated fast analysis system. Spectra were pretreated using mean centering and 1st derivative to reduce the influence of spectral noise and baseline shift A PLS calibration model for the induction period was established by correlating the known induction period values of the samples with their spectra. The correlation coefficient (R2), standard error of calibration (SEC) and standard error of prediction (SEP) of the model are 0.897, 68.3 and 91.9 minutes, respectively. The relative deviation of the model for gasoline induction period prediction is less than 5%, which meets the requirements of repeatability tolerance in GB method. The new method is simple and fast. It takes no more than 3 minutes to detect one sample. Therefore, the method is feasible for implementing fast determination of gasoline induction period, and of a positive meaning in the evaluation of fuel quality.

Comparability of HbA1c and lipids measured with dried blood spot versus venous samples: a systematic review and meta-analysis

PubMed Central

2014-01-01

Background Levels of haemoglobin A1c (HbA1c) and blood lipids are important determinants of risk in patients with diabetes. Standard analysis methods based upon venous blood samples can be logistically challenging in resource-poor settings where much of the diabetes epidemic is occurring. Dried blood spots (DBS) provide a simple alternative method for sample collection but the comparability of data from analyses based on DBS is not well established. Methods We conducted a systematic review and meta-analysis to define the association of findings for HbA1c and blood lipids for analyses based upon standard methods compared to DBS. The Cochrane, Embase and Medline databases were searched for relevant reports and summary regression lines were estimated. Results 705 abstracts were found by the initial electronic search with 6 further reports identified by manual review of the full papers. 16 studies provided data for one or more outcomes of interest. There was a close agreement between the results for HbA1c assays based on venous and DBS samples (DBS = 0.9858venous + 0.3809), except for assays based upon affinity chromatography. Significant adjustment was required for assays of total cholesterol (DBS = 0.6807venous + 1.151) but results for triglycerides (DBS = 0.9557venous + 0.1427) were directly comparable. Conclusions For HbA1c and selected blood lipids, assays based on DBS samples are clearly associated with assays based on standard venous samples. There are, however, significant uncertainties about the nature of these associations and there is a need for standardisation of the sample collection, transportation, storage and analysis methods before the technique can be considered mainstream. This should be a research priority because better elucidation of metabolic risks in resource poor settings, where venous sampling is infeasible, will be key to addressing the global epidemic of cardiovascular diseases. PMID:25045323

Quality by design (QbD) based development and validation of an HPLC method for amiodarone hydrochloride and its impurities in the drug substance.

PubMed

Karmarkar, S; Yang, X; Garber, R; Szajkovics, A; Koberda, M

2014-11-01

The USP monograph describes an HPLC method for seven impurities in the amiodarone drug substance using a L1 column, 4.6mm×150mm, 5μm packing (PF listed ODS2 GL-Science, Inertsil column) at 30°C with detection at 240nm. The standard contains 0.01mg/mL of amiodarone, and USP specified impurities D and E with a resolution requirement of NLT 3.5 between peaks D and E. Impurities in a 5mg/mL sample are quantitated against the standard. Impurity A peak elutes just before peak D. We observed two problems with the method; the column lot-to-lot variability resulted in unresolved A, D, and E peaks, and peak D in the sample preparation eluted much later than that in the standard solution. Therefore, optimization experiments were conducted on the USP method following the QbD approach with Fusion AE™ software (S-Matrix Corporation). The resulting optimized conditions were within the allowable changes per USP 〈621〉. Lot-to-lot variability was negligible with the Atlantis T3 (Waters Corporation) L1 column. Peak D retention time remained constant from standard to sample. The optimized method was validated in terms of accuracy, precision, linearity, range, LOQ/LOD, specificity, robustness, equivalency to the USP method, and solution stability. The QbD based development helped in generating a design space and operating space with knowledge of all method performance characteristics and limitations and successful method robustness within the operating space. Copyright © 2014 Elsevier B.V. All rights reserved.

The Impact of Using Different Methods to Assess Completeness of 24-Hour Urine Collection on Estimating Dietary Sodium.

PubMed

Wielgosz, Andreas; Robinson, Christopher; Mao, Yang; Jiang, Ying; Campbell, Norm R C; Muthuri, Stella; Morrison, Howard

2016-06-01

The standard for population-based surveillance of dietary sodium intake is 24-hour urine testing; however, this may be affected by incomplete urine collection. The impact of different indirect methods of assessing completeness of collection on estimated sodium ingestion has not been established. The authors enlisted 507 participants from an existing community study in 2009 to collect 24-hour urine samples. Several methods of assessing completeness of urine collection were tested. Mean sodium intake varied between 3648 mg/24 h and 7210 mg/24 h depending on the method used. Excluding urine samples collected for longer or shorter than 24 hours increased the estimated urine sodium excretion, even when corrections for the variation in timed collections were applied. Until an accurate method of indirectly assessing completeness of urine collection is identified, the gold standard of administering para-aminobenzoic acid is recommended. Efforts to ensure participants collect complete urine samples are also warranted. ©2015 Wiley Periodicals, Inc.

A modified method for COD determination of solid waste, using a commercial COD kit and an adapted disposable weighing support.

PubMed

André, L; Pauss, A; Ribeiro, T

2017-03-01

The chemical oxygen demand (COD) is an essential parameter in waste management, particularly when monitoring wet anaerobic digestion processes. An adapted method to determine COD was developed for solid waste (total solids >15%). This method used commercial COD tubes and did not require sample dilution. A homemade plastic weighing support was used to transfer the solid sample into COD tubes. Potassium hydrogen phthalate and glucose used as standards showed an excellent repeatability. A small underestimation of the theoretical COD value (standard values around 5% lower than theoretical values) was also observed, mainly due to the intrinsic COD of the weighing support and to measurement uncertainties. The adapted COD method was tested using various solid wastes in the range of 1-8 mg COD , determining the COD of dried and ground cellulose, cattle manure, straw and a mixed-substrate sample. This new adapted method could be used to monitor and design dry anaerobic digestion processes.

[Determination of 21 fragrance allergens in toys by gas chromatography-ion trap mass spectrometry].

PubMed

Lü, Qing; Zang, Qing; Bai, Hua; Li, Haiyu; Kang, Suyuan; Wang, Chao

2012-05-01

A method of gas chromatography-ion trap mass spectrometry (GC-IT-MS) was developed for the determination of 21 fragrance allergens in sticker toys, plush toys and plastic toys. The experimental conditions, such as sample pretreatment conditions, and the analytical conditions of GC-IT-MS, were optimized. The sticker toy samples and plush toy samples were extracted with acetone by ultrasonic wave, and the extracts were separated on an Agilent HP-1 MS column (50 m x 0.2 mm x 0.5 microm), then determined by IT-MS and quantified by external standard method. The plastic toy samples were extracted by the dissolution-precipitation approach, cleaned up with an Envi-carb solid phase extraction column and concentrated by rotary evaporation and nitrogen blowing, then determined by GC-IT-MS and quantified by external standard method. The calibration curves showed good linearity in the range of 0.002-50 mg/L with the correlation coefficients greater than 0.996 8. The limits of quantification (LOQ, S/N > 10) were 0.02-40 mg/kg. The average recoveries of the target compounds spiked in the sample at three concentration levels were in the range of 82.2%-110.8% with the relative standard deviations (RSDs) of 0.6%-10.5%. These results show that this method is accurate and sensitive for the qualitative and quantitative determination of the 21 fragrance allergens in the 3 types of toys.

Quantitative determination of atmospheric hydroperoxyl radical

DOEpatents

Springston, Stephen R.; Lloyd, Judith; Zheng, Jun

2007-10-23

A method for the quantitative determination of atmospheric hydroperoxyl radical comprising: (a) contacting a liquid phase atmospheric sample with a chemiluminescent compound which luminesces on contact with hydroperoxyl radical; (b) determining luminescence intensity from the liquid phase atmospheric sample; and (c) comparing said luminescence intensity from the liquid phase atmospheric sample to a standard luminescence intensity for hydroperoxyl radical. An apparatus for automating the method is also included.

Grain reconstruction of porous media: application to a Bentheim sandstone.

PubMed

Thovert, J-F; Adler, P M

2011-05-01

The two-point correlation measured on a thin section can be used to derive the probability density of the radii of a population of penetrable spheres. The geometrical, transport, and deformation properties of samples derived by this method compare well with the properties of the digitized real sample and of the samples generated by the standard grain reconstruction method. © 2011 American Physical Society

NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR COLLECTION, STORAGE AND SHIPMENT OF DRINKING AND TAP WATER SAMPLES FOR VOCS (EPA METHOD 524.2) (UA-F-18.1)

EPA Science Inventory

The purpose of this SOP is to describe the collection, storage, and shipment of tap and drinking water samples for analysis by EPA method 524.2 (revision 4.0) for the NHEXAS Arizona project. This SOP provides a brief description of the sample containers, collection, preservation...

40 CFR 63.7824 - What test methods and other procedures must I use to establish and demonstrate initial compliance...

Code of Federal Regulations, 2010 CFR

2010-07-01

... select sampling port locations and the number of traverse points. Sampling ports must be located at the... Method 25 (40 CFR part 60, appendix A), milligrams per dry standard cubic meters (mg/dscm) for each day... = Conversion factor (mg/lb); and K = Daily production rate of sinter, tons/hr. (4) Continue the sampling and...

40 CFR 63.7824 - What test methods and other procedures must I use to establish and demonstrate initial compliance...

Code of Federal Regulations, 2011 CFR

2011-07-01

... select sampling port locations and the number of traverse points. Sampling ports must be located at the... Method 25 (40 CFR part 60, appendix A), milligrams per dry standard cubic meters (mg/dscm) for each day... = Conversion factor (mg/lb); and K = Daily production rate of sinter, tons/hr. (4) Continue the sampling and...

Determination of non-certified levoglucosan, sugar polyols and ergosterol in NIST Standard Reference Material 1649a

NASA Astrophysics Data System (ADS)

Pomata, Donatella; Di Filippo, Patrizia; Riccardi, Carmela; Buiarelli, Francesca; Gallo, Valentina

2014-02-01

Organic component of airborne particulate matter originates from both natural and anthropogenic sources whose contributions can be identified through the analysis of chemical markers. The validation of analytical methods for analysis of compounds used as chemical markers is of great importance especially if they must be determined in rather complex matrices. Currently, standard reference materials (SRM) with certified values for all those analytes are not available. In this paper, we report a method for the simultaneous determination of levoglucosan and xylitol as tracers for biomass burning emissions, and arabitol, mannitol and ergosterol as biomarkers for airborne fungi in SRM 1649a, by GC/MS. Their quantitative analysis in SRM 1649a was carried out using both internal standard calibration curves and standard addition method. A matrix effect was observed for all analytes, minor for levoglucosan and major for polyols and ergosterol. The results related to levoglucosan around 160 μg g-1 agreed with those reported by other authors, while no comparison was possible for xylitol (120 μg g-1), arabitol (15 μg g-1), mannitol (18 μg g-1), and ergosterol (0.5 μg g-1). The analytical method used for SRM 1649a was also applied to PM10 samples collected in Rome during four seasonal sampling campaigns. The ratios between annual analyte concentrations in PM10 samples and in SRM 1649a were of the same order of magnitude although particulate matter samples analyzed were collected in two different sites and periods.

Measurement of water-soluble B vitamins in infant formula by liquid chromatography/tandem mass spectrometry.

PubMed

Huang, Min; Winters, Doug; Crowley, Richard; Sullivan, Darryl

2009-01-01

A method has been developed for the simultaneous measurement of multiple B vitamins (i.e., B1, B2, B3, B5, and B6) in infant formulas by LC-MSIMS. The vitamins were extracted with acidic solvent, followed by protein precipitation at a pH range of 4.5 to 5.5, and filtered. This simplified procedure eliminates many of the potential sources of laboratory error and facilitates rapid and efficient analysis. As is common in most cases, isotope internal standards were added to account for variations in sample preparation, as well as changes in MS measurement. In this method, isotope-labeled internal standards of B1, B3, B5, and B6 were used. The factors affecting analytical performance were investigated and optimized. In addition, the stability of these vitamins in the extraction solution was investigated. An acidic condition (5 mM HCl) was applied to successfully stabilize B1, which had shown a decrease in signal when other solvents were used. The quantitative extraction and good stability allowed isotope standards to be added to the filtered sample solution, instead of to the extraction solvent. The addition of the isotope to the small portion of the filtered sample solution significantly reduces cost. A comprehensive evaluation of the analysis of the standard reference material and good spike recovery of the vitamins (100 +/- 6%) demonstrates the accuracy of the method. The results for commercially available infant formula samples were also compared with those obtained using the current microbiological method.

Sample sizes needed for specified margins of relative error in the estimates of the repeatability and reproducibility standard deviations.

PubMed

McClure, Foster D; Lee, Jung K

2005-01-01

Sample size formulas are developed to estimate the repeatability and reproducibility standard deviations (Sr and S(R)) such that the actual error in (Sr and S(R)) relative to their respective true values, sigmar and sigmaR, are at predefined levels. The statistical consequences associated with AOAC INTERNATIONAL required sample size to validate an analytical method are discussed. In addition, formulas to estimate the uncertainties of (Sr and S(R)) were derived and are provided as supporting documentation. Formula for the Number of Replicates Required for a Specified Margin of Relative Error in the Estimate of the Repeatability Standard Deviation.

A Randomized Trial of Sheathed vs. Standard Forceps for Obtaining Uncontaminated Biopsy Specimens of Microbiota from the Terminal Ileum

PubMed Central

Dave, Maneesh; Johnson, Laura A.; Walk, Seth; Young, Vincent B.; Stidham, Ryan W.; Chaudhary, Meghana N.; FunNell, Jessica; Higgins, Peter D.R.

2014-01-01

Background The study of intestinal microbiota has been revolutionized by the use of molecular methods, including terminal restriction fragment length polymorphism (T-RFLP) analysis. A number of microbiota studies of Crohn’s disease patients have examined samples from stool or from the neoterminal ileum with a standard biopsy forceps, which could be contaminated by colonic bacteria when the forceps passes through the colonoscope channel. Objective To determine whether sheathed biopsy forceps are able to obtain terminal ileal microbiota samples with less colonic bacterial contamination compared to unsheathed (standard) biopsy forceps. Design Prospective randomized single center-study. Patients and Methods We obtained four (paired) biopsy specimens from adjacent locations in the terminal ileum using the sheathed and standard forceps of 27 consecutive subjects undergoing colonoscopy and characterized the microbiota using T-RFLP. We calculated the Bray Curtis similarity index (BCI) between samples (sheathed vs. unsheathed forceps) within patients and tested for significant differences across all patients. Results There was not a significant difference in the microbial diversity of samples obtained using sheathed vs. unsheathed forceps. The difference in microbial diversity between patients was much greater than the variability within patients by proximal vs. distal site or by forceps type. Limitations T-RFLP is based on PCR amplification, so it is not always sensitive to rare bacterial species. Conclusion Standard unsheathed forceps appear to be sufficient for microbiota sample collection from the terminal ileum. PMID:21317176

Evaluation of digestion methods for analysis of trace metals in mammalian tissues and NIST 1577c.

PubMed

Binder, Grace A; Metcalf, Rainer; Atlas, Zachary; Daniel, Kenyon G

2018-02-15

Digestion techniques for ICP analysis have been poorly studied for biological samples. This report describes an optimized method for analysis of trace metals that can be used across a variety of sample types. Digestion methods were tested and optimized with the analysis of trace metals in cancerous as compared to normal tissue as the end goal. Anthropological, forensic, oncological and environmental research groups can employ this method reasonably cheaply and safely whilst still being able to compare between laboratories. We examined combined HNO 3 and H 2 O 2 digestion at 170 °C for human, porcine and bovine samples whether they are frozen, fresh or lyophilized powder. Little discrepancy is found between microwave digestion and PFA Teflon pressure vessels. The elements of interest (Cu, Zn, Fe and Ni) yielded consistently higher and more accurate values on standard reference material than samples heated to 75 °C or samples that utilized HNO 3 alone. Use of H 2 SO 4 does not improve homogeneity of the sample and lowers precision during ICP analysis. High temperature digestions (>165 °C) using a combination of HNO 3 and H 2 O 2 as outlined are proposed as a standard technique for all mammalian tissues, specifically, human tissues and yield greater than 300% higher values than samples digested at 75 °C regardless of the acid or acid combinations used. The proposed standardized technique is designed to accurately quantify potential discrepancies in metal loads between cancerous and healthy tissues and applies to numerous tissue studies requiring quick, effective and safe digestions. Copyright © 2017 Elsevier Inc. All rights reserved.

MRI-determined liver proton density fat fraction, with MRS validation: Comparison of regions of interest sampling methods in patients with type 2 diabetes.

PubMed

Vu, Kim-Nhien; Gilbert, Guillaume; Chalut, Marianne; Chagnon, Miguel; Chartrand, Gabriel; Tang, An

2016-05-01

To assess the agreement between published magnetic resonance imaging (MRI)-based regions of interest (ROI) sampling methods using liver mean proton density fat fraction (PDFF) as the reference standard. This retrospective, internal review board-approved study was conducted in 35 patients with type 2 diabetes. Liver PDFF was measured by magnetic resonance spectroscopy (MRS) using a stimulated-echo acquisition mode sequence and MRI using a multiecho spoiled gradient-recalled echo sequence at 3.0T. ROI sampling methods reported in the literature were reproduced and liver mean PDFF obtained by whole-liver segmentation was used as the reference standard. Intraclass correlation coefficients (ICCs), Bland-Altman analysis, repeated-measures analysis of variance (ANOVA), and paired t-tests were performed. ICC between MRS and MRI-PDFF was 0.916. Bland-Altman analysis showed excellent intermethod agreement with a bias of -1.5 ± 2.8%. The repeated-measures ANOVA found no systematic variation of PDFF among the nine liver segments. The correlation between liver mean PDFF and ROI sampling methods was very good to excellent (0.873 to 0.975). Paired t-tests revealed significant differences (P < 0.05) with ROI sampling methods that exclusively or predominantly sampled the right lobe. Significant correlations with mean PDFF were found with sampling methods that included higher number of segments, total area equal or larger than 5 cm(2) , or sampled both lobes (P = 0.001, 0.023, and 0.002, respectively). MRI-PDFF quantification methods should sample each liver segment in both lobes and include a total surface area equal or larger than 5 cm(2) to provide a close estimate of the liver mean PDFF. © 2015 Wiley Periodicals, Inc.

Improving the analysis of composite endpoints in rare disease trials.

PubMed

McMenamin, Martina; Berglind, Anna; Wason, James M S

2018-05-22

Composite endpoints are recommended in rare diseases to increase power and/or to sufficiently capture complexity. Often, they are in the form of responder indices which contain a mixture of continuous and binary components. Analyses of these outcomes typically treat them as binary, thus only using the dichotomisations of continuous components. The augmented binary method offers a more efficient alternative and is therefore especially useful for rare diseases. Previous work has indicated the method may have poorer statistical properties when the sample size is small. Here we investigate small sample properties and implement small sample corrections. We re-sample from a previous trial with sample sizes varying from 30 to 80. We apply the standard binary and augmented binary methods and determine the power, type I error rate, coverage and average confidence interval width for each of the estimators. We implement Firth's adjustment for the binary component models and a small sample variance correction for the generalized estimating equations, applying the small sample adjusted methods to each sub-sample as before for comparison. For the log-odds treatment effect the power of the augmented binary method is 20-55% compared to 12-20% for the standard binary method. Both methods have approximately nominal type I error rates. The difference in response probabilities exhibit similar power but both unadjusted methods demonstrate type I error rates of 6-8%. The small sample corrected methods have approximately nominal type I error rates. On both scales, the reduction in average confidence interval width when using the adjusted augmented binary method is 17-18%. This is equivalent to requiring a 32% smaller sample size to achieve the same statistical power. The augmented binary method with small sample corrections provides a substantial improvement for rare disease trials using composite endpoints. We recommend the use of the method for the primary analysis in relevant rare disease trials. We emphasise that the method should be used alongside other efforts in improving the quality of evidence generated from rare disease trials rather than replace them.

Chapter 3. Determination of semivolatile organic compounds and polycyclic aromatic hydrocarbons in solids by gas chromatography/mass spectrometry

USGS Publications Warehouse

Zaugg, Steven D.; Burkhardt, Mark R.; Burbank, Teresa L.; Olson, Mary C.; Iverson, Jana L.; Schroeder, Michael P.

2006-01-01

A method for the determination of 38 polycyclic aromatic hydrocarbons (PAHs) and semivolatile organic compounds in solid samples is described. Samples are extracted using a pressurized solvent extraction system. The compounds of interest are extracted from the solid sample twice at 13,800 kilopascals; first at 120 degrees Celsius using a water/isopropyl alcohol mixture (50:50, volume-to-volume ratio), and then the sample is extracted at 200 degrees Celsius using a water/isopropyl alcohol mixture (80:20, volume-to-volume ratio). The compounds are isolated using disposable solid-phase extraction (SPE) cartridges containing divinylbenzene-vinylpyrrolidone copolymer resin. The cartridges are dried with nitrogen gas, and then sorbed compounds are eluted from the SPE material using a dichloromethane/diethyl ether mixture (80:20, volume-to-volume ratio) and passed through a sodium sulfate/Florisil SPE cartridge to remove residual water and to further clean up the extract. The concentrated extract is solvent exchanged into ethyl acetate and the solvent volume reduced to 0.5 milliliter. Internal standard compounds are added prior to analysis by capillary-column gas chromatography/mass spectrometry. Comparisons of PAH data for 28 sediment samples extracted by Soxhlet and the accelerated solvent extraction (ASE) method described in this report produced similar results. Extraction of PAH compounds from standard reference material using this method also compared favorably with Soxhlet extraction. The recoveries of PAHs less than molecular weight 202 (pyrene or fluoranthene) are higher by up to 20 percent using this ASE method, whereas the recoveries of PAHs greater than or equal to molecular weight 202 are equivalent. This ASE method of sample extraction of solids has advantages over conventional Soxhlet extraction by increasing automation of the extraction process, reducing extraction time, and using less solvent. Extract cleanup also is greatly simplified because SPE replaces commonly used gel permeation chromatography. The performance of the method (as expressed by mean recoveries and mean precision) was determined using Ottawa sand, a commercially available topsoil, and an environmental stream sediment, fortified at 1.5 and 15 micrograms per compound. Recoveries of PAH and semivolatile compounds in Ottawa sand samples fortified at 1.5 micrograms averaged 88 percent ? 9.4 percent relative standard deviation, and calculated initial method detection limits per compound averaged 14 micrograms per kilogram, assuming a 25-gram sample size. The recovery for 1,2,4-trichlorobenzene is less than 60 percent; thus, the concentration of this compound will always be reported as estimated with the E remark code. The analysis of 25 alkylated PAH homolog groups also can be determined with this method with extra data analysis and review, but because of the lack of authentic reference standard compounds, these results are considered to be semiquantitative. The PAH homolog groups are quantitated using the response factor of a parent PAH method compound, if available. Precision data for the alkylated PAH homologs detected in a marine sediment standard reference material (SRM 1944) also are presented to document and demonstrate method capability.

Gross alpha and beta activity analyses in urine-a routine laboratory method for internal human radioactivity detection.

PubMed

Chen, Xiaowen; Zhao, Luqian; Qin, Hongran; Zhao, Meijia; Zhou, Yirui; Yang, Shuqiang; Su, Xu; Xu, Xiaohua

2014-05-01

The aim of this work was to develop a method to provide rapid results for humans with internal radioactive contamination. The authors hypothesized that valuable information could be obtained from gas proportional counter techniques by screening urine samples from potentially exposed individuals rapidly. Recommended gross alpha and beta activity screening methods generally employ gas proportional counting techniques. Based on International Standards Organization (ISO) methods, improvements were made in the evaporation process to develop a method to provide rapid results, adequate sensitivity, and minimum sample preparation and operator intervention for humans with internal radioactive contamination. The method described by an American National Standards Institute publication was used to calibrate the gas proportional counter, and urine samples from patients with or without radionuclide treatment were measured to validate the method. By improving the evaporation process, the time required to perform the assay was reduced dramatically. Compared with the reference data, the results of the validation samples were very satisfactory with respect to gross-alpha and gross-beta activities. The gas flow proportional counting method described here has the potential for radioactivity monitoring in the body. This method was easy, efficient, and fast, and its application is of great utility in determining whether a sample should be analyzed by a more complicated method, for example radiochemical and/or γ-spectroscopy. In the future, it may be used commonly in medical examination and nuclear emergency treatment.Health Phys. 106(5):000-000; 2014.

Quantitative determination of galantamine in human plasma by sensitive liquid chromatography-tandem mass spectrometry using loratadine as an internal standard.

PubMed

Nirogi, Ramakrishna V S; Kandikere, Vishwottam N; Mudigonda, Koteshwara; Maurya, Santosh

2007-02-01

A simple, rapid, sensitive, and selective liquid chromatography-tandem mass spectrometry method is developed and validated for the quantitation of galantamine, an acetylcholinesterase inhibitor in human plasma, using a commercially available compound, loratadine, as the internal standard. Following liquid-liquid extraction, the analytes are separated using an isocratic mobile phase on a reverse-phase C18 column and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective (M+H)+ ions, m/z 288 to 213 for galantamine and m/z 383 and 337 for the internal standard. The assay exhibit a linear dynamic range of 0.5-100 ng/mL for galantamine in human plasma. The lower limit of quantitation is 0.5 ng/mL, with a relative standard deviation of less than 8%. Acceptable precision and accuracy are obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample makes it possible to analyze more than 400 human plasma samples per day. The validated method is successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability, or bioequivalence studies.

A comparative appraisal of two equivalence tests for multiple standardized effects.

PubMed

Shieh, Gwowen

2016-04-01

Equivalence testing is recommended as a better alternative to the traditional difference-based methods for demonstrating the comparability of two or more treatment effects. Although equivalent tests of two groups are widely discussed, the natural extensions for assessing equivalence between several groups have not been well examined. This article provides a detailed and schematic comparison of the ANOVA F and the studentized range tests for evaluating the comparability of several standardized effects. Power and sample size appraisals of the two grossly distinct approaches are conducted in terms of a constraint on the range of the standardized means when the standard deviation of the standardized means is fixed. Although neither method is uniformly more powerful, the studentized range test has a clear advantage in sample size requirements necessary to achieve a given power when the underlying effect configurations are close to the priori minimum difference for determining equivalence. For actual application of equivalence tests and advance planning of equivalence studies, both SAS and R computer codes are available as supplementary files to implement the calculations of critical values, p-values, power levels, and sample sizes. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

[Immuno-affinity chromatographic purification: the study of methods to test citrinin in monascus products by high performance liquid chromatography].

PubMed

Qiu, Wen-qian; Liu, Xiao-xia; Zheng, Kui-cheng; Fu, Wu-sheng

2012-08-01

To establish a method to test citrinin (CIT) in monascus products by immuno-affinity chromatography (IAC)-high performance liquid chromatography (HPLC), and to detect the content of CIT in monascus products in Fujian province. IAC-HPLC was applied to detect the CIT content in monascus products. The conditions to use HPLC were as follows: C(18) reversed-phase chromatographic column, 150.0 mm×4.6mm×3 µm; mobile phase: the volume ratio of acetonitrile and 0.1% phosphoric acid solution at 65:35; isocratic elution; column temperature: 28°C; flow velocity: 0.8 ml/min; fluorescence detector, excitation wavelength (λ(ex)) was 331 nm and emission wavelength (λ(em)) was 500 nm. The standard curved was established by the linear regression of peak area (Y) to CIT content (X, ng/ml). The accuracy and precision of the method would then be verified. And 32 kinds of monascus products were determined and their color values were compared by this method. The standard curve established in this study was Y = 4634.8X-136.42, r = 1.000; whose limits of detection was 20 µg/kg and the limits of qualification was 64 µg/kg. In the range between 200 and 800 µg/kg, the standard recovery rate was 98.9% - 110.0% (n = 3), and the relative standard deviation (RSD) was 0.51% - 1.76%. Out of the 32 samples, CIT was detected from 11 samples of monascus rice, 9 samples of monascus powder and 5 samples of monascus pigments, the content was around 0.212 - 14.500 mg/kg. 4 out of 7 functional monascus samples were detected out CIT, whose content at 0.142 - 0.275 mg/kg. The method to detect CIT in monascus products by IAC-HPLC has been established.

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

Hoenig, M.; Elsen, Y.V.; Cauter, R.V.

The progressive degradation of the pyrolytic graphite surface of atomizers provides variable and misleading results of molybdenum peak-height measurements. The changes in the peak shapes produce no analytical problems during the lifetime of the atomizer (approx.300 firings) when integrated absorbance (A.s signals) is considered and the possible base-line drifts are controlled. This was demonstrated on plant samples mineralized by simple digestion with a mixture of HNO/sub 3/ and H/sub 2/O/sub 2/. The value of this method was assessed by comparison with a standard dry oxidation method and by molybdenum determination in National Bureau of Standards reference plant samples. The relativemore » standard deviations (n = 5) of the full analytical procedure do not exceed 7%. 13 references, 3 figures, 3 tables.« less

Rapid detection of proteins in transgenic crops without protein reference standards by targeted proteomic mass spectrometry.

PubMed

Schacherer, Lindsey J; Xie, Weiping; Owens, Michaela A; Alarcon, Clara; Hu, Tiger X

2016-09-01

Liquid chromatography coupled with tandem mass spectrometry is increasingly used for protein detection for transgenic crops research. Currently this is achieved with protein reference standards which may take a significant time or efforts to obtain and there is a need for rapid protein detection without protein reference standards. A sensitive and specific method was developed to detect target proteins in transgenic maize leaf crude extract at concentrations as low as ∼30 ng mg(-1) dry leaf without the need of reference standards or any sample enrichment. A hybrid Q-TRAP mass spectrometer was used to monitor all potential tryptic peptides of the target proteins in both transgenic and non-transgenic samples. The multiple reaction monitoring-initiated detection and sequencing (MIDAS) approach was used for initial peptide/protein identification via Mascot database search. Further confirmation was achieved by direct comparison between transgenic and non-transgenic samples. Definitive confirmation was provided by running the same experiments of synthetic peptides or protein standards, if available. A targeted proteomic mass spectrometry method using MIDAS approach is an ideal methodology for detection of new proteins in early stages of transgenic crop research and development when neither protein reference standards nor antibodies are available. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Determination of Wastewater Compounds in Sediment and Soil by Pressurized Solvent Extraction, Solid-Phase Extraction, and Capillary-Column Gas Chromatography/Mass Spectrometry

USGS Publications Warehouse

Burkhardt, Mark R.; Zaugg, Steven D.; Smith, Steven G.; ReVello, Rhiannon C.

2006-01-01

A method for the determination of 61 compounds in environmental sediment and soil samples is described. The method was developed in response to increasing concern over the effects of endocrine-disrupting chemicals in wastewater and wastewater-impacted sediment on aquatic organisms. This method also may be used to evaluate the effects of combined sanitary and storm-sewer overflow on the water and sediment quality of urban streams. Method development focused on the determination of compounds that were chosen on the basis of their endocrine-disrupting potential or toxicity. These compounds include the alkylphenol ethoxylate nonionic surfactants and their degradates, food additives, fragrances, antioxidants, flame retardants, plasticizers, industrial solvents, disinfectants, fecal sterols, polycyclic aromatic hydrocarbons, and high-use domestic pesticides. Sediment and soil samples are extracted using a pressurized solvent extraction system. The compounds of interest are extracted from interfering matrix components by high-pressure water/isopropyl alcohol extraction. The compounds were isolated using disposable solid-phase extraction (SPE) cartridges containing chemically modified polystyrene-divinylbenzene resin. The cartridges were dried with nitrogen gas, and then sorbed compounds were eluted with methylene chloride (80 percent)-diethyl ether (20 percent) through Florisil/sodium sulfate SPE cartridge, and then determined by capillary-column gas chromatography/mass spectrometry. Recoveries in reagent-sand samples fortified at 4 to 72 micrograms averaged 76 percent ?13 percent relative standard deviation for all method compounds. Initial method reporting levels for single-component compounds ranged from 50 to 500 micrograms per kilogram. The concentrations of 20 out of 61 compounds initially will be reported as estimated with the 'E' remark code for one of three reasons: (1) unacceptably low-biased recovery (less than 60 percent) or highly variable method performance (greater than 25 percent relative standard deviation), (2) reference standards prepared from technical mixtures, or (3) potential blank contamination. Samples were preserved by freezing to -20 degrees Celsius. The U.S. Geological Survey National Water Quality Laboratory has established a 1-year sample-holding time limit (prior to sample extraction) from the date of sample collection (if the sample is kept at -20?C) until a statistically accepted method can be used to determine the effectiveness of the sample-freezing procedure.

Pre-capture multiplexing improves efficiency and cost-effectiveness of targeted genomic enrichment.

