SQUARE-WAVE AND SQUARE-WAVE ADSORPTIVE STRIPPING VOLTAMMETRIC COMPARISON OF THE ANTIINFLAMMATORY DRUGS PIROXICAM AND TENOXICAM

Two nonsteroid anti-inflammatory drugs, Piroxicam and Tenoxicam, are shown to be strongly adsorbed on mercury electrodes. Using this phenomenon to accumulate these compounds at the static mercury-drop electrode prior to square-wave voltammetric measurement, sub-nanomole sensitivities are readily achieved. A preconcentration potential of -0.6 V vs. Ag/AgCl/KCl(s) was used for both drugs. The adsorptive stripping response was evaluated with respect to accumulation time and potential, analyte concentration, and electrolyte nature and concentration. Ascorbic acid up to 1×10-4 M has no effect on the Piroxicam peak, but results in enhanced response for the Tenoxicam adsorptive stripping peak. Studies were performed at pH 4.0 and 2.0 for the two drugs; at these values two and four electrons are transferred, respectively. The detection limit was 7×10-10 M for Piroxicam and 1×10-10 M for Tenoxicam, the latter being even more sensitive (5×10-11 M) in the presence of ascorbic acid. Applicability of square wave voltammetry to urine samples was demonstrated. The detection limit is 5×10-8 M and 5×10-9 M (in presence of 1×10-5 M ascorbic acid) for Piroxicam and Tenoxicam, respectively, in urine samples diluted ten-fold with the supporting electrolyte. © 1990, The Japan Society for Analytical Chemistry. All rights reserved.