Desenvolvimento, otimização e validação de metodologia para determinação de tiametoxam em folhas de feijoeiro

Abstract

Insecticides play an essential role in combating insects in agriculture and, therefore, have been the fastest and most efficient solution to avoid loss of productivity and economic losses. Thiamethoxam, an insecticide of the neonicotinoid class, proved to be efficient in combating insects that affect common bean plants. However, the forms of pesticide application contaminate the soil and bean grains, affecting the environment and human health. Thus, the present study aimed the development a methodology for the thiamethoxam quantification in bean leaves. The sample preparation method was based on solid-liquid extraction with a low temperature partition (SLE-LTP), in which the analyte partition occurred from bean leaves in an aqueous solution to an organic solution collected for analysis. The extracts were analyzed using high-performance liquid chromatography with detection by diode array (HPLC-DAD). The SLE-LTP was selected because it is easy to automate, simple, with a short execution time, little intervention by the analyst, and less generation of organic waste compared to the literature. The optimized method showed excellent analyte recoveries, close to 100%, using 100 mg of leaf sample, water:acetonitrile ratio of 2.0:4.0 mL, and 2 hours of freezing. The merit figures of the method validated it as linear in the range of concentrations from 0.005 to 0.5 mg L-1, the first point being the quantification limit, which is below the maximum residue limit for thiamethoxam in bean grains. In addition, other parameters such as good selectivity, sensitivity, good precision and accuracy, and robustness suggest a reliable method for thiamethoxam extraction. Therefore, since the figures of merit met the specifications of the method validation guide, document SANTE/11312/2021, the proposed methodology is adequate and efficient for the thiamethoxam determination in bean leaves.