ABSTRACT
The excessive use of pesticides is a serious health problem due to their toxicity and bioaccumulation through the food chain. Due to the complexity of foods, the analysis of pesticides is challenging often giving large matrix effects and co-extracted compounds. To overcome this problem, a selective and "green" supercritical fluid extraction method was developed, using neat carbon dioxide as a solvent at pressures of up to 800 bars. A Box-Behnken response surface experimental design was used, with the independent variables of density (0.70-1.0 g mL-1), temperature (40-70 C), and volume (10-40 mL) of solvent, and the dependent variable of extracted amount of pesticides. The optimum extraction condition was found at the use of 29 mL of supercritical CO2 at 0.90 g mL-1 and 53C (corresponding to 372 bars of pressure). It was observed that increasing the density of CO2 significantly increased the extraction recovery of endrin and 2,4'-dichlorodiphenyldichloroethane. Matrix-matched calibration curves showed satisfactory linearity (R2 ≥ 0.994), and LODs ranged from 0.2 to 2.0 ng g-1. Precision was lower than 11% and recoveries between 80%-103%. Thus, the developed method could efficiently be used for trace analysis of pesticides in complex food matrices without the use of organic solvents.
Subject(s)
Carbon Dioxide/chemistry , Chromatography, Supercritical Fluid/methods , Food Analysis/methods , Onions/chemistry , Pesticide Residues/isolation & purification , Solvents/chemistry , Dichlorodiphenyldichloroethane/isolation & purification , Endrin/isolation & purification , Factor Analysis, Statistical , Food Contamination , Humans , Limit of Detection , TemperatureABSTRACT
It has been discovered previously that clay minerals may have a greater potential for sorption of pesticides. In this paper, the sorption of endrin, a nonionic persistent organochlorine pesticide, to montmorillonite and kaolinite was investigated. The effect of pH, ionic strength on the sorption was studied. The effect of intercalation of hydroxyl aluminium species on sorption of endrin to montmorillonite was also investigated. The results show that, the sorption isotherm of endrin to montmorillonite and kaolinite was linear. The sorption increases with the increase in ionic strength. pH has effect on the sorption and the sorption on both montmorillonite and kaolinite has obvious troughs at pH about 7.2 and 5.4, respectively. The intercalation of hydroxyl aluminium species decreases the sorption. Sorption mechanism of endrin to montmorillonite and kaolinite was suggested to be a combination of hydrophobic interaction and charge-dipole interaction and troughs in the effect of pH on sorption was attributed to the proton shift reaction of the broken bonds at the clay edges.
