Combination of hollow-fiber-supported liquid membrane and dispersive liquid-liquid microextraction as a fast and sensitive technique for the extraction of pesticides from grape juice followed by high-performance liquid chromatography.

The simultaneous use of a hollow-fiber-supported liquid membrane and dispersive liquid-liquid microextraction for the determination of pesticides directly in grape juice was investigated. The detection and quantification were performed by liquid chromatography with diode array detection. The optimum extraction condition was reached by filling the pores of the membrane wall with dodecanol and using hexane/acetone as extraction/dispersion solvents. Salt addition had a highly negative effect on the extraction efficiency and the optimum extraction time was 60 min. The volume of hexane/acetone mixture and the sample pH did not affect the signal at the levels studied. Therefore, an intermediate amount of these solvents (250 µL; 1:7.5 v/v) and pH 6 were selected. The optimum desorption condition was obtained with acetonitrile and 10 min of desorption time. The linear working range varied from 58 to 500 µg/L (parathion-methyl), 62-500 µg/L (difenoconazole) and 107-500 µg/L (chlorpyrifos), with correlation coefficients ranging from 0.9980-0.9942. The limits of detection and quantification found were, respectively, 17 and 58 µg/L for parathion-methyl, 19 and 62 µg/L for difenoconazole and 32 and 107 µg/L for chlorpyrifos. The relative standard deviation ranged between 3.5 and 11.2%.