Direct Quantitation of PCB Congeners Using a Helium Discharge Detector and Internal Standard Techniques

1988 ◽  
Vol 42 (4) ◽  
pp. 586-588 ◽  
Author(s):  
Peter J. McAteer ◽  
Tom B. Ryerson ◽  
Mark D. Argentine ◽  
Margaret L. Ware ◽  
Gary W. Rice
Keyword(s):  
Internal Standard ◽  
Average Error ◽  
Detector Response ◽  
Selective Detection ◽  
Response Factor ◽  
Internal Standards ◽  
Pcb Congeners ◽  
Peak Areas ◽  
Helium Discharge ◽  
Standard Techniques

Individual PCB congeners have been quantitated at ppm levels, with an average error of ±3.2%, with the use of a helium discharge detector (HDD) for element-selective detection of Cl emission. Chlorinated internal standards of known concentrations were added to each solution determined to establish the relative peak areas per unit concentration of Cl present. No detector precalibration or response factor formulations were required, since the detector response is based solely on the moles of Cl present. The same methodology was utilized to determine the % Cl in Aroclor samples without prior identification of the PCB congeners present.

scholarly journals Internal Standards for Quantitative Analysis of Chemical Warfare Agents by the GC/MS Method: Nerve Agents

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Tomas Capoun ◽  
Jana Krykorkova
Keyword(s):  
Internal Standard ◽  
Chemical Warfare Agents ◽  
Chemical Warfare ◽  
Linear Functions ◽  
Mass Detection ◽  
Response Factors ◽  
Internal Standards ◽  
Rescue Service ◽  
Warfare Agents ◽  
Peak Areas

General conditions and requirements for an internal standard useful in the determination of chemical warfare agents (CWAs) by the method of gas chromatography coupled with mass detection (GC/MS) were defined. The determination is based on a GC/MS analysis of a mixture of a CWA with an internal standard, conversion of the TIC chromatogram to a chromatogram extracted at a particular m/z ratio, and calculation of the CWA concentration from the internal standard concentration, response factor, and chromatographic peak areas. Available internal standards were identified, and they were verified for seven organophosphorus nerve-paralysing agents. Corresponding response factors were determined as a ratio of gradients of the linear functions of the peak area and compound concentration. Linearity, repeatability, and accuracy of the measurements were evaluated. The determination can be performed on all GC/MS systems of the Fire Rescue Service of the Czech Republic (FRS), where no CWA standards are available.

scholarly journals Effect of temperature on alkane extraction from faeces and herbage

1999 ◽  
Vol 132 (3) ◽  
pp. 305-311 ◽  
Author(s):  
M. OLIVÁN ◽  
K. OSORO
Keyword(s):  
Solvent Extraction ◽  
Internal Standard ◽  
Carbon Chain ◽  
Effect Of Temperature ◽  
Internal Standards ◽  
Sample Matrix ◽  
Different Temperatures ◽  
Peak Areas ◽  
Cattle Faeces ◽  
Long Chain

The solvent extraction of alkanes from faeces and herbage samples at two different temperatures (cold: 15–25°C and hot: 65°C) was studied in four samples of different matrix types (cattle faeces, sheep faeces, hill grass and heather), in two experiments performed at Villaviciosa, Asturias, Spain in 1994. Two internal standards (IS) of different chain length (C22 and C34) were used to estimate alkane concentrations. Significant differences were detected in alkane extraction derived from temperature of extraction, IS and sample matrix. At the cold temperature, long-chain alkane extraction was not complete, resulting in errors in the estimation of alkane concentration when a long-chain alkane (C34) was used as the only internal standard. However, under hot extraction, long- chain alkanes were completely extracted by the heptane, although estimates made with C22 or C34 as IS were not identical. These results suggest that it would be appropriate to use two internal standards with short and long carbon chain, such as C22 and C34, in routine analyses to establish the completeness of alkane extraction, even under hot conditions, by calculating the relative ratio of both IS in extracts compared to the original C22[ratio ]C34 ratio added to the samples. Any increase or decrease in expected peak areas could be adjusted for all the alkanes in the extracts, and the accuracy of alkane concentration measurements (and therefore the reliability of estimates of intake and especially of diet selection) would be improved.

