Development and validation of methods for quantitative analyses of roxithromycin in pharmaceutical capsules / Desenvolvimento e validação de métodos de análise quantitativa da roxitromicina em cápsulas farmacêuticas

Roxithromycin is a macrolide antibiotic derived from erythromycin, with poor solubility in water, and has been commercially available as capsules. Thus, this paper reports the development and validation of an analytical method by reversed-phase high performance liquid chromatography (RP-HPLC), using a C18 column, detector DAD, λ = 205 nm and mobile phase consisting of acetonitrile and ammonium phosphate buffer 35:65 v/v. Similarly, an alternative agar diffusion bioassay technique was also performed, using the cylinder plate method, with a strain of Micrococcus luteus INCQS 011 as the test organism. The validation of the chromatographic method showed selectivity, linearity (r = 0.9995), precision (RSD = 1.08 %), accuracy (100.85 %) and robustness. Additionally, the limits of quantitation (5 µg/mL) and detection (1.45 µg/mL) were defined. The prospective validation of the microbiological assay showed that method developed is selective, linear (r = 0.9985), precise (RSD = 1.53 %), accurate (100.53 %) and robust. The limit of detection (0.5 µg/mL) was also defined. The methods developed were compared for the determination of roxithromycin, and there was no significant difference between them. Furthermore, the alternative agar diffusion bioassay is useful, low-cost, simple, and beneficial to the environment.