![]() Unlike the absolute calibration and standard addition methods, pure analyte standard is not required. The internal standard method has several significant advantages. This ratio is called the response or calibration factor : where F R is the response factor, A CWA is the CWA chromatographic peak area, A ISTD is internal standard chromatographic peak area, c CWA is the CWA concentration in the solution, and c ISTD is internal standard concentration in the solution. This method is based on the fact that within a certain concentration range, the ratio of chromatographic peak areas and concentrations is constant. Therefore, we had to turn our attention to a procedure based on an internal standard, i.e., addition of a known amount of a substance different from the analyte into the sample, to determine these substances. The fundamental issue is that pure and certified CWA standards are not available in the Czech Republic. Usually, quantitative analysis is performed by the absolute calibration method on these machines, but only for those analytes where a standard of corresponding purity is available. Three types of systems are used in the FRS: GC/MS 7890A/5975 (Agilent), GC/MS Intuvo 9000/5977B of the same manufacturer, and EM 640 (Bruker Daltonik). All laboratories are equipped by gas chromatography with mass detection (GC/MS) as most frequent analytical systems. This activity is ensured by specialized FRS chemical laboratories. The countermeasures include chemical reconnaissance, detection, identification, and determination of CWAs. IntroductionĪccording to the Czech Republic law, competences of the FRS include chemical countermeasures in case of CWA spills or abuse. ![]() 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. ![]() Linearity, repeatability, and accuracy of the measurements were evaluated. Corresponding response factors were determined as a ratio of gradients of the linear functions of the peak area and compound concentration. Available internal standards were identified, and they were verified for seven organophosphorus nerve-paralysing agents. 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. 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. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |