Abstract：The charge-transfer reaction of 7,7,8,8-tetracyano-quinodimethane(TCNQ)as a π-electron acceptors 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 μg·mL-1 for codeine. The apparent molar absorptivity of the complex at 843 nm is 1.7×104 L·mol-1·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)%.
[1] Hanaee J. Pharm. Acta Helvet., 1997, 72(4): 239. [2] Ramos M N, Molina D A, Navalon A, et al. J. Pharm. Biomed. Anal., 2000, 23(5): 837. [3] XU Qing-qin, DU Li-ming, CAO Xi-min(许庆琴，杜黎明，曹玺珉). Chin. J. Anal. Chem.(分析化学)，2003，31(8): 961. [4] Svensson J O, Yue O Y, Sawe J. J. Chromatogr. B, 1995, 674(1): 49. [5] Ragonese R, Mulholand. M, Kalman J. J. Chromatogr. A, 2000, 870(1-2): 45. [6] Molden E, Helen B G, Christensen H, et al. J. Pharm. Biomed. Anal., 2003, 33(2): 275. [7] Tagliao F, Smith F P, Turrina S, et al. J. Chromatogr. A, 1999, 735(1-2): 227. [8] Buuckenmaie S M C, Mccalley D V, Euerby M R. J. Chromatogr. A, 2004, 1026(1-2): 251. [9] YU Zhao-lou, CHEN Yi, CHANG Li-wen(余兆楼，陈 义，常理文). Chin. J. Anal. Chem.(分析化学), 1996, 24(4): 444. [10] YANG Cai-qin, DING Li-yu, LIU Wei-na, et al(杨彩琴，丁里玉，刘伟娜，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 1999, 19(2): 236. [11] Editoral Committee of the Pharmacopoeia of the People’s Republic of China(中华人民共和国卫生部国家药典委员会编). The Pharmacopoeia of the People’s Republic of China (PartⅡ) (中华人民共和国药典二部). Beijing: Chemical Industry Press(北京: 化学工业出版社)，2005. 870. [12] Foster R. Organic Charge-Transfer Complexes. London: Academic Press, 1969. 51, 387.
