Ionization of dichlorophenols for their analysis by capillary electrophoresis-mass spectrometry

In order to develop an advanced analytical method using capillary electroph oresis (CE) for non-volatile environmental pollutants such as endocrine dis ruptors, combination with mass spectrometry (MS) is necessary for their ide ntification. We chose dichlorophenols (DCPs) as test samples because one of their isomers, 2,4-DCP, is suspected to have endocrine disrupting effects. A preliminary study on their separation by CE-MS was performed using a lab oratory-made electrospray ionization (ESI) interface. For the effective ion ization of 2,4-DCP at the ESI interface, applied voltage, assisted nitrogen -gas flow-rate, salts and their concentration, and organic solvents in the sample matrix were optimized according to the signal intensity. The intensi ty of other DCPs under the same conditions, however, was quite different. W e tried to modify the atmospheric chemical pressure ionization (APCI) inter face in order to reduce the flow-rate. The intensity of directly injected D CPs was not so different from one another using the modified prototype APCI interface. (C) 2001 Elsevier Science B.V. All rights reserved.