Gas Chromatographic Detection of the Mycotoxin Zearalenone in Blood Serum

1980 ◽  
Vol 63 (3) ◽  
pp. 604-611
Author(s):  
H Locksley Trenholm ◽  
Robert Warner ◽  
Edward R Farnworth
Keyword(s):  
Blood Serum ◽  
Standard Procedure ◽  
Internal Standard ◽  
Detector Response ◽  
Acid Extraction ◽  
Standard Curve ◽  
Percent Recovery ◽  
Peak Areas ◽  
Chromatographic Detection ◽  
Gas Chromatographic Method

Abstract A sensitive gas chromatographic method for the quantitative analysis of zearalenone in blood serum is described. Zearalenone is eluted from blood serum by column chromatography followed by base-acid extraction with dichloromethane as the organic phase. After epicoprostanol (internal standard) is added, the sample is evaporated to dryness, derivatized, and injected onto the gas chromatographic column. A number of silylating agents and reaction conditions were investigated. Derivatizing zearalenone with N-methyl-N-trimethylsilyltrifluoroacetamide in the presence of acetone at room temperature for at least 2 hr gave best results. Sensitivity limit is <0.5 ng injected, equivalent to 100 ng zearalenone/mL blood serum. A linear standard curve is observed when 0.5–30 ng zearalenone derivative is injected onto the Perkin-Elmer gas chromatograph. For quantitation, a standard curve is prepared by plotting amounts of zearalenone (ng) injected vs. ratios for peak areas of zearalenone and epicoprostanol derivatives. The internal standard procedure improves the precision by minimizing variations in sample injections and detector response. Percent recovery from blood serum is 68–75 in the range of 1.6–8.0 Mg zearalenone/mL blood

Bioanalytical method development and validation of simultaneous analysis of telmisartan and hydrochlorthiazide in human plasma using LC-MS/MS

2016 ◽  
Vol 5 (03) ◽  
pp. 4862 ◽  
Author(s):  
Mathew George* ◽  
Lincy Joseph ◽  
Arpit Kumar Jain ◽  
Anju V.
Keyword(s):  
Human Plasma ◽  
Retention Time ◽  
High Performance ◽  
Method Development ◽  
Matrix Effects ◽  
Solid Phase ◽  
Internal Standard ◽  
Assay Method ◽  
Buffer System ◽  
Internal Standards

A simple, sensitive, rapid and economic high performance thin layer chromatographic method and a mass spectroscopic assay method has been developed for the quantification of telmisartan and hydrochlorthiazide combination in human plasma. The internal standards and analytes were extracted from human plasma by solid-phase extraction with HLB Oasis1cc (30mg) catridges. The scanning and optimization for the samples are done using methanol: water (50:50). The samples were chromatographed using reverse phase chromatography with C-18 column of different manufacturers like Ascentis C18 (150×4. 6, 5µ) using the buffer system Acetonitrile: Buffer (80:20%v/v) which consist of 2±0. 1Mm ammonium format at a flow rate of 0. 7ml/min at a column oven temperature 35±10c. The internal standard used was hydrochlorthiazide13c1, d2 and telmisartand3. The extraction techniques include conditioning, loading, washing and elution, drying followed by reconstitution of the dried samples. The volume injected was 10µl with the retention time of 3-4 min for telmisartan, 1-2 min for hydrochlorthiazide and for the internal standards the retention time was 3-4 min for telmisartand3 and 1-2 min for hydrochlorthiazide c13d2. The rinsing solution was Acetonitrile: HPLC grade water in the ratio (50:50). The above developed method was validated using various parameters like selectivity and sensitivity, accuracy and precision, matrix effects, % recovery and various stability studies. The method was proved to be sensitive, accurate, precise and reproducible. The preparation showed high recovery for the quantitative determination of telmisartan and hydrochlorthiazide in human plasma.