PubMed

Shearer, A Eliot; Hildebrand, Michael S; Ravi, Harini; Joshi, Swati; Guiffre, Angelica C; Novak, Barbara; Happe, Scott; LeProust, Emily M; Smith, Richard J H

2012-11-14

Targeted genomic enrichment (TGE) is a widely used method for isolating and enriching specific genomic regions prior to massively parallel sequencing. To make effective use of sequencer output, barcoding and sample pooling (multiplexing) after TGE and prior to sequencing (post-capture multiplexing) has become routine. While previous reports have indicated that multiplexing prior to capture (pre-capture multiplexing) is feasible, no thorough examination of the effect of this method has been completed on a large number of samples. Here we compare standard post-capture TGE to two levels of pre-capture multiplexing: 12 or 16 samples per pool. We evaluated these methods using standard TGE metrics and determined the ability to identify several classes of genetic mutations in three sets of 96 samples, including 48 controls. Our overall goal was to maximize cost reduction and minimize experimental time while maintaining a high percentage of reads on target and a high depth of coverage at thresholds required for variant detection. We adapted the standard post-capture TGE method for pre-capture TGE with several protocol modifications, including redesign of blocking oligonucleotides and optimization of enzymatic and amplification steps. Pre-capture multiplexing reduced costs for TGE by at least 38% and significantly reduced hands-on time during the TGE protocol. We found that pre-capture multiplexing reduced capture efficiency by 23 or 31% for pre-capture pools of 12 and 16, respectively. However efficiency losses at this step can be compensated by reducing the number of simultaneously sequenced samples. Pre-capture multiplexing and post-capture TGE performed similarly with respect to variant detection of positive control mutations. In addition, we detected no instances of sample switching due to aberrant barcode identification. Pre-capture multiplexing improves efficiency of TGE experiments with respect to hands-on time and reagent use compared to standard post-capture TGE. A decrease in capture efficiency is observed when using pre-capture multiplexing; however, it does not negatively impact variant detection and can be accommodated by the experimental design.

Methods of Analysis by the U.S. Geological Survey National Water Quality Laboratory - Determination of Elements in Whole-Water Digests Using Inductively Coupled Plasma-Optical Emission Spectrometry and Inductively Coupled Plasma-Mass Spectrometry

USGS Publications Warehouse

Garbarino, John R.; Struzeski, Tedmund M.

1998-01-01

Inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) can be used to determine 26 elements in whole-water digests. Both methods have distinct advantages and disadvantages--ICP-OES is capable of analyzing samples with higher elemental concentrations without dilution, however, ICP-MS is more sensitive and capable of determining much lower elemental concentrations. Both techniques gave accurate results for spike recoveries, digested standard reference-water samples, and whole-water digests. Average spike recoveries in whole-water digests were 100 plus/minus 10 percent, although recoveries for digests with high dissolved-solid concentrations were lower for selected elements by ICP-MS. Results for standard reference-water samples were generally within 1 standard deviation of hte most probable values. Statistical analysis of the results from 43 whole-water digest indicated that there was no significant difference among ICP-OES, ICP-MS, and former official methods of analysis for 24 of the 26 elements evaluated.

Comparison of Uriswab to alternative methods for urine culture collection and transport: confirmation of standard culture methodology for investigation of urinary tract infections.

PubMed

Rennie, Robert P; Turnbull, Lee-Ann; Gauchier-Pitts, Kaylee; Bennett, Tracy; Dyrland, Debbie; Blonski, Susan

2016-08-01

The ability to isolate and identify causative agents of urinary tract infections relies primarily on the quality of the urine sample that is submitted to the microbiology. The most important factors are the method of collection, the maintenance of viability of the potential pathogens during transport, and standardization of the culturing of the urine sample. This report is a composite of several investigations comparing collection and transport on urine culture paddles, with a preservative urine sponge (Uriswab), and a comparison of Uriswab with the BD preservative transport tube as methods of preservation of urinary pathogens. Primary studies showed that Uriswab maintained significantly more urinary pathogens than the urine culture paddle with fewer mixed or contaminated cultures. The two preservative transport systems were comparable for maintenance of viability of the pathogens, but there were fewer mixed cultures when samples were collected with Uriswab. This study confirms the importance of a standard volume of 1 μL of urine for culture. Copyright © 2016 Elsevier Inc. All rights reserved.

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of Cr, Fe, Cu, Zn and Se in cereals

NASA Astrophysics Data System (ADS)

Huang, Shih-Yi; Jiang, Shiuh-Jen; Sahayam, A. C.

2014-11-01

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) has been applied to determine Cr, Fe, Cu, Zn and Se in several cereal samples. Thioacetamide was used as the modifier to enhance the ion signals. The background ions at the masses of interest were reduced in intensity significantly by using 1.0 mL min- 1 methane (CH4) as reaction cell gas in the dynamic reaction cell (DRC). Since the sensitivities of Cr, Fe, Cu, Zn and Se in different matrices were quite different, standard addition and isotope dilution methods were used for the determination of Cr, Fe, Cu, Zn and Se in these cereal samples. The method detection limits estimated from standard addition curves were about 1, 10, 4, 12 and 2 ng g- 1 for Cr, Fe, Cu, Zn and Se, respectively, in original cereal samples. This procedure has been applied to the determination of Cr, Fe, Cu, Zn and Se whose concentrations are in μg g- 1 (except Cr and Se) in standard reference materials (SRM) of National institute of standards and technology (NIST), NIST SRM 1568a Rice Flour and NIST SRM 1567a Wheat Flour and two cereal samples purchased from a local market. The analysis results of reference materials agreed with certified values at 95% confidence level according to Student's T-test. The results for the real world cereal samples were also found to be in good agreement with the pneumatic nebulization DRC ICP-MS results of the sample solutions.

MACRO- MICRO-PURGE SOIL GAS SAMPLING METHODS FOR THE COLLECTION OF CONTAMINANT VAPORS

EPA Science Inventory

Purging influence on soil gas concentrations for volatile organic compounds (VOCs), as affected by sampling tube inner diameter and sampling depth (i.e., dead-space purge volume), was evaluated at different field sites. A macro-purge sampling system consisted of a standard hollo...

CTEPP STANDARD OPERATING PROCEDURE FOR SETTING UP A HOUSEHOLD SAMPLING SCHEDULE (SOP-2.10)

EPA Science Inventory

This SOP describes the method for scheduling study subjects for field sampling activities in North Carolina (NC) and Ohio (OH). There are three field sampling teams with two staff members on each team. Two field sampling teams collect the field data simultaneously. A third fiel...

Determination of benzylpenicillin in pharmaceuticals by capillary zone electrophoresis

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

Hoyt, A.M. Jr.; Sepaniak, M.J.

A rapid and direct method is described for the determination of benzylpenicillin (penicillin G) in pharmaceutical preparations. The method involves very little sample preparation and total analysis time for duplicate results is less 30 minutes per sample. The method takes advantage of the speed and separating power of capillary zone electrophoresis (CZE). Detection of penicillin is by absorption at 228 nm. An internal standard is employed to reduce sample injection error. The method was applied successfully to both tablets and injectable preparations. 14 refs., 5 figs., 3 tabs.

Optimization of Sample Preparation and Instrumental Parameters for the Rapid Analysis of Drugs of Abuse in Hair samples by MALDI-MS/MS Imaging

NASA Astrophysics Data System (ADS)

Flinders, Bryn; Beasley, Emma; Verlaan, Ricky M.; Cuypers, Eva; Francese, Simona; Bassindale, Tom; Clench, Malcolm R.; Heeren, Ron M. A.

2017-08-01

Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) has been employed to rapidly screen longitudinally sectioned drug user hair samples for cocaine and its metabolites using continuous raster imaging. Optimization of the spatial resolution and raster speed were performed on intact cocaine contaminated hair samples. The optimized settings (100 × 150 μm at 0.24 mm/s) were subsequently used to examine longitudinally sectioned drug user hair samples. The MALDI-MS/MS images showed the distribution of the most abundant cocaine product ion at m/z 182. Using the optimized settings, multiple hair samples obtained from two users were analyzed in approximately 3 h: six times faster than the standard spot-to-spot acquisition method. Quantitation was achieved using longitudinally sectioned control hair samples sprayed with a cocaine dilution series. A multiple reaction monitoring (MRM) experiment was also performed using the `dynamic pixel' imaging method to screen for cocaine and a range of its metabolites, in order to differentiate between contaminated hairs and drug users. Cocaine, benzoylecgonine, and cocaethylene were detectable, in agreement with analyses carried out using the standard LC-MS/MS method. [Figure not available: see fulltext.

Internal Standards: A Source of Analytical Bias For Volatile Organic Analyte Determinations

EPA Science Inventory

The use of internal standards in the determination of volatile organic compounds as described in SW-846 Method 8260C introduces a potential for bias in results once the internal standards (ISTDs) are added to a sample for analysis. The bias is relative to the dissimilarity betw...

DISCUSSION AND EVALUATION OF THE VOLATILITY TEST FOR EQUIVALENCY OF OTHER METHODS TO THE FEDERAL REFERENCE METHOD FOR FINE PARTICULATE MATTER

EPA Science Inventory

In July 1997, EPA promulgated a new National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM2.5). This new standard was based on collection of an integrated mass sample on a filter. Field studies have demonstrated that the collection of semivolatile compoun...

40 CFR 80.582 - What are the sampling and testing methods for the fuel marker?

Code of Federal Regulations, 2013 CFR

2013-07-01

... marker content of distillate fuels and how will EPA qualify or decline to qualify a test method?—(1... developed by a Voluntary Consensus-Based Standards Body, such as the American Society for Testing and... this standard from the American Society for Testing and Materials, 100 Barr Harbor Dr., West...

40 CFR 80.582 - What are the sampling and testing methods for the fuel marker?

Code of Federal Regulations, 2012 CFR

2012-07-01

... marker content of distillate fuels and how will EPA qualify or decline to qualify a test method?—(1... developed by a Voluntary Consensus-Based Standards Body, such as the American Society for Testing and... this standard from the American Society for Testing and Materials, 100 Barr Harbor Dr., West...

40 CFR 80.582 - What are the sampling and testing methods for the fuel marker?

Code of Federal Regulations, 2014 CFR

2014-07-01

... marker content of distillate fuels and how will EPA qualify or decline to qualify a test method?—(1... developed by a Voluntary Consensus-Based Standards Body, such as the American Society for Testing and... this standard from the American Society for Testing and Materials, 100 Barr Harbor Dr., West...

Direct injection GC method for measuring light hydrocarbon emissions from cooling-tower water.

PubMed

Lee, Max M; Logan, Tim D; Sun, Kefu; Hurley, N Spencer; Swatloski, Robert A; Gluck, Steve J

2003-12-15

A Direct Injection GC method for quantifying low levels of light hydrocarbons (C6 and below) in cooling water has been developed. It is intended to overcome the limitations of the currently available technology. The principle of this method is to use a stripper column in a GC to strip waterfrom the hydrocarbons prior to entering the separation column. No sample preparation is required since the water sample is introduced directly into the GC. Method validation indicates that the Direct Injection GC method offers approximately 15 min analysis time with excellent precision and recovery. The calibration studies with ethylene and propylene show that both liquid and gas standards are suitable for routine calibration and calibration verification. The sampling method using zero headspace traditional VOA (Volatile Organic Analysis) vials and a sample chiller has also been validated. It is apparent that the sampling method is sufficient to minimize the potential for losses of light hydrocarbons, and samples can be held at 4 degrees C for up to 7 days with more than 93% recovery. The Direct Injection GC method also offers <1 ppb (w/v) level method detection limits for ethylene, propylene, and benzene. It is superior to the existing El Paso stripper method. In addition to lower detection limits for ethylene and propylene, the Direct Injection GC method quantifies individual light hydrocarbons in cooling water, provides better recoveries, and requires less maintenance and setup costs. Since the instrumentation and supplies are readily available, this technique could easily be established as a standard or alternative method for routine emission monitoring and leak detection of light hydrocarbons in cooling-tower water.

Simultaneous determination of nickel and copper by H-point standard addition method-first-order derivative spectrophotometry in plant samples after separation and preconcentration on modified natural clinoptilolite as a new sorbent.

PubMed

Roohparvar, Rasool; Taher, Mohammad Ali; Mohadesi, Alireza

2008-01-01

For the simultaneous determination of nickel(ll) and copper(ll) in plant samples, a rapid and accurate method was developed. In this method, solid-phase extraction (SPE) and first-order derivative spectrophotometry (FDS) are combined, and the result is coupled with the H-point standard addition method (HPSAM). Compared with normal spectrophotometry, derivative spectrophotometry offers the advantages of increased selectivity and sensitivity. As there is no need for carrying out any pretreatment of the sample, the spectrophotometry method is easy, but because of a high detection limit, it is not so practical. In order to decrease the detection limit, it is suggested to combine spectrophotometry with a preconcentration method such as SPE. In the present work, after separation and preconcentration of Ni(ll) and Cu(ll) on modified clinoptilolite zeolite that is loaded with 2-[1-(2-hydroxy-5-sulforphenyl)-3-phenyl-5-formaza-no]-benzoic acid monosodium salt (zincon) as a selective chromogenic reagent, FDS-HPSAM, which is a simple and selective spectrophotometric method, has been applied for simultaneous determination of these ions. With optimum conditions, the detection limit in original solutions is 0.7 and 0.5 ng/mL, respectively, for nickel and copper. The linear concentration ranges in the proposed method for nickel and copper ions in original solutions are 1.1 to 3.0 x 10(3) and 0.9 to 2.0 x 10(3) ng/mL, respectively. The recommended procedure is applied to successful determination of Cu(ll) and Ni(ll) in standard and real samples.

UK audit of glomerular filtration rate measurement from plasma sampling in 2013.

PubMed

Murray, Anthony W; Lawson, Richard S; Cade, Sarah C; Hall, David O; Kenny, Bob; O'Shaughnessy, Emma; Taylor, Jon; Towey, David; White, Duncan; Carson, Kathryn

2014-11-01

An audit was carried out into UK glomerular filtration rate (GFR) calculation. The results were compared with an identical 2001 audit. Participants used their routine method to calculate GFR for 20 data sets (four plasma samples) in millilitres per minute and also the GFR normalized for body surface area. Some unsound data sets were included to analyse the applied quality control (QC) methods. Variability between centres was assessed for each data set, compared with the national median and a reference value calculated using the method recommended in the British Nuclear Medicine Society guidelines. The influence of the number of samples on variability was studied. Supplementary data were requested on workload and methodology. The 59 returns showed widespread standardization. The applied early exponential clearance correction was the main contributor to the observed variability. These corrections were applied by 97% of centres (50% - 2001) with 80% using the recommended averaged Brochner-Mortenson correction. Approximately 75% applied the recommended Haycock body surface area formula for adults (78% for children). The effect of the number of samples used was not significant. There was wide variability in the applied QC techniques, especially in terms of the use of the volume of distribution. The widespread adoption of the guidelines has harmonized national GFR calculation compared with the previous audit. Further standardization could further reduce variability. This audit has highlighted the need to address the national standardization of QC methods. Radionuclide techniques are confirmed as the preferred method for GFR measurement when an unequivocal result is required.

Parameter recovery, bias and standard errors in the linear ballistic accumulator model.

PubMed

Visser, Ingmar; Poessé, Rens

2017-05-01

The linear ballistic accumulator (LBA) model (Brown & Heathcote, , Cogn. Psychol., 57, 153) is increasingly popular in modelling response times from experimental data. An R package, glba, has been developed to fit the LBA model using maximum likelihood estimation which is validated by means of a parameter recovery study. At sufficient sample sizes parameter recovery is good, whereas at smaller sample sizes there can be large bias in parameters. In a second simulation study, two methods for computing parameter standard errors are compared. The Hessian-based method is found to be adequate and is (much) faster than the alternative bootstrap method. The use of parameter standard errors in model selection and inference is illustrated in an example using data from an implicit learning experiment (Visser et al., , Mem. Cogn., 35, 1502). It is shown that typical implicit learning effects are captured by different parameters of the LBA model. © 2017 The British Psychological Society.

Determination of chloramphenicol residues in meat, seafood, egg, honey, milk, plasma and urine with liquid chromatography-tandem mass spectrometry, and the validation of the method based on 2002/657/EC.

PubMed

Rønning, Helene Thorsen; Einarsen, Kristin; Asp, Tone Normann

2006-06-23

A simple and rapid method for the determination and confirmation of chloramphenicol in several food matrices with LC-MS/MS was developed. Following addition of d5-chloramphenicol as internal standard, meat, seafood, egg, honey and milk samples were extracted with acetonitrile. Chloroform was then added to remove water. After evaporation, the residues were reconstituted in methanol/water (3+4) before injection. The urine and plasma samples were after addition of internal standard applied to a Chem Elut extraction cartridge, eluted with ethyl acetate, and hexane washed. Also these samples were reconstituted in methanol/water (3+4) after evaporation. By using an MRM acquisition method in negative ionization mode, the transitions 321-->152, 321-->194 and 326-->157 were used for quantification, confirmation and internal standard, respectively. Quantification of chloramphenicol positive samples regardless of matrix could be achieved with a common water based calibration curve. The validation of the method was based on EU-decision 2002/657 and different ways of calculating CCalpha and CCbeta were evaluated. The common CCalpha and CCbeta for all matrices were 0.02 and 0.04 microg/kg for the 321-->152 ion transition, and 0.02 and 0.03 microg/kg for the 321-->194 ion transition. At fortification level 0.1 microg/kg the within-laboratory reproducibility is below 25%.

IMPROVED METHOD FOR THE STORAGE OF GROUND WATER SAMPLES CONTAINING VOLATILE ORGANIC ANALYTES

EPA Science Inventory

The sorption of volatile organic analytes from water samples by the Teflon septum surface used with standard glass 40-ml sample collection vials was investigated. Analytes tested included alkanes, isoalkanes, olefins, cycloalkanes, a cycloalkene, monoaromatics, a polynuclear arom...

A multiresidue method for determination of trace levels of pesticides in air and water.

PubMed

Millet, M; Wortham, H; Sanusi, A; Mirabel, P

1996-11-01

A multiresidue analytical method is described for the analysis of 13 pesticides in fogwater, rainwater, gas, and particles. This method is based upon solid-liquid extraction using Sep-Pak tC18 light cartridges for aqueous samples, soxhlet for gas (adsorbed on XAD-2) and particles (on glass fiber filters), HPLC-based fractionation of the extracted residues using a silica column, and a linear gradient of n-hexane/tert butyl methyl ether followed by GC-ECD and HPLC-UV analyses of each fraction. Prior to analysis with GC-ECD, a methylation procedure using BF3/methanol was developed for the analysis of the fraction which contains chlorophenoxy acid herbicides. The recoveries of the extraction procedure of liquid samples and of the methylation were greater than 92 and 97% with a standard deviation lower than 8 and 5%, respectively. The detection limits varied between 0.1 and 0.01 microgram.ml-1 for the 13 pesticides studied with a standard deviation less than 9%. This method was used for the determination of pesticides in 18 fogwater samples (soluble + insoluble), 31 rainwater samples, and 17 air (gas + particles) samples collected between 1991 and 1993 in Colmar (east of France).

Use of lignin extracted from different plant sources as standards in the spectrophotometric acetyl bromide lignin method.

PubMed

Fukushima, Romualdo S; Kerley, Monty S

2011-04-27

A nongravimetric acetyl bromide lignin (ABL) method was evaluated to quantify lignin concentration in a variety of plant materials. The traditional approach to lignin quantification required extraction of lignin with acidic dioxane and its isolation from each plant sample to construct a standard curve via spectrophotometric analysis. Lignin concentration was then measured in pre-extracted plant cell walls. However, this presented a methodological complexity because extraction and isolation procedures are lengthy and tedious, particularly if there are many samples involved. This work was targeted to simplify lignin quantification. Our hypothesis was that any lignin, regardless of its botanical origin, could be used to construct a standard curve for the purpose of determining lignin concentration in a variety of plants. To test our hypothesis, lignins were isolated from a range of diverse plants and, along with three commercial lignins, standard curves were built and compared among them. Slopes and intercepts derived from these standard curves were close enough to allow utilization of a mean extinction coefficient in the regression equation to estimate lignin concentration in any plant, independent of its botanical origin. Lignin quantification by use of a common regression equation obviates the steps of lignin extraction, isolation, and standard curve construction, which substantially expedites the ABL method. Acetyl bromide lignin method is a fast, convenient analytical procedure that may routinely be used to quantify lignin.

Community of Inquiry Method and Language Skills Acquisition: Empirical Evidence

ERIC Educational Resources Information Center

Preece, Abdul Shakhour Duncan

2015-01-01

The study investigates the effectiveness of community of inquiry method in preparing students to develop listening and speaking skills in a sample of junior secondary school students in Borno state, Nigeria. A sample of 100 students in standard classes was drawn in one secondary school in Maiduguri metropolis through stratified random sampling…

Standard addition with internal standardisation as an alternative to using stable isotope labelled internal standards to correct for matrix effects-Comparison and validation using liquid chromatography-​tandem mass spectrometric assay of vitamin D.

PubMed

Hewavitharana, Amitha K; Abu Kassim, Nur Sofiah; Shaw, Paul Nicholas

2018-06-08

With mass spectrometric detection in liquid chromatography, co-eluting impurities affect the analyte response due to ion suppression/enhancement. Internal standard calibration method, using co-eluting stable isotope labelled analogue of each analyte as the internal standard, is the most appropriate technique available to correct for these matrix effects. However, this technique is not without drawbacks, proved to be expensive because separate internal standard for each analyte is required, and the labelled compounds are expensive or require synthesising. Traditionally, standard addition method has been used to overcome the matrix effects in atomic spectroscopy and was a well-established method. This paper proposes the same for mass spectrometric detection, and demonstrates that the results are comparable to those with the internal standard method using labelled analogues, for vitamin D assay. As conventional standard addition procedure does not address procedural errors, we propose the inclusion of an additional internal standard (not co-eluting). Recoveries determined on human serum samples show that the proposed method of standard addition yields more accurate results than the internal standardisation using stable isotope labelled analogues. The precision of the proposed method of standard addition is superior to the conventional standard addition method. Copyright © 2018 Elsevier B.V. All rights reserved.

Development and validation of an improved method for the determination of chloropropanols in paperboard food packaging by GC-MS.

PubMed

Mezouari, S; Liu, W Yun; Pace, G; Hartman, T G

2015-01-01

The objective of this study was to develop an improved analytical method for the determination of 3-chloro-1,2-propanediol (3-MCPD) and 1,3-dichloropropanol (1,3-DCP) in paper-type food packaging. The established method includes aqueous extraction, matrix spiking of a deuterated surrogate internal standard (3-MCPD-d₅), clean-up using Extrelut solid-phase extraction, derivatisation using a silylation reagent, and GC-MS analysis of the chloropropanols as their corresponding trimethyl silyl ethers. The new method is applicable to food-grade packaging samples using European Commission standard aqueous extraction and aqueous food stimulant migration tests. In this improved method, the derivatisation procedure was optimised; the cost and time of the analysis were reduced by using 10 times less sample, solvents and reagents than in previously described methods. Overall the validation data demonstrate that the method is precise and reliable. The limit of detection (LOD) of the aqueous extract was 0.010 mg kg(-1) (w/w) for both 3-MCPD and 1,3-DCP. Analytical precision had a relative standard deviation (RSD) of 3.36% for 3-MCPD and an RSD of 7.65% for 1,3-DCP. The new method was satisfactorily applied to the analysis of over 100 commercial paperboard packaging samples. The data are being used to guide the product development of a next generation of wet-strength resins with reduced chloropropanol content, and also for risk assessments to calculate the virtual safe dose (VSD).

Derivatization coupled to headspace programmed-temperature vaporizer gas chromatography with mass spectrometry for the determination of amino acids: Application to urine samples.

PubMed

González Paredes, Rosa María; García Pinto, Carmelo; Pérez Pavón, José Luis; Moreno Cordero, Bernardo

2016-09-01

A new method based on headspace programmed-temperature vaporizer gas chromatography with mass spectrometry has been developed and validated for the determination of amino acids (alanine, sarcosine, ethylglycine, valine, leucine, and proline) in human urine samples. Derivatization with ethyl chloroformate was employed successfully to determine the amino acids. The derivatization reaction conditions as well as the variables of the headspace sampling were optimized. The existence of a matrix effect was checked and the analytical characteristics of the method were determined. The limits of detection were 0.15-2.89 mg/L, and the limits of quantification were 0.46-8.67 mg/L. The instrumental repeatability was 1.6-11.5%. The quantification of the amino acids in six urine samples from healthy subjects was performed with the method developed with the one-point standard additions protocol, with norleucine as the internal standard. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of uranium in tap water by ICP-MS.

PubMed

El Himri, M; Pastor, A; de la Guardia, M

2000-05-01

A fast and accurate procedure has been developed for the determination of uranium at microg L(-1) level in tap and mineral water. The method is based on the direct introduction of samples, without any chemical pre-treatment, into an inductively coupled plasma mass spectrometer (ICP-MS). Uranium was determined at the mass number 238 using Rh as internal standard. The method provides a limit of detection of 2 ng L(-1) and a good repeatability with relative standard deviation values (RSD) about 3% for five independent analyses of samples containing 73 microg L(-1) of uranium. Recovery percentage values found for the determination of uranium in spiked natural samples varied between 91% and 106%. Results obtained are comparable with those found by radiochemical methods for natural samples and of the same order for the certified content of a reference material, thus indicating the accuracy of the ICP-MS procedure without the need of using isotope dilution. A series of mineral and tap waters from different parts of Spain and Morocco were analysed.

Standard deviation and standard error of the mean.

PubMed

Lee, Dong Kyu; In, Junyong; Lee, Sangseok

2015-06-01

In most clinical and experimental studies, the standard deviation (SD) and the estimated standard error of the mean (SEM) are used to present the characteristics of sample data and to explain statistical analysis results. However, some authors occasionally muddle the distinctive usage between the SD and SEM in medical literature. Because the process of calculating the SD and SEM includes different statistical inferences, each of them has its own meaning. SD is the dispersion of data in a normal distribution. In other words, SD indicates how accurately the mean represents sample data. However the meaning of SEM includes statistical inference based on the sampling distribution. SEM is the SD of the theoretical distribution of the sample means (the sampling distribution). While either SD or SEM can be applied to describe data and statistical results, one should be aware of reasonable methods with which to use SD and SEM. We aim to elucidate the distinctions between SD and SEM and to provide proper usage guidelines for both, which summarize data and describe statistical results.

Standard deviation and standard error of the mean

PubMed Central

In, Junyong; Lee, Sangseok

2015-01-01

In most clinical and experimental studies, the standard deviation (SD) and the estimated standard error of the mean (SEM) are used to present the characteristics of sample data and to explain statistical analysis results. However, some authors occasionally muddle the distinctive usage between the SD and SEM in medical literature. Because the process of calculating the SD and SEM includes different statistical inferences, each of them has its own meaning. SD is the dispersion of data in a normal distribution. In other words, SD indicates how accurately the mean represents sample data. However the meaning of SEM includes statistical inference based on the sampling distribution. SEM is the SD of the theoretical distribution of the sample means (the sampling distribution). While either SD or SEM can be applied to describe data and statistical results, one should be aware of reasonable methods with which to use SD and SEM. We aim to elucidate the distinctions between SD and SEM and to provide proper usage guidelines for both, which summarize data and describe statistical results. PMID:26045923

Method development for gypenosides fingerprint by high performance liquid chromatography with diode-array detection and the addition of internal standard.

PubMed

Liu, Fang; Ren, Dequan; Guo, De-an; Pan, Yifeng; Zhang, Huzhe; Hu, Ping

2008-03-01

In this paper, a new method for liquid chromatographic fingerprint of saponins in Gynostemma pentaphyllum (THUNB.) MAKINO was developed. The G. pentaphyllum powder was defatted by Soxhlet extraction with petroleum ether and then gypenosides were extracted from the residue with methanol by sonicating. Column chromatography with macro pore resin was then used to separate and enrich gypenosides. HPLC fingerprint analysis of gypenosides fraction was performed on a C18 column, with an isocratic elution of 34% acetonitrile for 60 min at 0.8 ml/min, sample injection volume was 20 microl and the wavelength was 203 nm. To cover the lack of standard compounds, the addition of an internal standard of ginsenoside Rb2 was employed in the gypenosides fingerprint profile. The relative retention time (RRT) and relative peak area (RPA) of the gypenosides peaks in the fingerprint were calculated by setting the ginsenoside Rb2 as the marker compound. The relative standard deviation (RSDs) of RRT of five common peaks vs. ginsenoside Rb2 in precision, repeatability and stability test were less than 1%, and the RSDs of RPA were less than 5%. The method validation data proved that the proposed method for the fingerprint with internal standard of G. pentaphyllum saponins is adequate, valid and applicable. Finally, three batches of crude drug samples collected from Shanxi province were tested by following the established method.

Development of a low-cost method of analysis for the qualitative and quantitative analysis of butyltins in environmental samples.

PubMed

Bangkedphol, Sornnarin; Keenan, Helen E; Davidson, Christine; Sakultantimetha, Arthit; Songsasen, Apisit

2008-12-01

Most analytical methods for butyltins are based on high resolution techniques with complicated sample preparation. For this study, a simple application of an analytical method was developed using High Performance Liquid Chromatography (HPLC) with UV detection. The developed method was studied to determine tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) in sediment and water samples. The separation was performed in isocratic mode on an ultra cyanopropyl column with a mobile phase of hexane containing 5% THF and 0.03% acetic acid. This method was confirmed using standard GC/MS techniques and verified by statistical paired t-test method. Under the experimental conditions used, the limit of detection (LOD) of TBT and DBT were 0.70 and 0.50 microg/mL, respectively. The optimised extraction method for butyltins in water and sediment samples involved using hexane containing 0.05-0.5% tropolone and 0.2% sodium chloride in water at pH 1.7. The quantitative extraction of butyltin compounds in a certified reference material (BCR-646) and naturally contaminated samples was achieved with recoveries ranging from 95 to 108% and at %RSD 0.02-1.00%. This HPLC method and optimum extraction conditions were used to determine the contamination level of butyltins in environmental samples collected from the Forth and Clyde canal, Scotland, UK. The values obtained severely exceeded the Environmental Quality Standard (EQS) values. Although high resolution methods are utilised extensively for this type of research, the developed method is cheaper in both terms of equipment and running costs, faster in analysis time and has comparable detection limits to the alternative methods. This is advantageous not just as a confirmatory technique but also to enable further research in this field.

Comparison of direct and indirect methods of measuring airborne chrysotile fibre concentration.

PubMed

Eypert-Blaison, Celine; Veissiere, Sylvie; Rastoix, Olivier; Kauffer, Edmond

2010-01-01

Transmission electron microscopy observations most frequently form a basis for estimating asbestos fibre concentration in the environment and in buildings with asbestos-containing materials. Sampled fibres can be transferred to microscope grids by applying either a direct [ISO (1995) Draft International ISO/DIS 10312. Ambient air. Determination of asbestos fibres. Direct transfer transmission electron microscopy procedure. Geneva, Switzerland: International Standardization Organization] or an indirect [AFNOR (1996) Détermination de la concentration en fibres d'amiante par microscopie électronique à transmission-Méthode indirecte. Cedex, France: AFNOR, p. 42; ISO (1997) Draft International ISO/DIS 13794. Ambient air. Determination of asbestos fibres. Indirect-transfer transmission electron microscopy procedure. Geneva, Switzerland: International Standardization Organization] method. In the latter case, ISO Standard 13794 recommends filtering calcination residues either on a polycarbonate (PC) filter (PC indirect method) or on a cellulose ester (CE) membrane (CE indirect method). The PC indirect method requires that fibres deposited on a PC filter be covered by a carbon layer, whereas in the CE indirect method, the CE membrane has to be directly processed using a method described in ISO Standard 10312. The purpose of this study was to compare results obtained using, on the one hand, direct preparation methods and, on the other hand, PC indirect or CE indirect methods, for counting asbestos fibres deposited on filters as a result of liquid filtration or air sampling. In direct method-based preparation, we observed that an etching time of 6-14 min does not affect the measured densities, except for fibres <1 microm deposited by liquid filtration. Moreover, in all cases, the direct method gives higher densities than the PC indirect method because of possible fibre disappearance when using the carbon evaporator implemented in the PC indirect method. The CE membrane used for sample preparation in the CE indirect method is collapsed prior to passing it through the carbon evaporator, so the fibres are less likely to disappear at this stage. We then note that the resulting fibre densities for chrysotile-loaded filters prepared using the direct method are close to those obtained with filters prepared using the CE indirect method. Our study therefore shows that, under the implemented experimental conditions, the PC and CE indirect preparation methods described in ISO Standard 13794 are not equivalent.

Development and validation of a Pneumocystis jirovecii real-time polymerase chain reaction assay for diagnosis of Pneumocystis pneumonia

PubMed Central

Church, Deirdre L; Ambasta, Anshula; Wilmer, Amanda; Williscroft, Holly; Ritchie, Gordon; Pillai, Dylan R; Champagne, Sylvie; Gregson, Daniel G

2015-01-01

BACKGROUND: Pneumocystis jirovecii (PJ), a pathogenic fungus, causes severe interstitial Pneumocystis pneumonia (PCP) among immunocompromised patients. A laboratory-developed real-time polyermase chain reaction (PCR) assay was validated for PJ detection to improve diagnosis of PCP. METHODS: Forty stored bronchoalveolar lavage (BAL) samples (20 known PJ positive [PJ+] and 20 known PJ negative [PJ−]) were initially tested using the molecular assay. Ninety-two sequentially collected BAL samples were then analyzed using an immunofluorescence assay (IFA) and secondarily tested using the PJ real-time PCR assay. Discrepant results were resolved by retesting BAL samples using another real-time PCR assay with a different target. PJ real-time PCR assay performance was compared with the existing gold standard (ie, IFA) and a modified gold standard, in which a true positive was defined as a sample that tested positive in two of three methods in a patient suspected to have PCP. RESULTS: Ninety of 132 (68%) BAL fluid samples were collected from immunocompromised patients. Thirteen of 92 (14%) BALs collected were PJ+ when tested using IFA. A total of 40 BAL samples were PJ+ in the present study including: all IFA positive samples (n=13); all referred PJ+ BAL samples (n=20); and seven additional BAL samples that were IFA negative, but positive using the modified gold standard. Compared with IFA, the PJ real-time PCR had sensitivity, specificity, and positive and negative predictive values of 100%, 91%, 65% and 100%, respectively. Compared with the modified gold standard, PJ real-time PCR had a sensitivity, specificity, and positive and negative predictive values of 100%. CONCLUSION: PJ real-time PCR improved detection of PJ in immunocompromised patients. PMID:26600815

U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR COLLECTION, STORAGE, AND SHIPMENT OF DRINKING AND TAP WATER SAMPLES FOR VOCS (EPA METHOD 524.2) ANALYSIS (UA-F-18.1)

EPA Science Inventory

The purpose of this SOP is to describe the collection, storage, and shipment of tap and drinking water samples for analysis by EPA method 524.2 (revision 4.0). This SOP provides a brief description of the sample containers, collection, preservation, storage, shipping, and custod...

NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR COLLECTION, STORAGE AND SHIPMENT OF DRINKING AND TAP WATER SAMPLES FOR TRACE METALS (EPA METHOD 200.8) (UA-F-16.1)

EPA Science Inventory

The purpose of this SOP is to describe how to collect, store, and ship tap and drinking water samples for analysis by EPA Method 200.8 (revision 4.4) for the NHEXAS Arizona project. This SOP provides a brief description of the sample containers, collection, preservation, storage...

Stable isotope dilution analysis of hydrologic samples by inductively coupled plasma mass spectrometry

USGS Publications Warehouse

Garbarino, John R.; Taylor, Howard E.

1987-01-01

Inductively coupled plasma mass spectrometry is employed in the determination of Ni, Cu, Sr, Cd, Ba, Ti, and Pb in nonsaline, natural water samples by stable isotope dilution analysis. Hydrologic samples were directly analyzed without any unusual pretreatment. Interference effects related to overlapping isobars, formation of metal oxide and multiply charged ions, and matrix composition were identified and suitable methods of correction evaluated. A comparability study snowed that single-element isotope dilution analysis was only marginally better than sequential multielement isotope dilution analysis. Accuracy and precision of the single-element method were determined on the basis of results obtained for standard reference materials. The instrumental technique was shown to be ideally suited for programs associated with certification of standard reference materials.

Investigation of chemical modifiers for the direct determination of arsenic in fish oil using high-resolution continuum source graphite furnace atomic absorption spectrometry.

PubMed

Pereira, Éderson R; de Almeida, Tarcísio S; Borges, Daniel L G; Carasek, Eduardo; Welz, Bernhard; Feldmann, Jörg; Campo Menoyo, Javier Del

2016-04-01

High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) has been applied for the development of a method for the determination of total As in fish oil samples using direct analysis. The method does not use any sample pretreatment, besides dilution with 1-propanole, in order to decrease the oil viscosity. The stability and sensitivity of As were evaluated using ruthenium and iridium as permanent chemical modifiers and palladium added in solution over the sample. The best results were obtained with ruthenium as the permanent modifier and palladium in solution added to samples and standard solutions. Under these conditions, aqueous standard solutions could be used for calibration for the fish oil samples diluted with 1-propanole. The pyrolysis and atomization temperatures were 1400 °C and 2300 °C, respectively, and the limit of detection and characteristic mass were 30 pg and 43 pg, respectively. Accuracy and precision of the method have been evaluated using microwave-assisted acid digestion of the samples with subsequent determination by HR-CS GF AAS and ICP-MS; the results were in agreement (95% confidence level) with those of the proposed method. Copyright © 2015 Elsevier B.V. All rights reserved.

Standardization, evaluation and early-phase method validation of an analytical scheme for batch-consistency N-glycosylation analysis of recombinant produced glycoproteins.

PubMed

Zietze, Stefan; Müller, Rainer H; Brecht, René

2008-03-01

In order to set up a batch-to-batch-consistency analytical scheme for N-glycosylation analysis, several sample preparation steps including enzyme digestions and fluorophore labelling and two HPLC-methods were established. The whole method scheme was standardized, evaluated and validated according to the requirements on analytical testing in early clinical drug development by usage of a recombinant produced reference glycoprotein (RGP). The standardization of the methods was performed by clearly defined standard operation procedures. During evaluation of the methods, the major interest was in the loss determination of oligosaccharides within the analytical scheme. Validation of the methods was performed with respect to specificity, linearity, repeatability, LOD and LOQ. Due to the fact that reference N-glycan standards were not available, a statistical approach was chosen to derive accuracy from the linearity data. After finishing the validation procedure, defined limits for method variability could be calculated and differences observed in consistency analysis could be separated into significant and incidental ones.

Application of advanced sampling and analysis methods to predict the structure of adsorbed protein on a material surface

PubMed Central

Abramyan, Tigran M.; Hyde-Volpe, David L.; Stuart, Steven J.; Latour, Robert A.

2017-01-01

The use of standard molecular dynamics simulation methods to predict the interactions of a protein with a material surface have the inherent limitations of lacking the ability to determine the most likely conformations and orientations of the adsorbed protein on the surface and to determine the level of convergence attained by the simulation. In addition, standard mixing rules are typically applied to combine the nonbonded force field parameters of the solution and solid phases the system to represent interfacial behavior without validation. As a means to circumvent these problems, the authors demonstrate the application of an efficient advanced sampling method (TIGER2A) for the simulation of the adsorption of hen egg-white lysozyme on a crystalline (110) high-density polyethylene surface plane. Simulations are conducted to generate a Boltzmann-weighted ensemble of sampled states using force field parameters that were validated to represent interfacial behavior for this system. The resulting ensembles of sampled states were then analyzed using an in-house-developed cluster analysis method to predict the most probable orientations and conformations of the protein on the surface based on the amount of sampling performed, from which free energy differences between the adsorbed states were able to be calculated. In addition, by conducting two independent sets of TIGER2A simulations combined with cluster analyses, the authors demonstrate a method to estimate the degree of convergence achieved for a given amount of sampling. The results from these simulations demonstrate that these methods enable the most probable orientations and conformations of an adsorbed protein to be predicted and that the use of our validated interfacial force field parameter set provides closer agreement to available experimental results compared to using standard CHARMM force field parameterization to represent molecular behavior at the interface. PMID:28514864

Sample Collection Information Document for Pathogens and Biotoxins − Companion to Standardized Analytical Methods for Environmental Restoration Following Homeland Security Events (SAM) Revision 5.0

EPA Pesticide Factsheets

Sample Collection Information Document is intended to provide sampling information to be used during site assessment, remediation and clearance activities following a biological or biotoxin contamination incident.

ISSUES RELATED TO SOLUTION CHEMISTRY IN MERCURY SAMPLING IMPINGERS

EPA Science Inventory

Analysis of mercury (Hg) speciation in combustion flue gases is often accomplished in standardized sampling trains in which the sample is passed sequentially through a series of aqueous solutions to capture and separate oxidized Hg (Hg2+) and elemental Hg (Hgo). Such methods incl...

Simultaneous determination of thirteen organophosphate esters in settled indoor house dust and a comparison between two sampling techniques.

PubMed

Fan, Xinghua; Kubwabo, Cariton; Rasmussen, Pat E; Wu, Fang

2014-09-01

An analytical method for the simultaneous determination of 13 organophosphate esters (OPEs) in house dust was developed. The method is based on solvent extraction by sonication, sample cleanup by solid phase extraction (SPE), and analysis by gas chromatography-positive chemical ionization-tandem mass spectrometry (GC/PCI-MS/MS). Method detection limits (MDLs) ranged from 0.03 to 0.43 μg/g and recoveries from 60% to 118%. The inter- and intra-day variations ranged from 3% to 23%. The method was applied to dust samples collected using two vacuum sampling techniques from 134 urban Canadian homes: a sample of fresh or "active" dust (FD) collected by technicians and a composite sample taken from the household vacuum cleaner (HD). Results show that the two sampling methods (i.e., FD vs HD) provided comparable results. Tributoxyethyl phosphate (TBEP), triphenyl phosphate (TPhP), tris(chloropropyl) phosphate (TCPP), tri(2-chloroethyl) phosphate (TCEP), tris(dichloro-isopropyl) phosphate (TDCPP), tricresyl phosphate (TCrP), and tri-n-butyl phosphate (TnBP) were detected in the majority of samples. The most predominant OPE was TBEP, with median concentrations of 31.9 μg/g and 22.8 μg/g in FD and HD samples, respectively, 1 to 2 orders of magnitude higher than other OPEs. The method was also applied to the analysis of OPEs in the National Institute of Standards and Technology (NIST) standard reference material (NIST SRM 2585, organic contaminants in house dust). The results from SRM 2585 may contribute to the certification of OPE concentration values in this SRM. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

The use of wavelength dispersive X-ray fluorescence in the identification of the elemental composition of vanilla samples and the determination of the geographic origin by discriminant function analysis.

PubMed

Hondrogiannis, Ellen; Rotta, Kathryn; Zapf, Charles M

2013-03-01

Sixteen elements found in 37 vanilla samples from Madagascar, Uganda, India, Indonesia (all Vanilla planifolia species), and Papa New Guinea (Vanilla tahitensis species) were measured by wavelength dispersive X-ray fluorescence (WDXRF) spectroscopy for the purpose of determining the elemental concentrations to discriminate among the origins. Pellets were prepared of the samples and elemental concentrations were calculated based on calibration curves created using 4 Natl. Inst. of Standards and Technology (NIST) standards. Discriminant analysis was used to successfully classify the vanilla samples by their species and their geographical region. Our method allows for higher throughput in the rapid screening of vanilla samples in less time than analytical methods currently available. Wavelength dispersive X-ray fluorescence spectroscopy and discriminant function analysis were used to classify vanilla from different origins resulting in a model that could potentially serve to rapidly validate these samples before purchasing from a producer. © 2013 Institute of Food Technologists®

Application of Internal Standard Method for Several 3d-Transition Metallic Elements in Flame Atomic Absorption Spectrometry Using a Multi-wavelength High-resolution Spectrometer.

PubMed

Toya, Yusuke; Itagaki, Toshiko; Wagatsuma, Kazuaki

2017-01-01

We investigated a simultaneous internal standard method in flame atomic absorption spectrometry (FAAS), in order to better the analytical precision of 3d-transition metals contained in steel materials. For this purpose, a new spectrometer system for FAAS, comprising a bright xenon lamp as the primary radiation source and a high-resolution Echelle monochromator, was employed to measure several absorption lines at a wavelength width of ca. 0.3 nm at the same time, which enables the absorbances of an analytical line and also an internal standard line to be estimated. In considering several criteria for selecting an internal standard element and the absorption line, it could be suggested that platinum-group elements: ruthenium, rhodium, or palladium, were suitable for an internal standard element to determine the 3d-transition metal elements, such as titanium, iron, and nickel, by measuring an appropriate pair of these absorption lines simultaneously. Several variances of the absorption signal, such as a variation in aspirated amounts of sample solution and a short-period drift of the primary light source, would be corrected and thus reduced, when the absorbance ratio of the analytical line to the internal standard line was measured. In Ti-Pd, Ni-Rh, and Fe-Ru systems chosen as typical test samples, the repeatability of the signal respnses was investigated with/without the internal standard method, resulting in better precision when the internal standard method was applied in the FAAS with a nitrous oxide-acetylene flame rather than an air-acetylene flame.

Use of laser ablation-inductively coupled plasma-time of flight-mass spectrometry to identify the elemental composition of vanilla and determine the geographic origin by discriminant function analysis.

PubMed

Hondrogiannis, Ellen M; Ehrlinger, Erin; Poplaski, Alyssa; Lisle, Meredith

2013-11-27

A total of 11 elements found in 25 vanilla samples from Uganda, Madagascar, Indonesia, and Papua New Guinea were measured by laser ablation-inductively coupled plasma-time-of-flight-mass spectrometry (LA-ICP-TOF-MS) for the purpose of collecting data that could be used to discriminate among the origins. Pellets were prepared of the samples, and elemental concentrations were obtained on the basis of external calibration curves created using five National Institute of Standards and Technology (NIST) standards and one Chinese standard with (13)C internal standardization. These curves were validated using NIST 1573a (tomato leaves) as a check standard. Discriminant analysis was used to successfully classify the vanilla samples by their origin. Our method illustrates the feasibility of using LA-ICP-TOF-MS with an external calibration curve for high-throughput screening of spice screening analysis.

Method validation for control determination of mercury in fresh fish and shrimp samples by solid sampling thermal decomposition/amalgamation atomic absorption spectrometry.

PubMed

Torres, Daiane Placido; Martins-Teixeira, Maristela Braga; Cadore, Solange; Queiroz, Helena Müller

2015-01-01

A method for the determination of total mercury in fresh fish and shrimp samples by solid sampling thermal decomposition/amalgamation atomic absorption spectrometry (TDA AAS) has been validated following international foodstuff protocols in order to fulfill the Brazilian National Residue Control Plan. The experimental parameters have been previously studied and optimized according to specific legislation on validation and inorganic contaminants in foodstuff. Linearity, sensitivity, specificity, detection and quantification limits, precision (repeatability and within-laboratory reproducibility), robustness as well as accuracy of the method have been evaluated. Linearity of response was satisfactory for the two range concentrations available on the TDA AAS equipment, between approximately 25.0 and 200.0 μg kg(-1) (square regression) and 250.0 and 2000.0 μg kg(-1) (linear regression) of mercury. The residues for both ranges were homoscedastic and independent, with normal distribution. Correlation coefficients obtained for these ranges were higher than 0.995. Limits of quantification (LOQ) and of detection of the method (LDM), based on signal standard deviation (SD) for a low-in-mercury sample, were 3.0 and 1.0 μg kg(-1), respectively. Repeatability of the method was better than 4%. Within-laboratory reproducibility achieved a relative SD better than 6%. Robustness of the current method was evaluated and pointed sample mass as a significant factor. Accuracy (assessed as the analyte recovery) was calculated on basis of the repeatability, and ranged from 89% to 99%. The obtained results showed the suitability of the present method for direct mercury measurement in fresh fish and shrimp samples and the importance of monitoring the analysis conditions for food control purposes. Additionally, the competence of this method was recognized by accreditation under the standard ISO/IEC 17025.

[Study on rapid determination and analysis of rocket kerosene by near infrared spectrum and chemometrics].

PubMed

Xia, Ben-Li; Cong, Ji-Xin; Li, Xia; Wang, Xuan-Jun

2011-06-01

The rocket kerosene quality properties such as density, distillation range, viscosity and iodine value were successfully measured based on their near-infrared spectrum (NIRS) and chemometrics. In the present paper, more than 70 rocket kerosene samples were determined by near infrared spectrum, the models were built using the partial least squares method within the appropriate wavelength range. The correlation coefficients (R2) of every rocket kerosene's quality properties ranged from 0.862 to 0.999. Ten unknown samples were determined with the model, and the result showed that the prediction accuracy of near infrared spectrum method accords with standard analysis requirements. The new method is well suitable for replacing the traditional standard method to rapidly determine the properties of the rocket kerosene.

Personalized monitoring of therapeutic salicylic acid in dried blood spots using a three-layer setup and desorption electrospray ionization mass spectrometry.

PubMed

Siebenhaar, Markus; Küllmer, Kai; Fernandes, Nuno Miguel de Barros; Hüllen, Volker; Hopf, Carsten

2015-09-01

Desorption electrospray ionization (DESI) mass spectrometry is an emerging technology for direct therapeutic drug monitoring in dried blood spots (DBS). Current DBS methods require manual application of small molecules as internal standards for absolute drug quantification. With industrial standardization in mind, we superseded the manual addition of standard and built a three-layer setup for robust quantification of salicylic acid directly from DBS. We combined a dioctyl sodium sulfosuccinate weave facilitating sample spreading with a cellulose layer for addition of isotope-labeled salicylic acid as internal standard and a filter paper for analysis of the standard-containing sample by DESI-MS. Using this setup, we developed a quantification method for salicylic acid from whole blood with a validated linear curve range from 10 to 2000 mg/L, a relative standard deviation (RSD%) ≤14%, and determination coefficients of 0.997. The limit of detection (LOD) was 8 mg/L and the lower limit of quantification (LLOQ) was 10 mg/L. Recovery rates in method verification by LC-MS/MS were 97 to 101% for blinded samples. Most importantly, a study in healthy volunteers after administration of a single dose of Aspirin provides evidence to suggest that the three-layer setup may enable individual pharmacokinetic and endpoint testing following blood collection by finger pricking by patients at home. Taken together, our data suggests that DBS-based quantification of drugs by DESI-MS on pre-manufactured three-layer cartridges may be a promising approach for future near-patient therapeutic drug monitoring.

Evaluation of the PrioCHECK™ Trichinella AAD Kit for the digestion and recovery of larvae in pork, horse meat and wild meat.

PubMed

Konecsni, Kelly; Scheller, Cheryl; Scandrett, Brad; Buholzer, Patrik; Gajadhar, Alvin

2017-08-30

The artificial digestion magnetic stirrer method using pepsin protease and hydrochloric acid is the standard assay for the detection of Trichinella larvae in muscle of infected animals. Recently, an alternative enzyme, serine protease, was employed in the development of a commercially available digestion kit (PrioCHECK™ Trichinella AAD Kit). This assay requires a higher digestion temperature of 60°C which kills the larvae during the digestion process, mitigating the risk of environmental contamination from the parasite. The present study was conducted to determine the performance of the PrioCHECK™ Trichinella AAD Kit compared to the conventional pepsin/HCl digestion. Replicate paired 115g samples of Trichinella-negative pork diaphragm and masseter, and of horse tongue and masseter, were used to compare the two methods for tissue digestibility. Similarly, paired 100g samples of pork diaphragm and horse tongue were spiked with proficiency samples containing known numbers of Trichinella spiralis first stage larvae to compare larval recoveries for the two methods. Masseter samples from wild bears and wolves naturally infected with Trichinella nativa or T6 were also used to compare the performance of the methods. The results of the study showed that the PrioCHECK™ Trichinella AAD Kit, when used according to the manufacturer's instructions, was effective in detecting Trichinella infection in all samples that contained 0.05 or more larvae per gram of tissue. Although there was no significant difference between the Kit method and the standard pepsin/HCl digestion procedure in the average number of larvae recovered from spiked pork diaphragm, 38% fewer larvae were recovered from similarly spiked samples of horse tongue by digestion using serine protease (one way ANOVA, P value <0.001). Additional clarification was also more often required for both horse meat and pork when using the Kit compared to the pepsin/HCl method. The results of testing wildlife samples were similar for the two methods. Overall, the performance of the Kit method was suitable for the digestion of muscle samples and recovery of Trichinella larvae, according to international standards. It also provides advantages of faster digestion, safer reagents and recovered parasites that are non-hazardous for analysts and the environment. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of dissolved arsenic, boron, lithium, selenium, strontium, thallium, and vanadium using inductively coupled plasma-mass spectrometry

USGS Publications Warehouse

Garbarino, John R.

1999-01-01

The inductively coupled plasma?mass spectrometric (ICP?MS) methods have been expanded to include the determination of dissolved arsenic, boron, lithium, selenium, strontium, thallium, and vanadium in filtered, acidified natural water. Method detection limits for these elements are now 10 to 200 times lower than by former U.S. Geological Survey (USGS) methods, thus providing lower variability at ambient concentrations. The bias and variability of the method was determined by using results from spike recoveries, standard reference materials, and validation samples. Spike recoveries at 5 to 10 times the method detection limit and 75 micrograms per liter in reagent-water, surface-water, and groundwater matrices averaged 93 percent for seven replicates, although selected elemental recoveries in a ground-water matrix with an extremely high iron sulfate concentration were negatively biased by 30 percent. Results for standard reference materials were within 1 standard deviation of the most probable value. Statistical analysis of the results from about 60 filtered, acidified natural-water samples indicated that there was no significant difference between ICP?MS and former USGS official methods of analysis.

An ion-selective electrode method for determination of chlorine in geological materials

USGS Publications Warehouse

Aruscavage, P. J.; Campbell, E.Y.

1983-01-01

A method is presented for the determination of chlorine in geological materials, in which a chloride-selective ion electrode is used after decomposition of the sample with hydrofluoric acid and separation of chlorine in a gas-diffusion cell. Data are presented for 30 geological standard materials. The relative standard deviation of the method is estimated to be better than 8% for amounts of chloride of 10 ??g and greater. ?? 1983.

A new dimethyl labeling-based SID-MRM-MS method and its application to three proteases involved in insulin maturation.

PubMed

Cheng, Dongwan; Zheng, Li; Hou, Junjie; Wang, Jifeng; Xue, Peng; Yang, Fuquan; Xu, Tao

2015-01-01

The absolute quantification of target proteins in proteomics involves stable isotope dilution coupled with multiple reactions monitoring mass spectrometry (SID-MRM-MS). The successful preparation of stable isotope-labeled internal standard peptides is an important prerequisite for the SID-MRM absolute quantification methods. Dimethyl labeling has been widely used in relative quantitative proteomics and it is fast, simple, reliable, cost-effective, and applicable to any protein sample, making it an ideal candidate method for the preparation of stable isotope-labeled internal standards. MRM mass spectrometry is of high sensitivity, specificity, and throughput characteristics and can quantify multiple proteins simultaneously, including low-abundance proteins in precious samples such as pancreatic islets. In this study, a new method for the absolute quantification of three proteases involved in insulin maturation, namely PC1/3, PC2 and CPE, was developed by coupling a stable isotope dimethyl labeling strategy for internal standard peptide preparation with SID-MRM-MS quantitative technology. This method offers a new and effective approach for deep understanding of the functional status of pancreatic β cells and pathogenesis in diabetes.

Harmonisation of microbial sampling and testing methods for distillate fuels

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

Hill, G.C.; Hill, E.C.

1995-05-01

Increased incidence of microbial infection in distillate fuels has led to a demand for organisations such as the Institute of Petroleum to propose standards for microbiological quality, based on numbers of viable microbial colony forming units. Variations in quality requirements, and in the spoilage significance of contaminating microbes plus a tendency for temporal and spatial changes in the distribution of microbes, makes such standards difficult to implement. The problem is compounded by a diversity in the procedures employed for sampling and testing for microbial contamination and in the interpretation of the data obtained. The following paper reviews these problems andmore » describes the efforts of The Institute of Petroleum Microbiology Fuels Group to address these issues and in particular to bring about harmonisation of sampling and testing methods. The benefits and drawbacks of available test methods, both laboratory based and on-site, are discussed.« less

[TLC-SERS study on evodiamine in evodia rutaecarpa].

PubMed

Zhang, Jin-zhi; Wang, Yuan; Chen, Hui; Shao, Hui-bo

2007-05-01

A new method for analyzing the ingredients of evodiamine (EV), rutaecarpine (RU), hydroxyevodiamine (HYD), evodiamide (ED), dihydrorutaecarpine (DRU) and 14-formyldihydrorutaecarpine (FDRU) in evodia rutaecarpa using high performance thin layer chromatography (TLC) and surface enhanced Raman spectroscopy (SERS) technique is reported. The character of this method is that standard samples are not needed. The results show that the characteristic spectral bands of EV, RU, HYD, and ED can be obtained from the TLC spot with microgramme of sample. The spectral band at 1562 cm(-1) was obtained with great enhancement. Molecule absorbed in surface silver sol by nr electrons in ring. The spectral bands of EV, RU, HYD and ED are obviously different due to their differences in structure. The TLC and SERS techniques standard samples are a convenient and speedy method to analyze chemical ingredients with high sensitivity for the study of the Chinese traditional medicine.

Improvements to sample processing and measurement to enable more widespread environmental application of tritium

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

Moran, James; Alexander, Thomas; Aalseth, Craig

2017-08-01

Previous measurements have demonstrated the wealth of information that tritium (T) can provide on environmentally relevant processes. We present modifications to sample preparation approaches that enable T measurement by proportional counting on small sample sizes equivalent to 120 mg of water and demonstrate the accuracy of these methods on a suite of standardized water samples. This enhanced method should provide the analytical flexibility needed to address persistent knowledge gaps in our understanding of T behavior in the environment.

Quantitative determination of mineral composition by powder x-ray diffraction

DOEpatents

Pawloski, G.A.

1984-08-10

An external standard intensity ratio method is used for quantitatively determining mineralogic compositions of samples by x-ray diffraction. The method uses ratios of x-ray intensity peaks from a single run. Constants are previously determined for each mineral which is to be quantitatively measured. Ratios of the highest intensity peak of each mineral to be quantified in the sample and the highest intensity peak of a reference mineral contained in the sample are used to calculate sample composition.

Quantitative determination of mineral composition by powder X-ray diffraction

DOEpatents

Pawloski, Gayle A.

1986-01-01

An external standard intensity ratio method is used for quantitatively determining mineralogic compositions of samples by x-ray diffraction. The method uses ratios of x-ray intensity peaks from a single run. Constants are previously determined for each mineral which is to be quantitatively measured. Ratios of the highest intensity peak of each mineral to be quantified in the sample and the highest intensity peak of a reference mineral contained in the sample are used to calculate sample composition.

Measuring and mitigating inhibition during real-time, quantitative PCR analysis of viral nucleic acid extracts from large-volume environmental water samples

USDA-ARS?s Scientific Manuscript database

Naturally-occurring inhibitory compounds are a major concern during qPCR and RT-qPCR analysis of environmental samples, particularly large volume water samples. Here, a standardized method for measuring and mitigating sample inhibition in environmental water concentrates is described. Specifically, ...

The Kjeldahl method as a primary reference procedure for total protein in certified reference materials used in clinical chemistry. I. A review of Kjeldahl methods adopted by laboratory medicine.

PubMed

Chromý, Vratislav; Vinklárková, Bára; Šprongl, Luděk; Bittová, Miroslava

2015-01-01

We found previously that albumin-calibrated total protein in certified reference materials causes unacceptable positive bias in analysis of human sera. The simplest way to cure this defect is the use of human-based serum/plasma standards calibrated by the Kjeldahl method. Such standards, commutative with serum samples, will compensate for bias caused by lipids and bilirubin in most human sera. To find a suitable primary reference procedure for total protein in reference materials, we reviewed Kjeldahl methods adopted by laboratory medicine. We found two methods recommended for total protein in human samples: an indirect analysis based on total Kjeldahl nitrogen corrected for its nonprotein nitrogen and a direct analysis made on isolated protein precipitates. The methods found will be assessed in a subsequent article.

Multielement trace determination in SiC powders: assessment of interlaboratory comparisons aimed at the validation and standardization of analytical procedures with direct solid sampling based on ETV ICP OES and DC arc OES.

PubMed

Matschat, Ralf; Hassler, Jürgen; Traub, Heike; Dette, Angelika

2005-12-01

The members of the committee NMP 264 "Chemical analysis of non-oxidic raw and basic materials" of the German Standards Institute (DIN) have organized two interlaboratory comparisons for multielement determination of trace elements in silicon carbide (SiC) powders via direct solid sampling methods. One of the interlaboratory comparisons was based on the application of inductively coupled plasma optical emission spectrometry with electrothermal vaporization (ETV ICP OES), and the other on the application of optical emission spectrometry with direct current arc (DC arc OES). The interlaboratory comparisons were organized and performed in the framework of the development of two standards related to "the determination of mass fractions of metallic impurities in powders and grain sizes of ceramic raw and basic materials" by both methods. SiC powders were used as typical examples of this category of material. The aim of the interlaboratory comparisons was to determine the repeatability and reproducibility of both analytical methods to be standardized. This was an important contribution to the practical applicability of both draft standards. Eight laboratories participated in the interlaboratory comparison with ETV ICP OES and nine in the interlaboratory comparison with DC arc OES. Ten analytes were investigated by ETV ICP OES and eleven by DC arc OES. Six different SiC powders were used for the calibration. The mass fractions of their relevant trace elements were determined after wet chemical digestion. All participants followed the analytical requirements described in the draft standards. In the calculation process, three of the calibration materials were used successively as analytical samples. This was managed in the following manner: the material that had just been used as the analytical sample was excluded from the calibration, so the five other materials were used to establish the calibration plot. The results from the interlaboratory comparisons were summarized and used to determine the repeatability and the reproducibility (expressed as standard deviations) of both methods. The calculation was carried out according to the related standard. The results are specified and discussed in this paper, as are the optimized analytical conditions determined and used by the authors of this paper. For both methods, the repeatability relative standard deviations were <25%, usually ~10%, and the reproducibility relative standard deviations were <35%, usually ~15%. These results were regarded as satifactory for both methods intended for rapid analysis of materials for which decomposition is difficult and time-consuming. Also described are some results from an interlaboratory comparison used to certify one of the materials that had been previously used for validation in both interlaboratory comparisons. Thirty laboratories (from eight countries) participated in this interlaboratory comparison for certification. As examples, accepted results are shown from laboratories that used ETV ICP OES or DC arc OES and had performed calibrations by using solutions or oxides, respectively. The certified mass fractions of the certified reference materials were also compared with the mass fractions determined in the interlaboratory comparisons performed within the framework of method standardization. Good agreement was found for most of the analytes.

Development and application of a validated HPLC method for the analysis of dissolution samples of levothyroxine sodium drug products.

PubMed

Collier, J W; Shah, R B; Bryant, A R; Habib, M J; Khan, M A; Faustino, P J

2011-02-20

A rapid, selective, and sensitive gradient HPLC method was developed for the analysis of dissolution samples of levothyroxine sodium tablets. Current USP methodology for levothyroxine (L-T(4)) was not adequate to resolve co-elutants from a variety of levothyroxine drug product formulations. The USP method for analyzing dissolution samples of the drug product has shown significant intra- and inter-day variability. The sources of method variability include chromatographic interferences introduced by the dissolution media and the formulation excipients. In the present work, chromatographic separation of levothyroxine was achieved on an Agilent 1100 Series HPLC with a Waters Nova-pak column (250 mm × 3.9 mm) using a 0.01 M phosphate buffer (pH 3.0)-methanol (55:45, v/v) in a gradient elution mobile phase at a flow rate of 1.0 mL/min and detection UV wavelength of 225 nm. The injection volume was 800 μL and the column temperature was maintained at 28°C. The method was validated according to USP Category I requirements. The validation characteristics included accuracy, precision, specificity, linearity, and analytical range. The standard curve was found to have a linear relationship (r(2)>0.99) over the analytical range of 0.08-0.8 μg/mL. Accuracy ranged from 90 to 110% for low quality control (QC) standards and 95 to 105% for medium and high QC standards. Precision was <2% at all QC levels. The method was found to be accurate, precise, selective, and linear for L-T(4) over the analytical range. The HPLC method was successfully applied to the analysis of dissolution samples of marketed levothyroxine sodium tablets. Published by Elsevier B.V.

Development and application of a validated HPLC method for the analysis of dissolution samples of levothyroxine sodium drug products

PubMed Central

Collier, J.W.; Shah, R.B.; Bryant, A.R.; Habib, M.J.; Khan, M.A.; Faustino, P.J.

2011-01-01

A rapid, selective, and sensitive gradient HPLC method was developed for the analysis of dissolution samples of levothyroxine sodium tablets. Current USP methodology for levothyroxine (l-T4) was not adequate to resolve co-elutants from a variety of levothyroxine drug product formulations. The USP method for analyzing dissolution samples of the drug product has shown significant intra- and inter-day variability. The sources of method variability include chromatographic interferences introduced by the dissolution media and the formulation excipients. In the present work, chromatographic separation of levothyroxine was achieved on an Agilent 1100 Series HPLC with a Waters Nova-pak column (250mm × 3.9mm) using a 0.01 M phosphate buffer (pH 3.0)–methanol (55:45, v/v) in a gradient elution mobile phase at a flow rate of 1.0 mL/min and detection UV wavelength of 225 nm. The injection volume was 800 µL and the column temperature was maintained at 28 °C. The method was validated according to USP Category I requirements. The validation characteristics included accuracy, precision, specificity, linearity, and analytical range. The standard curve was found to have a linear relationship (r2 > 0.99) over the analytical range of 0.08–0.8 µg/mL. Accuracy ranged from 90 to 110% for low quality control (QC) standards and 95 to 105% for medium and high QC standards. Precision was <2% at all QC levels. The method was found to be accurate, precise, selective, and linear for l-T4 over the analytical range. The HPLC method was successfully applied to the analysis of dissolution samples of marketed levothyroxine sodium tablets. PMID:20947276

Estimation of Standard Error of Regression Effects in Latent Regression Models Using Binder's Linearization. Research Report. ETS RR-07-09

ERIC Educational Resources Information Center

Li, Deping; Oranje, Andreas

2007-01-01

Two versions of a general method for approximating standard error of regression effect estimates within an IRT-based latent regression model are compared. The general method is based on Binder's (1983) approach, accounting for complex samples and finite populations by Taylor series linearization. In contrast, the current National Assessment of…

Molecular Weights of Bovine and Porcine Heparin Samples: Comparison of Chromatographic Methods and Results of a Collaborative Survey.

PubMed

Bertini, Sabrina; Risi, Giulia; Guerrini, Marco; Carrick, Kevin; Szajek, Anita Y; Mulloy, Barbara

2017-07-19

In a collaborative study involving six laboratories in the USA, Europe, and India the molecular weight distributions of a panel of heparin sodium samples were determined, in order to compare heparin sodium of bovine intestinal origin with that of bovine lung and porcine intestinal origin. Porcine samples met the current criteria as laid out in the USP Heparin Sodium monograph. Bovine lung heparin samples had consistently lower average molecular weights. Bovine intestinal heparin was variable in molecular weight; some samples fell below the USP limits, some fell within these limits and others fell above the upper limits. These data will inform the establishment of pharmacopeial acceptance criteria for heparin sodium derived from bovine intestinal mucosa. The method for MW determination as described in the USP monograph uses a single, broad standard calibrant to characterize the chromatographic profile of heparin sodium on high-resolution silica-based GPC columns. These columns may be short-lived in some laboratories. Using the panel of samples described above, methods based on the use of robust polymer-based columns have been developed. In addition to the use of the USP's broad standard calibrant for heparin sodium with these columns, a set of conditions have been devised that allow light-scattering detected molecular weight characterization of heparin sodium, giving results that agree well with the monograph method. These findings may facilitate the validation of variant chromatographic methods with some practical advantages over the USP monograph method.

Rapid Determination of Salmonella in Samples of Egg Noodles, Cake Mixes, and Candies

PubMed Central

Banwart, George J.; Kreitzer, Madeleine J.

