Comparison of different GC-MS configurations for the determination of prevalent drugs and related metabolites

Abstract

Cocaine, cannabis, heroin, and other opioids are among the prevalent drugs in Europe. The use of these drugs is demonstrated by the determination of either parent drugs or related metabolites in a variety of biological samples. Various analytical methodologies can be applied for this purpose, all of which might show relevant differences in analytical performance. In this work we used different GC-MS configurations for the quantitation of cocaine, cocaethylene, benzoylecgonine, morphine, and Delta9-tetrahydrocannabinol with the aim of comparing the analytical performance of different GC-MS instruments, different injectors, ion sources, ionization modes, mass analyzers, operating modes, and acquisition modes, in order to find the optimal configuration in terms of sensitivity and precision. Other important factors, such as the derivatization process for GC analysis or the injection mode, were also investigated for the same purpose. A comparative study of different methods used for the calculation of the limits of detection was also performed, in order to compare them in terms of the obtained values and their veracity. Differences found in the results obtained with different configurations showed different limits of detection and different precision. These results allowed us to indicate advantages and limitations, which depended on the configuration of the GC-MS used. Finally, differences up to seven orders of magnitude were found in the LOD values obtained with different methods, some of them being too small to show any measurable peak.