A rapid evaluation of tetracycline and its dehydration products by UV derivative spectrophotometry.

This paper described a rapid ultraviolet spectrophotometric assay for simultaneous determination of tetracyclines (TC + ETC) and their anhydroderivatives (ATC + EATC), by using third- or fourth-derivative spectra recorded on samples in ethanol or dioxane. The analytical procedures are based on linear relationships between specific peak-trough values and the relative concentrations of tetracycline and of ATC-EATC, in mixtures containing TC, ATC and EATC. The toxic EATC can be estimated about half of the anhydrotetracyclines concentration values. The determination limit of anhydroderivatives is 0.05%. A simple purity test of the antibiotic is also reported. Accuracy, precision and linearity are discussed. The method is particularly applicable to routine analysis of products containing TC, in bulk and in some pharmaceutical formulations.