1969-01-01

A glass apparatus system was compared with a standard enrichment broth-selective agar method to test samples of egg noodles, cake mixes, and candy for the presence or absence of salmonellae. The glass apparatus system used fermentation of mannitol, production of H2S, or motility, in conjunction with a serological test of flagellar antigens, to detect salmonellae. No salmonellae were detected in 173 samples of food products. Of these samples, 171 were found to be Salmonella-negative after 48 hr with the glass apparatus system. After 72 hr, the standard Salmonella procedure yielded 38 samples which produced Salmonella false-positive results on selective agars. Inoculation of samples with cultures of Salmonella showed that approximately one inoculated cell could be detected after 48 hr of incubation with the glass apparatus. The standard Salmonella test requires a minimum of 72 hr for completion. Compared with the standard Salmonella test, the glass apparatus system is a more rapid and simple system that can be used to determine the presence or absence of Salmonella in these food products. Images PMID:5370460

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

NONE

The first part covers standards for gaseous fuels. The standard part covers standards on coal and coke including the classification of coals, determination of major elements in coal ash and trace elements in coal, metallurgical properties of coal and coke, methods of analysis of coal and coke, petrographic analysis of coal and coke, physical characteristics of coal, quality assurance and sampling.

Standards for electron probe microanalysis of silicates prepared by convenient method

NASA Technical Reports Server (NTRS)

Walter, L. S.

1966-01-01

Standard compositions suitable for electron probe microanalysis of various silicates are prepared by coprecipitation of specified salts with colloidal silica to form a gel which is decomposed into a powdered oxide mixture and compressed into thin pellets. These pellets of predetermined standard are compared with a silicate sample to determine its composition.

40 CFR Appendix B to Subpart Hhhh... - Method for the Determination of Loss-on-Ignition

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FOR SOURCE CATEGORIES (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Wet-Formed Fiberglass Mat...). 4.2Remove the test sample from the furnace and cool in the desiccator for 30 minutes in the standard...

Analysis of hydrazine in drinking water by isotope dilution gas chromatography/tandem mass spectrometry with derivatization and liquid-liquid extraction.

PubMed

Davis, William E; Li, Yongtao

2008-07-15

A new isotope dilution gas chromatography/chemical ionization/tandem mass spectrometric method was developed for the analysis of carcinogenic hydrazine in drinking water. The sample preparation was performed by using the optimized derivatization and multiple liquid-liquid extraction techniques. Using the direct aqueous-phase derivatization with acetone, hydrazine and isotopically labeled hydrazine-(15)N2 used as the surrogate standard formed acetone azine and acetone azine-(15)N2, respectively. These derivatives were then extracted with dichloromethane. Prior to analysis using methanol as the chemical ionization reagent gas, the extract was dried with anhydrous sodium sulfate, concentrated through evaporation, and then fortified with isotopically labeled N-nitrosodimethylamine-d6 used as the internal standard to quantify the extracted acetone azine-(15)N2. The extracted acetone azine was quantified against the extracted acetone azine-(15)N2. The isotope dilution standard calibration curve resulted in a linear regression correlation coefficient (R) of 0.999. The obtained method detection limit was 0.70 ng/L for hydrazine in reagent water samples, fortified at a concentration of 1.0 ng/L. For reagent water samples fortified at a concentration of 20.0 ng/L, the mean recoveries were 102% with a relative standard deviation of 13.7% for hydrazine and 106% with a relative standard deviation of 12.5% for hydrazine-(15)N2. Hydrazine at 0.5-2.6 ng/L was detected in 7 out of 13 chloraminated drinking water samples but was not detected in the rest of the chloraminated drinking water samples and the studied chlorinated drinking water sample.

Modified procedure to determine acid-insoluble lignin in wood and pulp

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

Effland, M.J.

1977-10-01

If wood is treated with strong acid, carbohydrates are hydrolyzed and solubilized. The insoluble residue is by definition lignin and can be measured gravimetrically. The standard method of analysis requires samples of 1 or 2 g of wood or pulp. In research at this laboratory these amounts of sample are often not available for analytical determinations. Thus we developed a modification of the standard procedure suitable for much smaller sample amounts. The modification is based on the procedure of Saeman. Wood samples require extraction prior to lignin analysis to remove acid-insoluble extractives that will be measured as lignin. Usually thismore » involves only a standard extraction with ethanol--benzene. However, woods high in tannin must also be subjected to extraction with alcohol. Pulps seldom require extraction.« less

Comparison of Optimal Design Methods in Inverse Problems

PubMed Central

Banks, H. T.; Holm, Kathleen; Kappel, Franz

2011-01-01

Typical optimal design methods for inverse or parameter estimation problems are designed to choose optimal sampling distributions through minimization of a specific cost function related to the resulting error in parameter estimates. It is hoped that the inverse problem will produce parameter estimates with increased accuracy using data collected according to the optimal sampling distribution. Here we formulate the classical optimal design problem in the context of general optimization problems over distributions of sampling times. We present a new Prohorov metric based theoretical framework that permits one to treat succinctly and rigorously any optimal design criteria based on the Fisher Information Matrix (FIM). A fundamental approximation theory is also included in this framework. A new optimal design, SE-optimal design (standard error optimal design), is then introduced in the context of this framework. We compare this new design criteria with the more traditional D-optimal and E-optimal designs. The optimal sampling distributions from each design are used to compute and compare standard errors; the standard errors for parameters are computed using asymptotic theory or bootstrapping and the optimal mesh. We use three examples to illustrate ideas: the Verhulst-Pearl logistic population model [13], the standard harmonic oscillator model [13] and a popular glucose regulation model [16, 19, 29]. PMID:21857762

75 FR 6332 - Wyoming Regulatory Program

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-09

... practices, shrub reclamation standards, fish and wildlife enhancement measures, cultural and historic... normal husbandry practices, reorganize and clarify species diversity and shrub density requirements, and... vegetation sampling methods and reclamation success standards for shrubs on reclaimed lands. In August of...

Direct Analysis of Low-Volatile Molecular Marker Extract from Airborne Particulate Matter Using Sensitivity Correction Method

PubMed Central

Irei, Satoshi

2016-01-01

Molecular marker analysis of environmental samples often requires time consuming preseparation steps. Here, analysis of low-volatile nonpolar molecular markers (5-6 ring polycyclic aromatic hydrocarbons or PAHs, hopanoids, and n-alkanes) without the preseparation procedure is presented. Analysis of artificial sample extracts was directly conducted by gas chromatography-mass spectrometry (GC-MS). After every sample injection, a standard mixture was also analyzed to make a correction on the variation of instrumental sensitivity caused by the unfavorable matrix contained in the extract. The method was further validated for the PAHs using the NIST standard reference materials (SRMs) and then applied to airborne particulate matter samples. Tests with the SRMs showed that overall our methodology was validated with the uncertainty of ~30%. The measurement results of airborne particulate matter (PM) filter samples showed a strong correlation between the PAHs, implying the contributions from the same emission source. Analysis of size-segregated PM filter samples showed that their size distributions were found to be in the PM smaller than 0.4 μm aerodynamic diameter. The observations were consistent with our expectation of their possible sources. Thus, the method was found to be useful for molecular marker studies. PMID:27127511

Improved sample treatment for the determination of insoluble soap in sewage sludge samples by liquid chromatography with fluorescence detection.

PubMed

Cantarero, Samuel; Zafra-Gómez, A; Ballesteros, O; Navalón, A; Vílchez, J L; Crovetto, G; Verge, C; de Ferrer, J A

2010-09-15

A new selective and sensitive method for the determination of insoluble fatty acid salts (soap) in sewage sludge samples is proposed. The method involves a clean up of sample with petroleum ether, the conversion of calcium and magnesium insoluble salts into soluble potassium salts, potassium salts extraction with methanol, and a derivatization procedure previous to the liquid chromatography with fluorescence detection (LC-FLD) analysis. Three different extraction techniques (Soxhlet, microwave-assisted extraction and ultrasounds) were compared and microwave-assisted extraction (MAE) was selected as appropriate for our purpose. This allowed to reduce the extraction time and solvent waste (50 mL of methanol in contrast with 250 mL for Soxhlet procedure). The absence of matrix effect was demonstrated with two standards (C(13:0) and C(17:0)) that are not commercials and neither of them has been detected in sewage sludge samples. Therefore, it was possible to evaluate the matrix effect since both standards have similar environmental behaviour (adsorption and precipitation) to commercial soaps (C(10:0)-C(18:0)). The method was successfully applied to samples from different sources and consequently, with different composition. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Evaluation of extraction methods for ochratoxin A detection in cocoa beans employing HPLC.

PubMed

Mishra, Rupesh K; Catanante, Gaëlle; Hayat, Akhtar; Marty, Jean-Louis

2016-01-01

Cocoa is an important ingredient for the chocolate industry and for many food products. However, it is prone to contamination by ochratoxin A (OTA), which is highly toxic and potentially carcinogenic to humans. In this work, four different extraction methods were tested and compared based on their recoveries. The best protocol was established which involves an organic solvent-free extraction method for the detection of OTA in cocoa beans using 1% sodium hydrogen carbonate (NaHCO3) in water within 30 min. The extraction method is rapid (as compared with existing methods), simple, reliable and practical to perform without complex experimental set-ups. The cocoa samples were freshly extracted and cleaned-up using immunoaffinity column (IAC) for HPLC analysis using a fluorescence detector. Under the optimised condition, the limit of detection (LOD) and limit of quantification (LOQ) for OTA were 0.62 and 1.25 ng ml(-1) respectively in standard solutions. The method could successfully quantify OTA in naturally contaminated samples. Moreover, good recoveries of OTA were obtained up to 86.5% in artificially spiked cocoa samples, with a maximum relative standard deviation (RSD) of 2.7%. The proposed extraction method could determine OTA at the level 1.5 µg kg(-)(1), which surpassed the standards set by the European Union for cocoa (2 µg kg(-1)). In addition, an efficiency comparison of IAC and molecular imprinted polymer (MIP) column was also performed and evaluated.

Advancing the Use of Passive Sampling in Risk Assessment and Management of Sediments Contaminated with Hydrophobic Organic Chemicals: Results of an International Ex Situ Passive Sampling Interlaboratory Comparison

PubMed Central

2018-01-01

This work presents the results of an international interlaboratory comparison on ex situ passive sampling in sediments. The main objectives were to map the state of the science in passively sampling sediments, identify sources of variability, provide recommendations and practical guidance for standardized passive sampling, and advance the use of passive sampling in regulatory decision making by increasing confidence in the use of the technique. The study was performed by a consortium of 11 laboratories and included experiments with 14 passive sampling formats on 3 sediments for 25 target chemicals (PAHs and PCBs). The resulting overall interlaboratory variability was large (a factor of ∼10), but standardization of methods halved this variability. The remaining variability was primarily due to factors not related to passive sampling itself, i.e., sediment heterogeneity and analytical chemistry. Excluding the latter source of variability, by performing all analyses in one laboratory, showed that passive sampling results can have a high precision and a very low intermethod variability (

Evaluation of a standardized micro-vacuum sampling method for collection of surface dust.

PubMed

Ashley, Kevin; Applegate, Gregory T; Wise, Tamara J; Fernback, Joseph E; Goldcamp, Michael J

2007-03-01

A standardized procedure for collecting dust samples from surfaces using a micro-vacuum sampling technique was evaluated. Experiments were carried out to investigate the collection efficiency of the vacuum sampling method described in ASTM Standard D7144, "Standard Practice for Collection of Surface Dust by Micro-Vacuum Sampling for Subsequent Metals Determination." Weighed masses ( approximately 5, approximately 10 and approximately 25 mg) of three NIST Standard Reference Materials (SRMs) were spiked onto surfaces of various substrates. The SRMs used were: (1) Powdered Lead-Based Paint; (2) Urban Particulate Matter; and (3) Trace Elements in Indoor Dust. Twelve different substrate materials were chosen to be representative of surfaces commonly encountered in occupational and/or indoor settings: (1) wood, (2) tile, (3) linoleum, (4) vinyl, (5) industrial carpet, (6) plush carpet, (7,8) concrete block (painted and unpainted), (9) car seat material, (10) denim, (11) steel, and (12) glass. Samples of SRMs originally spiked onto these surfaces were collected using the standardized micro-vacuum sampling procedure. Gravimetric analysis of material collected within preweighed Accucapinserts (housed within the samplers) was used to measure SRM recoveries. Recoveries ranged from 21.6% (+/- 10.4%, 95% confidence limit [CL]) for SRM 1579 from industrial carpet to 59.2% (+/- 11.0%, 95% CL) for SRM 1579 from glass. For most SRM/substrate combinations, recoveries ranged from approximately 25% to approximately 50%; variabilities differed appreciably. In general, SRM recoveries were higher from smooth and hard surfaces and lower from rough and porous surfaces. Material captured within collection nozzles attached to the sampler inlets was also weighed. A significant fraction of SRM originally spiked onto substrate surfaces was captured within collection nozzles. Percentages of SRMs captured within collection nozzles ranged from approximately 13% (+/- 4 - +/- 5%, 95% CLs) for SRMs 1579 and 2583 from industrial carpet to approximately 45% (+/- 7 - +/- 26%, 95% CLs) for SRM 1648 from glass, tile and steel. For some substrates, loose material from the substrate itself (i.e., substrate particles and fibers) was sometimes collected along with the SRM, both within Accucaps as well as collection nozzles. Co-collection of substrate material can bias results and contribute to sampling variability. The results of this work have provided performance data on the standardized micro-vacuum sampling procedure.

Quantitative Evaluation of Hard X-ray Damage to Biological Samples using EUV Ptychography

NASA Astrophysics Data System (ADS)

Baksh, Peter; Odstrcil, Michal; Parsons, Aaron; Bailey, Jo; Deinhardt, Katrin; Chad, John E.; Brocklesby, William S.; Frey, Jeremy G.

2017-06-01

Coherent diffractive imaging (CDI) has become a standard method on a variety of synchrotron beam lines. The high brilliance short wavelength radiation from these sources can be used to reconstruct attenuation and relative phase of a sample with nanometre resolution via CDI methods. However, the interaction between the sample and high energy ionising radiation can cause degradation to sample structure. We demonstrate, using a laboratory based high harmonic generation (HHG) based extreme ultraviolet (EUV) source, imaging a sample of hippocampal neurons using the ptychography method. The significant increase in contrast of the sample in the EUV light allows identification of damage induced from exposure to 7.3 keV photons, without causing any damage to the sample itself.

Validation of an Analytical Method for Determination of Benzo[a]pyrene Bread using QuEChERS Method by GC-MS

PubMed Central

Eslamizad, Samira; Yazdanpanah, Hassan; Javidnia, Katayon; Sadeghi, Ramezan; Bayat, Mitra; Shahabipour, Sara; Khalighian, Najmeh; Kobarfard, Farzad

2016-01-01

A fast and simple modified QuEChERS (quick, easy, cheap, rugged and safe) extraction method based on spiked calibration curves and direct sample introduction was developed for determination of Benzo [a] pyrene (BaP) in bread by gas chromatography-mass spectrometry single quadrupole selected ion monitoring (GC/MS-SQ-SIM). Sample preparation includes: extraction of BaP into acetone followed by cleanup with dispersive solid phase extraction. The use of spiked samples for constructing the calibration curve substantially reduced adverse matrix-related effects. The average recovery of BaP at 6 concentration levels was in range of 95-120%. The method was proved to be reproducible with relative standard deviation less than 14.5% for all of the concentration levels. The limit of detection and limit of quantification were 0.3 ng/g and 0.5 ng/g, respectively. Correlation coefficient of 0.997 was obtained for spiked calibration standards over the concentration range of 0.5-20 ng/g. To the best of our knowledge, this is the first time that a QuEChERS method is used for the analysis of BaP in breads. The developed method was used for determination of BaP in 29 traditional (Sangak) and industrial (Senan) bread samples collected from Tehran in 2014. These results showed that two Sangak samples were contaminated with BaP. Therefore, a comprehensive survey for monitoring of BaP in Sangak bread samples seems to be needed. This is the first report concerning contamination of bread samples with BaP in Iran. PMID:27642317

[Determination of eight pesticide residues in tea by liquid chromatography-tandem mass spectrometry and its uncertainty evaluation].

PubMed

Hu, Beizhen; Cai, Haijiang; Song, Weihua

2012-09-01

A method was developed for the determination of eight pesticide residues (fipronil, imidacloprid, acetamiprid, buprofezin, triadimefon, triadimenol, profenofos, pyridaben) in tea by liquid chromatography-tandem mass spectrometry. The sample was extracted by accelerated solvent extraction with acetone-dichloromethane (1:1, v/v) as solvent, and the extract was then cleaned-up with a Carb/NH2 solid phase extraction (SPE) column. The separation was performed on a Hypersil Gold C, column (150 mm x 2. 1 mm, 5 microm) and with the gradient elution of acetonitrile and 0. 1% formic acid. The eight pesticides were determined in the modes of electrospray ionization (ESI) and multiple reaction monitoring (MRM). The analytes were quantified by matrix-matched internal standard method for imidacloprid and acetamiprid, by matrix-matched external standard method for the other pesticides. The calibration curves showed good linearity in 1 - 100 microg/L for fipronil, and in 5 -200 microg/L for the other pesticides. The limits of quantification (LOQs, S/N> 10) were 2 p.g/kg for fipronil and 10 microg/kg for the other pesticides. The average recoveries ranged from 75. 5% to 115.0% with the relative standard deviations of 2.7% - 7.7% at the spiked levels of 2, 5, 50 microg/kg for fipronil and 10, 50, 100 microg/kg for the other pesticides. The uncertainty evaluation for the results was carried out according to JJF 1059-1999 "Evaluation and Expression of Uncertainty in Measurement". Items constituting measurement uncertainty involved standard solution, weighing of sample, sample pre-treatment, and the measurement repeatability of the equipment were evaluated. The results showed that the measurement uncertainty is mainly due to sample pre-treatment, standard curves and measurement repeatability of the equipment. The method developed is suitable for the conformation and quantification of the pesticides in tea.

Performance of Bootstrapping Approaches To Model Test Statistics and Parameter Standard Error Estimation in Structural Equation Modeling.

ERIC Educational Resources Information Center

Nevitt, Jonathan; Hancock, Gregory R.

2001-01-01

Evaluated the bootstrap method under varying conditions of nonnormality, sample size, model specification, and number of bootstrap samples drawn from the resampling space. Results for the bootstrap suggest the resampling-based method may be conservative in its control over model rejections, thus having an impact on the statistical power associated…

40 CFR Table 1 to Subpart III of... - Emission Limitations

Code of Federal Regulations, 2011 CFR

2011-07-01

... determining compliance using this method Cadmium 0.004 milligrams per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Performance test (Method 29 of appendix A of part 60). Carbon monoxide 157 parts per million by dry volume 3-run average (1 hour minimum sample time per run) Performance...

40 CFR Table 1 to Subpart Eeee of... - Emission Limitations

Code of Federal Regulations, 2011 CFR

2011-07-01

... determiningcompliance using this method 1. Cadmium 18 micrograms per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Method 29 of appendix A of this part. 2. Carbon monoxide 40 parts per million by dry volume 3-run average (1 hour minimum sample time per run during performance test), and 12-hour...

40 CFR Table 1 to Subpart III of... - Emission Limitations

Code of Federal Regulations, 2010 CFR

2010-07-01

... determining compliance using this method Cadmium 0.004 milligrams per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Performance test (Method 29 of appendix A of part 60). Carbon monoxide 157 parts per million by dry volume 3-run average (1 hour minimum sample time per run) Performance...

40 CFR Table 1 to Subpart Eeee of... - Emission Limitations

Code of Federal Regulations, 2010 CFR

2010-07-01

... determiningcompliance using this method 1. Cadmium 18 micrograms per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Method 29 of appendix A of this part. 2. Carbon monoxide 40 parts per million by dry volume 3-run average (1 hour minimum sample time per run during performance test), and 12-hour...

CTEPP STANDARD OPERATING PROCEDURE FOR COLLECTION OF FOOD PREPARATION SURFACE WIPE SAMPLES FOR PERSISTENT ORGANIC POLLUTANTS (SOP-2.17)

EPA Science Inventory

This SOP describes the method for collection of the food preparation surface wipe samples for the measurement of persistent organic pollutants (POP). This method uses a wipe to collect POP residues from a surface where a study participant prepares food the most often (i.e., kitch...

Atmospheric Fluoroform (CHF3, HFC-23) at Cape Grim, Tasmania (1978-1995)

DOE Data Explorer

Oram, D. E. [University of East Anglia, Norwich, United Kingdom; Sturges, W. T. [University of East Anglia, Norwich, United Kingdom; Penkett, S. A. [University of East Anglia, Norwich, United Kingdom; McCulloch, A. [ICI Chemicals and Polymers, Ltd., Cheshire, United Kingdom; Fraser, P. J. [CRC for Southern Hemisphere Meteorology, Victoria, Australia

2000-10-01

The sampling and analytical methods are described more fully in Oram et al. (1998). In summary, air samples were taken from the archive of Cape Grim, Tasmania (41oS, 145oE) air samples collected from 1978 through 1995. Comparisons of CFC-11, CFC-12, CFC-113, CH3CCl3, and CH4 data between archive samples and corresponding in-situ samples for the same dates confirm that the archive samples are both representative and stable over time. Samples were analyzed by gas chromatography-mass spectrometry (GC-MS), using a KCl-passivated alumina PLOT column. Fluoroform was monitored on mass 69 (CF3+). The analytical precision (one standard deviation of the mean) for two or three replicate analyses was typically ± 1% of the mean measured value. The overall uncertainty of the observed data is ± 10%, taking into account uncertainties in the preparation of the primary standards, the purity of the fluoroform used to make the primary standards, as well as the analytical precision.

[Pretreatment of Aluminum-Lithium Alloy Sample and Determination of Argentum and Lithium by Spectral Analysis].

PubMed

Zhou, Hui; Tan, Qian; Gao, Ya-ling; Sang, Shi-hua; Chen, Wen

2015-10-01

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Flame Atomic Absorption Spectrometry (FAAS) and Visible Spectrometry (VS) was applied for determination of Ag and Li in lithium-aluminium alloy standard sample and test sample, their respective advantages and disadvantages were compared, the excellent selectivity of ICP-OES was confirmed by analyses of certified standard sample. Three different sample digestion methods were compared and discussed in this study. It was found that the better accuracy would be obtained by digesting sample with chloroazotic acid while the content of Li was measured by FAAS, and it was better to digest sample with hydrochloric acid and hydrogen peroxide while determining Ag and Li by ICP-OES simultaneously and determining Ag by FAAS and VS. The interference of co-existing elements and elimination methods was detailedly discussed. Ammonium hydroxide was added to adjust the sample solution into alkalescent and Al, Ti, Zr was precipitated by forming hydroxide precipitation, Mg and Cu was formed complex precipitation with 8-hydroxyquinoline in this condition, then the interference from matrix element to determinate Ag by FAAS was eliminated. In addition, phosphate was used to precipitate Ti to eliminate its interference for determination of Li by FAAS. The same treatment of determination for Ag by FAAS was used to eliminate the interference of matrix element for determination of Ag by VS, the excess of nitrate was added into sample and heated to release Ag+ from silver chloride complex, and the color of 8-hydroxyquinoline was eliminated because of decomposed by heating. The accuracy of analysis result for standard sample was conspicuously improved which confirms the efficient of the method to eliminate interference in this study. The optimal digestion method and eliminate interference method was applied to lithium-aluminium alloy samples. The recovery of samples was from 100.39% to 103.01% by ICP-OES determination for Ag, and from 100.42% to 103.01% by ICP-OES determination for Li. The recovery ranged from 95.91% to 99.98% by FAAS determination for Ag, and ranged from 98.04% to 99.98% for FAAS determination of Li. The recovery was from 98.00% to 101.00 by VS determination for Ag, the analysis results all meet the analysis requirement.

Fast and accurate preparation fatty acid methyl esters by microwave-assisted derivatization in the yeast Saccharomyces cerevisiae.

PubMed

Khoomrung, Sakda; Chumnanpuen, Pramote; Jansa-ard, Suwanee; Nookaew, Intawat; Nielsen, Jens

2012-06-01

We present a fast and accurate method for preparation of fatty acid methyl esters (FAMEs) using microwave-assisted derivatization of fatty acids present in yeast samples. The esterification of free/bound fatty acids to FAMEs was completed within 5 min, which is 24 times faster than with conventional heating methods. The developed method was validated in two ways: (1) through comparison with a conventional method (hot plate) and (2) through validation with the standard reference material (SRM) 3275-2 omega-3 and omega-6 fatty acids in fish oil (from the Nation Institute of Standards and Technology, USA). There were no significant differences (P>0.05) in yields of FAMEs with both validations. By performing a simple modification of closed-vessel microwave heating, it was possible to carry out the esterification in Pyrex glass tubes kept inside the closed vessel. Hereby, we are able to increase the number of sample preparations to several hundred samples per day as the time for preparation of reused vessels was eliminated. Pretreated cell disruption steps are not required, since the direct FAME preparation provides equally quantitative results. The new microwave-assisted derivatization method facilitates the preparation of FAMEs directly from yeast cells, but the method is likely to also be applicable for other biological samples.

Analysis of four toxic metals in a single rice seed by matrix solid phase dispersion -inductively coupled plasma mass spectrometry

NASA Astrophysics Data System (ADS)

He, Xiufen; Chen, Lixia; Chen, Xin; Yu, Huamei; Peng, Lixu; Han, Bingjun

2016-12-01

Toxic metals in rice pose great risks to human health. Metal bioaccumulation in rice grains is a criterion of breeding. Rice breeding requires a sensitive method to determine metal content in single rice grains to assist the variety selection. In the present study, four toxic metals of arsenic (As), cadmium (Cd), chromium (Cr) and lead (Pb) in a single rice grain were determined by a simple and rapid method. The developed method is based on matrix solid phase dispersion using multi-wall carbon nanotubes (MWCNTs) as dispersing agent and analyzed by inductively coupled plasma mass spectrometry. The experimental parameters were systematically investigated. The limits of detection (LOD) were 5.0, 0.6, 10 and 2.1 ng g-1 for As, Cd, Cr, and Pb, respectively, with relative standard deviations (n = 6) of <7.7%, demonstrating the good sensitivity and precision of the method. The results of 30 real world rice samples analyzed by this method agreed well with those obtained by the standard microwave digestion. The amount of sample required was reduced approximately 100 fold in comparison with the microwave digestion. The method has a high application potential for other sample matrices and elements with high sensitivity and sample throughput.

Analysis of four toxic metals in a single rice seed by matrix solid phase dispersion -inductively coupled plasma mass spectrometry.

PubMed

He, Xiufen; Chen, Lixia; Chen, Xin; Yu, Huamei; Peng, Lixu; Han, Bingjun

2016-12-06

Toxic metals in rice pose great risks to human health. Metal bioaccumulation in rice grains is a criterion of breeding. Rice breeding requires a sensitive method to determine metal content in single rice grains to assist the variety selection. In the present study, four toxic metals of arsenic (As), cadmium (Cd), chromium (Cr) and lead (Pb) in a single rice grain were determined by a simple and rapid method. The developed method is based on matrix solid phase dispersion using multi-wall carbon nanotubes (MWCNTs) as dispersing agent and analyzed by inductively coupled plasma mass spectrometry. The experimental parameters were systematically investigated. The limits of detection (LOD) were 5.0, 0.6, 10 and 2.1 ng g -1 for As, Cd, Cr, and Pb, respectively, with relative standard deviations (n = 6) of <7.7%, demonstrating the good sensitivity and precision of the method. The results of 30 real world rice samples analyzed by this method agreed well with those obtained by the standard microwave digestion. The amount of sample required was reduced approximately 100 fold in comparison with the microwave digestion. The method has a high application potential for other sample matrices and elements with high sensitivity and sample throughput.

Determination of the rare-earth elements in geological materials by inductively coupled plasma mass spectrometry

USGS Publications Warehouse

Lichte, F.E.; Meier, A.L.; Crock, J.G.

1987-01-01

A method of analysis of geological materials for the determination of the rare-earth elements using the Inductively coupled plasma mass spectrometric technique (ICP-MS) has been developed. Instrumental parameters and factors affecting analytical results have been first studied and then optimized. Samples are analyzed directly following an acid digestion, without the need for separation or preconcentration with limits of detection of 2-11 ng/g, precision of ?? 2.5% relative standard deviation, and accuracy comparable to inductively coupled plasma emission spectrometry and instrumental neutron activation analysis. A commercially available ICP-MS instrument is used with modifications to the sample introduction system, torch, and sampler orifice to reduce the effects of high salt content of sample solutions prepared from geologic materials. Corrections for isobaric interferences from oxide ions and other diatomic and triatomic ions are made mathematically. Special internal standard procedures are used to compensate for drift in metahmetal oxide ratios and sensitivity. Reference standard values are used to verify the accuracy and utility of the method.

Metal leaching in drinking water domestic distribution system: an Italian case study.

PubMed

Sorlini, Sabrina; Gialdini, Francesca; Collivignarelli, Carlo

2014-01-01

The objective of this study was to evaluate metal contamination of tap water in seven public buildings in Brescia (Italy). Two monitoring periods were performed using three different sampling methods (overnight stagnation, 30-min stagnation, and random daytime). The results show that the water parameters exceeding the international standards (Directive 98/83/EC) at the tap were lead (max = 363 μg/L), nickel (max = 184 μg/L), zinc (max = 4900 μg/L), and iron (max = 393 μg/L). Compared to the total number of tap water samples analyzed (122), the values higher than limits of Directive 98/83/EC were 17% for lead, 11% for nickel, 14% for zinc, and 7% for iron. Three buildings exceeded iron standard while five buildings exceeded the standard for nickel, lead, and zinc. Moreover, there is no evident correlation between the leaching of contaminants in the domestic distribution system and the age of the pipes while a significant influence is shown by the sampling methods.

U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR COLLECTION, STORAGE, AND SHIPMENT OF DRINKING AND TAP WATER SAMPLES FOR TRACE METALS (EPA METHOD 200.8) ANALYSIS (UA-F-16.1)

EPA Science Inventory

The purpose of this SOP is to describe how to collect, store, and ship tap and drinking water samples for analysis by EPA Method 200.8 (revision 4.4) for the NHEXAS Arizona project. This SOP provides a brief description of the sample containers, collection, preservation, storage...

Comparison of methods for measurement of organic compounds at ultra-trace level: analytical criteria and application to analysis of amino acids in extraterrestrial samples.

PubMed

Vandenabeele-Trambouze, O; Claeys-Bruno, M; Dobrijevic, M; Rodier, C; Borruat, G; Commeyras, A; Garrelly, L

2005-02-01

The need for criteria to compare different analytical methods for measuring extraterrestrial organic matter at ultra-trace levels in relatively small and unique samples (e.g., fragments of meteorites, micrometeorites, planetary samples) is discussed. We emphasize the need to standardize the description of future analyses, and take the first step toward a proposed international laboratory network for performance testing.

Comparison between the triglycerides standardization of routine methods used in Japan and the chromotropic acid reference measurement procedure used by the CDC Lipid Standardization Programme.

PubMed

Nakamura, Masakazu; Iso, Hiroyasu; Kitamura, Akihiko; Imano, Hironori; Noda, Hiroyuki; Kiyama, Masahiko; Sato, Shinichi; Yamagishi, Kazumasa; Nishimura, Kunihiro; Nakai, Michikazu; Vesper, Hubert W; Teramoto, Tamio; Miyamoto, Yoshihiro

2016-11-01

Background The US Centers for Disease Control and Prevention ensured adequate performance of the routine triglycerides methods used in Japan by a chromotropic acid reference measurement procedure used by the Centers for Disease Control and Prevention lipid standardization programme as a reference point. We examined standardized data to clarify the performance of routine triglycerides methods. Methods The two routine triglycerides methods were the fluorometric method of Kessler and Lederer and the enzymatic method. The methods were standardized using 495 Centers for Disease Control and Prevention reference pools with 98 different concentrations ranging between 0.37 and 5.15 mmol/L in 141 survey runs. The triglycerides criteria for laboratories which perform triglycerides analyses are used: accuracy, as bias ≤5% from the Centers for Disease Control and Prevention reference value and precision, as measured by CV, ≤5%. Results The correlation of the bias of both methods to the Centers for Disease Control and Prevention reference method was: y (%bias) = 0.516 × (Centers for Disease Control and Prevention reference value) -1.292 ( n = 495, R 2  = 0.018). Triglycerides bias at medical decision points of 1.13, 1.69 and 2.26 mmol/L was -0.71%, -0.42% and -0.13%, respectively. For the combined precision, the equation y (CV) = -0.398 × (triglycerides value) + 1.797 ( n = 495, R 2  = 0.081) was used. Precision was 1.35%, 1.12% and 0.90%, respectively. It was shown that triglycerides measurements at Osaka were stable for 36 years. Conclusions The epidemiologic laboratory in Japan met acceptable accuracy goals for 88.7% of all samples, and met acceptable precision goals for 97.8% of all samples measured through the Centers for Disease Control and Prevention lipid standardization programme and demonstrated stable results for an extended period of time.

