Du Li-ming, Li Li, Wu Hao
Center of Analysis and Test, Shanxi Normal University, Linfen 041004, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2007 Feb;27(2):364-6.
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)%.
采用分光光度法研究了作为π电子受体的7,7,8,8-四氰基对苯二醌二甲烷（TCNQ）与作为电子供体的可待因之间的电荷转移反应。发现TCNQ与可待因在丙酮中反应生成稳定的电荷转移络合物。同时，所研究的药物发生了相当大的红移（从216 nm至843 nm）。详细研究了电荷转移反应的影响因素以及测定可待因的最佳条件。因此，建立了一种简单、快速、准确且选择性良好的可待因测定方法。结果表明，可待因在0.1 - 1.6 μg·mL⁻¹范围内符合比尔定律。该络合物在843 nm处的表观摩尔吸光系数为1.7×10⁴ L·mol⁻¹·cm⁻¹。此外，研究了缔合常数和标准自由能变化，并初步探讨了电荷转移反应的机理。该方法已成功应用于药物制剂中可待因的测定。回收率为（98.94±0.96）%至（99.12±1.21）%。
