Improvement of the etodolac purity test by reversed phase high-performance liquid chromatography

The resolution of etodolac by reversed phase HPLC applied in the European Pharmacopeia (EP) was found to be greatly affected by using methanol as the injection solvent and the system of gradient elution, which leads to peak broadening as well as poor separation of etodolac from the impurities such as 2-(7-ethylindol-3-yl) ethanol respectively. Changing the type of injection solvent (methanol) by the mobile phase, which is a mixture of methanol, buffer (KH2PO4, PH = 7), and acetonitril as well as monitoring the gradient program (increasing the polarity) leads to enhance the selectivity and efficiency of the analysis of etodolac by eliminating the peak broadening and markedly improving the separation of etodolac from 2-(7-ethylindol-3-yl) ethanol. The method was validated by parameters such as selectivity, repeatability, and intermediate precision.