Electrospray and atmospheric pressure chemical ionisation of aromatic compounds in dichloromethane solvent

Atmospheric pressure chemical ionisation (APCI) of chlorinated benzene deri vatives was studied to develop a mass spectrometry technique for qualitativ e and quantitative determination of their aerobic and anaerobic microbial d egradation products. Using conventional reversed phase-high performance liq uid chromatography (RP-HPLC) eluents, such as methanol, water or acetonitri le, non-polar aromatic compounds showed very low response factors both in e lectrospray (ES) and in APCI either in positive or negative ion mode. Use o f dichloromethane solvent in positive ion APCI showed high sensitivity both for polar and for apolar aromatics, Oxygen containing compounds gave [M H](+) ions while ionisation of aromatic hydrocarbons and their chlorinated derivatives was found to be a complex process, generating mainly [M + 13]() ions. Detailed investigations showed that ionisation proceeds by the addi tion of CH2Cl+ followed by HCl elimination.