High-performance liquid chromatography with resonance Rayleigh scattering detection for determining four tetracycline antibiotics

A rapid high-performance liquid chromatography (HPLC) technique incorporating resonance Rayleigh scattering (RRS) detection was developed for the determination of tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC) and doxycycline (DOTC). This method was based on the weak intensity of the RRS of the TCs and its enhancement with the addition of titan yellow (TY) and CuSO4 in a pH 3.5 Britton-Robinson buffer solution. The RRS signal was detected at lambda(ex) = lambda(em) = 450 nm. The chromatographic separation used (25 : 75, v/v) methanol-phosphate buffer (pH 3) as the mobile phase. The analytical technique was validated for intra-and inter-day variations and the detection limits of the assay were 0.668 mu g mL(-1) for TC, 0.342 mu g mL(-1) for OTC, 0.480 mu g mL(-1) for CTC and 0.132 mu g mL(-1) for DOTC at a signal-to-noise ratifo of 3.0. The conditions for separation and detection were optimized and the reasons for the RRS enhancement were evaluated. The developed method was validated for the analysis of TCs in water samples. The recoveries were acceptable (ranging from 97.4-102.4%).