An environmentally reliable analytical methodology was developed for direct quantification of tetracycline (TC)
and oxytetracycline (OTC) using continuous flow injection analysis with spectrophotometric detection. The
method is based on the diazo coupling reaction between the tetracyclines and diazotized sulfanilic acid in a
basic medium, resulting in the formation of an intense orange azo compound that presents maximum absorption
at 434 nm. Experimental design was used to optimize the analytical conditions. The proposed technique was validated
over the concentration range of 1 to 40 μg mL−1
, and was successfully applied to samples of commercial
veterinary pharmaceuticals. The detection (LOD) and quantification (LOQ) limits were 0.40 and 1.35 μg mL−1
, respectively.
The samples were also analyzed by an HPLC method, and the results showed agreement with the proposed
technique. The new flow injection method can be immediately used for quality control purposes in the
pharmaceutical industry, facilitating monitoring in real time during the production processes of tetracycline formulations
for veterinary use.