Application of a clean-up procedure using a ternary liquid phase system combined with pre-concentration by microextraction in the analysis of seven pesticides from soya milk.

BACKGROUND: A method has been developed based on a three-phase system, followed by dispersive liquid-liquid microextraction for the extraction of seven pesticides from soya milk prior to analysis by gas chromatography-flame ionization detection. The base of this method is the different extraction capability of the components of soya milk according to each of the phases involved. In this procedure, a homogeneous solution consisting of soya milk and a water-miscible solvent (acetonitrile) is separated into two phases in the presence of Na2 SO4 and the analytes are extracted into the produced acetonitrile droplets. The acetonitrile phase is mixed with a pre-concentration solvent to perform the next microextraction procedure for further enrichment of the analytes. RESULTS: Limits of detection and quantification were reached in the ranges of 0.11-0.35 and 0.35-1.20 µg L-1 , respectively. Enrichment factors and extraction recoveries were in the ranges of 562-933 and 56-93%, respectively. Relative standard deviations were ≤7% for intra- (n = 6) and inter-day (n = 5) precisions at two concentrations of 10 and 50 µg L-1 of each analyte. CONCLUSION: The proposed method was applied to the analysis of pesticides in soya milk samples at µg L-1 concentrations. © 2019 Society of Chemical Industry.