Flame ionization detector response to coeluting hydrocarbons and carbon disulphide and its application to the determination of the sum of C6-C11 alkanes and cycloalkanes in air

1983 ◽  
Vol 48 (3) ◽  
pp. 722-734
Author(s):  
Martin Koval
Keyword(s):  
Carbon Disulphide ◽  
Internal Standard ◽  
Calibration Procedure ◽  
Detector Response ◽  
Column Temperature ◽  
Flame Ionization ◽  
Other Substances ◽  
Flame Ionisation Detector ◽  
Ionisation Detector

The flame ionisation detector response to C6-C11 aliphatic hydrocarbon solutions in carbon disulphide in the concentration range between 1.3-9.5 mg ml-1 retained lineary despite the excess of solvent entering the detector simultaneously with the analyte. Pure carbon disulphide exhibited a small positive detector response which did not interfere in calibration procedure and which, under certain GC conditions, inverted to negative values. This response was not proportional to the injected volume and was strongly influenced by the column temperature and/or bleed. On the basis of these findings, a method compatible with the widely used charcoal tube carbon disulphide desorption procedure was developed and evaluated. It consists of static desorption of the sum of aliphatic alkanes and cycloalkanes from the activated charcoal after which an internal standard is added to the supernatant eluate. The resulting carbon disulphide solution is analysed on a highly polar stationary phase 1,2,3-tris(2-cyanoethoxy)propane where the solvent and the analyte coelute in a single peak, the height of which is practically proportional to the sum of alkanes and cycloalkanes present. This also makes determinations of other substances present in the sample more simple. The field test of the proposed method yielded values comparable in precision and accuracy with a control infrared spectrophotometric method.

Program for Computation of Response Data from Five Different Gas Chromatograph Detectors Operating Simultaneously

1978 ◽  
Vol 61 (1) ◽  
pp. 18-25
Author(s):  
Harry A Mcleod ◽  
David Lewis
Keyword(s):  
Gas Chromatograph ◽  
Internal Standards ◽  
Baseline Drift ◽  
Response Data ◽  
Flame Ionization ◽  
Relative Retention ◽  
Data Points ◽  
Peak Areas ◽  
Smoothing Procedure ◽  
Spurious Signals

Abstract A novel digital computer program for evaluating data from a gas chromatograph with 5 different detectors—electron capture, flame ionization, nitrogen, phosphorus, and sulfur—operating simultaneously is described. Detector signals are recorded on a 9-channel incremental tape, and then processed off-line by using a NOVA 8K computer system. Spurious signals from each detector are minimized by applying a simplified least squares smoothing procedure to the raw data points. Peak detection logic operating parameters may be varied for each detector. Relative retention times are calculated for 2 internal standards as references and peak areas are corrected for baseline drift. Operator interaction is maximal and several different data reporting formats are used to tabulate the raw and processed data.

scholarly journals Estimation of the Effects of Food on the Pharmacokinetic Results in Bioequivalence Studies

2019 ◽  
Vol 70 (8) ◽  
pp. 2805-2810
Author(s):  
Ion Mircioiu ◽  
Valentina Anuta ◽  
Constantin Mircioiu ◽  
Victor Voicu ◽  
Roxana Sandulovici
Keyword(s):  
Statistical Analysis ◽  
Food Intake ◽  
Methylene Chloride ◽  
Internal Standard ◽  
Extraction Yield ◽  
Two Phase ◽  
Peak Areas ◽  
Effect Of Food ◽  
Lower Effect ◽  
Almost All

Paper presents the effect of food on the pharmacokinetics of omeprazole and on the extraction yield of its internal standard, lansoprazole. The experimental data were obtained over three bioequivalence studies performed by the authors. Statistical analysis of plasma level curves of omeprazole indicated that food induces a delay of the time of maximum concentrations, but had a lower effect on maximum concentration and area under curves. Peak areas of lansoprazole were not constant, presenting a similar pattern in all seven periods of the clinical experiment, both in feeding and fasting conditions: an increase after the standard meal at four hours from the administration of drug followed by relatively constant, but higher areas afterwards. Statistical analysis of data (1500 points) in the 3 - 6 h interval, i.e. from immediately before until two hours after food intake revealed a two phase effect: an initial decrease of areas followed by an increase to a higher level than in the preprandial conditions, leading to the appearance of a minimum in curves one hour after food intake. In almost all cases a good parabolic fitting of data was obtained, which is in agreement with authors previous results on extraction of ketoconazole from pasma in methylene chloride in the presence of bile salts. The increase of peak areas of lansoprazole from two hours after meal by 24 h lead to an artificial decrease of calculated omeprazole concentrations. This effect could explain the unexpected lack of food effect on the area under curve of omeprazole, observed in the comparison between areas in fasting and fed conditions.

