Multiresidue determination of pesticides in industrial and fresh orange juice by hollow fiber microporous membrane liquid-liquid extraction and detection by liquid chromatography-electrospray-tandem mass spectrometry

A procedure involving hollow fiber microporous membrane liquid-liquid extraction (HF-MMLLE) and detection by liquid chromatography with tandem mass spectrometry was developed and applied. The extraction is based on liquid-liquid microextraction with a polypropylene porous membrane as a solid support for the solvent. On the membrane walls the solvent forms a renewable liquid membrane which improves the trueness of the method and promotes the sample clean-up. The applicability of this method was evaluated through the simultaneous extraction of 18 pesticides of different classes: polar organophosphates, carbamates, neonicotinoids, amides, pyrimidines, benzimidazoles and triazoles in industrial and fresh orange juice. The parameters affecting the extraction efficiency were optimized by multivariable designs. Under optimized conditions, analytes were concentrated onto 1.5 cm long microporous membranes placed directly into the sample containing 9 mL of juice at pH 7.0, 4g of ammonium sulfate and 400 mu L of toluene:ethyl acetate (85:15, v/v). The best extraction conditions were achieved at 25 degrees C with 35 min of extraction time. The analyte desorption was carried out using 50 mu L of methanol:acetone (50:50, v/v) for 2 min in an ultrasonic bath. Limits of detection ranging between 0.003-0.33 mg L-1, 0.003-0.35 mg L-1 and 0.003-0.15 mg L-1 were obtained for the carton orange juice, carton light orange juice and fresh orange juice samples, respectively. Good repeatability (lower than 7.6%) was obtained for all three sample types. The method was applied to five different juice samples containing soybean extract, orange pulp, nectar, light juice and fresh orange juice. The results suggest that the proposed method represents a very simple and low-cost alternative microextraction procedure rendering adequate limits of quantification for the determination of these pesticides in juice samples. (C) 2011 Elsevier B.V. All rights reserved.