荷移分光光度法测定可待因

采用分光光度法研究了电子受体7,7,8,8-四氰基对苯醌(TCNQ)与电子供体可待因的荷移反应, 发现TCNQ与可待因在丙酮介质中易发生荷移反应，并生成稳定的络合物，药物的最大的吸收峰由紫外区移至近红外区。据此建立了一种测定药物制剂中可待因含量的高选择性的荷移分光光度法，在最佳条件下，可待因浓度在0.1～1.6 μg·mL-1范围内符合朗伯-比尔定律，在最大吸收波长845 nm处，表观摩尔吸光系数为1.7×104 L·mol-1·cm-1。文章还研究了缔合常数和自由能变化并探讨了荷移反应的机理。该方法已用于片剂中可待因含量的测定，其回收率为(98.94±0.96)%～(99.12±1.21)%。

Spectrophotometric Determination of Codeine Through Charge-Transfer Reaction

The charge-transfer reaction of 7,7,8,8-tetracyano-quinodimethane (TCNQ) as a pi-electron acceptor with codeine as electron donors was investigated by spectrophotometry. TCNQ was found to react with codeine to produce stable charge-transfer complexes in acetone. Meanwhile, the studied drugs suffer a considerable bathochromic shift (from 216 to 843 nm). The influential factor of charge-transfer reaction and the optimum conditions for the determination of codeine were investigated in detail. Therefore a simple, rapid and accurate method with a good selectivity for the determination of codeine has been developed. The results show that Beer's law is obeyed in the ranges 0.1-1.6 microg x mL(-1) for codeine. The apparent molar absorptivity of the complex at 843 nm is 1.7 x 10(4) L x mol(-1) x cm(-1). Furthermore, the association constants and standard free energy changes were studied, and the mechanism of charge-transfer reaction was explored elementarily. The proposed method has been applied successfully to the determination of codeine in pharmaceutical preparations. The recoveries are from (98.94+/-0.96)% to (99.12+/-1.21)%.