Comparison between the triglycerides standardization of routine methods used in Japan and the chromotropic acid reference measurement procedure used by the CDC Lipid Standardization Programme

PubMed Central

Nakamura, Masakazu; Iso, Hiroyasu; Kitamura, Akihiko; Imano, Hironori; Noda, Hiroyuki; Kiyama, Masahiko; Sato, Shinichi; Yamagishi, Kazumasa; Nishimura, Kunihiro; Nakai, Michikazu; Vesper, Hubert W; Teramoto, Tamio; Miyamoto, Yoshihiro

2017-01-01

Background The US Centers for Disease Control and Prevention ensured adequate performance of the routine triglycerides methods used in Japan by a chromotropic acid reference measurement procedure used by the Centers for Disease Control and Prevention lipid standardization programme as a reference point. We examined standardized data to clarify the performance of routine triglycerides methods. Methods The two routine triglycerides methods were the fluorometric method of Kessler and Lederer and the enzymatic method. The methods were standardized using 495 Centers for Disease Control and Prevention reference pools with 98 different concentrations ranging between 0.37 and 5.15 mmol/L in 141 survey runs. The triglycerides criteria for laboratories which perform triglycerides analyses are used: accuracy, as bias ≤5% from the Centers for Disease Control and Prevention reference value and precision, as measured by CV, ≤5%. Results The correlation of the bias of both methods to the Centers for Disease Control and Prevention reference method was: y (%bias) = 0.516 × (Centers for Disease Control and Prevention reference value) −1.292 (n = 495, R2 = 0.018). Triglycerides bias at medical decision points of 1.13, 1.69 and 2.26 mmol/L was −0.71%, −0.42% and −0.13%, respectively. For the combined precision, the equation y (CV) = −0.398 × (triglycerides value) + 1.797 (n = 495, R2 = 0.081) was used. Precision was 1.35%, 1.12% and 0.90%, respectively. It was shown that triglycerides measurements at Osaka were stable for 36 years. Conclusions The epidemiologic laboratory in Japan met acceptable accuracy goals for 88.7% of all samples, and met acceptable precision goals for 97.8% of all samples measured through the Centers for Disease Control and Prevention lipid standardization programme and demonstrated stable results for an extended period of time. PMID:26680645

Serum Ropivacaine Concentrations and Systemic Local Anesthetic Toxicity in Trauma Patients Receiving Long-Term Continuous Peripheral Nerve Block Catheters

DTIC Science & Technology

2010-02-01

concentrations were calculated from the following 2 methods: 1. Using peak area ratio of ropivacaine/ bupivacaine of samples versus peak area ratio of...ropivacaine/ bupivacaine of standards (0–3000 ng/mL) using the following formula: RopS (PA of Rop)/(PA of Bup)S /(PA of Rop)/(PA of Bup)STD Bup...1/mL serum used) where Rop ropivacaine, Bup bupivacaine , PA peak area, S sample, and STD standard. 2. Samples of ropivacaine concentrations

[Simultaneous determination of pyraclostrobin and thiophanate-methyl and its metabolite carbendazim residues in soil and citrus by QuEChERS-liquid chromatography- tandem mass spectrometry].

PubMed

Li, Fuqin; Shi, Lihong; Wang, Fei; Sun, Caiyuan; Kang, Di; Zhang, Yuping; Chen, Lingzhu; Hu, Deyu

2017-06-08

A QuEChERS-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of pyraclostrobin, thiophanate-methyl and its metabolite carbendazim in soil and citrus. The samples were extracted with methanol or acetonitrile, purified by primary secondary amine (PSA), then separated by LC, detected in multiple reaction monitoring (MRM) mass spectrometry mode via positive electrospray ionization. The analytes were quantified by matrix-matched standard solutions with external standard method. The limits of quantification (LOQs) of pyraclostrobin, thiophanate-methyl and carbendazim in different matrices were 5.8-7.0 μg/kg, 9.3-14.1 μg/kg and 2.1-2.6 μg/kg, respectively. For all the samples, the spiked recoveries ranged from 75.48% to 109.18%, and the relative standard deviations (RSDs) were 0.60%-5.11% ( n =5). The method is quick, easy, effective, sensitive and accurate. The matrix-matched calibration solutions can efficiently compensate matrix effects of the pyraclostrobin, thiophanate-methyl and carbendazim in LC-MS/MS analysis. The established method can be applied to the residue analysis of the real samples of soil, citrus peel, citrus pulp and citrus fruits.

An on-spot internal standard addition approach for accurately determining colistin A and colistin B in dried blood spots using ultra high-performance liquid chromatography-tandem mass spectrometry.

PubMed

Tsai, I-Lin; Kuo, Ching-Hua; Sun, Hsin-Yun; Chuang, Yu-Chung; Chepyala, Divyabharathi; Lin, Shu-Wen; Tsai, Yun-Jung

2017-10-25

Outbreaks of multidrug-resistant Gram-negative bacterial infections have been reported worldwide. Colistin, an antibiotic with known nephrotoxicity and neurotoxicity, is now being used to treat multidrug-resistant Gram-negative strains. In this study, we applied an on-spot internal standard addition approach coupled with an ultra high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify colistin A and B from dried blood spots (DBSs). Only 15μL of whole blood was required for each sample. An internal standard with the same yield of extraction recoveries as colistin was added to the spot before sample extraction for accurate quantification. Formic acid in water (0.15%) with an equal volume of acetonitrile (50:50v/v) was used as the extraction solution. With the optimized extraction process and LC-MS/MS conditions, colistin A and B could be quantified from a DBS with respective limits of quantification of 0.13 and 0.27μgmL -1 , and the retention times were < 2min. The relative standard deviations of within-run and between-run precisions for peak area ratios were all < 17.3%. Accuracies were 91.5-111.2% for lower limit of quantification, low, medium, and high QC samples. The stability of the easily hydrolyzed prodrug, colistin methanesulfonate, was investigated in DBSs. Less than 4% of the prodrug was found to be hydrolyzed in DBSs at room temperature after 48h. The developed method applied an on-spot internal standard addition approach which benefited the precision and accuracy. Results showed that DBS sampling coupled with the sensitive LC-MS/MS method has the potential to be an alternative approach for colistin quantification, where the bias of prodrug hydrolysis in liquid samples is decreased. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of a High-Resolution Laser Absorption Spectroscopy Method with Application to the Determination of Absolute Concentration of Gaseous Elemental Mercury in Air.

PubMed

Srivastava, Abneesh; Hodges, Joseph T

2018-06-05

Isotope dilution-cold-vapor-inductively coupled plasma mass spectrometry (ID-CV-ICPMS) has become the primary standard for measurement of gaseous elemental mercury (GEM) mass concentration. However, quantitative mass spectrometry is challenging for several reasons including (1) the need for isotopic spiking with a standard reference material, (2) the requirement for bias-free passive sampling protocols, (3) the need for stable mass spectrometry interface design, and (4) the time and cost involved for gas sampling, sample processing, and instrument calibration. Here, we introduce a high-resolution laser absorption spectroscopy method that eliminates the need for sample-specific calibration standards or detailed analysis of sample treatment losses. This technique involves a tunable, single-frequency laser absorption spectrometer that measures isotopically resolved spectra of elemental mercury (Hg) spectra of 6 1 S 0 ← 6 3 P 1 intercombination transition near λ = 253.7 nm. Measured spectra are accurately modeled from first-principles using the Beer-Lambert law and Voigt line profiles combined with literature values for line positions, line shape parameters, and the spontaneous emission Einstein coefficient to obtain GEM mass concentration values. We present application of this method for the measurement of the equilibrium concentration of mercury vapor near room temperature. Three closed systems are considered: two-phase mixtures of liquid Hg and its vapor and binary two-phase mixtures of Hg-air and Hg-N 2 near atmospheric pressure. Within the experimental relative standard uncertainty, 0.9-1.5% congruent values of the equilibrium Hg vapor concentration are obtained for the Hg-only, Hg-air, Hg-N 2 systems, in confirmation with thermodynamic predictions. We also discuss detection limits and the potential of the present technique to serve as an absolute primary standard for measurements of gas-phase mercury concentration and isotopic composition.

On-line double isotope dilution laser ablation inductively coupled plasma mass spectrometry for the quantitative analysis of solid materials.

PubMed

Fernández, Beatriz; Rodríguez-González, Pablo; García Alonso, J Ignacio; Malherbe, Julien; García-Fonseca, Sergio; Pereiro, Rosario; Sanz-Medel, Alfredo

2014-12-03

We report on the determination of trace elements in solid samples by the combination of on-line double isotope dilution and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method requires the sequential analysis of the sample and a certified natural abundance standard by on-line IDMS using the same isotopically-enriched spike solution. In this way, the mass fraction of the analyte in the sample can be directly referred to the certified standard so the previous characterization of the spike solution is not required. To validate the procedure, Sr, Rb and Pb were determined in certified reference materials with different matrices, including silicate glasses (SRM 610, 612 and 614) and powdered samples (PACS-2, SRM 2710a, SRM 1944, SRM 2702 and SRM 2780). The analysis of powdered samples was carried out both by the preparation of pressed pellets and by lithium borate fusion. Experimental results for the analysis of powdered samples were in agreement with the certified values for all materials. Relative standard deviations in the range of 6-21% for pressed pellets and 3-21% for fused solids were obtained from n=3 independent measurements. Minimal sample preparation, data treatment and consumption of the isotopically-enriched isotopes are the main advantages of the method over previously reported approaches. Copyright © 2014 Elsevier B.V. All rights reserved.

U.S. Geological Survey Standard Reference Sample Project: Performance Evaluation of Analytical Laboratories

USGS Publications Warehouse

Long, H. Keith; Daddow, Richard L.; Farrar, Jerry W.

1998-01-01

Since 1962, the U.S. Geological Survey (USGS) has operated the Standard Reference Sample Project to evaluate the performance of USGS, cooperator, and contractor analytical laboratories that analyze chemical constituents of environmental samples. The laboratories are evaluated by using performance evaluation samples, called Standard Reference Samples (SRSs). SRSs are submitted to laboratories semi-annually for round-robin laboratory performance comparison purposes. Currently, approximately 100 laboratories are evaluated for their analytical performance on six SRSs for inorganic and nutrient constituents. As part of the SRS Project, a surplus of homogeneous, stable SRSs is maintained for purchase by USGS offices and participating laboratories for use in continuing quality-assurance and quality-control activities. Statistical evaluation of the laboratories results provides information to compare the analytical performance of the laboratories and to determine possible analytical deficiences and problems. SRS results also provide information on the bias and variability of different analytical methods used in the SRS analyses.

Essential Limitations of the Standard THz TDS Method for Substance Detection and Identification and a Way of Overcoming Them

PubMed Central

Trofimov, Vyacheslav A.; Varentsova, Svetlana A.

2016-01-01

Low efficiency of the standard THz TDS method of the detection and identification of substances based on a comparison of the spectrum for the signal under investigation with a standard signal spectrum is demonstrated using the physical experiments conducted under real conditions with a thick paper bag as well as with Si-based semiconductors under laboratory conditions. In fact, standard THz spectroscopy leads to false detection of hazardous substances in neutral samples, which do not contain them. This disadvantage of the THz TDS method can be overcome by using time-dependent THz pulse spectrum analysis. For a quality assessment of the standard substance spectral features presence in the signal under analysis, one may use time-dependent integral correlation criteria. PMID:27070617

Essential Limitations of the Standard THz TDS Method for Substance Detection and Identification and a Way of Overcoming Them.

PubMed

Trofimov, Vyacheslav A; Varentsova, Svetlana A

2016-04-08

Low efficiency of the standard THz TDS method of the detection and identification of substances based on a comparison of the spectrum for the signal under investigation with a standard signal spectrum is demonstrated using the physical experiments conducted under real conditions with a thick paper bag as well as with Si-based semiconductors under laboratory conditions. In fact, standard THz spectroscopy leads to false detection of hazardous substances in neutral samples, which do not contain them. This disadvantage of the THz TDS method can be overcome by using time-dependent THz pulse spectrum analysis. For a quality assessment of the standard substance spectral features presence in the signal under analysis, one may use time-dependent integral correlation criteria.

Commutability of the First World Health Organization International Standard for Human Cytomegalovirus

PubMed Central

Preiksaitis, J.; Tong, Y.; Pang, X.; Sun, Y.; Tang, L.; Cook, L.; Pounds, S.; Fryer, J.; Caliendo, A. M.

2015-01-01

Quantitative detection of cytomegalovirus (CMV) DNA has become a standard part of care for many groups of immunocompromised patients; recent development of the first WHO international standard for human CMV DNA has raised hopes of reducing interlaboratory variability of results. Commutability of reference material has been shown to be necessary if such material is to reduce variability among laboratories. Here we evaluated the commutability of the WHO standard using 10 different real-time quantitative CMV PCR assays run by eight different laboratories. Test panels, including aliquots of 50 patient samples (40 positive samples and 10 negative samples) and lyophilized CMV standard, were run, with each testing center using its own quantitative calibrators, reagents, and nucleic acid extraction methods. Commutability was assessed both on a pairwise basis and over the entire group of assays, using linear regression and correspondence analyses. Commutability of the WHO material differed among the tests that were evaluated, and these differences appeared to vary depending on the method of statistical analysis used and the cohort of assays included in the analysis. Depending on the methodology used, the WHO material showed poor or absent commutability with up to 50% of assays. Determination of commutability may require a multifaceted approach; the lack of commutability seen when using the WHO standard with several of the assays here suggests that further work is needed to bring us toward true consensus. PMID:26269622

Estimate of standard deviation for a log-transformed variable using arithmetic means and standard deviations.

PubMed

Quan, Hui; Zhang, Ji

2003-09-15

Analyses of study variables are frequently based on log transformations. To calculate the power for detecting the between-treatment difference in the log scale, we need an estimate of the standard deviation of the log-transformed variable. However, in many situations a literature search only provides the arithmetic means and the corresponding standard deviations. Without individual log-transformed data to directly calculate the sample standard deviation, we need alternative methods to estimate it. This paper presents methods for estimating and constructing confidence intervals for the standard deviation of a log-transformed variable given the mean and standard deviation of the untransformed variable. It also presents methods for estimating the standard deviation of change from baseline in the log scale given the means and standard deviations of the untransformed baseline value, on-treatment value and change from baseline. Simulations and examples are provided to assess the performance of these estimates. Copyright 2003 John Wiley & Sons, Ltd.

Comparison and harmonization of measuring methods for air contaminants in the working environment.

PubMed

Leichnitz, K

1998-09-01

The objective of this work was to demonstrate that the measurement of air contaminants in the workplace requires a special approach. Decisive in carrying out the measuring task is the quality of the sampling strategy, including selection of the appropriate measuring method. Methods developed at a national level may be more suitable for this purpose than methods described in international standards. Measurements of air contaminants in the workplace should always be the basis for the prevention and control of occupational hazards. Such measurements, therefore, are also an essential element of risk assessment. Industrial processes and chemical agents are myriad. Each manufacturing stage may apply different conditions (e.g., batch production or continuous process, temperature, pressure) and agents (e.g. a wide variety of chemical substances): In each of these stages, different job functions may be necessary and may be subject to different exposure conditions. Distance from emission sources and physical parameters, such as rates of release, air current, meteorological variations, also have a profound influence. The measuring task in the workplace is quite different in comparison to many others (e.g., blood or soil sample analysis). Firstly, the selection of sampling time and sampling location are crucial steps in air analysis. Transportation and storage of the samples, may however, also influence measuring results; interlaboratory tests show the existing problems. Generally, in analytics, the substance to be determined remains "well covered" in its matrix during sampling, transportation and storage. In air analysis, however, the contaminant is usually "torn" from its surrounding matrix (the air) and "forced" into the sorbent, where it finds a completely new environment; reactions yielding artefacts may take place. Several international organizations have issued guidelines and standards on measuring methods for air contaminants in the working environment, such as the World Health Organization (WHO), the International Union of Pure and Applied Chemistry (IUPAC), and the International Organization for Standardization (ISO). Most of these international documents are substance-related and mainly cover the analytical steps, which constitute only part of the whole measuring process. The approach of the Commission of the European Union is useful in solving the task of air testing in the workplace. This body has issued an EU Directive which includes general requirements for measuring methods. In the Directive it is also stated that persons who carry out measurements must possess the necessary expertise. The Directive, in addition, refers to the European Committee for Standardization (CEN), and that to general requirements for measuring procedures. The advantage of the EU/CEN approach is its aspect of general requirements. This allows the development of new or improved methods without any restricting effect on existing substance-related standards.

Surface Sampling Collection and Culture Methods for Escherichia coli in Household Environments with High Fecal Contamination

PubMed Central

Kosek, Margaret N.; Schwab, Kellogg J.

2017-01-01

Empiric quantification of environmental fecal contamination is an important step toward understanding the impact that water, sanitation, and hygiene interventions have on reducing enteric infections. There is a need to standardize the methods used for surface sampling in field studies that examine fecal contamination in low-income settings. The dry cloth method presented in this manuscript improves upon the more commonly used swabbing technique that has been shown in the literature to have a low sampling efficiency. The recovery efficiency of a dry electrostatic cloth sampling method was evaluated using Escherichia coli and then applied to household surfaces in Iquitos, Peru, where there is high fecal contamination and enteric infection. Side-by-side measurements were taken from various floor locations within a household at the same time over a three-month period to compare for consistency of quantification of E. coli bacteria. The dry cloth sampling method in the laboratory setting showed 105% (95% Confidence Interval: 98%, 113%) E. coli recovery efficiency off of the cloths. The field application demonstrated strong agreement of side-by-side results (Pearson correlation coefficient for dirt surfaces was 0.83 (p < 0.0001) and 0.91 (p < 0.0001) for cement surfaces) and moderate agreement for results between entrance and kitchen samples (Pearson (0.53, p < 0.0001) and weighted Kappa statistic (0.54, p < 0.0001)). Our findings suggest that this method can be utilized in households with high bacterial loads using either continuous (quantitative) or categorical (semi-quantitative) data. The standardization of this low-cost, dry electrostatic cloth sampling method can be used to measure differences between households in intervention and non-intervention arms of randomized trials. PMID:28829392

Surface Sampling Collection and Culture Methods for Escherichia coli in Household Environments with High Fecal Contamination.

PubMed

Exum, Natalie G; Kosek, Margaret N; Davis, Meghan F; Schwab, Kellogg J

2017-08-22

Empiric quantification of environmental fecal contamination is an important step toward understanding the impact that water, sanitation, and hygiene interventions have on reducing enteric infections. There is a need to standardize the methods used for surface sampling in field studies that examine fecal contamination in low-income settings. The dry cloth method presented in this manuscript improves upon the more commonly used swabbing technique that has been shown in the literature to have a low sampling efficiency. The recovery efficiency of a dry electrostatic cloth sampling method was evaluated using Escherichia coli and then applied to household surfaces in Iquitos, Peru, where there is high fecal contamination and enteric infection. Side-by-side measurements were taken from various floor locations within a household at the same time over a three-month period to compare for consistency of quantification of E. coli bacteria. The dry cloth sampling method in the laboratory setting showed 105% (95% Confidence Interval: 98%, 113%) E. coli recovery efficiency off of the cloths. The field application demonstrated strong agreement of side-by-side results (Pearson correlation coefficient for dirt surfaces was 0.83 ( p < 0.0001) and 0.91 ( p < 0.0001) for cement surfaces) and moderate agreement for results between entrance and kitchen samples (Pearson (0.53, p < 0.0001) and weighted Kappa statistic (0.54, p < 0.0001)). Our findings suggest that this method can be utilized in households with high bacterial loads using either continuous (quantitative) or categorical (semi-quantitative) data. The standardization of this low-cost, dry electrostatic cloth sampling method can be used to measure differences between households in intervention and non-intervention arms of randomized trials.

Design and Weighting Methods for a Nationally Representative Sample of HIV-infected Adults Receiving Medical Care in the United States-Medical Monitoring Project

PubMed Central

Iachan, Ronaldo; H. Johnson, Christopher; L. Harding, Richard; Kyle, Tonja; Saavedra, Pedro; L. Frazier, Emma; Beer, Linda; L. Mattson, Christine; Skarbinski, Jacek

2016-01-01

Background: Health surveys of the general US population are inadequate for monitoring human immunodeficiency virus (HIV) infection because the relatively low prevalence of the disease (<0.5%) leads to small subpopulation sample sizes. Objective: To collect a nationally and locally representative probability sample of HIV-infected adults receiving medical care to monitor clinical and behavioral outcomes, supplementing the data in the National HIV Surveillance System. This paper describes the sample design and weighting methods for the Medical Monitoring Project (MMP) and provides estimates of the size and characteristics of this population. Methods: To develop a method for obtaining valid, representative estimates of the in-care population, we implemented a cross-sectional, three-stage design that sampled 23 jurisdictions, then 691 facilities, then 9,344 HIV patients receiving medical care, using probability-proportional-to-size methods. The data weighting process followed standard methods, accounting for the probabilities of selection at each stage and adjusting for nonresponse and multiplicity. Nonresponse adjustments accounted for differing response at both facility and patient levels. Multiplicity adjustments accounted for visits to more than one HIV care facility. Results: MMP used a multistage stratified probability sampling design that was approximately self-weighting in each of the 23 project areas and nationally. The probability sample represents the estimated 421,186 HIV-infected adults receiving medical care during January through April 2009. Methods were efficient (i.e., induced small, unequal weighting effects and small standard errors for a range of weighted estimates). Conclusion: The information collected through MMP allows monitoring trends in clinical and behavioral outcomes and informs resource allocation for treatment and prevention activities. PMID:27651851

Determination of calcium, magnesium and zinc in lubricating oils by flame atomic absorption spectrometry using a three-component solution.

PubMed

Zmozinski, Ariane V; de Jesus, Alexandre; Vale, Maria G R; Silva, Márcia M

2010-12-15

Lubricating oils are used to decrease wear and friction of movable parts of engines and turbines, being in that way essential for the performance and the increase of that equipment lifespan. The presence of some metals shows the addition of specific additives such as detergents, dispersals and antioxidants that improve the performance of these lubricants. In this work, a method for determination of calcium, magnesium and zinc in lubricating oil by flame atomic absorption spectrometry (F AAS) was developed. The samples were diluted with a small quantity of aviation kerosene (AVK), n-propanol and water to form a three-component solution before its introduction in the F AAS. Aqueous inorganic standards diluted in the same way have been used for calibration. To assess the accuracy of the new method, it was compared with ABNT NBR 14066 standard method, which consists in diluting the sample with AVK and in quantification by F AAS. Two other validating methods have also been used: the acid digestion and the certified reference material NIST (SRM 1084a). The proposed method provides the following advantages in relation to the standard method: significant reduction of the use of AVK, higher stability of the analytes in the medium and application of aqueous inorganic standards for calibration. The limits of detection for calcium, magnesium and zinc were 1.3 μg g(-1), 0.052 μg g(-1) and 0.41 μg g(-1), respectively. Concentrations of calcium, magnesium and zinc in six different samples obtained by the developed method did not differ significantly from the results obtained by the reference methods at the 95% confidence level (Student's t-test and ANOVA). Therefore, the proposed method becomes an efficient alternative for determination of metals in lubricating oil. Copyright © 2010 Elsevier B.V. All rights reserved.

High-throughput Titration of Luciferase-expressing Recombinant Viruses

PubMed Central

Garcia, Vanessa; Krishnan, Ramya; Davis, Colin; Batenchuk, Cory; Le Boeuf, Fabrice; Abdelbary, Hesham; Diallo, Jean-Simon

2014-01-01

Standard plaque assays to determine infectious viral titers can be time consuming, are not amenable to a high volume of samples, and cannot be done with viruses that do not form plaques. As an alternative to plaque assays, we have developed a high-throughput titration method that allows for the simultaneous titration of a high volume of samples in a single day. This approach involves infection of the samples with a Firefly luciferase tagged virus, transfer of the infected samples onto an appropriate permissive cell line, subsequent addition of luciferin, reading of plates in order to obtain luminescence readings, and finally the conversion from luminescence to viral titers. The assessment of cytotoxicity using a metabolic viability dye can be easily incorporated in the workflow in parallel and provide valuable information in the context of a drug screen. This technique provides a reliable, high-throughput method to determine viral titers as an alternative to a standard plaque assay. PMID:25285536

Recommended operating procedure No. 51: Glass source assessment sampling system (glass SASS). Final report, Jul 90-Jan 91

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

Grote, R.A.

1991-05-01

The report is a recommended operating procedure (ROP), prepared for use in research activities conducted by EPA's Air and Energy Engineering Research Laboratory (AEERL). The method described is applicable to the stack sampling of flue gas from a rotary kiln and to associated equipment of AEERL's Combustion Research Branch. It has been the standard method of sampling kiln flue gas due to the transient nature of the puff development and its capability to sample the maximum volume over the shortest time period. ROPs describe non-routine or experimental research operations where some judgment in application may be warranted. ROPs may notmore » be applicable to activities conducted by other research groups, and should not be used in place of standard operating procedures. Use of ROPs must be accompanied by an understanding of the purpose and scope. Questions should be directed to the author.« less

1H NMR determination of beta-N-methylamino-L-alanine (L-BMAA) in environmental and biological samples.

PubMed

Moura, Sidnei; Ultramari, Mariah de Almeida; de Paula, Daniela Mendes Louzada; Yonamine, Mauricio; Pinto, Ernani

2009-04-01

A nuclear magnetic resonance (1H NMR) method for the determination of beta-N-methylamino-L-alanine (L-BMAA) in environmental aqueous samples was developed and validated. L-BMAA is a neurotoxic modified amino acid that can be produced by cyanobacteria in aqueous environments. This toxin was extracted from samples by means of solid-phase extraction (SPE) and identified and quantified by 1H NMR without further derivatization steps. The lower limit of quantification (LLOQ) was 5 microg/mL. Good inter and intra-assay precision was also observed (relative standard deviation <8.5%) with the use of 4-nitro-DL-phenylalanine as an internal standard (IS). This method of 1H NMR analysis is not time consuming and can be readily utilized to monitor L-BMAA and confirm its presence in environmental and biological samples.

Ion-selective electrodes in potentiometric titrations; a new method for processing and evaluating titration data.

PubMed

Granholm, Kim; Sokalski, Tomasz; Lewenstam, Andrzej; Ivaska, Ari

2015-08-12

A new method to convert the potential of an ion-selective electrode to concentration or activity in potentiometric titration is proposed. The advantage of this method is that the electrode standard potential and the slope of the calibration curve do not have to be known. Instead two activities on the titration curve have to be estimated e.g. the starting activity before the titration begins and the activity at the end of the titration in the presence of large excess of titrant. This new method is beneficial when the analyte is in a complexed matrix or in a harsh environment which affects the properties of the electrode and the traditional calibration procedure with standard solutions cannot be used. The new method was implemented both in a method of linearization based on the Grans's plot and in determination of the stability constant of a complex and the concentration of the complexing ligand in the sample. The new method gave accurate results when using titrations data from experiments with samples of known composition and with real industrial harsh black liquor sample. A complexometric titration model was also developed. Copyright © 2015 Elsevier B.V. All rights reserved.

Selection of reference standard during method development using the analytical hierarchy process.

PubMed

Sun, Wan-yang; Tong, Ling; Li, Dong-xiang; Huang, Jing-yi; Zhou, Shui-ping; Sun, Henry; Bi, Kai-shun

2015-03-25

Reference standard is critical for ensuring reliable and accurate method performance. One important issue is how to select the ideal one from the alternatives. Unlike the optimization of parameters, the criteria of the reference standard are always immeasurable. The aim of this paper is to recommend a quantitative approach for the selection of reference standard during method development based on the analytical hierarchy process (AHP) as a decision-making tool. Six alternative single reference standards were assessed in quantitative analysis of six phenolic acids from Salvia Miltiorrhiza and its preparations by using ultra-performance liquid chromatography. The AHP model simultaneously considered six criteria related to reference standard characteristics and method performance, containing feasibility to obtain, abundance in samples, chemical stability, accuracy, precision and robustness. The priority of each alternative was calculated using standard AHP analysis method. The results showed that protocatechuic aldehyde is the ideal reference standard, and rosmarinic acid is about 79.8% ability as the second choice. The determination results successfully verified the evaluation ability of this model. The AHP allowed us comprehensive considering the benefits and risks of the alternatives. It was an effective and practical tool for optimization of reference standards during method development. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparison of estimators of standard deviation for hydrologic time series

USGS Publications Warehouse

Tasker, Gary D.; Gilroy, Edward J.

1982-01-01

Unbiasing factors as a function of serial correlation, ρ, and sample size, n for the sample standard deviation of a lag one autoregressive model were generated by random number simulation. Monte Carlo experiments were used to compare the performance of several alternative methods for estimating the standard deviation σ of a lag one autoregressive model in terms of bias, root mean square error, probability of underestimation, and expected opportunity design loss. Three methods provided estimates of σ which were much less biased but had greater mean square errors than the usual estimate of σ: s = (1/(n - 1) ∑ (xi −x¯)2)½. The three methods may be briefly characterized as (1) a method using a maximum likelihood estimate of the unbiasing factor, (2) a method using an empirical Bayes estimate of the unbiasing factor, and (3) a robust nonparametric estimate of σ suggested by Quenouille. Because s tends to underestimate σ, its use as an estimate of a model parameter results in a tendency to underdesign. If underdesign losses are considered more serious than overdesign losses, then the choice of one of the less biased methods may be wise.

COMPARISON OF TAXONOMIC, COLONY MORPHOTYPE AND PCR-RFLP METHODS TO CHARACTERIZE MICROFUNGAL DIVERSITY

EPA Science Inventory

We compared three methods for estimating fungal species diversity in soil samples. A rapid screening method based on gross colony morphological features and color reference standards was compared with traditional fungal taxonomic methods and PCR-RFLP for estimation of ecological ...

Effects of Sample Preparation on the Infrared Reflectance Spectra of Powders

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

Brauer, Carolyn S.; Johnson, Timothy J.; Myers, Tanya L.

2015-05-22

While reflectance spectroscopy is a useful tool in identifying molecular compounds, laboratory measurement of solid (particularly powder) samples often is confounded by sample preparation methods. For example, both the packing density and surface roughness can have an effect on the quantitative reflectance spectra of powdered samples. Recent efforts in our group have focused on developing standard methods for measuring reflectance spectra that accounts for sample preparation, as well as other factors such as particle size and provenance. In this work, the effect of preparation method on sample reflectivity was investigated by measuring the directional-hemispherical spectra of samples that were hand-packedmore » as well as pressed into pellets using an integrating sphere attached to a Fourier transform infrared spectrometer. The results show that the methods used to prepare the sample have a substantial effect on the measured reflectance spectra, as do other factors such as particle size.« less

Effects of sample preparation on the infrared reflectance spectra of powders

NASA Astrophysics Data System (ADS)

Brauer, Carolyn S.; Johnson, Timothy J.; Myers, Tanya L.; Su, Yin-Fong; Blake, Thomas A.; Forland, Brenda M.

2015-05-01

While reflectance spectroscopy is a useful tool for identifying molecular compounds, laboratory measurement of solid (particularly powder) samples often is confounded by sample preparation methods. For example, both the packing density and surface roughness can have an effect on the quantitative reflectance spectra of powdered samples. Recent efforts in our group have focused on developing standard methods for measuring reflectance spectra that accounts for sample preparation, as well as other factors such as particle size and provenance. In this work, the effect of preparation method on sample reflectivity was investigated by measuring the directional-hemispherical spectra of samples that were hand-loaded as well as pressed into pellets using an integrating sphere attached to a Fourier transform infrared spectrometer. The results show that the methods used to prepare the sample can have a substantial effect on the measured reflectance spectra, as do other factors such as particle size.

Solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry for gold determination in geological samples after preconcentration onto carbon nanotubes

NASA Astrophysics Data System (ADS)

Dobrowolski, Ryszard; Mróz, Agnieszka; Dąbrowska, Marzena; Olszański, Piotr

2017-06-01

A novelty method for the determination of gold in geological samples by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (SS HR CS GF AAS) after solid-phase extraction onto modified carbon nanotubes (CNT) was described. The methodology developed is based on solid phase extraction of Au(III) ions from digested samples to eliminate strong interference caused by iron compounds and problems related to inhomogeneities of the samples. The use of aqueous or solid standard for calibration was studied and the slope of calibration curve was the same for both of these modes. This statement indicates the possibility to perform the calibration of the method using aqueous standard solutions. Under optimum conditions the absolute detection limit for gold was equal to 2.24 · 10- 6 μg g- 1 while the adsorption capacity of modified carbon nanotubes was 264 mg g- 1. The proposed procedure was validated by the application of certified reference materials (CRMs) with different content of gold and different matrix, the results were in good agreement with certified values. The method was successfully applied for separation and determination of gold ions in complex geological samples, with precision generally better than 8%.

CTEPP STANDARD OPERATING PROCEDURE FOR EXTRACTING AND PREPARING AIR SAMPLES FOR ANALYSIS OF POLAR PERSISTENT ORGANIC POLLUTANTS (SOP-5.13)

EPA Science Inventory

The method for extracting and preparing indoor and outdoor air samples for analysis of polar persistent organic pollutants is summarized in this SOP. It covers the preparation of samples that are to be analyzed by gas chromatography/mass spectrometry.

CTEPP STANDARD OPERATING PROCEDURE FOR EXTRACTING AND PREPARING DRINKING WATER SAMPLES FOR ANALYSIS OF PERSISTENT ORGANIC POLLUTANTS (SOP 5.23)

EPA Science Inventory

The method for extracting and preparing a drinking water sample for analysis of atrazine is summarized in this SOP. It covers the extraction and concentration of samples that are to be analyzed by gas chromatography/ mass spectrometry.

