[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)%.
Du
Li-ming
LM
Center of Analysis and Test, Shanxi Normal University, Linfen 041004, China. lmd@dns.sxnu.edu.cn
Li
Li
L
Wu
Hao
H
D003061:Codeine / Q000032:analysis* / Q000737:chemistry; D004583:Electrons; D015394:Molecular Structure; D013053:Spectrophotometry / Q000379:methods*
D003061:Codeine