Capillary zone electrophoresis electrospray mass spectrometry of priority phenols

Eleven priority phenols were separated by capillary zone electrophoresis (CZE) and detected on-line with electrospray ionization mass spectrometry (ESI-MS) in the negative-ion mode. Parameters critical to the coupling of CZE and MS were studied. The best result was obtained with 2-[N-cyclohexylamino]ethanesulfonic acid (CHES) as the running buffer and a solution of water-2-propanol (20:80) containing 0.5% ammonia as the sheath liquid. With the use of field amplification as the preconcentration technique and the mass spectrometer operated in the selected ion monitoring mode, the detection limit of most phenols was found to be in the range of 50 ppb. This method has been successfully applied to the determination of pentachlorophenol in a paper clay sample.