Adsorptive Stripping Voltammetric Determination of Azithromycin at a Glassy Carbon Electrode Modified by Electrochemical Oxidation

The adsorptive and electrochemical behaviors of azithromycin were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to +1.0 V. The resulting electrode showed good activity to improve the electrochemical response of the drug. An adsorptive stripping voltammetric method for the determination of azithromycin at an electrochemically activated glassy carbon electrode has been developed. Azithromycin was accumulated in phosphate buffer, pH 6, at a potential of +0.3 V (vs. Ag/AgCl electrode) for a certain time, and then determined by differential pulse voltammetry. The oxidative peak current at +0.82 V, at a scan rate of 20 mV s-1, was a linear function of the concentration in the ranges of 0.25 - 2 μg mL-1 and 1 - 10 μg mL-1 using a 240 or 60 s preconcentration time, respectively. Application of the method to the determination of azithromycin in pharmaceuticals resulted in an acceptable deviation from the stated concentration. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The peak current was linear with the drug concentration in the range of 0.5–3.5 μg per mL urine. The detection limit was 0.2 μg mL-1 urine. The recovery levels of the method reached 96.3%.