Spectrophotometric determination of tetracycline by coupling with diazonium salts

ABSTRACT

A simple, rapid and accurate spectrophotometric method for the determination of tetracycline [TC] in aqueous solution was developed. The method was based on the coupling reaction between TC and diazontized p-nitroaniline [I], sulfanilic acid [II], and sulfanilamide [III] to form stable dyes. The variables affecting development of the color were investigated and the conditions optimized. The Beer's law was obeyed for up to 19, 70 and 40 ppm on using I, II and III, respectively. Their absorptivities [L mol-1 cm-1] and Sandell's sensitivities [mug cm-2] are 125 x 104, 4.0 x 104 and 0.13 x 104 and 38.4 x 10-3, 175 x 10-3 and 148.0 x 10-3, respectively, for I, II and III. The recoveries of the method for I, II and III were 100.07 +/- 0.24, 98.97 +/- 0.64 and 99.95 +/- 0.45 for TC, while the recoveries for the dosage forms were 100.2 +/- 0.277, 100.0075 +/- 0.227 and 99.075 +/- 0.297, respectively. The proposed methods were applied for the quantitation of TC in pharmaceutical preparations with high precision and accuracy. The nature of the dye formation and the structure of mono azo dye was suggested