11. Utility of molybdophosphoric acid in qualitative and quantitative analysis of Sibutramine HCl, Sumatribtan succinate and Lomefloxacine HCl

A sensitive, reliable and reproducible spectrophotometric method is suggested for the determination of Sibutramine HCl (Ι), Sumatribtan succinate (Π) and Lomefloxacine HCl (Ш) in pure form and in pharmaceutical formulations. The method involves precipitation of the investigated drugs with Molybdophosphoric Acid (MPA) then reduction of MPA (released with acetone) with new reductant (Co(Π) – EDTA) complex to molybdenum blue which has maximum absorbance at 760nm. The different experimental parameters affecting development and stability of the colour are carefully studied and optimized. Adopting the procedure, Beer's law is valid for the three drugs over concentration range of 25-150μg/mL, 25-275μg/mL and 25-250μg/mL for Ι, Π and Ш, respectively. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy or precision. The proposed method has been successfully employed for determination of Ι, Π and Ш in pure form and in pharmaceutical formulations.