Analysis of Certain Tetracyclines and Oxytetracyclines through Charge Transfer Complexation

Problem statement: Several studies were carried out to develop and validate a simple, rapid and accurate spectrophotometric method for the analysis of tetracycline (TC) and oxytetracycline (OTC) in the pure form and in pharmaceutical dosage forms, despite the varieties of these analytical techniques, the literature revealed that no spectrophotometric method for determination of tetracycline and oxytetracycline using charge transfer complexation with chloranilic acid has been reported. Approach: In the present study, a new and simple spectrophotometric method is described for the determinations of tetracycline (TC) and oxytetracycline (OTC), the method is based on the molecular interaction between the tetracyclines and Chloranilic Acid (CA), to form a charge-transfer complex in which the drugs acts as n-donor and chloranilic acid as π-acceptor in acetonitrile. The spectra, various experimental parameters for the reaction, the stability of the complex and the validty of the method were investigated. Results: The formed complex was found to absorb maximally at 540nm, Beer’s law is obeyed in the concentration ranges 2.5-30 μg mL^-1 and 5.0-40 μg mL^-1 for TC and OTC, respectively. The limits of detection (S/N = 3) were 0.40 μg mL^-1 for tetracycline and 0.50 μg mL^-1 for oxytetracycline. The molar ratio was found to be approximately 1:1, confirming that one molecule of tetracycline or oxytetracycline combines with one molecule of chloranilic acid. Conclusions and Recommendations: The proposed method was found to be rapid, accurate and sensitive and may be applied for estimation of named drugs in pharmaceutical dosage forms without interferences from the common additives encountered. Percentage recoveries ranged from 99.17%±0.95-100.38%±0.82. From the statistical analysis of the obtained results one can conclude that no significant difference between the proposed method and other official methods as evident from the t-test and variance ratio. These findings recommend the utility of the proposed method in the quality control analysis of TC and OTC in the pure form and pharmaceutical dosage forms.