Flow-Injection Spectrophotometric and LC Determination of Doxycycline, Oxytetracycline and Chlortetracycline in Biological Fluids and Pharmaceutical Preparations

Original Paper

Abstract

Spectrophotometric and chromatographic methods have been developed for the determination of doxycycline (DC), oxytetracycline (OTC) and chlortetracycline (CTC) in biological fluids and pharmaceutical preparations. Zirconyl chloride is proposed as a reagent for the spectrophotometric determination of the antibiotics under investigation. The reagent forms yellow 1:1 complexes with the drugs in acidic medium. The absorption maximum of the formed complexes was at 390 nm. The method has been adapted for flow injection analysis and successfully used for the analysis of these compounds in human blood plasma, urine and pharmaceutical preparations. For the chromatographic method, a reversed-phase C18 column with a mobile phase composed of 29.5% of acetonitrile and 70% of 0.1M oxalate buffer adjusted to pH 2.5 with 0.5 M sodium hydroxide and 0.5% triethyl amine was used. The proposed methods were successfully applied to the determination of the antibiotics under investigation in pharmaceutical preparations and biological fluids. The common excipients and additives did not interfere with their determinations. Extraction recoveries from synthetic mixtures were close to 100% at all concentrations, while extraction recoveries from spiked human plasma and urine samples varied between 93.1 and 97.7% and an RSD of less than 5.3%.