Development and validation of a HPLC method to quantify DEET and IR3535 in insect repellents

Abstract

The increasing number of cases of dengue, chikungunya, yellow fever and Zika virus has caused many people to use repellents to try to protect themselves from the Aedes aegypti mosquito that transmits these diseases. There are a variety of products that have different ingredients, concentrations, durations of action and prices. However, not all repellants can be used by children and pregnant women and in some cases, medical guidance is required. Repellents are classified as cosmetics and the two most commonly used active ingredients are N,N-diethyl-3-methylbenzamide (DEET) and ethyl-3-(N-n-butyl-N-acetyl) aminopropionate (IR3535). This is a report on the development of a rapid and reliable HPLC-DAD method, validated for the quantification of DEET and IR3535 in insect repellents. The following chromatographic parameters were used: a mobile phase of water/acetonitrile at an 80 : 20 (v/v) ratio, a flow rate of 0.3 mL min⁻¹, and a detection wavelength of 210 nm. Before analysis, samples were diluted 20 000 and 10 000 times in water/acetonitrile (90 : 10, v/v) for DEET and IR3535, respectively. The method was validated and presented satisfactory linearity (0.25–22 mg L⁻¹, r² = 0.9986 and 0.5–40 mg L⁻¹, r² = 0.9976), limit of quantification (LOQ) (0.09 and 0.06 mg L⁻¹), with the intra- and inter-day precision calculated using a Horwitz ratio of less than 2, and recoveries (89.2–111.6% and 94.7–109.2%) for DEET and IR3535, respectively. It is important to highlight that there is no reference method that allows the quantification of both active ingredients, simultaneously, in the analyzed samples, which is proposed in this work.