Adsorptive stripping voltammetric determination of Tetracycline in pharmaceutical capsule formulation using Poly(Malachite green) modified glassy carbon electrode

A selective and sensitive electrochemical method based on glassy carbon electrode modified with poly(malachite green) was developed for determination of tetracycline in pharmaceutical capsule formulation. Cyclic voltammetry and electrochemical impedance spectroscopy using [Fe(CN)(6)](3-/4-) as a probe were used to characterize the potentiodynamiclly deposited poly(malachite green) on the surface of glassy carbon electrode. In contrast to the unmodified glassy carbon electrode, the fabricated poly(malachite green) modified glassy carbon electrode showed catalytic property towards two steps irreversible oxidation of tetracycline. Better correlation of the oxidative peak current with the scan rate than with the square root of scan rate supported by slope of 0.60 for log(current) versus log(scan rate) indicated that the oxidation reaction of tetracycline at the modified electrode was predominantly controlled by electron exchange step at the solution polymer interface. Under optimized solution pH, and accumulation parameters, the square wave adsorptive anodic striping peak current response of the modified electrode showed linear dependence on concentration of tetracycline in the range 5-100 mu M with determination coefficient, method detection limit, and quantification limit of 0.99588, 1.6 mu M, and 5.3 mu M, respectively. The tetracycline content of a capsule sample claimed to have 250 mg/capsule was found to be 250.53 mg/capsule with 0.21% deviation. Excellent spike recovery result of 99.80%, and 98.49-99.78% recovery of tetracycline in capsule sample in the presence of 50-200% of UA, AA, and ampicillin validated the applicability of the method for determination of tetracycline in real samples with complex matrix like capsule formulations.