Development of A Sample Preparation Method for evaluating Trace Residue of Bentazon Pesticide in Biological Matrices Using Dispersive Solid Phase Extraction (SPE) Method Based on Molecular Imprinted Polymer (MIP)

Pesticides are among the broadest chemical compounds used in the world and are also considered as the most dangerous compounds for living organisms. Although pesticides have significant impact on improving agricultural and food products, the processes of their production, formulation, storage, transportation, and marketing as well as the extensive use of these materials lead to occupational exposure, environmental pollution, and the presence of their residues in foodstuffs. Bentazon as a herbicide is considered as one of the most common pesticides used in agriculture and horticulture. Its effects on human health are widespread and of concern. Occupational and environmental exposure assessment of this compound is, therefore, considered necessary by conducting accurate and valid methods. The purpose of the present study was to synthesize a molecular imprinted polymer (MIP) as a specific adsorbent in the preparation process of bentazon for its selective analysis in biological matrices.

For synthesis, a precipitation polymerization method was used. This method has been used to prepare particle size distribution and shape appropriately. By applying the aforementioned method, nano particle size is obtained within the sub-micron and nano range. So, crushing and sieving of the sorbent is not necessary. The MIP was synthesized with 1: 4: 30 ratio of template molecule (bentazone): functional monomer (methacrylic acid): cross-linking monomer (ethylene glycol di methacrylate), respectively. Due to particle size and high porosity, the sorption and recovery of template compound was performed faster and with higher efficiency. Some variables affecting the efficiency of MIP for sorption and desorption of analyte were investigated and optimized. They included pH of solution, MIP amount (mg), and sonication time (min) in the sorption step and volume of eluent (ml), sonication time (s), and acid percentage in the desorption step.

The optimum levels of factors for the proposed method were pH of solution: 2، sonication time for sorption 7.3 min, polymer amount of 30.814 mg, acid percentage 1.1, and sonication time for desorption 165 s. According to the obtained results, the interfering factors in the matrix have no significant effect on the determination of analyte. The limit of detection (LOD) and relative standard deviation (RSD) of the optimized method were 0.79.ppb and 2.8931 %, respectively.

The results of this study indicated that the proposed method can be used to extract the bentazon herbicide from complex matrices such as urine samples with high efficiency and selectivity.