COMPARISON OF THE SENSITIVITIES OF 16 PHENOLS IN WATERS USING AN AUTOMATED PRECONCENTRATION SYSTEM AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRYIN DIFFERENT IONIZATION MODES

The analytical performances of the electron impact and chemical (posit ive and negative) ionization modes in the mass spectrometric identific ation and quantitation of phenols were studied simultaneously, Twenty phenols containing different substituents (viz. chloro, nitro, amino, alkyl and sulphonic groups) were initially tested, amino and sulfonic phenols being discarded after preliminary experiments, Samples contain ing phenols at the nanograms per millilitre level were preconcentrated by using a simple continuous solid-phase extraction system. Full-scan monitoring at a single m/z value for each analyte allowed the detecti on of the phenols at concentrations over the range 0.2 - 1.0 ng/mL in the electron impact mode and the ranges 1 - 20 and 10 - 35 ng/mL in th e negative (NCI) and positive methane chemical ionization (PCI) modes, respectively. The lower sensitivity obtained with chemical ionization is offset by the valuable structural information it provides from add uct formation (PCI) or different fragmentation patterns (NCI) for isom ers. (C) 1998 John Wiley & Sons, Ltd.