Desenvolvimento de método para determinação de clomazone em arroz empregando o método QuEChERS e UHPLC-MS/MS

Abstract

Modern agriculture, which seeks constantly increasing productivity and maximizing profits, employs a significant load of chemicals, among them pesticides, particularly herbicides, insecticides and fungicides, which may cause environmental pollution and imbalance in the environment. In this work, optimized and validated the presence of clomazone in rice samples from the Western Border of Rio Grande do Sul employing the modified QuEChERS method and Efficiency Ultra Performance Liquid Chromatography coupled to Mass Spectrometry in series (UHPLC-MS / MS) with electrospray ionization source (+). Performed the extraction of residues of clomazone employing the modified QuEChERS method. Was weighed into a 10 g sample of polypropylene at all (50 and 15 mL) was added after 10 mL of acetonitrile containing 1% (v / v) acetic acid. After, stirred by vortexing for 1 minute, then added with 4 g magnesium sulfate and 1.7 g of anhydrous sodium acetate. After, stirred by vortexing for 1 minute and centrifuged for 8 minutes at 10,000 rpm. In step clean-up of the extracts was transferred to 4 mL of the supernatant polypropylene tube containing 100 milligrams of Sorbent-PSA (primary amine), 600 mg of magnesium sulfate and 500 mg of carbon 18. After, stirred for 1 minute and centrifuged for 8 minutes at 10,000 rpm. The supernatant was filtered on nylon filter 0.45 m and 10 L was injected into the system UHPLC-MS/MS. After optimization of the extraction and quantification, the method was validated by evaluating the analytical curve, linearity, limit of detection, limit of quantification, precision and accuracy. The method showed good linearity of the calibration curve of clomazone showed coefficient of determination r² = 0.998. The method presented limit of quantitation of 1 mg kg-¹ and method detection limit of 0.3 mg kg-¹. For the three levels of recovery evaluated (10, 20 and 50 mg kg-¹) showed the method recovery values between 70-120% and coefficients of variation ≤ 20%. The evaluation results were also obtained intermediate precision in the range of 79-95%. The method was applied for the determination of residues of clomazone 8 samples of commercial rice Westermarck was observed in 4 samples that were not detected residues were detected three samples below the limit of quantitation and only one of the samples found if waste clomazone (2.5 mg kg-¹). The developed method enables the assessment of clomazone in adequate concentrations to a maximum residue level (MRL) with precision, accuracy and efficient.