DESENVOLVIMENTO E VALIDAÇÃO DE MÉTODO VOLTAMÉTRICO PARA DETERMINAÇÃO DE AMOXICILINA EM ÁGUA DE RIO

Abstract

Amoxicillin is an antibiotic that can accumulate in aquatic environments and lead the development of bacterial resistance. Thus, the drug must be determinate in these environments. For that, in this study, a glassy carbon electrode was modified with reduced graphene oxide and Nafion and it was used as a sensor in a square wave voltammetry methodology. The volumes of the modifiers used to construct the sensor were optimized as 6.0 μL, for both, using a 22 experimental design with central point in triplicate, and the peak current magnitude obtained was 108.9 μA. The study of scan rate effect, in cyclic voltammetry, allow to identify that the electronic transfer process of amoxicillin on the sensor is typical of electrodes with adsorbed species and it can be categorized as quasireversible. The electroanalytical method was developed in 0.1 mol L-1 Britton-Robinson buffer as supporting electrolyte, and the parameters were optimized through univariate approach as hidrogenionic potential of 2.0, frequency of 100 s-1, amplitude of 70 mV and step height of 2 mV. The method was validated for application in different samples of river water from Guarapuava – Paraná. The samples nominated P1 and P2 did not present a significative matrix effect, when compared to the pure electrolyte, and the forward estimations could be made from the electrolyte. On the other hand, the sample named P3 presented a significative matrix effect and the estimations were made using calibration by standard addition method. For both cases, the work range adopted was 1.8 to 5.4 μmol L-1 and the linearity was suitable, obtaining a significative linear regression and a no significative lack of fit, in 95 % level of confidence, through the application of F-tests. Besides, analysis of residual plots and Cochran tests pointed the variances homoscedasticity. The limits of detection to pure electrolyte and standard addition curves were, respectively, 0.39 and 0.63 μmol L-1 and the limits of quantification were 1,18 and 1.89 μmol L-1. The method was selective to amoxicillin compared to three-fold of benzylpenicillin and two-fold of humic acids and levofloxacin. Precision, as repetitivity and intermediate precision, for both approaches of calibration, was suitable and the relative standard deviations were in the range of 6.1 to 13.8 %. To estimate the accuracy, the mean recoveries were between 93.1 and 106.9 %. Furthermore, the method was compared to a chromatography one and the mean values obtained by both were statistically equals, so the accuracy was adequate. Therefore, the voltammetric method developed can be applied for determination of amoxicillin in river water, obtaining reliable and consistent measurements.