VALIDATION, UNCERTAINTY, AND QUALITY CONTROL OF QUALITATIVE ANALYSIS OF TEAR GAS WEAPONS BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY

摘要

The reliability of the identification/examination of compounds by gas chromatography hyphenated with mass spectrometry (GC-MS) can be significantly affected by the co-elution of interfering compounds and the use of noncharacteristic data of the mass spectrum of the analyte. This work presents a procedure for the examination of the presence of compounds in sample solutions, a strategy for procedure validation including the evaluation of examination uncertainty, and a quality control scheme for routine examinations. The examination uncertainty is evaluated using metrics of Bayes' theorem. The evidence of the presence of a compound is supported by the statistical agreement between retention time and two ratios of abundance of three characteristic ions of their mass spectra, observed in relevant sample and in standard solutions peaks collected under repeatability conditions. This strategy was successfully applied to the examination of active substances in tear gas weapons by GC-MS to check compliance with Portuguese legislation. Given the observation of all three evidences, the performed examinations present a posterior probability of the presence of the active substance, larger than the target minimum of 99.7%.