Adsorptive stripping voltammetric determination of erythromycin at a pretreated glassy carbon electrode

The voltammetric behavior of the antibiotic erythromycin and its determination was described. Erythromycin was found to give one oxidative peak by cyclic voltammetry at a glassy carbon electrode which was electrochemically treated in 0.025 mol l(-1) NH3-NH4Cl (pH 9.0) solution for 6 min. The reverse cyclic voltammograms did not show any reductive peaks. An adsorptive stripping voltammetric method for the determination of the antibiotic erythromycin at an electrochemically pretreated glassy carbon electrode has been developed. Erythromycin was accumulated in NH3-NH4Cl (pH 9.0) medium at the potential of +0.2 V (vs. Ag/AgCl electrode) for a certain time and then determined by second differential anodic stripping voltammetry. The second-order differential peak current (e ") at +0.86 V, at a scan rate of 445 mV s(-1), was a linear function of concentration of erythromycin in the range 2.5 x 10(-8) similar to 3.5 x 10(-7) mol l(-1) (90 s preconcentration) and 1.2 x 10(-8) similar to 2.5 x 10(-7) mol l(-1) (120 s preconcentration), and the detection limit was 5.0 x 10(-9) mol l(-1) (4 min preconcentration). The method has been applied to the determination of erythromycin in commercial tablets and spiked urine samples with satisfactory results. The relative standard deviation (n = 5) was less than 4.5%. (C) 2000 Elsevier Science B.V. All rights reserved.