Evaluation of dispersive liquid-liquid microextraction for the simultaneous determination of chlorophenols and haloanisoles in wines and cork stoppers using gas chromatography-mass spectrometry

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was evaluated for the simultaneous determination of five chlorophenols and seven haloanisoles in wines and cork stoppers. Parameters, such as the nature and volume of the extracting and disperser solvents, extraction time, salt addition, centrifugation time and sample volume or mass, affecting the DLLME were carefully optimized to extract and preconcentrate chlorophenols, in the form of their acetylated derivatives, and haloanisoles. In this extraction method, 1 mL of acetone (disperser solvent) containing 30 mu L of carbon tetrachloride (extraction solvent) was rapidly injected by a syringe into 5 mL of sample solution containing 200 mu L of acetic anhydride (derivatizing reagent) and 0.5 mL of phosphate buffer solution, thereby forming a cloudy solution. After extraction, phase separation was performed by centrifugation, and a volume of 4 mu L of the sedimented phase was analyzed by GC-MS. The wine samples were directly used for the DLLME extraction (red wines required a 1:1 dilution with water). For cork samples, the target analytes were first extracted with pentane, the solvent was evaporated and the residue reconstituted with acetone before DLLME. The use of an internal standard (2,4-dibromoanisole) notably improved the repeatability of the procedure. Under the optimized conditions, detection limits ranged from 0.004 to 0.108 ng mL(-1) in wine samples (24-220 pg g(-1) in corks), depending on the compound and the sample analyzed. The enrichment factors for haloanisoles were in the 380-700-fold range. (C) 2010 Elsevier B.V. All rights reserved.