Comparing efficiency of American Fisheries Society standard snorkeling techniques to environmental DNA sampling techniques

USGS Publications Warehouse

Ulibarri, Roy M.; Bonar, Scott A.; Rees, Christopher B.; Amberg, Jon J.; Ladell, Bridget; Jackson, Craig

2017-01-01

Analysis of environmental DNA (eDNA) is an emerging technique used to detect aquatic species through water sampling and the extraction of biological material for amplification. Our study compared the efficacy of eDNA methodology to American Fisheries Society (AFS) standard snorkeling surveys with regard to detecting the presence of rare fish species. Knowing which method is more efficient at detecting target species will help managers to determine the best way to sample when both traditional sampling methods and eDNA sampling are available. Our study site included three Navajo Nation streams that contained Navajo Nation Genetic Subunit Bluehead Suckers Catostomus discobolus and Zuni Bluehead Suckers C. discobolus yarrowi. We first divided the entire wetted area of streams into consecutive 100-m reaches and then systematically selected 10 reaches/stream for snorkel and eDNA surveys. Surface water samples were taken in 10-m sections within each 100-m reach, while fish presence was noted via snorkeling in each 10-m section. Quantitative PCR was run on each individual water sample in quadruplicate to test for the presence or absence of the target species. With eDNA sampling techniques, we were able to positively detect both species in two out of the three streams. Snorkeling resulted in positive detection of both species in all three streams. In streams where the target species were detected with eDNA sampling, snorkeling detected fish at 11–29 sites/stream, whereas eDNA detected fish at 3–12 sites/stream. Our results suggest that AFS standard snorkeling is more effective than eDNA for detecting target fish species. To improve our eDNA procedures, the amount of water collected and tested should be increased. Additionally, filtering water on-site may improve eDNA techniques for detecting fish. Future research should focus on standardization of eDNA sampling to provide a widely operational sampling tool.

Development of quantitative screen for 1550 chemicals with GC-MS.

PubMed

Bergmann, Alan J; Points, Gary L; Scott, Richard P; Wilson, Glenn; Anderson, Kim A

2018-05-01

With hundreds of thousands of chemicals in the environment, effective monitoring requires high-throughput analytical techniques. This paper presents a quantitative screening method for 1550 chemicals based on statistical modeling of responses with identification and integration performed using deconvolution reporting software. The method was evaluated with representative environmental samples. We tested biological extracts, low-density polyethylene, and silicone passive sampling devices spiked with known concentrations of 196 representative chemicals. A multiple linear regression (R 2  = 0.80) was developed with molecular weight, logP, polar surface area, and fractional ion abundance to predict chemical responses within a factor of 2.5. Linearity beyond the calibration had R 2  > 0.97 for three orders of magnitude. Median limits of quantitation were estimated to be 201 pg/μL (1.9× standard deviation). The number of detected chemicals and the accuracy of quantitation were similar for environmental samples and standard solutions. To our knowledge, this is the most precise method for the largest number of semi-volatile organic chemicals lacking authentic standards. Accessible instrumentation and software make this method cost effective in quantifying a large, customizable list of chemicals. When paired with silicone wristband passive samplers, this quantitative screen will be very useful for epidemiology where binning of concentrations is common. Graphical abstract A multiple linear regression of chemical responses measured with GC-MS allowed quantitation of 1550 chemicals in samples such as silicone wristbands.

Evaluation of standard methods for collecting and processing fuel moisture samples

Treesearch

Sally M. Haase; José Sánchez; David R. Weise

2016-01-01

A variety of techniques for collecting and processing samples to determine moisture content of wildland fuels in support of fire management activities were evaluated. The effects of using a chainsaw or handsaw to collect samples of largediameter wood, containers for storing and transporting collected samples, and quick-response ovens for estimating moisture content...

Miniprimer PCR, a New Lens for Viewing the Microbial World▿ †

PubMed Central

Isenbarger, Thomas A.; Finney, Michael; Ríos-Velázquez, Carlos; Handelsman, Jo; Ruvkun, Gary

2008-01-01

Molecular methods based on the 16S rRNA gene sequence are used widely in microbial ecology to reveal the diversity of microbial populations in environmental samples. Here we show that a new PCR method using an engineered polymerase and 10-nucleotide “miniprimers” expands the scope of detectable sequences beyond those detected by standard methods using longer primers and Taq polymerase. After testing the method in silico to identify divergent ribosomal genes in previously cloned environmental sequences, we applied the method to soil and microbial mat samples, which revealed novel 16S rRNA gene sequences that would not have been detected with standard primers. Deeply divergent sequences were discovered with high frequency and included representatives that define two new division-level taxa, designated CR1 and CR2, suggesting that miniprimer PCR may reveal new dimensions of microbial diversity. PMID:18083877

Quantitation of sugar content in pyrolysis liquids after acid hydrolysis using high-performance liquid chromatography without neutralization.

PubMed

Johnston, Patrick A; Brown, Robert C

2014-08-13

A rapid method for the quantitation of total sugars in pyrolysis liquids using high-performance liquid chromatography (HPLC) was developed. The method avoids the tedious and time-consuming sample preparation required by current analytical methods. It is possible to directly analyze hydrolyzed pyrolysis liquids, bypassing the neutralization step usually required in determination of total sugars. A comparison with traditional methods was used to determine the validity of the results. The calibration curve coefficient of determination on all standard compounds was >0.999 using a refractive index detector. The relative standard deviation for the new method was 1.13%. The spiked sugar recoveries on the pyrolysis liquid samples were between 104 and 105%. The research demonstrates that it is possible to obtain excellent accuracy and efficiency using HPLC to quantitate glucose after acid hydrolysis of polymeric and oligomeric sugars found in fast pyrolysis bio-oils without neutralization.

High-throughput real-time quantitative reverse transcription PCR.

PubMed

Bookout, Angie L; Cummins, Carolyn L; Mangelsdorf, David J; Pesola, Jean M; Kramer, Martha F

2006-02-01

Extensive detail on the application of the real-time quantitative polymerase chain reaction (QPCR) for the analysis of gene expression is provided in this unit. The protocols are designed for high-throughput, 384-well-format instruments, such as the Applied Biosystems 7900HT, but may be modified to suit any real-time PCR instrument. QPCR primer and probe design and validation are discussed, and three relative quantitation methods are described: the standard curve method, the efficiency-corrected DeltaCt method, and the comparative cycle time, or DeltaDeltaCt method. In addition, a method is provided for absolute quantification of RNA in unknown samples. RNA standards are subjected to RT-PCR in the same manner as the experimental samples, thus accounting for the reaction efficiencies of both procedures. This protocol describes the production and quantitation of synthetic RNA molecules for real-time and non-real-time RT-PCR applications.

Gravimetric screening method for fungal decay of paper: inoculation with Trametes versicolor.

PubMed

Råberg, Ulrika; Hafrén, Jonas

2009-10-01

The European standard test EN 113 for fungal degradation of solid wood has been adapted for degradation of paper by white rot fungus (Trametes versicolor). Fungal degradation of paper sheets may potentially be used for screening different wood preservatives on paper instead of solid wood. The paper samples showed higher relative mass losses compared to wood, and samples pretreated with boric acid, copper sulfate and polymerized linseed oil were successfully tested for biodegradation using the paper sheet method. The results on paper degradation were compared with wood, both as wood blocks (according to standard test) and wood cut in sections forming layered structures mimicking paper layers.

Optimized determination method for trans-10-hydroxy-2-decenoic acid content in royal jelly by high-performance liquid chromatography with an internal standard.

PubMed

Zhou, Jinhui; Xue, Xiaofeng; Li, Yi; Zhang, Jinzhen; Zhao, Jing

2007-01-01

An optimized reversed-phase high-performance liquid chromatography method was developed to detect the trans-10-hydroxy-2-decenoic acid (10-HDA) content in royal jelly cream and lyophilized powder. The sample was extracted using absolute ethanol. Chromatographic separation of 10-HDA and methyl 4-hydroxybenzoate as the internal standard was performed on a Nova-pak C18 column. The average recoveries were 95.0-99.2% (n = 5) with relative standard deviation (RSD) values of 1.3-2.1% for royal jelly cream and 98.0-100.0% (n = 5) with RSD values of 1.6-3.0% for lyophilized powder, respectively. The limits of detection and quantitation were 0.5 and 1.5 mg/kg, respectively, for both royal jelly cream and lyophilized powder. The method was validated for the determination of practical royal jelly products. The concentration of 10-HDA ranged from 1.26 to 2.21% for pure royal jelly cream samples and 3.01 to 6.19% for royal jelly lyophilized powder samples. For 30 royal jelly products, the 10-HDA content varied from not detectable to 0.98%.

Rapid exploration of configuration space with diffusion-map-directed molecular dynamics.

PubMed

Zheng, Wenwei; Rohrdanz, Mary A; Clementi, Cecilia

2013-10-24

The gap between the time scale of interesting behavior in macromolecular systems and that which our computational resources can afford often limits molecular dynamics (MD) from understanding experimental results and predicting what is inaccessible in experiments. In this paper, we introduce a new sampling scheme, named diffusion-map-directed MD (DM-d-MD), to rapidly explore molecular configuration space. The method uses a diffusion map to guide MD on the fly. DM-d-MD can be combined with other methods to reconstruct the equilibrium free energy, and here, we used umbrella sampling as an example. We present results from two systems: alanine dipeptide and alanine-12. In both systems, we gain tremendous speedup with respect to standard MD both in exploring the configuration space and reconstructing the equilibrium distribution. In particular, we obtain 3 orders of magnitude of speedup over standard MD in the exploration of the configurational space of alanine-12 at 300 K with DM-d-MD. The method is reaction coordinate free and minimally dependent on a priori knowledge of the system. We expect wide applications of DM-d-MD to other macromolecular systems in which equilibrium sampling is not affordable by standard MD.

Rapid Exploration of Configuration Space with Diffusion Map-directed-Molecular Dynamics

PubMed Central

Zheng, Wenwei; Rohrdanz, Mary A.; Clementi, Cecilia

2013-01-01

The gap between the timescale of interesting behavior in macromolecular systems and that which our computational resources can afford oftentimes limits Molecular Dynamics (MD) from understanding experimental results and predicting what is inaccessible in experiments. In this paper, we introduce a new sampling scheme, named Diffusion Map-directed-MD (DM-d-MD), to rapidly explore molecular configuration space. The method uses diffusion map to guide MD on the fly. DM-d-MD can be combined with other methods to reconstruct the equilibrium free energy, and here we used umbrella sampling as an example. We present results from two systems: alanine dipeptide and alanine-12. In both systems we gain tremendous speedup with respect to standard MD both in exploring the configuration space and reconstructing the equilibrium distribution. In particular, we obtain 3 orders of magnitude of speedup over standard MD in the exploration of the configurational space of alanine-12 at 300K with DM-d-MD. The method is reaction coordinate free and minimally dependent on a priori knowledge of the system. We expect wide applications of DM-d-MD to other macromolecular systems in which equilibrium sampling is not affordable by standard MD. PMID:23865517

Logical and Methodological Issues Affecting Genetic Studies of Humans Reported in Top Neuroscience Journals.

PubMed

Grabitz, Clara R; Button, Katherine S; Munafò, Marcus R; Newbury, Dianne F; Pernet, Cyril R; Thompson, Paul A; Bishop, Dorothy V M

2018-01-01

Genetics and neuroscience are two areas of science that pose particular methodological problems because they involve detecting weak signals (i.e., small effects) in noisy data. In recent years, increasing numbers of studies have attempted to bridge these disciplines by looking for genetic factors associated with individual differences in behavior, cognition, and brain structure or function. However, different methodological approaches to guarding against false positives have evolved in the two disciplines. To explore methodological issues affecting neurogenetic studies, we conducted an in-depth analysis of 30 consecutive articles in 12 top neuroscience journals that reported on genetic associations in nonclinical human samples. It was often difficult to estimate effect sizes in neuroimaging paradigms. Where effect sizes could be calculated, the studies reporting the largest effect sizes tended to have two features: (i) they had the smallest samples and were generally underpowered to detect genetic effects, and (ii) they did not fully correct for multiple comparisons. Furthermore, only a minority of studies used statistical methods for multiple comparisons that took into account correlations between phenotypes or genotypes, and only nine studies included a replication sample or explicitly set out to replicate a prior finding. Finally, presentation of methodological information was not standardized and was often distributed across Methods sections and Supplementary Material, making it challenging to assemble basic information from many studies. Space limits imposed by journals could mean that highly complex statistical methods were described in only a superficial fashion. In summary, methods that have become standard in the genetics literature-stringent statistical standards, use of large samples, and replication of findings-are not always adopted when behavioral, cognitive, or neuroimaging phenotypes are used, leading to an increased risk of false-positive findings. Studies need to correct not just for the number of phenotypes collected but also for the number of genotypes examined, genetic models tested, and subsamples investigated. The field would benefit from more widespread use of methods that take into account correlations between the factors corrected for, such as spectral decomposition, or permutation approaches. Replication should become standard practice; this, together with the need for larger sample sizes, will entail greater emphasis on collaboration between research groups. We conclude with some specific suggestions for standardized reporting in this area.

The Benefits of Latent Variable Modeling to Develop Norms for a Translated Version of a Standardized Scale

ERIC Educational Resources Information Center

Seo, Hyojeong; Shaw, Leslie A.; Shogren, Karrie A.; Lang, Kyle M.; Little, Todd D.

2017-01-01

This article demonstrates the use of structural equation modeling to develop norms for a translated version of a standardized scale, the Supports Intensity Scale-Children's Version (SIS-C). The latent variable norming method proposed is useful when the standardization sample for a translated version is relatively small to derive norms…

US Fish and Wildlife Service biomonitoring operations manual, Appendices A--K

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

Gianotto, D.F.; Rope, R.C.; Mondecar, M.

1993-04-01

Volume 2 contains Appendices and Summary Sheets for the following areas: A-Legislative Background and Key to Relevant Legislation, B- Biomonitoring Operations Workbook, C-Air Monitoring, D-Introduction to the Flora and Fauna for Biomonitoring, E-Decontamination Guidance Reference Field Methods, F-Documentation Guidance, Sample Handling, and Quality Assurance/Quality Control Standard Operating Procedures, G-Field Instrument Measurements Reference Field Methods, H-Ground Water Sampling Reference Field Methods, I-Sediment Sampling Reference Field Methods, J-Soil Sampling Reference Field Methods, K-Surface Water Reference Field Methods. Appendix B explains how to set up strategy to enter information on the ``disk workbook``. Appendix B is enhanced by DE97006389, an on-line workbook formore » users to be able to make revisions to their own biomonitoring data.« less

A Direct and Rapid Method to Determine Cyanide in Urine by Capillary Electrophoresis

PubMed Central

Zhang, Qiyang; Maddukuri, Naveen; Gong, Maojun

2015-01-01

Cyanides are poisonous chemicals that widely exist in nature and industrial processes as well as accidental fires. Rapid and accurate determination of cyanide exposure would facilitate forensic investigation, medical diagnosis, and chronic cyanide monitoring. Here, a rapid and direct method was developed for the determination of cyanide ions in urinary samples. This technique was based on an integrated capillary electrophoresis system coupled with laser-induced fluorescence (LIF) detection. Cyanide ions were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) and a primary amine (glycine) for LIF detection. Three separate reagents, NDA, glycine, and cyanide sample, were mixed online, which secured uniform conditions between samples for cyanide derivatization and reduced the risk of precipitation formation of mixtures. Conditions were optimized; the derivatization was completed in 2-4 minutes, and the separation was observed in 25 s. The limit of detection (LOD) was 4.0 nM at 3-fold signal-to-noise ratio for standard cyanide in buffer. The cyanide levels in urine samples from smokers and non-smokers were determined by using the method of standard addition, which demonstrated significant difference of cyanide levels in urinary samples from the two groups of people. The developed method was rapid and accurate, and is anticipated to be applicable to cyanide detection in waste water with appropriate modification. PMID:26342870

Simultaneous determination of the quantity and isotopic signature of dissolved organic matter from soil water using high-performance liquid chromatography/isotope ratio mass spectrometry.

PubMed

Scheibe, Andrea; Krantz, Lars; Gleixner, Gerd

2012-01-30

We assessed the accuracy and utility of a modified high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS) system for measuring the amount and stable carbon isotope signature of dissolved organic matter (DOM) <1 µm. Using a range of standard compounds as well as soil solutions sampled in the field, we compared the results of the HPLC/IRMS analysis with those from other methods for determining carbon and (13)C content. The conversion efficiency of the in-line wet oxidation of the HPLC/IRMS averaged 99.3% for a range of standard compounds. The agreement between HPLC/IRMS and other methods in the amount and isotopic signature of both standard compounds and soil water samples was excellent. For DOM concentrations below 10 mg C L(-1) (250 ng C total) pre-concentration or large volume injections are recommended in order to prevent background interferences. We were able to detect large differences in the (13)C signatures of soil solution DOM sampled in 10 cm depth of plots with either C3 or C4 vegetation and in two different parent materials. These measurements also demonstrated changes in the (13)C signature that demonstrate rapid loss of plant-derived C with depth. Overall the modified HLPC/IRMS system has the advantages of rapid sample preparation, small required sample volume and high sample throughput, while showing comparable performance with other methods for measuring the amount and isotopic signature of DOM. Copyright © 2011 John Wiley & Sons, Ltd.

Novel method for the determination of average molecular weight of natural polymers based on 2D DOSY NMR and chemometrics: Example of heparin.

PubMed

Monakhova, Yulia B; Diehl, Bernd W K; Do, Tung X; Schulze, Margit; Witzleben, Steffen

2018-02-05

Apart from the characterization of impurities, the full characterization of heparin and low molecular weight heparin (LMWH) also requires the determination of average molecular weight, which is closely related to the pharmaceutical properties of anticoagulant drugs. To determine average molecular weight of these animal-derived polymer products, partial least squares regression (PLS) was utilized for modelling of diffused-ordered spectroscopy NMR data (DOSY) of a representative set of heparin (n=32) and LMWH (n=30) samples. The same sets of samples were measured by gel permeation chromatography (GPC) to obtain reference data. The application of PLS to the data led to calibration models with root mean square error of prediction of 498Da and 179Da for heparin and LMWH, respectively. The average coefficients of variation (CVs) did not exceed 2.1% excluding sample preparation (by successive measuring one solution, n=5) and 2.5% including sample preparation (by preparing and analyzing separate samples, n=5). An advantage of the method is that the sample after standard 1D NMR characterization can be used for the molecular weight determination without further manipulation. The accuracy of multivariate models is better than the previous results for other matrices employing internal standards. Therefore, DOSY experiment is recommended to be employed for the calculation of molecular weight of heparin products as a complementary measurement to standard 1D NMR quality control. The method can be easily transferred to other matrices as well. Copyright © 2017 Elsevier B.V. All rights reserved.

Improved method for fluorescence cytometric immunohematology testing.

PubMed

Roback, John D; Barclay, Sheilagh; Hillyer, Christopher D

2004-02-01

A method for accurate immunohematology testing by fluorescence cytometry (FC) was previously described. Nevertheless, the use of vacuum filtration to wash RBCs and a standard-flow cytometer for data acquisition hindered efforts to incorporate this method into an automated platform. A modified procedure was developed that used low-speed centrifugation of 96-well filter plates for RBC staining. Small-footprint benchtop capillary cytometers (PCA and PCA-96, Guava Technologies, Inc.) were used for data acquisition. Authentic clinical samples from hospitalized patients were tested for ABO group and the presence of D antigen (n = 749) as well as for the presence of RBC alloantibodies (n = 428). Challenging samples with mixed-field reactions and weak antibodies were included. Results were compared to those obtained by column agglutination technology (CAT), and discrepancies were resolved by standard tube methods. Detailed investigations of FC sensitivity and reproducibility were also performed. The modified FC method with the PCA determined the correct ABO group and D type for 98.7 percent of 520 samples, compared to 98.8 percent for CAT (p > 0.05). No-type-determined (NTD) rates were 1.2 percent for both methods. In testing for unexpected alloantibodies, FC determined the correct result for 98.6 percent of 215 samples, compared to 96.3 percent for CAT (p > 0.05). When samples were automatically acquired in the 96-well plate format with the PCA-96, 98.7 percent of 229 samples had correct ABO group and D type determined by FC, compared to 97.4 percent for CAT (p > 0.05). NTD rates were 0.9 and 2.6 percent, respectively. Antibody screens were accurate for 99.1 percent of 213 samples with the PCA-96, compared to 99.5 percent for CAT (p > 0.05). Further investigations demonstrated that FC with the PCA-96 was better than CAT at detecting weak anti-A (p < 0.0001) and alloantibodies. An improved method for FC immunohematology testing has been described. This assay was comparable in accuracy to standard CAT techniques, but had better sensitivity for detecting weak antibodies and was superior in detecting mixed-field reactions (p < 0.005). The FC method demonstrated excellent reproducibility. The compatibility of this assay with the PCA-96 capillary cytometer with plate-handling capabilities should simplify development of a completely automated platform.

Molecular dynamics simulations using temperature-enhanced essential dynamics replica exchange.

PubMed

Kubitzki, Marcus B; de Groot, Bert L

2007-06-15

Today's standard molecular dynamics simulations of moderately sized biomolecular systems at full atomic resolution are typically limited to the nanosecond timescale and therefore suffer from limited conformational sampling. Efficient ensemble-preserving algorithms like replica exchange (REX) may alleviate this problem somewhat but are still computationally prohibitive due to the large number of degrees of freedom involved. Aiming at increased sampling efficiency, we present a novel simulation method combining the ideas of essential dynamics and REX. Unlike standard REX, in each replica only a selection of essential collective modes of a subsystem of interest (essential subspace) is coupled to a higher temperature, with the remainder of the system staying at a reference temperature, T(0). This selective excitation along with the replica framework permits efficient approximate ensemble-preserving conformational sampling and allows much larger temperature differences between replicas, thereby considerably enhancing sampling efficiency. Ensemble properties and sampling performance of the method are discussed using dialanine and guanylin test systems, with multi-microsecond molecular dynamics simulations of these test systems serving as references.

A general approach for sample size calculation for the three-arm 'gold standard' non-inferiority design.

PubMed

Stucke, Kathrin; Kieser, Meinhard

2012-12-10

In the three-arm 'gold standard' non-inferiority design, an experimental treatment, an active reference, and a placebo are compared. This design is becoming increasingly popular, and it is, whenever feasible, recommended for use by regulatory guidelines. We provide a general method to calculate the required sample size for clinical trials performed in this design. As special cases, the situations of continuous, binary, and Poisson distributed outcomes are explored. Taking into account the correlation structure of the involved test statistics, the proposed approach leads to considerable savings in sample size as compared with application of ad hoc methods for all three scale levels. Furthermore, optimal sample size allocation ratios are determined that result in markedly smaller total sample sizes as compared with equal assignment. As optimal allocation makes the active treatment groups larger than the placebo group, implementation of the proposed approach is also desirable from an ethical viewpoint. Copyright © 2012 John Wiley & Sons, Ltd.

[Simultaneous Determination of Sn and S in Methyltin Mercaptide by Microwave-Assisted Acid Digestion and ICP-OES].

PubMed

Chen, Qian; Wu, Xi; Hou, Xian-deng; Xu, Kai-lai

2015-09-01

Methyltin mercaptide is widely used as one of the best heat stabilizer in the polyvinylchloride (PVC) thermal processing due to its excellent stability, good transparency, high compatibility and weather resistance. The content of sulfur and tin significantly affects its quality and performance, so it is of great significance to develop an analytical method for the simultaneous determination of sulfur and tin. Inductively coupled plasma atomic emission spectrometry (ICP-OES) has been a powerful analytical tool for a myriad of complex samples owing to its advantages of the low detection limits, rapid and precise determinations over wide dynamic ranges, freedom from chemical inter-element interferences, the high sample throughput and above all, simultaneous multi-elements analysis. Microwave technique as a well-developed method for sample preparation can dramatically reduce the digestion time and the loss of volatile elements compared with the traditional open digestion. Hereby, a microwave-assisted acid digestion (MW-AAD) procedure followed by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis was developed for the simultaneous determination of Sn and S in methyltin mercaptide. This method has the advantages of simplicity, rapidness, good accuracy, green and less use of samples. Parameters affecting the MW-AAD such as the digestion solution and digestion time were optimized by using a chemical analyzed reference sample (DX-181) to attain tin and sulfur quantitative recoveries. HNO3-HCl-HClO4 (v/v/v=9:3:1) and 10 min were the optimum digestion solution and digestion time, respectively. Under optimum conditions, the standard addition method and the standard calibration curve method were both been used to detect Sn and S in DX-181. There was no significant difference between two methods and the relative deviations to the chemical analysis values were both less than 2%. Additionally, the accuracy of the MW-AAD method was examined by analyzing three methyltin mercaptide samples (DX-181, DX-990, DX-960). The results were satisfactory with the relative deviations (<3%) and the recoveries of standard addition (99%~102%).

Automated spectrophotometric bicarbonate analysis in duodenal juice compared to the back titration method.

PubMed

Erchinger, Friedemann; Engjom, Trond; Gudbrandsen, Oddrun Anita; Tjora, Erling; Gilja, Odd H; Dimcevski, Georg

2016-01-01

We have recently evaluated a short endoscopic secretin test for exocrine pancreatic function. Bicarbonate concentration in duodenal juice is an important parameter in this test. Measurement of bicarbonate by back titration as the gold standard method is time consuming, expensive and technically difficult, thus a simplified method is warranted. We aimed to evaluate an automated spectrophotometric method in samples spanning the effective range of bicarbonate concentrations in duodenal juice. We also evaluated if freezing of samples before analyses would affect its results. Patients routinely examined with short endoscopic secretin test suspected to have decreased pancreatic function of various reasons were included. Bicarbonate in duodenal juice was quantified by back titration and automatic spectrophotometry. Both fresh and thawed samples were analysed spectrophotometrically. 177 samples from 71 patients were analysed. Correlation coefficient of all measurements was r = 0.98 (p < 0.001). Correlation coefficient of fresh versus frozen samples conducted with automatic spectrophotometry (n = 25): r = 0.96 (p < 0.001) CONCLUSIONS: The measurement of bicarbonate in fresh and thawed samples by automatic spectrophotometrical analysis correlates excellent with the back titration gold standard. This is a major simplification of direct pancreas function testing, and allows a wider distribution of bicarbonate testing in duodenal juice. Extreme values for Bicarbonate concentration achieved by the autoanalyser method have to be interpreted with caution. Copyright © 2016 IAP and EPC. Published by Elsevier India Pvt Ltd. All rights reserved.

Development of particle induced gamma-ray emission methods for nondestructive determination of isotopic composition of boron and its total concentration in natural and enriched samples.

PubMed

Chhillar, Sumit; Acharya, Raghunath; Sodaye, Suparna; Pujari, Pradeep K

2014-11-18

We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

Effectiveness of Cool Roof Coatings with Ceramic Particles

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

Brehob, Ellen G; Desjarlais, Andre Omer; Atchley, Jerald Allen

2011-01-01

Liquid applied coatings promoted as cool roof coatings, including several with ceramic particles, were tested at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tenn., for the purpose of quantifying their thermal performances. Solar reflectance measurements were made for new samples and aged samples using a portable reflectometer (ASTM C1549, Standard Test Method for Determination of Solar Reflectance Near Ambient Temperature Using a Portable Solar Reflectometer) and for new samples using the integrating spheres method (ASTM E903, Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres). Thermal emittance was measured for the new samples using amore » portable emissometer (ASTM C1371, Standard Test Method for Determination of Emittance of Materials Near Room 1 Proceedings of the 2011 International Roofing Symposium Temperature Using Portable Emissometers). Thermal conductivity of the coatings was measured using a FOX 304 heat flow meter (ASTM C518, Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus). The surface properties of the cool roof coatings had higher solar reflectance than the reference black and white material, but there were no significant differences among coatings with and without ceramics. The coatings were applied to EPDM (ethylene propylene diene monomer) membranes and installed on the Roof Thermal Research Apparatus (RTRA), an instrumented facility at ORNL for testing roofs. Roof temperatures and heat flux through the roof were obtained for a year of exposure in east Tennessee. The field tests showed significant reduction in cooling required compared with the black reference roof (~80 percent) and a modest reduction in cooling compared with the white reference roof (~33 percent). The coating material with the highest solar reflectivity (no ceramic particles) demonstrated the best overall thermal performance (combination of reducing the cooling load cost and not incurring a large heating penalty cost) and suggests solar reflectivity is the significant characteristic for selecting cool roof coatings.« less

U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR COLLECTION, STORAGE, AND SHIPMENT OF DRINKING AND TAP WATER SAMPLES FOR PESTICIDES (EPA 225.2) AND CARBARYL (EPA 531.1) ANALYSIS (UA-F-17.1)

EPA Science Inventory

The purpose of this SOP is to describe how to collect, store, and ship tap and drinking water samples for analysis by EPA Method 525.2 (revision 1.0) and EPA method 531.1 (revision 3). This SOP provides a brief description of the sample containers, collection, preservation, stor...

NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR COLLECTION, STORAGE AND SHIPMENT OF DRINKING AND TAP WATER SAMPLES FOR PESTICIDES (EPA 225.2) AND CARBARYL (EPA 531.1) (UA-F-17.1)

EPA Science Inventory

The purpose of this SOP is to describe how to collect, store, and ship tap and drinking water samples for analysis by EPA Method 525.2 (revision 1.0) and EPA method 531.1 (revision 3) for the NHEXAS Arizona project. This SOP provides a brief description of the sample containers,...

Comparison of soil sampling and analytical methods for asbestos at the Sumas Mountain Asbestos Site-Working towards a toolbox for better assessment.

PubMed

Wroble, Julie; Frederick, Timothy; Frame, Alicia; Vallero, Daniel

2017-01-01

Established soil sampling methods for asbestos are inadequate to support risk assessment and risk-based decision making at Superfund sites due to difficulties in detecting asbestos at low concentrations and difficulty in extrapolating soil concentrations to air concentrations. Environmental Protection Agency (EPA)'s Office of Land and Emergency Management (OLEM) currently recommends the rigorous process of Activity Based Sampling (ABS) to characterize site exposures. The purpose of this study was to compare three soil analytical methods and two soil sampling methods to determine whether one method, or combination of methods, would yield more reliable soil asbestos data than other methods. Samples were collected using both traditional discrete ("grab") samples and incremental sampling methodology (ISM). Analyses were conducted using polarized light microscopy (PLM), transmission electron microscopy (TEM) methods or a combination of these two methods. Data show that the fluidized bed asbestos segregator (FBAS) followed by TEM analysis could detect asbestos at locations that were not detected using other analytical methods; however, this method exhibited high relative standard deviations, indicating the results may be more variable than other soil asbestos methods. The comparison of samples collected using ISM versus discrete techniques for asbestos resulted in no clear conclusions regarding preferred sampling method. However, analytical results for metals clearly showed that measured concentrations in ISM samples were less variable than discrete samples.

Comparison of soil sampling and analytical methods for asbestos at the Sumas Mountain Asbestos Site—Working towards a toolbox for better assessment

PubMed Central

2017-01-01

Established soil sampling methods for asbestos are inadequate to support risk assessment and risk-based decision making at Superfund sites due to difficulties in detecting asbestos at low concentrations and difficulty in extrapolating soil concentrations to air concentrations. Environmental Protection Agency (EPA)’s Office of Land and Emergency Management (OLEM) currently recommends the rigorous process of Activity Based Sampling (ABS) to characterize site exposures. The purpose of this study was to compare three soil analytical methods and two soil sampling methods to determine whether one method, or combination of methods, would yield more reliable soil asbestos data than other methods. Samples were collected using both traditional discrete (“grab”) samples and incremental sampling methodology (ISM). Analyses were conducted using polarized light microscopy (PLM), transmission electron microscopy (TEM) methods or a combination of these two methods. Data show that the fluidized bed asbestos segregator (FBAS) followed by TEM analysis could detect asbestos at locations that were not detected using other analytical methods; however, this method exhibited high relative standard deviations, indicating the results may be more variable than other soil asbestos methods. The comparison of samples collected using ISM versus discrete techniques for asbestos resulted in no clear conclusions regarding preferred sampling method. However, analytical results for metals clearly showed that measured concentrations in ISM samples were less variable than discrete samples. PMID:28759607

40 CFR Table 1 to Subpart Cccc of... - Emission Limitations

Code of Federal Regulations, 2011 CFR

2011-07-01

... per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Performance test (Method 29 of appendix A of this part). Carbon monoxide 157 parts per million by dry volume 3-run average (1 hour minimum sample time per run) Performance test (Method 10, 10A, or 10B of appendix A of this...

40 CFR Table 1 to Subpart Cccc of... - Emission Limitations

Code of Federal Regulations, 2010 CFR

2010-07-01

... per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Performance test (Method 29 of appendix A of this part). Carbon monoxide 157 parts per million by dry volume 3-run average (1 hour minimum sample time per run) Performance test (Method 10, 10A, or 10B of appendix A of this...

NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE--COMPENDIUM OF METHODS FOR ANALYSIS OF TRACE METALS AND PESTICIDES IN DIETARY SAMPLES USING TOTAL DIET STUDY PROCEDURES (FDA-COMPENDIUM)

EPA Science Inventory

This compendium contains seven SOPs developed by Food and Drug Administration (FDA) laboratories for methods of analyzing trace metals in dietary samples collected using Total Diet study procedures. The SOPs include the following: (1) Quality Control for Analysis of NHEXAS Food o...

Quantitative determinations of levofloxacin and rifampicin in pharmaceutical and urine samples using nuclear magnetic resonance spectroscopy

NASA Astrophysics Data System (ADS)

Salem, A. A.; Mossa, H. A.; Barsoum, B. N.

2005-11-01

Rapid, specific and simple methods for determining levofloxacin and rifampicin antibiotic drugs in pharmaceutical and human urine samples were developed. The methods are based on 1H NMR spectroscopy using maleic acid as an internal standard and DMSO-d6 as NMR solvent. Integration of NMR signals at 8.9 and 8.2 ppm were, respectively, used for calculating the concentration of levofloxacin and rifampicin drugs per unit dose. Maleic acid signal at 6.2 ppm was used as the reference signal. Recoveries of (97.0-99.4) ± 0.5 and (98.3-99.7) ± 1.08% were obtained for pure levofloxacin and rifampicin, respectively. Corresponding recoveries of 98.5-100.3 and 96.8-100.0 were, respectively, obtained in pharmaceutical capsules and urine samples. Relative standard deviations (R.S.D.) values ≤2.7 were obtained for analyzed drugs in pure, pharmaceutical and urine samples. Statistical Student's t-test gave t-values ≤2.87 indicating insignificant difference between the real and the experimental values at the 95% confidence level. F-test revealed insignificant difference in precisions between the developed NMR methods and each of fluorimetric and HPLC methods for analyzing levofloxacin and rifampicin.

