Sensitive determination of indomethacin in pharmaceuticals and urine by sequential injection analysis and optosensing.

A selective and sensitive method based on coupling of sequential injection analysis (SIA) and optosensing was developed and applied to the determination of indomethacin in pharmaceutical and urinary samples. After alkaline hydrolysis, the fluorescent product generated from indomethacin is inserted in the flow system, transitorily retained on an active solid support (Sephadex QAE A-25) filling the flowcell, and monitored at 283/371 nm (lamda ex / lamda em). The system was calibrated for two sample volumes, 100 and 1000 microL. It showed a linear dynamic range of 0.5-6.5 ng/mL, with an LOD of 0.15 ng/mL and an RSD of 3.9% (n=10) when the highest sample volume was used. The proposed fluorometric SIA optosensor was applied to the determination of indomethacin in both pharmaceuticals and urine samples, and satisfactory results were obtained.