Spectrophotometric determination of oxytetracycline by coupling with diazonium salts

ABSTRACT

Diazotized p-nitroaniline [I], sulfanilic acid [II] and sulfanilamide [III] were used for the spectrophotometric determination of oxytetracycline [OTC]. The procedure is based on the observation of that in slightly alkaline medium OTC reacts with I, II and III. A stable azo dye is formed and show maximum absorption at 550, 560, and 575 nm, respectively. The variable affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 25, 90 and 90 mug/ml on using I, II and III, respectively. Molar absorptivities [L mol-1 cm-1] and Sandell's sensitivities [mug cm-2 per 0.001 absorbance unit] are respectively; 0.83 x 104 and 57.8 x 10-3, 0.14 x 104 and 200 x 10-3 and 0.12 x 104 and 176.5 x 10-3. The mean percentage accuracies were 99.9 +/- 1.75, 99.95 +/- 0.71. The results obtained either in pure form or in pharmaceutical formulations are accurate and precise. The nature of the dye was discussed and the structure of a mono azo dye was suggested