Determinação de resíduos de herbicidas em diferentes variedades de arroz (branco, preto e vermelho) empregando método QuEChERS e LC-MS/MS

Abstract

Rice is the main component of the basic diet of the world population. This food is of utmost importance for world food security. Therefore, aspects related to its production and consumption must be continuously monitored and evaluated in depth, so that its supply is guaranteed. Pesticides are present in the environment, including water, soil and food, as a result of their application in modern agriculture. Therefore, the residues of these compounds play an important role as they are used to assess food safety and human health risks. The present work demonstrated the use of different sorbents in the QuEChERS cleanup step for the removal of coextratives present in rice samples extracts. Several tests were performed with different proportions and combinations of sorbents employing different methodologies for sample preparation and extract evaluation by auxiliary techniques such as HPLC-UV/vis and GC-MS / MS (full scan) and extraction efficiency evaluation. , for the purpose of optimization of the developed method and subsequent validation of it using LC-MS / MS to determine the selected pesticides. The proposed method involves an extraction step with acetonitrile acidified with 5% (v / v) formic acid, followed by partitioning with 4 g magnesium sulfate and 1 g sodium chloride. Afterwards, 1 mL of extract was submitted to d-SPE step with 125 mg of C18. The final extract was diluted 1: 1 with mobile phase, filtered through a 0.20 μm (13 mm) nylon filter and injected into the LC-MS / MS system. The C18 sorbent showed efficiency in extract cleaning, with satisfactory reduction of co-extract contents without significant analyte losses, considering that obtaining clean extracts is fundamental for the achievement of reliable results and for the preservation of the chromatographic system. . The original acidified QuEChERS method associated with d-SPE extract cleaning proved to be efficient for extraction and determination of residues of 28 herbicides in samples of polished white rice by LC-MS / MS. The recovery results obtained were satisfactory, ranging from 70 to 120% for the evaluated compounds, with RSD values ≤ 20%. This method showed good results, with LOD values of 6 μg kg-1 and LOQ 20 μg kg-1 for all compounds analyzed. In addition, the method had its matrix scope extended to red rice and black rice.