Comparative studies of univariate and multivariate optimizations for manganese determination in antihypertensive drugs by electrothermal atomic absorption spectrometry

Abstract

Comparative studies using the univariate and multivariate optimizations (factorial design) were undertaken to determine manganese in antihypertensive drugs by electrothermal atomic absorption spectrometry (ET AAS). For the univariate method, the optimum pyrolysis and atomization temperatures were 500 and 2200 °C, and for multivariate analysis, the temperatures were 500 and 2400 °C, respectively. No differences were observed between the methods with respect to the slopes of the calibration curves, recoveries, results for certified urine samples for the two levels, and the averages of the intra- and inter-assay coefficients of variation (CV) using Student t and F tests as a statistical tool (P < 0.05). Calibration was performed by matrix matching. All other studies were made using the optimized multivariate conditions. The characteristic mass was of 0.68 ± 0.17 pg (the recommended mass is 0.60 pg). The limits of detection and quantification were 0.23 and 0.77 µg L-1, respectively. Intra- and inter-assay studies on the drug spiked with 0.5, 1.0, and 1.5 µg L-1 of Mn yielded mean results of 3.6 ± 1.9% and 9.6 ± 2.2%, respectively. For the intra-assay evaluation, seven samples of each concentration were evaluated for Mn on the same day, whereas, for the inter-assay study, these solutions were analyzed in three replicates during three consecutive days. Recovery studies on the drug spiked with three levels of Mn (n = 7 for each level) furnished results between 101.4 ± 17.2% and 106.6 ± 7.5%. The results of a certified urine sample analysis (two levels of Mn) agreed at a 95% level of confidence. Forty eight antihy pertensive drug samples were analyzed, and the drug contents varied between 2.9 ng and 1.9 µg capsule-1.Key words: manganese, antihypertensive drugs, electrothermal atomic absorption spectrometry, multivariate optimization.