Spectrophotometric and spectroscopic studies on charge transfer complexes of the antifungal drug clotrimazole

Clotrimazole (CLZ) is an imidazole derivative that is therapeutically used as an antifungal drug. The routine control analysis of CLZ requires rapid, reliable, accurate and precise methods for the quantification of the drug in its pharmaceutical formulations. Spectrophotometric methods are presented for the determination of the antifungal agent that are based on the charge transfer complexation reaction of CLZ with the π-acceptors tetracyanoethylene (TCE) and 7,7′,8,8′-tetracyanoquinodimethane (TCNQ). The formation of coloured complexes was quantitated at 396 nm and 842 nm for CLZ-TCE and CLZ-TCNQ, respectively, which enabled the development of simple and accurate spectrophotometric methods for the analysis of CLZ in pure drug substances and its pharmaceutical products. Under the optimum reaction conditions, linear relationships with appreciable correlation coefficients (0.9985-0.9994) were found between the absorbance at the relevant maxima and the concentrations of CLZ in the range of 5.00-35.00 μg mL−1 for CLZ-TCE and 1.00-25.00 μg mL−1 for CLZ-TCNQ. The molar absorptivities and Sandell's sensitivity values were also statistically evaluated. The proposed methods were successfully applied to analyze CLZ in topical creams and sterile solutions with mean recovery percentages in the range of 99.60-100.20%, which indicated no interference from the inactive ingredients. Furthermore, the charge transfer complexes of CLZ were also characterized by FT-IR spectroscopy.