Chemometric-assisted UV spectrophotometric method for determination of N, N- diethyl-3-methylbenzamide in insect repellents.

Abstract

In recent years outbreaks of vector-borne diseases have caused great concern to the population, especially those diseases transmitted by mosquitoes. Repellents appear as an affordable alternative for prevention, making it increasingly important to control the quality of these products, since the content of the active ingredients are directly related to the efficiency and the protection time provided by the repellent. This paper proposes an analytical method for determining the DEET (N, N- Diethyl-3-methylbenzamide) content in insect repellents in lotion using UV spectroscopy. For this propose five different strategies of regression were evaluated: (a) Partial Least Squares (PLS) using full-spectrum; (b) interval PLS (iPLS); Multiple Linear Regression (MLR) with variable selection by the (c) Genetic Algorithm (MLR/GA), (d) Successive Projections Algorithm (MLR/SPA) and the (e) Stepwise (MLR/SW). Appropriate predictions were obtained with RMSEP values between 0.88 and 0.93%w w-1. No systematic error was observed and no significant differences were found between the predicted and reference values, according to a paired t-test at 95% confidence level. The results demonstrated the potential of UV spectroscopy associated to multivariate calibration to determine DEET content in repellents as a fast, simple strategy and with a suitable correlation between the values estimated by the model and the reference values.