COLORIMETRIC DETERMINATION OF CEFQUINOME SULPHATE IN BULK AND DOSAGE FORM USING AMMONIUM MOLYBDATE

This study was designed to develop two colorimetric methods for the determination of Cefquinome Sulphate (CS) in bulk and dosage forms using two different concentrations of molybdenum solution. The developed methods were based on the oxidation of CS with 2% ammonium molybdate, in the presence of sulphuric acid, producing a green colored product with λ_max at 409 nm (Method I) and the oxidation of CS with 10% ammonium molybdate in acidic media to produce a blue colored product with λ_max at 673 nm (Method II). The factors affecting the color development and stability were optimized and incorporated in the procedure. Beer’s law was obeyed over the concentration range 16-80 µg mL^-1 (Method I) and 40-80 µg mL^-1 (Method II) with a correlation coefficient not less than 0.999. The limit of detection and limit of quantification were 5.7 and 18.9 µg mL^-1 for Method I, 4.25 µg mL^-1 and 14.2 µg mL^-1 for Method II respectively. The average recovery for the dosage form (suspension 2.5%) was 100.30% ±0.59; n = 3, which reflected no interference by the suspension excipients. The results obtained by the developed methods for the suspension dosage form were statistically compared with those of a developed HPLC method and evaluated at 95% confidence limits. The developed methods were proved to be accurate and simple. The methods involved in the study covered, Colorimetric spectrophotometry, High Performance Liquid Chromatography. The molar ratio method is recommended to be conducted in order to determine the reaction stoichiometry.