Evaluation of hydrolysis and alcoholysis reactions in gas chromatography/mass spectrometry inlets

Abstract

During gas chromatography/mass spectrometry (GC–MS) analyses using water and methanol as injection solvents, hydrolysis reactions after injecting water control and alcoholysis reactions after injecting methanol control or ethanol into a GC–MS system were observed and studied. Two dominant hydrolysis/alcoholysis product series were detected, and were identified as being HO(CH3)2SiOR and HO(CH3)2SiO(CH3)2SiOR, where R=H, methyl, or ethyl, when pure water, methanol and ethanol were injected. The chemical structures of the reaction products were cross-checked by injecting H2O/D2O and H2O/MeOH/EtOH, and comparable EI mass fragmentation patterns were found. The water and alcohols injected reacted with silicones in septum particles which accumulated in the injection port liner after numerous injections, and both hydrolysis and alcoholysis reaction products gradually increased in concentration as the number of injections increased. Potential interferences from hydrolysis or alcoholysis reactions should be paid attention to, evaluated or eliminated when water or methanol was used as the GC or GC–MS solvent, and especially when underivatized methanol or ethanol was subject to GC and GC–MS analysis.