Method and apparatus for the preparation of liquid samples for determination of boron

DOEpatents

Siemer, Darryl D.

1986-01-01

A method and apparatus for the preparation of a liquid sample for the quantitative determination of boron by flame photometry. The sample is combined in a vessel with sulfuric acid, and an excess of methanol is added thereto. The methanol reacts with any boron present in the sample to form trimethyl borate which is volatilized by the heat of reaction between the excess methanol and sulfuric acid. The volatilized trimethyl borate is withdrawn from the vessel by either a partial vacuum or a positive pressure and is rapidly transferred to a standard flame photometer. The method is free of interference from typical boron concomitants.

Method and apparatus for the preparation of liquid samples for determination of boron

DOEpatents

Siemer, Darryl D.

1986-03-04

A method and apparatus for the preparation of a liquid sample for the quantitative determination of boron by flame photometry. The sample is combined in a vessel with sulfuric acid, and an excess of methanol is added thereto. The methanol reacts with any boron present in the sample to form trimethyl borate which is volatilized by the heat of reaction between the excess methanol and sulfuric acid. The volatilized trimethyl borate is withdrawn from the vessel by either a partial vacuum or a positive pressure and is rapidly transferred to a standard flame photometer. The method is free of interference from typical boron concomitants.

Method and apparatus for the preparation of liquid samples for determination of boron

DOEpatents

Siemer, D.D.

A method and apparatus are described for the preparation of a liquid sample for the quantitative determination of boron by flame photometry. The sample is combined in a vessel with sulfuric acid, and an excess of methanol is added thereto. The methanol reacts with any boron present in the sample to form trimethyl borate which is volatilized by the heat of reaction between the excess methanol and sulfuric acid. The volatilized trimethyl borate is withdrawn from the vessel by either a partial vacuum or a positive pressure and is rapidly transferred to a standard flame photometer. The method is free of interference from typical boron concomitants.

Evaluation of Petrifilms(TM) as a diagnostic test to detect bovine mastitis organisms in Kenya.

PubMed

Gitau, George K; Bundi, Royford M; Vanleeuwen, John; Mulei, Charles M

2013-03-01

The study purpose was to validate Petrifilms(TM) (3M Microbiology, 2005) against standard culture methods in the diagnosis of bovine mastitis organisms in Kenya. On 128 smallholder dairy cattle farms in Kenya, between June 21, 2010 and August 31, 2010, milk samples from 269 cows that were positive on California Mastitis Test (CMT) were cultured using standard laboratory culture methods and Petrifilms(TM) (Aerobic Count and Coliform Count -3M Microbiology, 2005), and results were compared. Staphylococcus aureus was the most common bacterium isolated (73 % of samples). Clinical mastitis was found in only three cows, and there were only two Gram-negative isolates, making it impossible to examine the agreement between the two tests for Gram-negative- or clinical mastitis samples. The observed agreement between the standard culture and Petrifilm(TM) (3M Microbiology, 2005) results for Gram-positive isolates was 85 %, and there was fair agreement beyond that expected due to chance alone, with a kappa (κ) of 0.38. Using culture results as a gold standard, the Petrifilms(TM) had a sensitivity of 90 % for Gram-positive samples and specificity of 51 %. With 87 % of CMT-positive samples resulting in Gram-positive pathogens cultured, there was a positive predictive value of 93 % and a negative predictive value of 43 %. Petrifilms(TM) should be considered for culture of mastitis organisms in developing countries, especially when Gram-positive bacteria are expected.

Development of a Highly Sensitive Nested-PCR Procedure Using a Single Closed Tube for Detection of Erwinia amylovora in Asymptomatic Plant Material

PubMed Central

Llop, Pablo; Bonaterra, Anna; Peñalver, Javier; López, María M.

2000-01-01

A novel method, which involves a nested PCR in a single closed tube, was developed for the sensitive detection of Erwinia amylovora in plant material. The external and internal primer pairs used had different annealing temperatures and directed the amplification of a specific DNA fragment from plasmid pEA29. The procedure involved two consecutive PCRs, the first of which was performed at a higher annealing temperature that allowed amplification only by the external primer pair. Using pure cultures of E. amylovora, the sensitivity of the nested PCR in one tube was similar to that of a standard nested PCR in two tubes. The specificity and sensitivity were greater than those of standard PCR procedures that used a single primer pair. The presence of inhibitors in plant material, very common in E. amylovora hosts, is overcome with this system in combination with a simple DNA extraction protocol because it eliminates many of the inhibitory compounds. In addition, it needs a very small sample volume (1 μl of DNA extracted). With 83 samples of naturally infected material, this method achieved better results than any other PCR technique: standard PCR detected 55% of positive samples, two-tube nested PCR detected 71% of positive samples, and nested PCR in a single closed tube detected 78% of positive samples. When analyzing asymptomatic plant material, the number of positive samples detected by the developed nested PCR was also the highest, compared with the PCR protocols indicated previously (17, 20, and 25% of 251 samples analyzed, respectively). This method is proposed for the detection of endophytic and epiphytic populations of E. amylovora in epidemiological studies and for routine use in quarantine surveys, due to its high sensitivity, specificity, speed, and simplicity. PMID:10788384

Aqueous nitrite ion determination by selective reduction and gas phase nitric oxide chemiluminescence

NASA Technical Reports Server (NTRS)

Dunham, A. J.; Barkley, R. M.; Sievers, R. E.; Clarkson, T. W. (Principal Investigator)

1995-01-01

An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemilluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 microL) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100-microL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2% relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 microL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well.

A simple method to recover Norovirus from fresh produce with large sample size by using histo-blood group antigen-conjugated to magnetic beads in a recirculating affinity magnetic separation system (RCAMS).

PubMed

Tian, Peng; Yang, David; Mandrell, Robert

2011-06-30

Human norovirus (NoV) outbreaks are major food safety concerns. The virus has to be concentrated from food samples in order to be detected. PEG precipitation is the most common method to recover the virus. Recently, histo-blood group antigens (HBGA) have been recognized as receptors for human NoV, and have been utilized as an alternative method to concentrate human NoV for samples up to 40 mL in volume. However, to wash off the virus from contaminated fresh food samples, at least 250 mL of wash volume is required. Recirculating affinity magnetic separation system (RCAMS) has been tried by others to concentrate human NoV from large-volume samples and failed to yield consistent results with the standard procedure of 30 min of recirculation at the default flow rate. Our work here demonstrates that proper recirculation time and flow rate are key factors for success in using the RCAMS. The bead recovery rate was increased from 28% to 47%, 67% and 90% when recirculation times were extended from 30 min to 60 min, 120 min and 180 min, respectively. The kinetics study suggests that at least 120 min recirculation is required to obtain a good recovery of NoV. In addition, different binding and elution conditions were compared for releasing NoV from inoculated lettuce. Phosphate-buffered saline (PBS) and water results in similar efficacy for virus release, but the released virus does not bind to RCAMS effectively unless pH was adjusted to acidic. Either citrate-buffered saline (CBS) wash, or water wash followed by CBS adjustment, resulted in an enhanced recovery of virus. We also demonstrated that the standard curve generated from viral RNA extracted from serially-diluted virus samples is more accurate for quantitative analysis than standard curves generated from serially-diluted plasmid DNA or transcribed-RNA templates, both of which tend to overestimate the concentration power. The efficacy of recovery of NoV from produce using RCAMS was directly compared with that of the PEG method in NoV inoculated lettuce. 40, 4, 0.4, and 0.04 RTU can be detected by both methods. At 0.004 RTU, NoV was detectable in all three samples concentrated by the RCAMS method, while none could be detected by the PEG precipitation method. RCAMS is a simple and rapid method that is more sensitive than conventional methods for recovery of NoV from food samples with a large sample size. In addition, the RTU value detected through RCAMS-processed samples is more biologically relevant. Published by Elsevier B.V.

A comparison of two estimates of standard error for a ratio-of-means estimator for a mapped-plot sample design in southeast Alaska.

Treesearch

Willem W.S. van Hees

2002-01-01

Comparisons of estimated standard error for a ratio-of-means (ROM) estimator are presented for forest resource inventories conducted in southeast Alaska between 1995 and 2000. Estimated standard errors for the ROM were generated by using a traditional variance estimator and also approximated by bootstrap methods. Estimates of standard error generated by both...

Quantification of drugs in plasma without primary reference standards by liquid chromatography-chemiluminescence nitrogen detection: application to tramadol metabolite ratios.

PubMed

Ojanperä, Suvi; Rasanen, Ilpo; Sistonen, Johanna; Pelander, Anna; Vuori, Erkki; Ojanperä, Ilkka

2007-08-01

Lack of availability of reference standards for drug metabolites, newly released drugs, and illicit drugs hinders the analysis of these substances in biologic samples. To counter this problem, an approach is presented here for quantitative drug analysis in plasma without primary reference standards by liquid chromatography-chemiluminescence nitrogen detection (LC-CLND). To demonstrate the feasibility of the method, metabolic ratios of the opioid drug tramadol were determined in the setting of a pharmacogenetic study. Four volunteers were given a single 100-mg oral dose of tramadol, and a blood sample was collected from each subject 1 hour later. Tramadol, O-desmethyltramadol, and nortramadol were determined in plasma by LC-CLND without reference standards and by a gas chromatography-mass spectrometry reference method. In contrast to previous CLND studies lacking an extraction step, a liquid-liquid extraction system was created for 5-mL plasma samples using n-butyl chloride-isopropyl alcohol (98 + 2) at pH 10. Extraction recovery estimation was based on model compounds chosen according to their similar physicochemical characteristics (retention time, pKa, logD). Instrument calibration was performed with a single secondary standard (caffeine) using the equimolar response of the detector to nitrogen. The mean differences between the results of the LC-CLND and gas chromatography-mass spectrometry methods for tramadol, O-desmethyltramadol, and nortramadol were 8%, 32%, and 19%, respectively. The sensitivity of LC-CLND was sufficient for therapeutic concentrations of tramadol and metabolites. A good correlation was obtained between genotype, expressed by the number of functional genes, and the plasma metabolite ratios. This experiment suggests that a recovery-corrected LC-CLND analysis produces sufficiently accurate results to be useful in a clinical context, particularly in instances in which reference standards are not readily accessible.

Validation of PCR methods for quantitation of genetically modified plants in food.

PubMed

Hübner, P; Waiblinger, H U; Pietsch, K; Brodmann, P

2001-01-01

For enforcement of the recently introduced labeling threshold for genetically modified organisms (GMOs) in food ingredients, quantitative detection methods such as quantitative competitive (QC-PCR) and real-time PCR are applied by official food control laboratories. The experiences of 3 European food control laboratories in validating such methods were compared to describe realistic performance characteristics of quantitative PCR detection methods. The limit of quantitation (LOQ) of GMO-specific, real-time PCR was experimentally determined to reach 30-50 target molecules, which is close to theoretical prediction. Starting PCR with 200 ng genomic plant DNA, the LOQ depends primarily on the genome size of the target plant and ranges from 0.02% for rice to 0.7% for wheat. The precision of quantitative PCR detection methods, expressed as relative standard deviation (RSD), varied from 10 to 30%. Using Bt176 corn containing test samples and applying Bt176 specific QC-PCR, mean values deviated from true values by -7to 18%, with an average of 2+/-10%. Ruggedness of real-time PCR detection methods was assessed in an interlaboratory study analyzing commercial, homogeneous food samples. Roundup Ready soybean DNA contents were determined in the range of 0.3 to 36%, relative to soybean DNA, with RSDs of about 25%. Taking the precision of quantitative PCR detection methods into account, suitable sample plans and sample sizes for GMO analysis are suggested. Because quantitative GMO detection methods measure GMO contents of samples in relation to reference material (calibrants), high priority must be given to international agreements and standardization on certified reference materials.

[Standard sample preparation method for quick determination of trace elements in plastic].

PubMed

Yao, Wen-Qing; Zong, Rui-Long; Zhu, Yong-Fa

2011-08-01

Reference sample was prepared by masterbatch method, containing heavy metals with known concentration of electronic information products (plastic), the repeatability and precision were determined, and reference sample preparation procedures were established. X-Ray fluorescence spectroscopy (XRF) analysis method was used to determine the repeatability and uncertainty in the analysis of the sample of heavy metals and bromine element. The working curve and the metrical methods for the reference sample were carried out. The results showed that the use of the method in the 200-2000 mg x kg(-1) concentration range for Hg, Pb, Cr and Br elements, and in the 20-200 mg x kg(-1) range for Cd elements, exhibited a very good linear relationship, and the repeatability of analysis methods for six times is good. In testing the circuit board ICB288G and ICB288 from the Mitsubishi Heavy Industry Company, results agreed with the recommended values.

Analysis of penicillin G in milk by liquid chromatography.

PubMed

Boison, J O; Keng, L J; MacNeil, J D

1994-01-01

A liquid chromatographic (LC) method that was previously developed for penicillin G residues in animal tissues has been adapted to milk and milk products. After protein precipitation with sodium tungstate, samples are applied to a C18 solid-phase extraction cartridge, from which penicillin is eluted, derivatized with 1,2,4-triazole-mercuric chloride solution, and analyzed by isocratic liquid chromatography (LC) on a C18 column with UV detection at 325 nm. Quantitation is done with reference to penicillin V as an internal standard. Penicillin G recoveries were determined to be > 70% on standards fortified at 3-60 ppb. Accuracy approached 100% using the penicillin V internal standard. The detection limit for penicillin G residues was 3 ppb in fluid milk. Samples may be confirmed by thermospray/LC at concentrations approaching the detection limit of the UV method.

Simultaneous identification and quantification of tetrodotoxin in fresh pufferfish and pufferfish-based products using immunoaffinity columns and liquid chromatography/quadrupole-linear ion trap mass spectrometry

NASA Astrophysics Data System (ADS)

Guo, Mengmeng; Wu, Haiyan; Jiang, Tao; Tan, Zhijun; Zhao, Chunxia; Zheng, Guanchao; Li, Zhaoxin; Zhai, Yuxiu

2017-07-01

In this study, we established a comprehensive method for simultaneous identification and quantification of tetrodotoxin (TTX) in fresh pufferfish tissues and pufferfish-based products using liquid chromatography/quadrupole-linear ion trap mass spectrometry (LC-QqLIT-MS). TTX was extracted by 1% acetic acid-methanol, and most of the lipids were then removed by freezing lipid precipitation, followed by purification and concentration using immunoaffinity columns (IACs). Matrix effects were substantially reduced due to the high specificity of the IACs, and thus, background interference was avoided. Quantitation analysis was therefore performed using an external calibration curve with standards prepared in mobile phase. The method was evaluated by fortifying samples at 1, 10, and 100 ng/g, respectively, and the recoveries ranged from 75.8%-107%, with a relative standard deviation of less than 15%. The TTX calibration curves were linear over the range of 1-1 000 μg/L, with a detection limit of 0.3 ng/g and a quantification limit of 1 ng/g. Using this method, samples can be further analyzed using an information-dependent acquisition (IDA) experiment, in the positive mode, from a single liquid chromatography-tandem mass spectrometry injection, which can provide an extra level of confirmation by matching the full product ion spectra acquired for a standard sample with those from an enhanced product ion (EPI) library. The scheduled multiple reaction monitoring method enabled TTX to be screened for, and TTX was positively identified using the IDA and EPI spectra. This method was successfully applied to analyze a total of 206 samples of fresh pufferfish tissues and pufferfish-based products. The results from this study show that the proposed method can be used to quantify and identify TTX in a single run with excellent sensitivity and reproducibility, and is suitable for the analysis of complex matrix pufferfish samples.

A generic standard additions based method to determine endogenous analyte concentrations by immunoassays to overcome complex biological matrix interference.

PubMed

Pang, Susan; Cowen, Simon

2017-12-13

We describe a novel generic method to derive the unknown endogenous concentrations of analyte within complex biological matrices (e.g. serum or plasma) based upon the relationship between the immunoassay signal response of a biological test sample spiked with known analyte concentrations and the log transformed estimated total concentration. If the estimated total analyte concentration is correct, a portion of the sigmoid on a log-log plot is very close to linear, allowing the unknown endogenous concentration to be estimated using a numerical method. This approach obviates conventional relative quantification using an internal standard curve and need for calibrant diluent, and takes into account the individual matrix interference on the immunoassay by spiking the test sample itself. This technique is based on standard additions for chemical analytes. Unknown endogenous analyte concentrations within even 2-fold diluted human plasma may be determined reliably using as few as four reaction wells.

[The uncertainty evaluation of analytical results of 27 elements in geological samples by X-ray fluorescence spectrometry].

PubMed

Wang, Yi-Ya; Zhan, Xiu-Chun

2014-04-01

Evaluating uncertainty of analytical results with 165 geological samples by polarized dispersive X-ray fluorescence spectrometry (P-EDXRF) has been reported according to the internationally accepted guidelines. One hundred sixty five pressed pellets of similar matrix geological samples with reliable values were analyzed by P-EDXRF. These samples were divided into several different concentration sections in the concentration ranges of every component. The relative uncertainties caused by precision and accuracy of 27 components were evaluated respectively. For one element in one concentration, the relative uncertainty caused by precision can be calculated according to the average value of relative standard deviation with different concentration level in one concentration section, n = 6 stands for the 6 results of one concentration level. The relative uncertainty caused by accuracy in one concentration section can be evaluated by the relative standard deviation of relative deviation with different concentration level in one concentration section. According to the error propagation theory, combining the precision uncertainty and the accuracy uncertainty into a global uncertainty, this global uncertainty acted as method uncertainty. This model of evaluating uncertainty can solve a series of difficult questions in the process of evaluating uncertainty, such as uncertainties caused by complex matrix of geological samples, calibration procedure, standard samples, unknown samples, matrix correction, overlap correction, sample preparation, instrument condition and mathematics model. The uncertainty of analytical results in this method can act as the uncertainty of the results of the similar matrix unknown sample in one concentration section. This evaluation model is a basic statistical method owning the practical application value, which can provide a strong base for the building of model of the following uncertainty evaluation function. However, this model used a lot of samples which cannot simply be applied to other types of samples with different matrix samples. The number of samples is too large to adapt to other type's samples. We will strive for using this study as a basis to establish a reasonable basis of mathematical statistics function mode to be applied to different types of samples.

Fingerprint chromatogram analysis of Pseudostellaria heterophylla (Miq.) Pax root by high performance liquid chromatography.

PubMed

Han, Chao; Chen, Junhui; Chen, Bo; Lee, Frank Sen-Chun; Wang, Xiaoru

2006-09-01

A simple and reliable high performance liquid chromatographic (HPLC) method has been developed and validated for the fingerprinting of extracts from the root of Pseudostellaria heterophylla (Miq.) Pax. HPLC with gradient elution was performed on an authentic reference standard of powdered P. heterophylla (Miq.) Pax root and 11 plant samples of the root were collected from different geographic locations. The HPLC chromatograms have been standardized through the selection and identification of reference peaks and the normalization of retention times and peak intensities of all the common peaks. The standardized HPLC fingerprints show high stability and reproducibility, and thus can be used effectively for the screening analysis or quality assessment of the root or its derived products. Similarity index calculations based on cosine angle values or correlation methods have been performed on the HPLC fingerprints. As a group, the fingerprints of the P. heterophylla (Miq.) Pax samples studied are highly correlated with closely similar fingerprints. Within the group, the samples can be further divided into subgroups based on hierarchical clustering analysis (HCA). Sample grouping based on HCA coincides nicely with those based on the geographical origins of the samples. The HPLC fingerprinting techniques thus have high potential in authentication or source-tracing types of applications.

DNA profiles from clothing fibers using direct PCR.

PubMed

Blackie, Renée; Taylor, Duncan; Linacre, Adrian

2016-09-01

We report on the successful use of direct PCR amplification of single fibers from items of worn clothing. Items of clothing were worn throughout the course of a day, with the individual commencing regular activities. Single fibers were taken from the cuff of the clothing at regular intervals and amplified directly. The same areas were subjected to tape-lifting, and also amplified directly for comparison. The NGM™ kit that amplifies 15 STR loci plus amelogenin was used. A total of 35 single fiber samples were processed and analyzed from five items of clothing, with 81 % of samples returning a profile of 14 alleles or more. All tape-lift samples amplified directly produced DNA profiles of 15 alleles or more. The aim was to develop a simple, operational method that could be used routinely in forensic science casework and that has the potential to generate more complete profiles, which would not be detected using standard extraction methods on this type of sample. For ease of implementation, the process also adheres to standard methods with no increase in the cycle number.

Paleogene stratigraphy of the Solomons Island, Maryland corehole

USGS Publications Warehouse

Gibson, Thomas G.; Bybell, Laurel M.

1994-01-01

Purge and trap capillary gas chromatography/mass spectrometry is a rapid, precise, accurate method for determining volatile organic compounds in samples of surface water and ground water. The method can be used to determine 59 selected compounds, including chlorofluorohydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. The volatile organic compounds are removed from the sample matrix by actively purging the sample with helium. The volatile organic compounds are collected onto a sorbant trap, thermally desorbed, separated by a Megabore gas chromatographic capillary column, ionized by electron impact, and determined by a full-scan quadrupole mass spectrometer. Compound identification is confirmed by the gas chromatographic retention time and by the resultant mass spectrum. Unknown compounds detected in a sample can be tentatively identified by comparing the unknown mass spectrum to reference spectra in the mass-spectra computer-data system library compiled by the National Institute of Standards and Technology. Method detection limits for the selected compounds range from 0.05 to 0.2 microgram per liter. Recoveries for the majority of the selected compounds ranged from 80 to 120 percent, with relative standard deviations of less than 10 percent.

A rapid analytical method for predicting the oxygen demand of wastewater.

PubMed

Fogelman, Shoshana; Zhao, Huijun; Blumenstein, Michael

2006-11-01

In this study, an investigation was undertaken to determine whether the predictive accuracy of an indirect, multiwavelength spectroscopic technique for rapidly determining oxygen demand (OD) values is affected by the use of unfiltered and turbid samples, as well as by the use of absorbance values measured below 200 nm. The rapid OD technique was developed that uses UV-Vis spectroscopy and artificial neural networks (ANNs) to indirectly determine chemical oxygen demand (COD) levels. It was found that the most accurate results were obtained when a spectral range of 190-350 nm was provided as data input to the ANN, and when using unfiltered samples below a turbidity range of 150 NTU. This is because high correlations of above 0.90 were obtained with the data using the standard COD method. This indicates that samples can be measured directly without the additional need for preprocessing by filtering. Samples with turbidity values higher than 150 NTU were found to produce poor correlations with the standard COD method, which made them unsuitable for accurate, real-time, on-line monitoring of OD levels.

HPLC fingerprint analysis combined with chemometrics for pattern recognition of ginger.

PubMed

Feng, Xu; Kong, Weijun; Wei, Jianhe; Ou-Yang, Zhen; Yang, Meihua

2014-03-01

Ginger, the fresh rhizome of Zingiber officinale Rosc. (Zingiberaceae), has been used worldwide; however, for a long time, there has been no standard approbated internationally for its quality control. To establish an efficacious and combinational method and pattern recognition technique for quality control of ginger. A simple, accurate and reliable method based on high-performance liquid chromatography with photodiode array (HPLC-PDA) detection was developed for establishing the chemical fingerprints of 10 batches of ginger from different markets in China. The method was validated in terms of precision, reproducibility and stability; and the relative standard deviations were all less than 1.57%. On the basis of this method, the fingerprints of 10 batches of ginger samples were obtained, which showed 16 common peaks. Coupled with similarity evaluation software, the similarities between each fingerprint of the sample and the simulative mean chromatogram were in the range of 0.998-1.000. Then, the chemometric techniques, including similarity analysis, hierarchical clustering analysis and principal component analysis were applied to classify the ginger samples. Consistent results were obtained to show that ginger samples could be successfully classified into two groups. This study revealed that HPLC-PDA method was simple, sensitive and reliable for fingerprint analysis, and moreover, for pattern recognition and quality control of ginger.

New robust bilinear least squares method for the analysis of spectral-pH matrix data.

PubMed

Goicoechea, Héctor C; Olivieri, Alejandro C

2005-07-01

A new second-order multivariate method has been developed for the analysis of spectral-pH matrix data, based on a bilinear least-squares (BLLS) model achieving the second-order advantage and handling multiple calibration standards. A simulated Monte Carlo study of synthetic absorbance-pH data allowed comparison of the newly proposed BLLS methodology with constrained parallel factor analysis (PARAFAC) and with the combination multivariate curve resolution-alternating least-squares (MCR-ALS) technique under different conditions of sample-to-sample pH mismatch and analyte-background ratio. The results indicate an improved prediction ability for the new method. Experimental data generated by measuring absorption spectra of several calibration standards of ascorbic acid and samples of orange juice were subjected to second-order calibration analysis with PARAFAC, MCR-ALS, and the new BLLS method. The results indicate that the latter method provides the best analytical results in regard to analyte recovery in samples of complex composition requiring strict adherence to the second-order advantage. Linear dependencies appear when multivariate data are produced by using the pH or a reaction time as one of the data dimensions, posing a challenge to classical multivariate calibration models. The presently discussed algorithm is useful for these latter systems.

Simultaneous determination of V, Ni and Fe in fuel fly ash using solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry.

PubMed

Cárdenas Valdivia, A; Vereda Alonso, E; López Guerrero, M M; Gonzalez-Rodriguez, J; Cano Pavón, J M; García de Torres, A

2018-03-01

A green and simple method has been proposed in this work for the simultaneous determination of V, Ni and Fe in fuel ash samples by solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry (SS HR CS GFAAS). The application of fast programs in combination with direct solid sampling allows eliminating pretreatment steps, involving minimal manipulation of sample. Iridium treated platforms were applied throughout the present study, enabling the use of aqueous standards for calibration. Correlation coefficients for the calibration curves were typically better than 0.9931. The concentrations found in the fuel ash samples analysed ranged from 0.66% to 4.2% for V, 0.23-0.7% for Ni and 0.10-0.60% for Fe. Precision (%RSD) were 5.2%, 10.0% and 9.8% for V, Ni and Fe, respectively, obtained as the average of the %RSD of six replicates of each fuel ash sample. The optimum conditions established were applied to the determination of the target analytes in fuel ash samples. In order to test the accuracy and applicability of the proposed method in the analysis of samples, five ash samples from the combustion of fuel in power stations, were analysed. The method accuracy was evaluated by comparing the results obtained using the proposed method with the results obtained by ICP OES previous acid digestion. The results showed good agreement between them. The goal of this work has been to develop a fast and simple methodology that permits the use of aqueous standards for straightforward calibration and the simultaneous determination of V, Ni and Fe in fuel ash samples by direct SS HR CS GFAAS. Copyright © 2017 Elsevier B.V. All rights reserved.

Resampling-based Methods in Single and Multiple Testing for Equality of Covariance/Correlation Matrices

PubMed Central

Yang, Yang; DeGruttola, Victor

2016-01-01

Traditional resampling-based tests for homogeneity in covariance matrices across multiple groups resample residuals, that is, data centered by group means. These residuals do not share the same second moments when the null hypothesis is false, which makes them difficult to use in the setting of multiple testing. An alternative approach is to resample standardized residuals, data centered by group sample means and standardized by group sample covariance matrices. This approach, however, has been observed to inflate type I error when sample size is small or data are generated from heavy-tailed distributions. We propose to improve this approach by using robust estimation for the first and second moments. We discuss two statistics: the Bartlett statistic and a statistic based on eigen-decomposition of sample covariance matrices. Both statistics can be expressed in terms of standardized errors under the null hypothesis. These methods are extended to test homogeneity in correlation matrices. Using simulation studies, we demonstrate that the robust resampling approach provides comparable or superior performance, relative to traditional approaches, for single testing and reasonable performance for multiple testing. The proposed methods are applied to data collected in an HIV vaccine trial to investigate possible determinants, including vaccine status, vaccine-induced immune response level and viral genotype, of unusual correlation pattern between HIV viral load and CD4 count in newly infected patients. PMID:22740584

Resampling-based methods in single and multiple testing for equality of covariance/correlation matrices.

PubMed

Yang, Yang; DeGruttola, Victor

2012-06-22

Traditional resampling-based tests for homogeneity in covariance matrices across multiple groups resample residuals, that is, data centered by group means. These residuals do not share the same second moments when the null hypothesis is false, which makes them difficult to use in the setting of multiple testing. An alternative approach is to resample standardized residuals, data centered by group sample means and standardized by group sample covariance matrices. This approach, however, has been observed to inflate type I error when sample size is small or data are generated from heavy-tailed distributions. We propose to improve this approach by using robust estimation for the first and second moments. We discuss two statistics: the Bartlett statistic and a statistic based on eigen-decomposition of sample covariance matrices. Both statistics can be expressed in terms of standardized errors under the null hypothesis. These methods are extended to test homogeneity in correlation matrices. Using simulation studies, we demonstrate that the robust resampling approach provides comparable or superior performance, relative to traditional approaches, for single testing and reasonable performance for multiple testing. The proposed methods are applied to data collected in an HIV vaccine trial to investigate possible determinants, including vaccine status, vaccine-induced immune response level and viral genotype, of unusual correlation pattern between HIV viral load and CD4 count in newly infected patients.

Evaluating an alternative method for rapid urinary creatinine determination

EPA Science Inventory

Creatinine (CR) is an endogenously-produced chemical routinely assayed in urine specimens to assess kidney function, sample dilution. The industry-standard method for CR determination, known as the kinetic Jaffe (KJ) method, relies on an exponential rate of a colorimetric change,...

14C sample preparation for AMS microdosing studies at Lund University using online combustion and septa-sealed vials

NASA Astrophysics Data System (ADS)

Sydoff, Marie; Stenström, Kristina

2010-04-01

The Department of Physics at Lund University is participating in a European Union project called EUMAPP (European Union Microdose AMS Partnership Programme), in which sample preparation and accelerator mass spectrometry (AMS) measurements of biological samples from microdosing studies have been made. This paper describes a simplified method of converting biological samples to solid graphite for 14C analysis with AMS. The method is based on online combustion of the samples, and reduction of CO 2 in septa-sealed vials. The septa-sealed vials and disposable materials are used to eliminate sample cross-contamination. Measurements of ANU and Ox I standards show deviations of 2% and 3%, respectively, relative to reference values. This level of accuracy is sufficient for biological samples from microdosing studies. Since the method has very few handling steps from sample to graphite, the risk of failure during the sample preparation process is minimized, making the method easy to use in routine preparation of samples.

A novel strategy to obtain quantitative data for modelling: combined enrichment and real-time PCR for enumeration of salmonellae from pig carcasses.

PubMed

Krämer, Nadine; Löfström, Charlotta; Vigre, Håkan; Hoorfar, Jeffrey; Bunge, Cornelia; Malorny, Burkhard

2011-03-01

Salmonella is a major zoonotic pathogen which causes outbreaks and sporadic cases of gastroenteritis in humans worldwide. The primary sources for Salmonella are food-producing animals such as pigs and poultry. For risk assessment and hazard analysis and critical control point (HACCP) concepts, it is essential to produce large amounts of quantitative data, which is currently not achievable with the standard cultural based methods for enumeration of Salmonella. This study presents the development of a novel strategy to enumerate low numbers of Salmonella in cork borer samples taken from pig carcasses as a first concept and proof of principle for a new sensitive and rapid quantification method based on combined enrichment and real-time PCR. The novelty of the approach is in the short pre-enrichment step, where for most bacteria, growth is in the log phase. The method consists of an 8h pre-enrichment of the cork borer sample diluted 1:10 in non-selective buffered peptone water, followed by DNA extraction, and Salmonella detection and quantification by real-time PCR. The limit of quantification was 1.4 colony forming units (CFU)/20 cm(2) (approximately 10 g) of artificially contaminated sample with 95% confidence interval of ± 0.7 log CFU/sample. The precision was similar to the standard reference most probable number (MPN) method. A screening of 200 potentially naturally contaminated cork borer samples obtained over seven weeks in a slaughterhouse resulted in 25 Salmonella-positive samples. The analysis of salmonellae within these samples showed that the PCR method had a higher sensitivity for samples with a low contamination level (<6.7 CFU/sample), where 15 of the samples negative with the MPN method was detected with the PCR method and 5 were found to be negative by both methods. For the samples with a higher contamination level (6.7-310 CFU/sample) a good agreement between the results obtained with the PCR and MPN methods was obtained. The quantitative real-time PCR method can easily be applied to other food and environmental matrices by adaptation of the pre-enrichment time and media. Copyright © 2010 Elsevier B.V. All rights reserved.

Protein quantification using a cleavable reporter peptide.

PubMed

Duriez, Elodie; Trevisiol, Stephane; Domon, Bruno

2015-02-06

Peptide and protein quantification based on isotope dilution and mass spectrometry analysis are widely employed for the measurement of biomarkers and in system biology applications. The accuracy and reliability of such quantitative assays depend on the quality of the stable-isotope labeled standards. Although the quantification using stable-isotope labeled peptides is precise, the accuracy of the results can be severely biased by the purity of the internal standards, their stability and formulation, and the determination of their concentration. Here we describe a rapid and cost-efficient method to recalibrate stable isotope labeled peptides in a single LC-MS analysis. The method is based on the equimolar release of a protein reference peptide (used as surrogate for the protein of interest) and a universal reporter peptide during the trypsinization of a concatenated polypeptide standard. The quality and accuracy of data generated with such concatenated polypeptide standards are highlighted by the quantification of two clinically important proteins in urine samples and compared with results obtained with conventional stable isotope labeled reference peptides. Furthermore, the application of the UCRP standards in complex samples is described.