Gas Chromatographic Profile Analysis of Basic Nitrogen-Containing Aromatic Compounds (Azaarenes) in High Protein Foods

1986 ◽  
Vol 69 (3) ◽  
pp. 537-541
Author(s):  
Gernot Grimmer ◽  
Klaus-Werner Naujack
Keyword(s):  
Aromatic Compounds ◽  
Limit Of Detection ◽  
Profile Analysis ◽  
Collaborative Study ◽  
Internal Standard ◽  
Exchange Chromatography ◽  
Basic Nitrogen ◽  
Chromatographic Profile ◽  
Polycyclic Aromatic ◽  
Peak Areas

Abstract A method is described for the determination of basic nitrogen-containing polycyclic aromatic compounds (N-PACs, azaarenes) in meat. The enrichment procedure includes liquid-liquid partition (dimethylformamide-water-cyclohexane), extraction of N-PACs by sulfuric acid, reextraction after neutralization by cyclohexane or, alternatively, by nonadsorbing ion exchange chromatography. Further purification is performed by column chromatography on Sephadex LH20 using a dosed system to avoid sample contamination by laboratory pollutants. N-PACs are analyzed by capillary gas chromatography and measured by comparing to the corresponding peak areas of an internal standard (e.g., lO-azabenzo(a)pyrene). The limit of detection of this method ranges from 0.1 to 0.4 ng for benzacridines, dibenzacridines, and their methyl derivatives. The results of a collaborative study, stimulated by IUPAC, are reported: Coefficients of variation for the various azaarenes were 4.0-13.6% for the check analysis and 10.4-25.4% for a spiked ham sample. Consequently, IUPAC suggests this procedure as a recommended method.

scholarly journals Production and Application of Stable Isotope-Labeled Internal Standards for RNA Modification Analysis

Genes ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 26 ◽  
Author(s):  
Kayla Borland ◽  
Jan Diesend ◽  
Taku Ito-Kureha ◽  
Vigo Heissmeyer ◽  
Christian Hammann ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Isotope Labeling ◽  
Rna Stability ◽  
Internal Standard ◽  
Modified Nucleosides ◽  
Rna Modification ◽  
Mouse Tissue ◽  
Rna Modifications ◽  
Internal Standards ◽  
Translation Fidelity

Post-transcriptional RNA modifications have been found to be present in a wide variety of organisms and in different types of RNA. Nucleoside modifications are interesting due to their already known roles in translation fidelity, enzyme recognition, disease progression, and RNA stability. In addition, the abundance of modified nucleosides fluctuates based on growth phase, external stress, or possibly other factors not yet explored. With modifications ever changing, a method to determine absolute quantities for multiple nucleoside modifications is required. Here, we report metabolic isotope labeling to produce isotopically labeled internal standards in bacteria and yeast. These can be used for the quantification of 26 different modified nucleosides. We explain in detail how these internal standards are produced and show their mass spectrometric characterization. We apply our internal standards and quantify the modification content of transfer RNA (tRNA) from bacteria and various eukaryotes. We can show that the origin of the internal standard has no impact on the quantification result. Furthermore, we use our internal standard for the quantification of modified nucleosides in mouse tissue messenger RNA (mRNA), where we find different modification profiles in liver and brain tissue.

A Survey of Mathematical Correction Procedures in X-Ray Spectrometry

1975 ◽  
Vol 19 ◽  
pp. 1-17 ◽  
Author(s):  
Ronald Jenkins
Keyword(s):  
First Principles ◽  
Quantitative Data ◽  
Internal Standard ◽  
Characteristic Line ◽  
X Rays ◽  
Matrix Correction ◽  
Internal Standards ◽  
X Ray ◽  
Correction Equations ◽  
Secondary Fluorescence

X-ray spectrometry is an old technique dating back some sixty-odd years and although most of the early interest revolved around the qualitative aspects of the method it wasn't long before attempts were made to obtain quantitative data. One of the first recorded attempts was that by Coster and von Hevesey who in 1923 accurately determined the amount of hafnium in zirconium using tantalum as an internal standard. Glocker and Schreiber were the first to attempt calculation of X-ray characteristic line intensity from first principles although no attempt was made at that time to correct for secondary fluorescence. In von Hevesey's book, “Chemical Analysis by X-Rays,” published in 1932 , a whole chapter is devoted to what is called “Disturbing effects and their avoidance.” Among the effects discussed were primary and secondary absorbtion and third element effects. Matrix correction equations were developed although most of the quantitative work at that time was done using internal standards.

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