Adsorption–desorption effects in ion trap mass spectrometry using in situ ionization

Quadrupole mass spectrometers were compared for the GC–MS analysis of six molecules frequently encountered in analytical toxicology: diazepam, alprazolam, triazolam, LSD (lysergic acid diethylamide), trimethylsilylated LSD and trimethylsilylated buprenorphine. Experiments performed with ion trap detectors using in situ ionization led to important chromatographic peak tailing for the most polar compounds; it was assumed to result from adsorption–desorption of neutral molecules in the mass spectrometer. This study showed that the degree of peak tailing is correlated with analyte polarity, with materials coating ion trap surfaces and with analysis temperature and that this anomaly can be greatly reduced using passivated surfaces and a high temperature of analysis.