Anodic Oxidation of Etodolac and its Linear Sweep, Square Wave and Differential Pulse Voltammetric Determination in Pharmaceuticals

Abstract

In this study, simple, fast and reliable cyclic voltammetry, linear sweep voltammetry, square wave voltammetry and differential pulse voltammetry methods were developed and validated for determination of etodolac in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of etodolac at platinum electrode in acetonitrile solution containing 0.1 M lithium perchlorate. The well-defined oxidation peak was observed at 1.03 V. The calibration curves were linear for etodolac at the concentration range of 2.5-50 μg/ml for linear sweep, square wave and differential pulse voltammetry methods, respectively. Intra- and inter-day precision values for etodolac were less than 4.69, and accuracy (relative error) was better than 2.00%. The mean recovery of etodolac was 100.6% for pharmaceutical preparations. No interference was found from three tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Etol, Tadolak and Etodin tablets as pharmaceutical preparation.

Keywords: Etodolac; cyclic voltammetry; differential pulse voltammetry; linear sweep voltammetry; square wave voltammetry.

Fig. 1

Chemical structure of etodolac.

Fig. 2

Cyclic voltammogram. Cyclic voltammogram for the oxidation of 30 μg/ml etodolac in acetonitrile containing 0.1 LiClO4 at Pt disk electrode, scan rate: 0.1 V/s.

Fig. 3

Linear sweep voltammograms. Linear sweep voltammograms for the oxidation of 30 μg/ml etodolac in acetonitrile containing 0.1 M LiClO4 as a function of scan rate.

Fig. 4

Dependence of peak current on the scan rate (30 μg/ml). a and b are different scan rates and c is logarithmic scan rate.

Fig. 5

Dependence of anodic peak potentials of voltammetric peak for the oxidation of 30 μg/ml etodolac on the scan rate.

Fig. 6

Linear sweep voltammograms for different concentrations of etodolac. Linear sweep voltammograms for different concentrations of etodolac in acetonitrile solution containing 0.1 M LiCIO₄ (2.5, 5, 7.5, 10, 15, 20, 25, 30, 40 and 50 μg/ml).

Fig. 7

Square wave voltammograms for different concentrations of etodolac. Square wave voltammograms for different concentrations of etodolac in acetonitrile solution containing 0.1 M LiCIO₄ (2.5, 5, 7.5, 10, 15, 20, 25, 30, 40 and 50 μg/ml).

Fig. 8

Differential pulse voltammograms for different concentrations of etodolac. Differential pulse voltammograms for different concentrations of etodolac in acetonitrile solution containing 0.1 M LiCIO₄ (2.5, 5, 7.5, 10, 15, 20, 25, 30, 40 and 50 μg/ml).