Flow injection analysis of tetracycline in pharmaceutical formulation with pulsed amperometric detection

A flow injection method with pulsed amperometric detection (PAD) was proposed for the determination of tetracycline in pharmaceutical formulations. Tetracycline was also studied at a gold rotating disk electrode with cyclic voltammetry as a function of the pH of supporting electrolyte solution. The well-defined cyclic voltammogram, providing the highest peak current at 1.15 V versus Ag/AgCl, was obtained when using potassium dihydrogen phosphate solution at pH 2. The optimized pulsed amperometric detection conditions were 1150 mV (versus Ag/AgCl) detection potential (E-det) for 600 ms (500 ms delay time and 100 ms integration time), 1600 mV (versus Ag/AgCl) oxidation potential (E-oxd) for 150 ms oxidation time (t(oxd)) and 100 mV (versus Ag/AgCl reference electrode) reduction potential (E-red) for 300 ms reactivation time (t(red)). The optimized PAD waveform was applied to the determination of tetracycline standard solution and tetracycline in pharmaceutical formulations. The sensitivity of this method was found to be 13.7 muA/mM. The determination of tetracycline in commercially available tablet dosage forms by the proposed method (254.3 +/- 9.3 mg per capsule) was comparable to those labeled (250 mg per capsule). (C) 2003 Elsevier B.V. All rights reserved.