Rapid determination of alkylphenols in aqueous samples by in situ acetylation and microwave-assisted headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry

A rapid and solvent-free procedure for the determination of 4-tert-octylphenol and 4-nonylphenol isomers in aqueous samples is described. The method involves in-situ acetylation and microwave-assisted headspace solid-phase microextraction prior to their determination using gas chromatographyion trap mass spectrometry operated in the selected ion storage mode. The dual experimental protocols to evaluate the effects of various derivatization and extraction parameters were investigated and the conditions optimized. Under optimized conditions, 300 mu L of acetic anhydride mixed with 1 g of potassium hydrogencarbonate and 2 g of sodium chloride in a 20 mL aqueous sample were efficiently extracted by a 65 mu m polydimethylsiloxane-divinylbenzene fiber that was located in the headspace when the system was microwave irradiated at 80 W for 5 min. The limits of quantitation were 5 and 50 ng/L for 4-tert-octylphenol and 4-nonylphenol isomers, respectively. The precision for these analytes, as indicated by relative standard deviations, were less than 8% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was between 74 to 88%. A standard addition method was used to quantitate 4-tert-octylphenol and 4-nonylphenol isomers, and the concentrations ranged from 120 to 930 ng/L in various environmental water samples.