Abstract
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.
Highlights
According to the Czech Republic law, competences of the FRS include chemical countermeasures in case of chemical warfare agents (CWAs) spills or abuse. e countermeasures include chemical reconnaissance, detection, identification, and determination of CWAs. is activity is ensured by specialized FRS chemical laboratories
Study of Chromatographic Peak Area Dependence on Concentration. e primary aim of this work was to find a suitable internal standard, applicable on all gas chromatography with mass detection (GC/MS) systems across the FRS chemical laboratories in a universal procedure. e procedure would be used especially for a quick and simple determination of the active ingredient of own CWA preparates which are used for the calibration of the existing determination procedures. is means a binary mixture of the CWA and the internal standard is analysed, and neither similarity of chemical properties of the analyte and the internal standard nor close physical characteristics are an issue here as these matter mostly in case of sample preparation before the analysis itself
Where A is the chromatographic peak area, k is the gradient, c is concentration, and q is the intercept on the peak area axis. is equation can be combined with the response factor equation (1): (k CWA · c CWA + q CWA) · c ISTD
Summary
According to the Czech Republic law, competences of the FRS include chemical countermeasures in case of CWA spills or abuse. e countermeasures include chemical reconnaissance, detection, identification, and determination of CWAs. is activity is ensured by specialized FRS chemical laboratories. E countermeasures include chemical reconnaissance, detection, identification, and determination of CWAs. is activity is ensured by specialized FRS chemical laboratories. Unlike the absolute calibration and standard addition methods, pure analyte standard is not required. E absolute calibration and standard addition methods include analysis of two separate samples which often introduces significant errors into the results [1, 2]. When using the internal standard method, the response factor value needs to be known in order to arrive at reliable analytical results. The concentration range where the analyte and internal standard chromatographic peak area is a linear function must be known, as only the constant value of the response factor is ensured [1, 3]
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