ABSTRACT:
In this study, three different analytical methods for manganese determination (volumetric, spectrophotometric, FAAS) were compared regarding sensitivity, accuracy, specificity and cost. The spectrophotometric method was chosen to analyze pharmaceutical formulations which are available in Syrian markets as Dietary supplements containing many minerals including manganese. Manganese was determined first quantitatively by complexometric direct titration with EDTA at pH 10 using Eriochrome black T as an indicator, the linearity range was 16-26µg/ml (R2=0.9963). The precision as RSD was <2%, and accuracy was determined as recovery which ranged between 100.18 – 105.31%. The spectrophotometric method depends on manganese oxidation to permanganate. The absorbance of the resulting permanganate solution is measured by visible-spectrophotometer at the maximum absorption wavelength (? max) at 525nm. Beer’s law is obeyed over the concentration ranges of 5-30µg/ml (R2=0.9971). The precision as RSD was <2%, and accuracy was determined as recovery which ranged between 93.94 – 103.13%. Previous methods were compared to one of the most sensitive but costly processes to measure manganese by Atomic Absorption Spectroscopy (AAS) using a manganese bulb with the maximum absorption wavelength (? max) at 279.5nm. Beer’s law is obeyed over the concentration ranges of (0.5-3µg/ml) and the correlation coefficient value (R2 = 0.9993). The precision as RSD was <2% and accuracy was determined as recovery which ranged between 97.24 and 100.04%. Manganese content in a number of dietary supplements samples was estimated, and the results did not coincide with the addressed limits on the labelled cards and the authorized global values.