Pesticide Residues Determination In Food By Matrix Solid-phase Dispersion Extraction And Gas Chromatography-mass Spectrometry

In this experiment, adsorbent capability and adsorbent model for multi-walled carbon nanotubes (MWCNTs) adsorbing atrazine were studied, and a new analytical technology using MWCNTs as absorbent in matrix solid-phase dispersion (MSPD) and following determined by gas chromatography-mass spectrometry (GC/MS) was developed.The results showed that the maximum amount is 15.7 mg/g for atrazine adsorbed onto MWCNTs in water when the pH is 7, and the adsorbent process meets I type adsorbing mode and can be well modeled by isothermic equations of Freundlich and Langmuir.Parameters of MSPD were optimized by orthogonal experiment, and the optimal processes is as following: 0.6 g MWCNTs and 2 g sample were blended and transfer to syringe barrel, and the compounds in the mixture were eluted by 15 mL acetone and hexane (1+1, v/v). Under the optimal parameters, recoveries were 75.1-109.1% with relative standard deviations (RSDs) ranging from 2.8 to 7.9%, and limits of detection (LODs) were 0.1- 4.5μg/kg for apple, potato and cabbage matrices.Based on the developed method, comparison of advantages for MWCNTs, C₁₈, diatomite and activated carbon were studied. To the most pesticides, the recoveries obtained by using MWCNTs and C₁₈ are similar, and the most recoveries are above 70%. However, those obtained by using diatomite are a little lower and the recoveries are the lowest obtained by activated carbon. The proposed method was applied to real samples and Methidathion was determined in apple. Prometryn and Isocarbafos were determined in potato. In cabbage, Heptachlor, DDD and Ethion were determined.Weather the developed method was suitable for analyzing multi-residues of pesticide in cereal matrices was studied. Recovery was 84.3-106.1% with RSD ranging from 2.7 to 8.7% for rice, and recovery was 80.5-103.4% with RSD ranging from 3.5-9.8% for maize. To rice and maize, LODs were 0.2-4.0μg/kg and 0.2-3.5μg/kg, respectively. The results showed the proposed method can be used in analyzing multi-residues of pesticide in cereal samples. At last, five pesticides (parathion-methyl, parathion, ethion, cypermethrin and fenvalerate) were determined in real cereal samples.