Determination of three chlorophenols in red wine by sweeping-micellar electrokinetic chromatography coupled with dispersive liquid-liquid microextraction and reversed phase liquid-liquid microextraction

A method of dispersive liquid-liquid microextraction (DLLME) and reversed phase liquid-liquid microextraction (RP-LLME) procedures coupled with sweeping-micellar electroldnetic chromatography (sweeping-MEKC ) was established to extract and determine the three chlorophenols (CPs) including pentachlorophenol (PCP) , 2,4 , 6-trichlorophenol (TCP) and 2,4-dichlorophenol (DCP) in red wine. The influences of the parameters of two extraction steps and the electrophoresis conditions were investigated. The optimum extraction conditions were as follows : for DLLME, 3.5 mL red wine sample (pH 3.0, 120 g/L NaC1) , 300 mu L hexane (extraction solvent) , extraction for 3 min, centrifugation for 3 min at 5 000 r/min; for RP-LLME , 25 mu L 0. 16 mol/L NaOH solution, extraction for 2 min, centrifugation for 2 min at 5 000 r/min. The optimum running buffer ( pH 2. 3) was an aqueous solution containing 25 mmol/L NaH2PO4, 100 mmol/L sodium dodecyl sulfate ( SDS) and 30% ( v/v ) acetonitrile. The optimum on-line concentration conditions were as follows : sample matrix, 80 mmoVL NaH2PO4; hydrodynamic injection of 20 s at 20. 67 kPa (3 psi). Under the optimum conditions, the excel- lent linearity was obtained over the range of 0. 5-100 mu g/L (r >= 0.991 0) for PCP and TCP, and 1.5-80 mu g/L ( r >= 0. 985 1) for DCP. The limits of detection ( S/N=3) were in the range of 0. 035-0. 114 mu g/L. The average recoveries were in the range of 75. 2%-104. 7% with the relative standard deviations (RSDs) not more than 6. 17%. The results indicated that the proposed method may find wide applications for the determination of trace CPs in various sample matrixes and other weak acidic organic contaminants.