Determination of doxycycline in bovine tissues and body fluids by high-performance liquid chromatography using photodiode array ultraviolet-visible detection.

A sensitive and selective high-performance liquid chromatographic assay was developed to quantitate doxycycline concentrations in bovine tissues and body fluids. The method involved sonication of doxycycline-spiked minced tissues with appropriate solutions to extract tissue-bound drug. Acetonitrile:85% phosphoric acid:water (20:2:78) was added to doxycycline-spiked serum or urine. The mixtures were ultrafiltered through 30,000 or 10,000 Da molecular weight cutoff microseparation systems. Separation was obtained by a reversed-phase microbore column. Absorbance of the column effluent was measured by an ultraviolet-visible photodiode array detector scanning from 235 to 380 nm and/or a photometric detector operated at 268 or 345 nm. Chromatographic peak homogeneity was evaluated by three-dimensional spectrochromatograms, contour maps, and absorbance ratios.