Iso standardization of theoretical activity evaluation method for low and intermediate level activated waste generated at nuclear power plants

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

Makoto Kashiwagi; Garamszeghy, Mike; Lantes, Bertrand

Disposal of low-and intermediate-level activated waste generated at nuclear power plants is being planned or carried out in many countries. The radioactivity concentrations and/or total quantities of long-lived, difficult-to-measure nuclides (DTM nuclides), such as C-14, Ni-63, Nb-94, α emitting nuclides etc., are often restricted by the safety case for a final repository as determined by each country's safety regulations, and these concentrations or amounts are required to be known and declared. With respect to waste contaminated by contact with process water, the Scaling Factor method (SF method), which is empirically based on sampling and analysis data, has been applied asmore » an important method for determining concentrations of DTM nuclides. This method was standardized by the International Organization for Standardization (ISO) and published in 2007 as ISO21238 'Scaling factor method to determine the radioactivity of low and intermediate-level radioactive waste packages generated at nuclear power plants' [1]. However, for activated metal waste with comparatively high concentrations of radioactivity, such as may be found in reactor control rods and internal structures, direct sampling and radiochemical analysis methods to evaluate the DTM nuclides are limited by access to the material and potentially high personnel radiation exposure. In this case, theoretical calculation methods in combination with empirical methods based on remote radiation surveys need to be used to best advantage for determining the disposal inventory of DTM nuclides while minimizing exposure to radiation workers. Pursuant to this objective a standard for the theoretical evaluation of the radioactivity concentration of DTM nuclides in activated waste, is in process through ISO TC85/SC5 (ISO Technical Committee 85: Nuclear energy, nuclear technologies, and radiological protection; Subcommittee 5: Nuclear fuel cycle). The project team for this ISO standard was formed in 2011 and is composed of experts from 11 countries. The project team has been conducting technical discussions on theoretical methods for determining concentrations of radioactivity, and has developed the draft International Standard of ISO16966 'Theoretical activation calculation method to evaluate the radioactivity of activated waste generated at nuclear reactors' [2]. This paper describes the international standardization process developed by the ISO project team, and outlines the following two theoretical activity evaluation methods:? Point method? Range method. (authors)« less

Rapid determination of tafenoquine in small volume human plasma samples by high-performance liquid chromatography-tandem mass spectrometry.

PubMed

Doyle, E; Fowles, S E; Summerfield, S; White, T J

2002-03-25

A method was developed for the determination of tafenoquine (I) in human plasma using high-performance liquid chromatography-tandem mass spectrometry. Prior to analysis, the protein in plasma samples was precipitated with methanol containing [2H3(15N)]tafenoquine (II) to act as an internal standard. The supernatant was injected onto a Genesis-C18 column without any further clean-up. The mass spectrometer was operated in the positive ion mode, employing a heat assisted nebulisation, electrospray interface. Ions were detected in multiple reaction monitoring mode. The assay required 50 microl of plasma and was precise and accurate within the range 2 to 500 ng/ml. The average within-run and between-run relative standard deviations were < 7% at 2 ng/ml and greater concentrations. The average accuracy of validation standards was generally within +/- 4% of the nominal concentration. There was no evidence of instability of I in human plasma following three complete freeze-thaw cycles and samples can safely be stored for at least 8 months at approximately -70 degrees C. The method was very robust and has been successfully applied to the analysis of clinical samples from patients and healthy volunteers dosed with I.

Ultrasound-assisted emulsification microextraction for determination of 2,4,6-trichloroanisole in wine samples by gas chromatography tandem mass spectrometry.

PubMed

Fontana, Ariel R; Patil, Sangram H; Banerjee, Kaushik; Altamirano, Jorgelina C

2010-04-28

A fast and effective microextraction technique is proposed for preconcentration of 2,4,6-trichloroanisole (2,4,6-TCA) from wine samples prior gas chromatography tandem mass spectrometric (GC-MS/MS) analysis. The proposed technique is based on ultrasonication (US) for favoring the emulsification phenomenon during the extraction stage. Several variables influencing the relative response of the target analyte were studied and optimized. Under optimal experimental conditions, 2,4,6-TCA was quantitatively extracted achieving enhancement factors (EF) > or = 400 and limits of detection (LODs) 0.6-0.7 ng L(-1) with relative standard deviations (RSDs) < or = 11.3%, when 10 ng L(-1) 2,4,6-TCA standard-wine sample blend was analyzed. The calibration graphs for white and red wine were linear within the range of 5-1000 ng L(-1), and estimation coefficients (r(2)) were > or = 0.9995. Validation of the methodology was carried out by standard addition method at two concentrations (10 and 50 ng L(-1)) achieving recoveries >80% indicating satisfactory robustness of the method. The methodology was successfully applied for determination of 2,4,6-TCA in different wine samples.

CTEPP NC DATA QA/QC RESULTS

EPA Science Inventory

This data set contains the method performance results. This includes field blanks, method blanks, duplicate samples, analytical duplicates, matrix spikes, and surrogate recovery standards.

The Children’s Total Exposure to Persistent Pesticides and Other Persistent Pollutant (...

Selective extraction based on poly(MAA-VB-EGMDA) monolith followed by HPLC for determination of hordenine in plasma and urine samples.

PubMed

Chen, Yonggang; Meng, Junhua; Zou, Jili; An, Jing

2015-06-01

Hordenine is an active compound found in several foods, herbs and beer. In this work, a novel sorbent was fabricated for selective solid-phase extraction (SPE) of hordenine in biological samples. The organic polymer sorbent was synthesized in one step in the plastic barrel of a syringe by a pre-polymerization solution consisting of methacrylic acid (MAA), 4-vinylphenylboronic acid (VB) and ethylene glycol dimethacrylate (EGDMA). The conditions for preparation were optimized to generate a poly(MAA-VB-EGMDA) monolith with good permeability. The monolith exhibited good enrichment efficiency towards hordenine. By using tyramine as the internal standard, a poly(MAA-VB-EGMDA)-based SPE-HPLC method was established for analysis of hordenine. Conditions for SPE, including volume of eluting solvent, pH of sample solution, sampling rate and sample volume, were optimized. The proposed SPE-HPLC method presented good linearity (R(2)  = 0.9992) within 10-2000 ng/mL and the detection limits was 3 ng/mL, which is significantly more sensitive than reported methods. The method was also applied in plasma and urine samples; good capability of removing matrices was observed, while hordenine in low content was well extracted and enriched. The recoveries were from 90.6 to 94.7% and from 89.3 to 91.5% for the spiked plasma and urine samples, respectively, with the relative standard deviations <4.7%. Copyright © 2014 John Wiley & Sons, Ltd.

Determination of neonicotinoid pesticides residues in agricultural samples by solid-phase extraction combined with liquid chromatography-tandem mass spectrometry.

PubMed

Xie, Wen; Han, Chao; Qian, Yan; Ding, Huiying; Chen, Xiaomei; Xi, Junyang

2011-07-15

This work reports a new sensitive multi-residue liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detection, confirmation and quantification of six neonicotinoid pesticides (dinotefuran, thiamethoxam, clothiandin, imidacloprid, acetamiprid and thiacloprid) in agricultural samples (chestnut, shallot, ginger and tea). Activated carbon and HLB solid-phase extraction cartridges were used for cleaning up the extracts. Analysis is performed by LC-MS/MS operated in the multiple reaction monitoring (MRM) mode, acquiring two specific precursor-product ion transitions per target compound. Quantification was carried by the internal standard method with D(4)-labeled imidacloprid. The method showed excellent linearity (R(2)≥0.9991) and precision (relative standard deviation, RSD≤8.6%) for all compounds. Limits of quantification (LOQs) were 0.01 mg kg(-1) for chestnut, shallot, ginger sample and 0.02 mg kg(-1) for tea sample. The average recoveries, measured at three concentrations levels (0.01 mg kg(-1), 0.02 mg kg(-1) and 0.1 mg kg(-1) for chestnut, shallot, ginger sample, 0.02 mg kg(-1), 0.04 mg kg(-1) and 0.2 mg kg(-1) for tea sample), were in the range 82.1-108.5%. The method was satisfactorily validated for the analysis of 150 agricultural samples (chestnut, shallot, ginger and tea). Imidacloprid and acetamiprid were detected at concentration levels ranging from 0.05 to 3.6 mg kg(-1). Copyright © 2011 Elsevier B.V. All rights reserved.

50 CFR 600.315 - National Standard 2-Scientific Information.

Code of Federal Regulations, 2013 CFR

2013-10-01

... from surveys or sampling programs, and models that are mathematical representations of reality... static and ideally entails developing and following a research plan with the following elements: Clear... predictions, or testing hypotheses; study design with an explicit and standardized method of collecting data...

Best-Matched Internal Standard Normalization in Liquid Chromatography-Mass Spectrometry Metabolomics Applied to Environmental Samples.

PubMed

Boysen, Angela K; Heal, Katherine R; Carlson, Laura T; Ingalls, Anitra E

2018-01-16

The goal of metabolomics is to measure the entire range of small organic molecules in biological samples. In liquid chromatography-mass spectrometry-based metabolomics, formidable analytical challenges remain in removing the nonbiological factors that affect chromatographic peak areas. These factors include sample matrix-induced ion suppression, chromatographic quality, and analytical drift. The combination of these factors is referred to as obscuring variation. Some metabolomics samples can exhibit intense obscuring variation due to matrix-induced ion suppression, rendering large amounts of data unreliable and difficult to interpret. Existing normalization techniques have limited applicability to these sample types. Here we present a data normalization method to minimize the effects of obscuring variation. We normalize peak areas using a batch-specific normalization process, which matches measured metabolites with isotope-labeled internal standards that behave similarly during the analysis. This method, called best-matched internal standard (B-MIS) normalization, can be applied to targeted or untargeted metabolomics data sets and yields relative concentrations. We evaluate and demonstrate the utility of B-MIS normalization using marine environmental samples and laboratory grown cultures of phytoplankton. In untargeted analyses, B-MIS normalization allowed for inclusion of mass features in downstream analyses that would have been considered unreliable without normalization due to obscuring variation. B-MIS normalization for targeted or untargeted metabolomics is freely available at https://github.com/IngallsLabUW/B-MIS-normalization .

Indices of polarimetric purity for biological tissues inspection

NASA Astrophysics Data System (ADS)

Van Eeckhout, Albert; Lizana, Angel; Garcia-Caurel, Enric; Gil, José J.; Sansa, Adrià; Rodríguez, Carla; Estévez, Irene; González, Emilio; Escalera, Juan C.; Moreno, Ignacio; Campos, Juan

2018-02-01

We highlight the interest of using the Indices of Polarimetric Purity (IPPs) for the biological tissue inspection. These are three polarimetric metrics focused on the study of the depolarizing behaviour of the sample. The IPPs have been recently proposed in the literature and provide different and synthetized information than the commonly used depolarizing indices, as depolarization index (PΔ) or depolarization power (Δ). Compared with the standard polarimetric images of biological samples, IPPs enhance the contrast between different tissues of the sample and show differences between similar tissues which are not observed using the other standard techniques. Moreover, they present further physical information related to the depolarization mechanisms inherent to different tissues. In addition, the algorithm does not require advanced calculations (as in the case of polar decompositions), being the indices of polarimetric purity fast and easy to implement. We also propose a pseudo-coloured image method which encodes the sample information as a function of the different indices weights. These images allow us to customize the visualization of samples and to highlight certain of their constitutive structures. The interest and potential of the IPP approach are experimentally illustrated throughout the manuscript by comparing polarimetric images of different ex-vivo samples obtained with standard polarimetric methods with those obtained from the IPPs analysis. Enhanced contrast and retrieval of new information are experimentally obtained from the different IPP based images.

Validation of an optimized method for the determination of iodine in human breast milk by inductively coupled plasma mass spectrometry (ICPMS) after tetramethylammonium hydroxide extraction.

PubMed

Huynh, Dao; Zhou, Shao Jia; Gibson, Robert; Palmer, Lyndon; Muhlhausler, Beverly

2015-01-01

In this study a novel method to determine iodine concentrations in human breast milk was developed and validated. The iodine was analyzed by inductively coupled plasma mass spectrometry (ICPMS) following tetramethylammonium hydroxide (TMAH) extraction at 90°C in disposable polypropylene tubes. While similar approaches have been used previously, this method adopted a shorter extraction time (1h vs. 3h) and used antimony (Sb) as the internal standard, which exhibited greater stability in breast milk and milk powder matrices compared to tellurium (Te). Method validation included: defining iodine linearity up to 200μgL(-1); confirming recovery of iodine from NIST 1549 milk powder. A recovery of 94-98% was also achieved for the NIST 1549 milk powder and human breast milk samples spiked with sodium iodide and thyroxine (T4) solutions. The method quantitation limit (MQL) for human breast milk was 1.6μgL(-1). The intra-assay and inter-assay coefficient of variation for the breast milk samples and NIST powder were <1% and <3.5%, respectively. NIST 1549 milk powder, human breast milk samples and calibration standards spiked with the internal standard were all stable for at least 2.5 months after extraction. The results of the validation process confirmed that this newly developed method provides greater accuracy and precision in the assessment of iodine concentrations in human breast milk than previous methods and therefore offers a more reliable approach for assessing iodine concentrations in human breast milk. Copyright © 2014 Elsevier GmbH. All rights reserved.

International Standards for Genomes, Transcriptomes, and Metagenomes

PubMed Central

Mason, Christopher E.; Afshinnekoo, Ebrahim; Tighe, Scott; Wu, Shixiu; Levy, Shawn

2017-01-01

Challenges and biases in preparing, characterizing, and sequencing DNA and RNA can have significant impacts on research in genomics across all kingdoms of life, including experiments in single-cells, RNA profiling, and metagenomics (across multiple genomes). Technical artifacts and contamination can arise at each point of sample manipulation, extraction, sequencing, and analysis. Thus, the measurement and benchmarking of these potential sources of error are of paramount importance as next-generation sequencing (NGS) projects become more global and ubiquitous. Fortunately, a variety of methods, standards, and technologies have recently emerged that improve measurements in genomics and sequencing, from the initial input material to the computational pipelines that process and annotate the data. Here we review current standards and their applications in genomics, including whole genomes, transcriptomes, mixed genomic samples (metagenomes), and the modified bases within each (epigenomes and epitranscriptomes). These standards, tools, and metrics are critical for quantifying the accuracy of NGS methods, which will be essential for robust approaches in clinical genomics and precision medicine. PMID:28337071

The Next-Generation PCR-Based Quantification Method for Ambient Waters: Digital PCR.

PubMed

Cao, Yiping; Griffith, John F; Weisberg, Stephen B

2016-01-01

Real-time quantitative PCR (qPCR) is increasingly being used for ambient water monitoring, but development of digital polymerase chain reaction (digital PCR) has the potential to further advance the use of molecular techniques in such applications. Digital PCR refines qPCR by partitioning the sample into thousands to millions of miniature reactions that are examined individually for binary endpoint results, with DNA density calculated from the fraction of positives using Poisson statistics. This direct quantification removes the need for standard curves, eliminating the labor and materials associated with creating and running standards with each batch, and removing biases associated with standard variability and mismatching amplification efficiency between standards and samples. Confining reactions and binary endpoint measurements to small partitions also leads to other performance advantages, including reduced susceptibility to inhibition, increased repeatability and reproducibility, and increased capacity to measure multiple targets in one analysis. As such, digital PCR is well suited for ambient water monitoring applications and is particularly advantageous as molecular methods move toward autonomous field application.

Study on the influence of X-ray tube spectral distribution on the analysis of bulk samples and thin films: Fundamental parameters method and theoretical coefficient algorithms

NASA Astrophysics Data System (ADS)

Sitko, Rafał

2008-11-01

Knowledge of X-ray tube spectral distribution is necessary in theoretical methods of matrix correction, i.e. in both fundamental parameter (FP) methods and theoretical influence coefficient algorithms. Thus, the influence of X-ray tube distribution on the accuracy of the analysis of thin films and bulk samples is presented. The calculations are performed using experimental X-ray tube spectra taken from the literature and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al. (X-Ray Spectrom. 14 (1985) 125-135), Ebel (X-Ray Spectrom. 28 (1999) 255-266), and Finkelshtein and Pavlova (X-Ray Spectrom. 28 (1999) 27-32). In this study, Fe-Cr-Ni system is selected as an example and the calculations are performed for X-ray tubes commonly applied in X-ray fluorescence analysis (XRF), i.e., Cr, Mo, Rh and W. The influence of X-ray tube spectra on FP analysis is evaluated when quantification is performed using various types of calibration samples. FP analysis of bulk samples is performed using pure-element bulk standards and multielement bulk standards similar to the analyzed material, whereas for FP analysis of thin films, the bulk and thin pure-element standards are used. For the evaluation of the influence of X-ray tube spectra on XRF analysis performed by theoretical influence coefficient methods, two algorithms for bulk samples are selected, i.e. Claisse-Quintin (Can. Spectrosc. 12 (1967) 129-134) and COLA algorithms (G.R. Lachance, Paper Presented at the International Conference on Industrial Inorganic Elemental Analysis, Metz, France, June 3, 1981) and two algorithms (constant and linear coefficients) for thin films recently proposed by Sitko (X-Ray Spectrom. 37 (2008) 265-272).

Carcass enrichment detects Salmonella from broiler carcasses found to be negative by other sampling methods

USDA-ARS?s Scientific Manuscript database

The most frequently used methods to recover Salmonella from processed broiler chicken carcasses involve carcass rinsing or neck skin maceration. These methods are nondestructive and practical, but have limited sensitivity. The standard carcass rinse method uses only 7.5% of the residual rinsate an...

EVALUATION OF A CRYPTOSPORIDIUM INTERNAL STANDARD FOR DETERMINING RECOVERY WITH ENVIRONMENTAL PROTECTION AGENCY METHOD 1623

EPA Science Inventory

The current benchmark method for detecting Cryptosporidium oocysts in water is the U.S. Environmental Protection Agency (U.S. EPA) Method 1623. Studies evaluating this method report that recoveries are highly variable and dependent upon laboratory, water sample, and analyst. Ther...

CTEPP STANDARD OPERATING PROCEDURE FOR EXTRACTING AND PREPARING DUST AND SOIL SAMPLES FOR ANALYSIS OF NEUTRAL PERSISTENT ORGANIC POLLUTANTS (SOP-5.14)

EPA Science Inventory

This SOP summarizes the method for extracting and preparing a dust or soil sample for analysis of neutral persistent organic pollutants. It covers the extraction and concentration of samples that are to be analyzed by gas chromatography/mass spectrometry.

CTEPP STANDARD OPERATING PROCEDURE FOR EXTRACTING AND PREPARING DERMAL WIPE SAMPLES FOR ANALYSIS OF NEUTRAL PERSISTENT ORGANIC POLLUTANTS (SOP-5.16)

EPA Science Inventory

The method for extracting and preparing a dermal (hand) wipe sample for analysis of neutral persistent organic pollutants is summarized in this SOP. It covers the extraction and concentration of samples that are to be analyzed by gas chromatography/mass spectrometry.

CTEPP STANDARD OPERATING PROCEDURE FOR COLLECTION OF DISLODGEABLE RESIDUES -- PUF ROLLER SAMPLES FOR PERSISTENT ORGANIC POLLUTANTS (SOP-2.18)

EPA Science Inventory

This SOP describes the method to collect transferable residues from indoor floor surfaces. The sampling procedures described are applicable to bare floors or covered floor surfaces, e.g., carpeting and vinyl flooring. The samples will be collected only in the day care centers o...

CTEPP STANDARD OPERATING PROCEDURE FOR COLLECTION OF FIXED SITE INDOOR AND OUTDOOR AIR SAMPLES FOR PERSISTENT ORGANIC POLLUTANTS (SOP-2.12)

EPA Science Inventory

This SOP describes the procedures to set up, calibrate, initiate and terminate air sampling for persistent organic pollutants. This method is used to sample air, indoors and outdoors, at homes and at day care centers over a 48-hr period.

Sample Selection in Randomized Experiments: A New Method Using Propensity Score Stratified Sampling

ERIC Educational Resources Information Center

Tipton, Elizabeth; Hedges, Larry; Vaden-Kiernan, Michael; Borman, Geoffrey; Sullivan, Kate; Caverly, Sarah

2014-01-01

Randomized experiments are often seen as the "gold standard" for causal research. Despite the fact that experiments use random assignment to treatment conditions, units are seldom selected into the experiment using probability sampling. Very little research on experimental design has focused on how to make generalizations to well-defined…

A Method Based on Artificial Intelligence To Fully Automatize The Evaluation of Bovine Blastocyst Images.

PubMed

Rocha, José Celso; Passalia, Felipe José; Matos, Felipe Delestro; Takahashi, Maria Beatriz; Ciniciato, Diego de Souza; Maserati, Marc Peter; Alves, Mayra Fernanda; de Almeida, Tamie Guibu; Cardoso, Bruna Lopes; Basso, Andrea Cristina; Nogueira, Marcelo Fábio Gouveia

2017-08-09

Morphological analysis is the standard method of assessing embryo quality; however, its inherent subjectivity tends to generate discrepancies among evaluators. Using genetic algorithms and artificial neural networks (ANNs), we developed a new method for embryo analysis that is more robust and reliable than standard methods. Bovine blastocysts produced in vitro were classified as grade 1 (excellent or good), 2 (fair), or 3 (poor) by three experienced embryologists according to the International Embryo Technology Society (IETS) standard. The images (n = 482) were subjected to automatic feature extraction, and the results were used as input for a supervised learning process. One part of the dataset (15%) was used for a blind test posterior to the fitting, for which the system had an accuracy of 76.4%. Interestingly, when the same embryologists evaluated a sub-sample (10%) of the dataset, there was only 54.0% agreement with the standard (mode for grades). However, when using the ANN to assess this sub-sample, there was 87.5% agreement with the modal values obtained by the evaluators. The presented methodology is covered by National Institute of Industrial Property (INPI) and World Intellectual Property Organization (WIPO) patents and is currently undergoing a commercial evaluation of its feasibility.

Sampling and analytical methods of stable isotopes and dissolved inorganic carbon from CO2 injection sites

NASA Astrophysics Data System (ADS)

van Geldern, Robert; Myrttinen, Anssi; Becker, Veith; Barth, Johannes A. C.

2010-05-01

The isotopic composition (δ13C) of dissolved inorganic carbon (DIC), in combination with DIC concentration measurements, can be used to quantify geochemical trapping of CO2 in water. This is of great importance in monitoring the fate of CO2 in the subsurface in CO2 injection projects. When CO2 mixes with water, a shift in the δ13C values, as well as an increase in DIC concentrations is observed in the CO2-H2O system. However, when using standard on-site titration methods, it is often challenging to determining accurate in-situ DIC concentrations. This may be due to CO2 degassing and CO2-exchange between the sample and the atmosphere during titration, causing a change in the pH value or due to other unfavourable conditions such as turbid water samples or limited availability of fluid samples. A way to resolve this problem is by simultaneously determining the DIC concentration and carbon isotopic composition using a standard continuous flow Isotope Ratio Mass Spectrometry (CF-IRMS) setup with a Gasbench II coupled to Delta plusXP mass spectrometer. During sampling, in order to avoid atmospheric contact, water samples taken from the borehole-fluid-sampler should be directly transferred into a suitable container, such as a gasbag. Also, to avoid isotope fractionation due to biological activity in the sample, it is recommended to stabilize the gasbags prior to sampling with HgCl2 for the subsequent stable isotope analysis. The DIC concentration of the samples can be determined from the area of the sample peaks in a chromatogram from a CF-IRMS analysis, since it is directly proportional to the CO2 generated by the reaction of the water with H3PO4. A set of standards with known DIC concentrations should be prepared by mixing NaHCO3 with DIC free water. Since the DIC concentrations of samples taken from CO2 injection sites are expected to be exceptionally high due to the additional high amounts of added CO2, the DIC concentration range of the standards should be set high enough to cover the sample concentrations. In order to assure methodological reproducibility, this 'calibration set' should be included in every sequence analysed with the Gasbench CF-IRMS system. The standards, therefore, should also be treated in the same way as the samples. For accurate determination, it is essential to know the exact amount of water in the vial and the density of the sample. This requires weighing of each vial before and after injection of the water sample. For stable isotope analysis, the required signal height can be adjusted by the sample amount. Therefore this method is suitable for analysing samples with highly differing DIC concentrations. Reproducibility and accuracy of the quantitative analysis of the dissolved inorganic carbon need to be verified by independent control standards, treated as samples. This study was conducted as a part of the R&D programme CLEAN, which is funded by the German Federal Ministry of Education in the framework of the programme GEOTECHNOLOGIEN. We would like to thank GDF SUEZ for permitting us to conduct sampling campaigns at their site.

Validation of odor concentration from mechanical-biological treatment piles using static chamber and wind tunnel with different wind speed values.

PubMed

Szyłak-Szydłowski, Mirosław

2017-09-01

The basic principle of odor sampling from surface sources is based primarily on the amount of air obtained from a specific area of the ground, which acts as a source of malodorous compounds. Wind tunnels and flux chambers are often the only available, direct method of evaluating the odor fluxes from small area sources. There are currently no widely accepted chamber-based methods; thus, there is still a need for standardization of these methods to ensure accuracy and comparability. Previous research has established that there is a significant difference between the odor concentration values obtained using the Lindvall chamber and those obtained by a dynamic flow chamber. Thus, the present study compares sampling methods using a streaming chamber modeled on the Lindvall cover (using different wind speeds), a static chamber, and a direct sampling method without any screens. The volumes of chambers in the current work were similar, ~0.08 m 3 . This study was conducted at the mechanical-biological treatment plant in Poland. Samples were taken from a pile covered by the membrane. Measured odor concentration values were between 2 and 150 ou E /m 3 . Results of the study demonstrated that both chambers can be used interchangeably in the following conditions: odor concentration is below 60 ou E /m 3 , wind speed inside the Lindvall chamber is below 0.2 m/sec, and a flow value is below 0.011 m 3 /sec. Increasing the wind speed above the aforementioned value results in significant differences in the results obtained between those methods. In all experiments, the results of the concentration of odor in the samples using the static chamber were consistently higher than those from the samples measured in the Lindvall chamber. Lastly, the results of experiments were employed to determine a model function of the relationship between wind speed and odor concentration values. Several researchers wrote that there are no widely accepted chamber-based methods. Also, there is still a need for standardization to ensure full comparability of these methods. The present study compared the existing methods to improve the standardization of area source sampling. The practical usefulness of the results was proving that both examined chambers can be used interchangeably. Statistically similar results were achieved while odor concentration was below 60 ou E /m 3 and wind speed inside the Lindvall chamber was below 0.2 m/sec. Increasing wind speed over these values results in differences between these methods. A model function of relationship between wind speed and odor concentration value was determined.

A rapid method for quantification of 242Pu in urine using extraction chromatography and ICP-MS

DOE PAGES

Gallardo, Athena Marie; Than, Chit; Wong, Carolyn; ...

2017-01-01

Occupational exposure to plutonium is generally monitored through analysis of urine samples. Typically, plutonium is separated from the sample and other actinides, and the concentration is determined using alpha spectroscopy. Current methods for separations and analysis are lengthy and require long count times. A new method for monitoring occupational exposure levels of plutonium has been developed, which requires fewer steps and overall less time than the alpha spectroscopy method. In this method, the urine is acidified, and a 239Pu internal standard is added. The urine is digested in a microwave oven, and plutonium is separated using an Eichrom TRU Resinmore » column. The plutonium is eluted, and the eluant is injected directly into the Inductively Coupled Plasma–Mass Spectrometer (ICP-MS). Compared to a direct “dilute and shoot” method, a 30-fold improvement in sensitivity is achieved. This method was validated by analyzing several batches of spiked samples. Based on these analyses, a combined standard uncertainty plot, which relates uncertainty to concentration, was produced. As a result, the MDA 95 was calculated to be 7.0 × 10 –7 μg L –1, and the Lc95 was calculated to be 3.5 × 10 –7 μg L –1 for this method.« less

Evaluation of direct saponification method for determination of cholesterol in meats.

PubMed

Adams, M L; Sullivan, D M; Smith, R L; Richter, E F

1986-01-01

A gas chromatographic (GC) method has been developed for determination of cholesterol in meats. The method involves ethanolic KOH saponification of the sample material, homogeneous-phase toluene extraction of the unsaponifiables, derivatization of cholesterol to its trimethylsilylether, and quantitation by GC-flame ionization detection using 5-alpha-cholestane as internal standard. This direct saponification method is compared with the current AOAC official method for determination of cholesterol in 20 different meat products. The direct saponification method eliminates the need for initial lipid extraction, thus offering a 30% savings in labor, and requires fewer solvents than the AOAC method. It produced comparable or slightly higher cholesterol results than the AOAC method in all meat samples examined. Precision, determined by assaying a turkey meat sample 16 times over 4 days, was excellent (CV = 1.74%). Average recovery of cholesterol added to meat samples was 99.8%.

Liquid chromatography/tandem mass spectrometry method to determine boldenone in bovine liver tissues.

PubMed

Granja, Rodrigo H M M; Salerno, Alessandro G; de Lima, Andreia C; Montalvo, Cynthia; Reche, Karine V G; Giannotti, Fabio M; Wanschel, Amarylis C B A

2014-01-01

Boldenone, an androgenic steroid, is forbidden for use in meat production in most countries worldwide. Residues of this drug in food present a potential risk to consumers. A sensitive LC/MS/MS method for analysis of 17β-boldenone using boldenone-d3 as an internal standard was developed. An enzymatic hydrolysis and extraction using ethyl acetate, methanol, and hexane were performed in the sample preparation. Parameters such as decision limit (CCα), detection capability (CCβ), precision, recovery, and ruggedness were evaluated according to the Brazilian Regulation 24/2009 (equivalent to European Union Decision 2002/657/EC) and International Organization for Standardization/International Electrotechnical Commission 17025:2005. CCα and CCβ were determined to be 0.17 and 0.29 μg/kg, respectively. Average recoveries from bovine liver samples fortified with 1, 1.5, and 2 μg/kg were around 100%. A complete statistical analysis was performed on the results obtained, including an estimation of the method uncertainty. The method is considered robust after being subjected to day-to-day analytical variations and has been used as a standard method in Brazil to report boldenone levels in bovine liver.

Comparison of sampling methods for radiocarbon dating of carbonyls in air samples via accelerator mass spectrometry

NASA Astrophysics Data System (ADS)

Schindler, Matthias; Kretschmer, Wolfgang; Scharf, Andreas; Tschekalinskij, Alexander

2016-05-01

Three new methods to sample and prepare various carbonyl compounds for radiocarbon measurements were developed and tested. Two of these procedures utilized the Strecker synthetic method to form amino acids from carbonyl compounds with either sodium cyanide or trimethylsilyl cyanide. The third procedure used semicarbazide to form crystalline carbazones with the carbonyl compounds. The resulting amino acids and semicarbazones were then separated and purified using thin layer chromatography. The separated compounds were then combusted to CO2 and reduced to graphite to determine 14C content by accelerator mass spectrometry (AMS). All of these methods were also compared with the standard carbonyl compound sampling method wherein a compound is derivatized with 2,4-dinitrophenylhydrazine and then separated by high-performance liquid chromatography (HPLC).

Monitoring benthic aIgal communides: A comparison of targeted and coefficient sampling methods

USGS Publications Warehouse

Edwards, Matthew S.; Tinker, M. Tim

2009-01-01

Choosing an appropriate sample unit is a fundamental decision in the design of ecological studies. While numerous methods have been developed to estimate organism abundance, they differ in cost, accuracy and precision.Using both field data and computer simulation modeling, we evaluated the costs and benefits associated with two methods commonly used to sample benthic organisms in temperate kelp forests. One of these methods, the Targeted Sampling method, relies on different sample units, each "targeted" for a specific species or group of species while the other method relies on coefficients that represent ranges of bottom cover obtained from visual esti-mates within standardized sample units. Both the field data and the computer simulations suggest that both methods yield remarkably similar estimates of organism abundance and among-site variability, although the Coefficient method slightly underestimates variability among sample units when abundances are low. In contrast, the two methods differ considerably in the effort needed to sample these communities; the Targeted Sampling requires more time and twice the personnel to complete. We conclude that the Coefficent Sampling method may be better for environmental monitoring programs where changes in mean abundance are of central concern and resources are limiting, but that the Targeted sampling methods may be better for ecological studies where quantitative relationships among species and small-scale variability in abundance are of central concern.

Capillary whole blood testing by a new portable monitor. Comparison with standard determination of the international normalized ratio.

PubMed

de Miguel, Dunia; Burgaleta, Carmen; Reyes, Eduardo; Pascual, Teresa

2003-07-01

We evaluated a new portable monitor (AvoSure PT PRO, Menarini Diagnostics, Firenze, Italy) developed to test the prothrombin time in capillary blood and plasma by comparing it with the standard laboratory determination. We studied 62 patients receiving acenocoumarol therapy. The international normalized ratio (INR) in capillary blood was analyzed by 2 methods: AvoSure PT PRO and Thrombotrack Nycomed Analyzer (Axis-Shield, Dundee, Scotland). Parallel studies were performed in plasma samples by a reference method using the Behring Coagulation Timer (Behring Diagnostics, Marburg, Germany). Plasma samples also were tested with the AvoSure PT PRO. Correlation was good for INR values for capillary blood and plasma samples by AvoSure PT PRO and our reference method (R2 = 0.8596) and for capillary blood samples tested by the AvoSure PT PRO and Thrombotrack Nycomed Analyzer (R2 = 0.8875). The correlation for INR in capillary blood and plasma samples by AvoSure PT PRO was 0.6939 (P < .0004). Capillary blood determinations are rapid and effective for monitoring oral anticoagulation therapy and have a high correlation to plasma determinations. AvoSure PT PRO is accurate for controlling INR in plasma and capillary blood samples, may be used in outpatient clinics, and has advantages over previous portable monitors.