scholarly journals Effects of Ramp Rate and Starting Temperature on Gas Chromatography-Mass Spectrometric Analyses of Petroleum Hydrocarbons

2020 ◽  
Vol 45 (6) ◽  
Author(s):  
S. U. Oghoje ◽  
J. E. Ukpebor ◽  
P. O. Agbaire ◽  
C. Ejeomo ◽  
P. O. Oviasogie
Keyword(s):  
Petroleum Hydrocarbons ◽  
Mass Spectrometric ◽  
Response Factor ◽  
Ramp Rate ◽  
Mass Unit ◽  
Modified Method ◽  
Ionic Mass ◽  
Peak Areas ◽  
Standard Calibration ◽  
Diesel Range Organics

The quest for better GC-MS/FID starting temperature and ramping conditions for the quantification of hydrocarbons in our environment necessitated this study. A surrogate n-alkane standard was screened using nine GC-MS conditions involving the alteration of ramp rates and/or initial temperatures. There was observed increase in the TIC chromatogram or ionic mass unit as the ramp rate or initial temperatures were increased. The peak areas of the analytes were significantly affected. The R2 and response factor values of the eight standard calibration curves (each for a modified method) varied from 0.9224 – 0.9971 and 0.0034 – 0.0045 respectively. Consequently, the quantification of the diesel concentration in diesel spiked water and soil by using the eight methods was different from each other and from the standard method. Average differences of 11.5 and 15 % from the theoretical values were observed for the water and soil analyses respectively. Increasing ramp rates or initial temperatures led to shorter throughput but less data accuracy. The use of 60 oC as starting temperature and ramp at 5 oC/minute was better for quantification of the diesel range organics.

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.

Gas-Chromatographic/Mass-Spectrometric Identification and Quantitation of Tetronic and Deoxytetronic Acids in Urine from Normal Adults and Neonates

1975 ◽  
Vol 21 (13) ◽  
pp. 1892-1898 ◽  
Author(s):  
John A Thompson ◽  
Sanford P Markey ◽  
Paul V Fennessey
Keyword(s):  
Mass Spectrometric ◽  
Response Factors ◽  
Computer Determination ◽  
Mass Spectrometric Identification ◽  
Computer Analyses ◽  
Peak Areas ◽  
Trimethylsilyl Derivatives ◽  
Trace Constituents ◽  
Chromatographic Mass

Abstract Gas chromatographic/mass spectrometric/computer analyses of trimethylsilyl derivatives of urine extracts, prepared by an anion-exchange procedure, reveal the presence of several tetronic and deoxytetronic acids. Identifications were confirmed by comparing gas-chromatographic methylene unit values and mass spectrometric characteristics with those of chemically synthesized samples. In addition, several 1,4-lactones corresponding to the acids were detected in small amounts. The acids were measured in groups of adults and neonates by gas chromatographic/computer determination of peak areas and the use of calculated response factors. In urines from adults, 4-deoxythreonic, threonic, and erythronic acids were present in relatively large amounts. 4-Deoxyerythronic and 2-deoxytetronic acids were present in small to moderate amounts; 3-deoxytetronic and 2-methylglyceric acids were only trace constituents. These latter two acids, in addition to 4-deoxyerythronic, were also trace constituents of several urines from neonates but could not be detected in others. Expressed in terms of creatinine excretion, both groups excreted similar amounts of 4-deoxythreonic acid and neonates excreted significantly more 2-deoxytetronic, erythronic, and threonic acids.

Proposal for Objective Evaluation of the Performance of Various Functional APC-resistance Tests in Genotyped Patients

1997 ◽  
Vol 78 (05) ◽  
pp. 1360-1365 ◽  
Author(s):  
G Freyburger ◽  
S Javorschi ◽  
S Labrouche ◽  
P Bernard
Keyword(s):  
Protein S ◽  
Objective Evaluation ◽  
Original Method ◽  
Screening Methods ◽  
Factor Xii ◽  
Factor V ◽  
Likelihood Ratios ◽  
Modified Method ◽  
Apc Resistance ◽  
Two Parameters

SummaryThe aim of the present study was to evaluate the relative performance of five screening methods for APC resistance caused by the factor V:Q506 mutation: the original method Coatest® APC™ Resistance Chromogenix, a modified method using the same reagents but a predilution 1+4 of the plasma in a factor V deficient plasma from Stago (Stago deficient V) or from Chromogenix (V-DEF Plasma), the Coatest® APC™ Resistance V (Chromogenix), and Accelerimat™ from bioMérieux. Normalization was done against a pool of normal plasmas for the methods from Chromogenix. The study included 350 subjects, 219 were genotyped (174 FV:R506R, 42 FV:Q506R, 3 FV:Q506Q) and most of them were assessed by more than one method. Uncertainty in predicting the FV genotype was evaluated by statistical analysis, which provided a way to quantitate the performance of the different diagnostic approaches. Performance of each test was evaluated by its sensitivity, specificity, R.O.C. curves, positive and negative likelihood ratios (LR), and the overall performance was determined by two parameters derived from the LR curves : the maximum LR value obtained at the crossover of the two curves, and the distance between the two curves for LR = 10. Coatest® APC™ Resistance V and Accelerimat™ were proven to be the methods most able to discriminate for factor V:Q506, while normalization was not shown to improve the screening performance. The original method from Chromogenix was confirmed to undergo many influences (factor XII, PAI-1, thrombin- antithrombin complexes, antithrombin III, hematocrit). Although a very good improvement was provided by the newest methods, they were shown to be influenced by protein S and/or factor V levels in the sample plasma.

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