Study on the charge-transfer reaction between 7,7,8,8-tetracyanoquinodimethane and drugs.

The charge-transfer (CT) reaction between 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a pi-electron acceptor and cinnarizine, analgin, norfloxacin as electron donors have been studied by spectrophotometric method. The charge transfer complexes between TCNQ and these drugs have stable blue color, therefore a simple, rapid, accurate and sensitive method for determination of these drugs has been developed. The optimization of the experimental conditions is described. Beer's law is obeyed in the ranges 2-18, 2-18 and 4-32 microg/ml for cinnarizine, analgin and norfloxacin, respectively. The apparent molar absorptivity of CT complexes at 743 nm is 1.58x10(4), 1.71x10(4) and 8.91x10(3) l/mol per cm, respectively. The composition of all these CT complexes are found to be 1:1 by different methods. The relative SDs are less than 3% (n = 10). The proposed method has been applied to the determination of these drugs in their each pharmaceutical dosage forms with satisfactory results.