Exploiting the transient matrix effect for improved GC-MS analysis of drugs in human plasma

Abstract Purpose This study aimed to develop and optimize a novel analytical approach utilizing the transient matrix effect (TME) to simultaneously enhance the determination of varying drug classes (tramadol, doxepin, diazepam) and anabolic-androgenic steroids (testosterone, nandrolone) in human blood plasma. Methods A GC-MS method combined with QuEChERS extraction was applied. To controllably induce TME, varying classes of analyte protectants (PEG-400, C14-NH2, IPM-98, and Triton X-100) were evaluated both individually and as multicomponent mixtures. The optimized procedure was subsequently evaluated for inter-source matrix variability across authentic human plasma samples. Results Combining protectants with different affinities significantly modified their protective action. While a four-component mixture provided the highest enhancement in pure solvent, it generated competitive adsorption in plasma extracts. A binary combination of PEG-400 and C14-NH2 was identified as the most effective mixture for plasma - yielding increases of 314% and 221% for nandrolone and diazepam, respectively, compared to standard samples. The induced matrix effect was strictly transient - protectants were completely flushed from the column between analyses. Conclusion Intentional modulation of TME using a binary mixture of high-boiling protectants (PEG-400 and C14-NH2) is proposed to initiate the formation of a transient condensation film at the beginning of the chromatographic column. Analytes condense onto this film, leading to the strong focusing of their concentration zone. This phenomenon significantly enhances the detection sensitivity of structurally diverse drugs and steroids in plasma. By normalizing the sorption environment, the method neutralizes endogenous matrix variability, representing a robust and reproducible tool for forensic toxicology and routine casework.