The use of rank annihilation factor analysis (RAFA) for spectrophotometric studies of electron donor–acceptor complex formation equilibria between lidocaine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone(DDQ) in chloroform, dichloromethane (DCM) and 1,2-dichloroethane (DCE) solutions at 25 ◦C has been reported. RAFA is proposed as an efficient chemometric algorithm for completely analysis of equilibrium systems by spectrophotometric mole ratio method. The RAFA is based on the principle that the rank of two-way bilinear matrix of pure compound is one. The proposed method makes it possible to obtain the stability equilibrium constants, pure absorption spectra and species concentration profiles in several electron donor–acceptor complex formation systems with sever spectral overlapping. The stoichiometry of the complex was found to be 1:1 by job‘s method of continuos variation. RAFA method was used for complete resolution of the measured spectrophotometric data. Stability of the resulting complex in the three solvents was also found to vary in the order of 1,2-DCE >DCM> CHCl3
