DESENVOLVIMENTO E VALIDAÇÃO DE MÉTODO ANALÍTICO PARA DETERMINAÇÃO SIMULTÂNEA DE SULFADIMETOXINA E METRONIDAZOL POR ESPECTROFOTOMETRIA DERIVADA EM FORMULAÇÃO FARMACÊUTICA DE USO ANIMAL

Abstract

Poor-quality medicines, including veterinary antimicrobials, constitute a significant threat to public health, and may cause a therapeutic failure and antimicrobial resistance. In this context, new analytical methodologies are needed for the quality control of these medicines. In the present study, a method based on derivative spectrophotometry was developed and validated for the simultaneous determination of sulfadimethoxine (SDM) associated with metronidazole (MTZ) in a veterinary medicine, without prior separation of the drugs. The method was developed using acetonitrile PA as solvent and at room temperature (25 ± 2ºC). The MTZ was determined by zero order spectrophotometry at 320 nm, while the SDM, due to the overlapping of the electronic transition bands of the zero order spectra, was determined from the first order spectrum (first derivative) at 266 nm, by the zero-crossing technique. The analytical validation demonstrated that the method is linear (r > 0.990) for both drugs, in the concentration range of 3.0-21.0 µg mL-1. The limits of detection and quantification found for MTZ (0.21 µg mL-1 and 0.63 µg mL-1) and SDM (0.17 µg mL-1 e 0.51 µg mL-1), respectively, were satisfactory, indicating the sensitivity of the method. In addition, the developed method was selective (without interference of excipients), precise (RSD<1.9), accurate (recovery percentage within acceptable limits of 98-102%) and robust (the selected factors and their interactions did not significantly affect the contents of MTZ and SDM). Therefore, the method developed proved to be simple and economical, and can be easily applicable in routine analysis of quality control of the drugs mentioned, isolated or associated, in pharmaceutical formulations for human or animal use.