Liquid-liquid extraction/low-temperature purification (LLE/LTP) followed by dispersive solid-phase extraction (d-SPE) cleanup for multiresidue analysis in palm oil by LC-QTOF-MS

Abstract

An evaluation of the extraction of multiresidue pesticides from palm oil by liquid-liquid extraction/low-temperature purification (LLE/LTP) coupled with dispersive solid-phase extraction (d-SPE) as the cleanup procedure with the determination by liquid chromatography mass spectrometry using electrospray as the ionization source (LC-ESI-MS) was carried out. Optimization approaches were studied in terms of d-SPE to select efficiency of type and mass of adsorbents to obtain the highest recovery yield of pesticides and the lowest coextract fat residues in the final extract. The optimal conditions of d-SPE were obtained using 3 g of palm oil, 4 g anhydrous MgSO4, 150 mg of PSA, and 50 mg of GCB (PSA: GCB (3: 1 w/w)). Recovery study was performed at three concentration levels (25, 50, and 100 ng kg-1), yielding recovery rates between 71.8 and 112.4% except diuron with relative standard deviations of 3.2-15.1%. Detection and quantification limits were lower than 2.7 and 8.2 ng kg-1, respectively. The proposed method was successfully applied to the analysis of market-purchased palm oil samples from two different brands collected in Kuala Lumpur, showing its potential applicability and revealing the presence of some of the target species in the ng g-1 range. © 2013 Elham Sobhanzadeh and Keivan Nemati.