TLC analysis of inhibitors of cyclooxygenase and videodensitometric determination of meloxicam and tiaprofenic acid

The cyclooxygenase inhibitors lornoxicam, meloxicam, piroxicam, and tiaprofenic acid have been separated by normal and reversed-phase TLC by ascending and horizontal development with suitable mobile phases on silica gel and silanized gel. The substances were identified by UV illumination at lambda = 254 nm and by use of dyeing reagents. Meloxicam and tiaprofenic acid were determined in pharmaceutical preparations by videodensitometric TLC on silica gel and ascending development with toluene-acetic acid-methanol, 11 + 1 + 0.5 (v/v), as mobile phase. The range of linearity was 0.5-5.0 mug per spot for both drugs. The method was applied satisfactorily to pharmaceutical preparations. Results from quantitative analysis were assessed statistically by determination of the correlation coefficient for the calibration equation obtained from the calibration procedure. The RSD for quantitation of meloxicam and tiaprofenic acid were 5.8 and 5.9%, respectively.