Flow-injection spectrophotometric determination of tetracycline and doxycycline in pharmaceutical formulations using chloramine-T as oxidizing agent

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A flow-injection (FI) spectrophotometric procedure is proposed for tetracycline (TC) and doxycycline (DXC) determination in pharmaceuticals. The method is based on the reaction of oxidation of these drugs by chloramine-T in alkaline medium producing red color products (lambda(max) = 535 and 525 nm). Beer's law is obeyed in the concentration range from 6.62 x 10(-5) to 7.72 x 10(-4) mol L(-1) and 5.37 x 10(-5) to 7.16 x 10(-4) mol L(-1) for TC and DXC, respectively. The analytical frequency was 50 h(-1) and 45 h(-1) for TC and DXC, respectively. The results obtained by the proposed method were in good agreement with those obtained by the official method at 95% confidence level.