On-line nonaqueous capillary electrophoresis and electrospray mass spectrometry of tricyclic antidepressants and metabolic profiling of amitriptylineby Cunninghamella elegans

An on-line nonaqueous capillary electrophoresis-electrospray mass spectrome try (ESI-MS) technique was developed using a commercial ion spray interface . The nonaqueous capillary electrophoresis ESI-MS system was used to profil e tricyclic antidepressants of similar structures and mass-to-charge ratios . We found that pure methanol can be used as a sheath liquid to obtain stab le ion spray from nonaqueous capillary electrophoresis. The flow rate of th e coaxial nebulizing gas affected baseline signals, separation efficiency, and migration times. Other nonaqueous capillary electrophoresis operating c onditions and electrospray parameters were optimized for enhanced baseline separation and high sensitivity detection. The effect of sample stacking on separation and detection was evaluated. The calculated detection limits we re approximately 3 pg injected onto the capillary. ESI mass spectra of tric yclic antidepressants from a single quadrupole MS were obtained and elucida ted. The information was used to propose fragmentation pathways of the tric yclic antidepressants. The method was also used to analyze the metabolites of amitriptyline produced by the fungus Cunninghamella elegans. Sixteen met abolites were detected and most of them were tentatively identified as deme thylated and/or hydroxylated, and/or N-oxidized products.