Abstract: A novel method for the simultaneous determination of the trace residues of four organochlorine pesticides such as p,p′-DDD, p,p′-DDT, o,p′-DDT and p,p′-DDE in agricultural products by multi-walled carbon nanotubes (MWNTs) modified by acid oxidation on the surface as solid phase extraction (SPE) adsorbent coupled with high performance liquid chromatography (HPLC) was developed. The effects of the surface acid oxidation, SPE operations and HPLC conditions on the determination of the four pesticide residues were investigated. Under the optimized experimental conditions, the novel method provided wide linear ranges for the pesticides with correlation coefficients of 0.9978~0.9995, the detection limit was 0.050 mg/L for each pesticides. The recoveries from the samples spiked with the pesticide standards at three concentration levels of 0.10, 2.0 and 50 mg/L were in the range of 78%~104% with the relative standard deviations (RSDs) of 2.7%~7.6%. This study indicated the MWNTs SPE was an efficient clean-up method to agricultural products (included dried orange peel, gin-seng, cabbage and tea). The proposed method showed the advantages of accuracy and sensitivity, and can meet the requirements for the determination of low residue pesticide in agricultural products. The study provides a useful method for the analysis of trace substance of agricultural products.

Key words: agricultural products, high performance liquid chromatography (HPLC), organochlorine pesticides, solid phase extraction (SPE), modified multi-walled carbon nanotubes