Determination and antioxidant activity evaluation of etodolac, an anti-inflammatory drug, by sequential injection analysis

A robust, accurate and sensitive automated procedure for the determination of etodolac, an anti-inflammatory drug, in pharmaceutical formulas by sequential injection analysis, is reported. The same system was also applied to evaluate the antioxidant activity of the drug expressed as Trolox equivalent antioxidant capacity (TEAC). The methodology is based on measuring at 734 nm the decay of absorbance of a solution with the radical 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) after its reduction by etodolac. Optimum ABTS+-etodolac reaction was achieved with 0.329 mL of sample and 0.205 mL of ABTS+ solution. Etodolac was determined at concentrations up to 4.5 × 10−5 mol L−1. A solution detection limit of 6.6 × 10−6 mol L−1 was obtained under the optimised experimental conditions. A relative standard deviation (n = 10) lower than 4.7% with a sample throughput of more than 21 samples/h was obtained. No interference from excipients was observed. The developed methodology was applied in the analysis of pharmaceutical preparations and the obtained results were in good agreement with those furnished by the reference procedure with relative deviations lower than 1.4%.