Determination of trace amount of thiabendazole residues in food and water samples by spectrofluorimetry after preconecentration with micro solid phase extraction based on new modified magnetic nanoparticles

Abstract

Background: Benzimidazole pesticides are widely used before and after harvesting to prevent fungal deterioration and persist over long periods of time in crop production. Their application includes improving the yield of the product and also increasing the amount of fresh fruit and vegetables. However, the presence of pesticides residues in food has a negative effect on human health [1]. The maximum amount of Thaibendazole (TBZ) as a antifungal pesticide in fruits and vegetables is 0.05-15 mg/kg, depending on the product [2]. Therefore, sensitive and reliable methods are needed to monitor pesticide residues in water and food to ensure their safety. Several methods have been reported for the extraction and measurement of TBZ [3]. One of the most sensitive methods for measuring TBZ is fluorescence. However, a preconcentration method is needed prior to the determination of TBZ to eliminate the effects of complex matrix and increase the sample detection limit. The aim of this work was to conduct a study on the micro solid phase extraction (μ-SPE) by employing a new adsorbent for preconcentration of trace levels of TBZ prior to the determination by spectrofluorimetry. This method reduces the amount of adsorbent, minimize the cost, and decrease the amount of waste in the determination. Methods: Micro solid phase extraction was carried out using functionalized Fe3O4 magnetic nanoparticles that were synthesized, purified and functionalized according to a previous work [4]. The adsorbent were characterized with FT-IR, SEM, EDX, and XRD. The absorbed analyte was then back-extracted into a small volume of a green solvent and was determined by spectrofluorimetry. Different parameters affect the extraction and determinations of the analyte were optimized. Results: The adsorbent could extract the TBZ from aqueous solution in five minutes and the analyte was back extracted into 2 mL solvent with high recovery. The calibration curve was linear in the concentration range of 1-25 μg mL-1 with the limit of quantification of 1 ng mL−1. The present method was applied to the analysis of water and food samples with the relative standard deviations less than 7%. Conclusion: The combination of μ-SPE and spectrofluorimetry provided the selective determination of trace TBZ in complex matrices. Compared to other conventional sample preparation methods, the proposed method offers advantages, such as simplicity, ease of operation, relatively short analysis time, and lower consumption of organic solvents. The proposed method was applied to the analysis of TBZ in food samples with satisfactory results.