Desenvolvimento de metodologia eletroanalítica para a determinação de resíduos de pesticidas em amostras de alimentos e de águas naturais

Abstract

The objective of this work was the development of analytical procedures for three pesticides, diquat, paraquat and chlorpyrifos on different surfaces using SWV. When diquat was detected on AgSAE, it was observed the presence of two reduction peaks at -0.56 V and -1.00 V. Under optimized conditions, the optimized results were obtained in Na2B407 0.01 mol L-1, with f = 100 s-1, a = 50 mV and AE, = 2 mV. Considering the peak at -0.56 V, analytical curves were constructed and were calculated with LOD = 9.98 fig L-1 and LOQ = 33.28 mg L-1. The methodology efficiency was evaluated obtaining a recovery in electrolyte of 99.78%, and the accuracy in terms of reproducibility showed a RSD of 1.71%. The methodology was applied in river water and potato samples, obtaining recovery values between 80.00 and 115.00% respectively. Using BDDE, it was verified the presence of two reduction peaks at -0.6 V and -1.0 V. The optimized conditions were obtained in Na2B407 0.05 mol L-1 medium using f = 40 s-1, a = 50 mV and AEs = 2 mV. The analytical curves were obtained with LOD = 0.08 pg L-1, LOQ = 0.19 p,g L-1 and recovery equals to 88.30%. The accuracy was tested and expressed with RSD = 2.24% of reproducibility. The methodology was applied in lemon, orange, tangerine and pineapple fresh juices, potato and sugar cane juice samples, with recovery values between 70.00 and 110.00%. When paraquat was detected on BDDE, it was observed two reduction peaks at -0.68 V and -1.00 V. After optmizing the experimental parameters, the results were obtained in Na2B407 0.01 mol L-1 medium, using f = 30 s-1, a = 50 mV and AZ = 3 mV. The analytical curves were constructed in the -0.68 V peak and the LOD and LOQ were calculated, such as 0.04 [ig L-1 and 0.13 L-1, respectively. The methodology had an efficiency of 99.42%, and the accuracy in terms of reproducibility showed RSD of 4.91%. The method was applied to coconut water and acerola fresh juice, obtaining recovery values of 96.60% and 95.08%, respectively. When Chlorpyrifos was detected on HIVIDE, it was observed the presence of a reduction peak at -1.10 V. After optimization of the parameters, the results were obtained in BR buffer 0.1 mol L-1 pH 2, f = 100 s-1, a = 25 mV and AE, = 5 mV, Eaccu= -0.4 V and taccu= 60 s. Analytical curves were constructed and calculated with LOD = 0.155 tig L-1, LOQ = 0.518 ijg L-1, recovery of 91.57% and RSD = 4.03%. The methodology was applied in river water and orange juice samples with recovery of 91.87% and 77.51% respectively. In all developed methodologies, we obtained low values of LOD and LOQ, recovery between 70.00 to 110.00% and reproducibility below 5.00%, showing that, those methods had excellent sensitivity, precision and efficiency.