Stability-indicating methods for the determination of pipazethate HCl in the presence of its alkaline degradation product

Abstract

Three different accurate, sensitive and reproducible stability-indicating methods for the determination of pipazethate HCl in the presence of its alkaline degradation product are presented. The first method is based on ratio-spectra 1st derivative (RSD 1) spectrophotometry of the drug at 305 nm, over a concentration range of 10–70 μg mL −1 with mean percentage recovery of 99.69 ± 1.10. The second method utilises quantitative densitometric evaluation of thin-layer chromatography of pipazethate HCl in the presence of its alkaline degradation product, using methanol: ethyl acetate: ammonia (8:2:0.2, v/v/v) as a mobile phase. Chromatograms are scanned at 251 nm. This method analyses pipazethate HCl in a concentration range of 4–14 μg/spot with mean percentage recovery of 100.19 ± 0.77. The third method is an HPLC method for the simultaneous determination of pipazethate HCl in the presence of its alkaline degradation product. The mobile phase consists of methanol: ammonium sulphate (1%), pH = 5.7, (80:20, v/v). The standard curve of pipazethate HCl shows a good linearity over a concentration range of 5–200 μg mL −1 with mean percentage recovery of 100.67 ± 0.91. These methods were successfully applied to the determination of pipazethate HCl in bulk powder, laboratory-prepared mixtures containing different percentages of the degradation product and pharmaceutical dosage forms. The validity of results was assessed by applying standard addition technique. The results obtained were found to agree statistically with those obtained by a reported method, showing no significant difference with respect to accuracy and precision.