Sensitive and selective electrochemical determination of doxycycline in pharmaceutical formulations using poly(dipicrylamine) modified glassy carbon electrode

A voltammetric sensor was developed by electropolymerization of 2, 4, 6–2′, 4′, 6′ hexanitrodiphenylamine (dipicrylamine) on a glassy carbon electrode. Poly(dipicrylamine) modified glassy carbon electrode (poly(DPA)/GCE) was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of doxycycline (DOX) in phosphate buffer solution (PBS) of pH 8.0 was investigated at the surface of poly(DPA)/GCE. Compared with glassy carbon electrode, doxycycline showed two well-resolved irreversible oxidative peaks (Ipa1 and Ipa2) at the poly(DPA)/GCE. Under optimized square wave voltammetric conditions, peaks current at poly(DPA)/GCE showed good linearity with the concentration of DOX in the range of 5–200 μM with a detection limit (LOD) of 0.15 μM and 0.13 μM for Ipa1 and Ipa2, respectively. Besides its high stability and reproducibility, the response of DOX at poly(DPA)/GCE was not affected in the presence of glucose, ascorbic acid and chloroquine phosphate. The developed sensor has been successfully applied for the detection of DOX in four brands of pharmaceutical samples and the detected amount of DOX in each brand was above 90.13% of the labeled value.