Desenvolvimento de metodologias analíticas baseadas em HPLC-DAD, espectroscopia no infravermelho e quimiometria para o controle de qualidade de repelentes de insetos

Abstract

The Aedes aegypti mosquitoes are vectors of diseases such as dengue, chikungunya, zika and yellow fever. With the increase in the incidence of these diseases, the population has resorted to the use of repellents to try to protect themselves from the attack of these mosquitoes. The Brazilian market offers a wide variety of products which have different active ingredients (with varying levels of concentration), protection time and different prices. The most important repellents are the base on DEET (N, N-diethyl-3-methylbenzamide), IR3535 (ethyl butyl acetylaminopropionate) and icaridin (hydroxyethyl isobutyl piperidine carboxylate) for use in adults and children. The action time of these repellents depends, among other factors, on the concentration of these active ingredients. This work proposes methodologies for classification and determination of active ingredients in insect repellents, considering that there is no reference method to perform the quality control of these products. In the first stage the development and validation of a method based on high performance liquid chromatography (HPLC-DAD) was carried out. The validated method according to EURACHEM showed good linearity (0.25 to 22 mg L-1 for DEET, r2 = 0.9986 and 0.5 to 40 mg L-1, r2 = 0.9976 for IR 3535 ), with intra- and inter-day precision calculated using a Horwitz ratio of less than 2 and recoveries of 89.2 - 111.6% and 94.7 - 109.2% for DEET and IR3535, respectively. Infrared spectroscopy and chemometric techniques for classification, calibration and calibration transfer of commercial repellents were used. In the multivariate classification part, the near infrared spectroscopy (NIR) was obtained the best result with the discriminant analysis by the partial least squares (PLS/DA) and MLR with selection of stepwise variables (MLR/SW), reaching a rate Correct Classification (TCC) of 100% for the three active ingredients studied (DEET, IR 3535 and icaridin). Regarding the multivariate calibration, NIR and medium infrared (MIR) spectroscopies were used to determine DEET and IR 3535 in repellents. For DEET, using the NIR data, satisfactory results were obtained using the interval partial least squares regression (iPLS) and multiple linear regression with variable selection by the successive projection algorithm (MLR/SPA), reaching a RMSEP of 0.70% and 0.74% (m m-1), respectively. The IR 3535 samples measured in the NIR showed better results with PLS and MLR/SW reaching RMSEP of 0.64% and 1.03% (m m-1), respectively. The best results using MIR were obtained with the PLS model, with RMSEP of 1.38% and 1.69% (m m-1), for DEET and IR 3535, respectively. Finally, a calibration transfer study was carried out using two NIR spectroscopy equipment. For this purpose, Direct Standardization (DS), Reverse Standardization (RS) and Piecewise Direct Standardization (PDS) techniques were used. For DEET, the best result was obtained with PLS applied to the RS technique, in which RMSEP decreased from 7.95% to 1.21%. For IR 3535, the lowest value was reached with MLR/SPA, in which RMSEP decreased from 25.18% to 1.58% (DS). The proposed alternative methodologies based on NIR and MIR spectroscopy presented advantages because they are fast, non destructive, low cost and do not use reagents. And they are promising in the classification and calibration for quality control of active ingredients in insect repellent samples.