Sensitivity enhancement in liquid chromatography/atmospheric pressure ionization mass spectrometry using derivatization and mobile phase additives

High performance liquid chromatography with atmospheric pressure ionization (API) mass spectrometry has been essential to a large number of quantitative analytical applications for a variety of compounds. Poor detection sensitivity however is a problem observed for a number of analytes because detection sensitivity can be affected by many factors. The two most critical factors are the chemical and physical properties of the analyte and the composition of the mobile phase. In order to address these critical factors which may lead to poor sensitivity, either the structure of the analyte must be modified or the mobile phase composition optimized.; This study investigated the enhancement of sensitivity for small molecules in biomedical analyses using atmospheric-pressure chemical ionization (APCI) following derivatization, as well as improvement of sensitivity in the electrospray ionization (ESI) mode using mobile-phase additives (alkylamines and ion-pair reagents). Propylene glycol (PG) was selected as the model compound for the former method. After introduction of a benzoyl moiety to increase the proton affinity of PG, a relatively high sensitivity of detection was achieved. Paclitaxel and docetaxel served as model compounds for the alkylamine additives method. Sensitivity and precision of detection were improved approximately five-fold through the formation of one predominant alkylamine adduct while suppressing the formation of other multiple molecule adduct ions. The volatile ion-pair reagents perfluorinated carboxylic acids were used to increase the retention of polar ionizable compounds. The sensitivity of detection was increased after matrix suppression was decreased by separating the analyte from the polar endogenous co-eluting substances. The model analyses evaluated were 1-methylnicotinamide (MNA), N-methyl 2-pyridone 5-carboxamide (2PY), phenylephrine.; Each method was validated in order to demonstrate its utility, and the mechanisms of each approach were investigated with a view to expanding their potential use in future applications.