Phosphorimetric determination of indomethacin in pharmaceutical formulations

A simple, rapid and sensitive method for the determination of indomethacin was developed based on solid-surface room-temperature phosphorimetry. Phosphorescence emission was induced by the indomethacin hydrolysis reaction in a basic medium. Chromatography paper treated for background reduction was employed as a solid substrate. The use of four heavy-atom salts and sodium dodecyl sulfate was optimized to estimate an absolute limit of detection at the subnanogram level. A calibration curve with a linear dynamic range extending over two orders of magnitude (3.0 x 10(-7)-1.0 x 10(-4) mol dm-3) was obtained. The recovery of the method (98.4 +/- 6.8%) was tested using commercial formulations containing indomethacin as the only anti-inflammatory agent.