美洛昔康的吸附伏安特性

ADSORPTIVE VOLTAMMETRIC BEHAVIOR OF MELOXICAM

目的 研究美洛昔康 (meloxicam ,简称MLX)的电化学行为和电极反应机理 ,拟定了测定MLX的吸附伏安法。方法 用单扫示波极谱法、循环伏安法和脉冲极谱法等多种技术进行研究。结果 在HAc NaAc(pH 4 76 )底液中 ,MLX在汞电极上有一线性扫描还原峰 ,峰电位Ep=- 1 19V(vsAg/AgCl) ,该峰有明显的吸附性。吸附粒子为MLX中性分子 ,测得MLX在汞电极上的饱和吸附量为 1 5 3× 10 -10 mol·cm-2 ,每个MLX分子所占电极面积为 1 0 8nm2 ,MLX在悬汞电极上的吸附符合Frumkin等温式。测得吸附系数 β =1 6 5× 10 6,电子转移数 (n)为 2 ,不可逆吸附的电子转移系数 (α)为 0 84,表面电极反应的速率常数ks=0 19·s-1。建立了吸附伏安法测定MLX的最佳条件 ,检出限为 1 0× 10 -9mol·L-1。

AIM To study the electrochemical behavior and reduction mechanism of meloxicam (MLX) in acetate buffer solution. A new method for the determination of MLX was established by adsorptive stripping voltammetry. METHODS Linear sweep polarography, cyclic voltammetry and pulse polarography were used in the present research. RESULTS In a supporting electrolyte containing HAc NaAc (pH 4 76), a reduction peak of MLX was observed by linear sweep voltammetry at Hg electrode. The peak showed a potential of -1 19 V ( vs Ag/AgCl) and adsorptive characteristics. The adsorbed species is most probably the neutral molecule of MLX. The saturated adsorption of MLX at Hg electrode is 1 53×10 -10 mol·cm -2 and every MLX molecule occupied an area of 1 08 nm 2. On the surface of the hanging mercury drop electrode, the adsorption of MLX obeys Frumkin adsorption isotherm. The adsorption coefficient (β) is 1 65×10 6. The number of electrons transferred per MLX molecule ( n ) is 2 and the transfer coefficient (α) of the irreversible adsorptive system of MLX is 0 84. The rate constant of surface electrode reaction ( k s) is 0 19·s -1 . The mechanism of electrochemical reduction of MLX at Hg electrode has been explored. The detection limit of the adsorptive stripping voltammetry of MLX is 1 0×10 -9 mol·L -1 under optimized conditions. CONCLUSION This indicates an irreversible process with adsorption.