Two stability-indicating UV spectrophotometric methods for the analysis of hydrolyzed tinidazole

Abstract

Two UV spectrophotometric methods have been validated for the analysis of hydrolyzed tinidazole solutions. The pH of the samples must be 5.00–7.00 for both methods. The multiwavelength method may be used for samples degraded at pH 6–12 if the amount of conserved 5-nitroimidazole species is at least 93 mol.% of the original; the amounts of tinidazole and its two known impurities may be determined simultaneously. The accuracy was within 100±8% and the repeatability of measurement was ⩽4% at 0.03–0.33 mM, which was the measuring and calibration range. The LOD and LOQ were determined to be 0.003–0.012 mM and 0.0274 mM, respectively. The single-wavelength method may be used for samples degraded at pH 1–5, at least until approximately 50–60% of the original tinidazole has decomposed; only the amount of tinidazole can be determined. The solutions were measured at 318 nm, and quadratic fitting was used for the calibration. The mean accuracies varied between 98.0 and 101.8% and all RSDs were ⩽1.7% for the precision at 0.041–0.15 mM, which was the measuring range. The calibration range was 0.049–0.12 mM. The LOD and LOQ were 0.25 and 0.75 μM, respectively. The two methods were shown to produce statistically different results by cross-validation. At pH 10.0, tinidazole was decomposed approximately 30 times faster than its 4-nitro isomer; 2-methyl-4(5)-nitroimidazole was stable during the study.