Pharmaceutica Analytica Acta

Abstract

Spectrophotometric Studies of Lamotrigine Charge Transfer Complexes:Synthesis and Characterization

Najma Sultana, Saeed Arayne M and Saeeda Nadir Ali

Charge transfer complexes of lamotrigine with 7,7,8,8-tetracyanoquinodimethane, bromothymol blue and picric acid have been investigated by spectrophotometric method. Optimum conditions for the reactions and validation data is reported. Resulting complexes absorb at 394, 404 and 374 nm in the Beer’s law range of 0.15-15, 0.25- 10 and 3.0-18 µg mL^-1 with correlation coefficient greater than 0.998 in each case and detection limits 45, 47 and 57 µg mL^-1 respectively. The data are discussed in terms of molar absorptivity, association constant and Gibb’s free energy. Spectral characteristics including oscillator’s strength, dipole moment, ionization potential, energy of complexes and resonance energy have been determined. Benesi-Hildebrand plots for each complex have been constructed. The proposed method was applied successfully for the determination of lamotrigine in pharmaceutical formulations. Satisfactory recovery values suggested that the method is reliable for the determination of lamotrigine in pharmaceutical formulations without interference of excipients. Further, solid charge transfer complexes were synthesized and characterized by IR and ¹H NMR spectroscopy.