Análise de degradação de ivermectina utilizando peroxidação assistida por radiação ultravioleta (H2O2/UV)

Abstract

Ivermectin (IVM) is a drug highly effective, relatively low-cost that is widely used in veterinary and human medicine. The presence of this drug, and others, in aquatic matrices has caused great concern today, since they have a great potential to cause adverse effects in animals and humans. Therefore, the application of efficient methods to remove this type of pollutant in aqueous solution is necessary. The Advanced Oxidative Processes (AOPs) have been widely used in the degradation of these compounds. Therefore, the present work aims to analyze the degradation of Ivermectin through the H2O2/UV process. The photoreactor used was built from an aluminum reservoir with capacity for 1L of solution, containing whips for its homogenization equipped with 1 germicid lamp of 95W, which emits radiation at wavelength of λmax = 254 nm, and a pump for recirculation. A validation of the analytical method was developed for the quantification of ivermectin, using the spectrophotometry-UV technique. Linearity, analytical limits, precision and accuracy parameters were evaluated according to ANVISA and INMETRO recommended guidelines. The method showed linearity in the range of 5 - 50 mg.L-1 and R² = 0.998. The limit of quantification was 10.95 mg.L-1 and the limit of detection equal to 3.61 mg.L-1. For precision, an average percentage recovery equal to 102.48% and a coefficient of variation of less than 5% was verified. The repeatability and intermediate precision showed a coefficient of variation less than 5% and there was no significant difference between the average of the ivermectin concentrations analyzed.From the experimental planning analysis made, it was seen that reaction time, H2O2 concentration and pH-concentration H2O2 interaction were the variables that most influenced the degradation process, to 95% confidence level. The best condition resulted in a concentration of 150 mg.L-1 H2O2, pH 9 and 180 minutes of reaction, degrading more than 80% of ivermectin present in the solution, obtaining a final concentration of 3.7 mg.L-1. It was possible to identify a modification in the molecule structure, according to the absorption spectra, evidencing the degradation of ivermectin. The proposed analytical method is sufficiently accurate, precise, reproducible and sensitive in the determination and quantification of ivermectin in aqueous solution. The built photoreactor showed to be efficient and and low cost. In alkaline conditions and at low oxidant concentrations a removal of 81% was obtained for 180 minutes of reaction.