INTERACTION OF TETRACYCLINE HYDROCHLORIDE WITH IRON: KINETIC SPECTROPHOTOMETRIC AND CONDUCTOMETRIC INVESTIGATIONS

The interaction of the antibiotic, tetracycline hydrochloride (TC.HCl) has been investigated employing three simple spectrophotometric and conductometric methods. In methods (A and B), a kinetic spectrophotometric procedure based on the oxidation of (TC.HCl) by Fe³⁺ ion in the presence of 1, 10 – Phenanthroline (o-phen) (A) and 2, 2′- Bipyridyl (bipy) (B) was developed. The formation of the ferroin complexes applying both methods was carefully optimized and their absorbance was measured at 509 and 520 nm respectively. The initial rate, rate-constant, fixed-time and fixed-concentration methods were adopted for constructing the calibration curves. In method (C), conductometric titration of (TC. HCl) with K₃Fe(CN)₆ was investigated. Mole ratio – molar conductance plots showed that a 1:1complex was formed. Methods (A and B) allowed the determination of (TC. HCl) in the range of 1.00–5.00 and1.25–10.00 µg/ml respectively, while method (C) was applicable over a wider concentration range0.2-20 mg/ml. The proposed procedures were successfully applied to determine the drug as per se and in its commercial dosage forms with no interference from adjuvants commonly co-formulated with the drug. Inter- and intra-day precision, limits of detection and quantification, and relative standard deviation have been assessed following ICH guidelines for evaluation of analytical procedures, and the results obtained were satisfactory.