Development and optimization of a method for the analysis of phenols and chlorophenols from aqueous samples by gas chromatography–mass spectrometry, after solid-phase extraction and trimethylsilylation

Abstract

A 3-step analytical procedure was developed and optimized for the simultaneous determination of 6 phenols (phenol, o-, m-, p-cresol, catechol and resorcinol) and 19 chlorophenols (all mono-, di-, tri-, and tetrachlorophenol isomers and pentachlorophenol) from environmental water samples. The analytical scheme consists of (1) solid-phase extraction (SPE) carried out on hypercrosslinked styrene-divinylbenzene (Isolute ENV+) cartridge; (2) derivatization with trimethylsilyl-N,N-dimethylcarbamate (TMSDMC); (3) analysis of the derivatives with capillary gas chromatography–mass spectrometry, in the selective ion monitoring mode. Ethyl acetate, ethyl acetate/acetic acid (5v/v%) mixture, dichloromethane and acetonitrile were compared as to their ability to elute the phenols and chlorophenols from the ENV+sorbent in the smallest solvent volume possible. The optimized extraction step uses a minimal amount of organic solvent (4mL ethyl acetate). Derivatization of the phenols and chlorophenols with TMSDMC was studied with respect to conversion, reagent excess, medium, temperature and the stability of the trimethylsilyl derivatives. If the reagent is applied in sufficient excess, the reaction takes place instantaneously at room temperature, and the derivatives remain stable for 24h, making the procedure simple, fast and convenient. The overall method gave detection limits of 0.05–100ng/L for all compounds except resorcinol which could not be retained on the SPE cartridge. The complete optimized analytical scheme was applied to ground water and river water samples collected in Hungary.