Otimização e validação do método VA-MSPD-LC-MS para determinação de agrotóxicos em tecidos de anuros

Abstract

Due to the intensification of human activities, more and more contaminants that may have consequences for the different life forms of the planet are being generated into the environment. Pesticides, which can poseb a threat to animals, such as amphibians, more precisely anurans, since they tend to bioaccumulate in lipid-rich tissues. Amphibians are suckable animals and are in population decline.Taking into account the above and knowing that the study region, Northwest of Rio Grande do Sul, makes heavy use of pesticides in agricultural crops, the present work aimed to optimize and validate the VA-MSPD-LC-MS (Vortex-Assisted Matrix Solid Phase Dispersion, Liquid Chromatography coupled to Mass Spectrometry) method to determine seven pesticides in frog tissues: atrazine, tebuconazole, chlorpyrifos, difenoconazole, trifloxystrobin, pirazosulfuron and fipronil. For method optimization, different mobile phase conditions and materials used for VA-MSPD were tested. The tests were based on univariates analysis to determine solid support type and sample quantity. A multivariate analysis was used to determine type and volume of solvent, amount of sodium sulfate and solid support. In order to evaluate the best conditions, the response between 70-120% recovery for all tests and relative standard deviation for univariate analyzes was considered. The best condition was found using 0.5 g of sample, 1 g of C18, 1 g of Na2SO4 and 4 ml of acetonitrile. The proposed method was validated according to the criteria required by ANVISA (2017) and INMETRO (2018), with recovery between 70 and 120% and RSD <20%. The LOQm (Limit of Quantification of the method) was between 8 and 80 µg kg-1 for the seven pesticides analyzed. The method is selective, linear, precise, accurate, economic and ecological. In agroecosystem samples, difenoconazole and trifloxystrobin were quantified. These data suggest that bioaccumulation may be occurring in anuran tissues. This work was an important step towards the monitoring of bioaccumulative pesticides in frog tissues, however, other studies need to be performed to better understand this phenomenon and the impacts it may cause.