Gas chromatographic profiling and screening for phenols as isobutoxycarbonyl derivatives in aqueous samples

An efficient method is described for the simultaneous determination of phenol and 49 substituted phenols present in aqueous samples. The method is based on the extractive two-phase isobutoxycarbonyl (isoBOC) derivatization with subsequent solid-phase extraction (SPE) for the direct analysis by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). Phenolic hydroxyl groups in acidic aqueous solutions were allowed to react with isobutyl chloroformate present in the dichloromethane phase containing triethylamine. The resulting isoBOC derivatives were then recovered by SPE using Chromosorb P in normal-phase partition mode, followed by direct GC and GC–MS analysis. Using this combined procedure, linear detector responses were obtained in the concentration range of 0.5–8 μg ml−1, with correlation coefficients varying from 0.925 to 0.999 for most of the phenols studied except for 2,4-dinitorphenol (0.789). The temperature-programmed retention index (I) sets as measured on DB-5 and DB-17 dual-capillary columns of different polarity were characteristic of each isoBOC phenol derivative and thus, useful in the screening for isomeric phenols by I matching only. The mass spectral patterns, exhibiting characteristic [M−100]+, [M−200]+ and [M−300]+ ions for the mono-, di- and trihydroxybezenes, respectively with common ions at m/z 57, facilitated their rapid structural confirmation. The present method allowed rapid screening for phenols when applied to water samples spiked with phenols.