Detection of tetracycline and oxytetracycline residues in pig and calf hair by ultra-high-performance liquid chromatography tandem mass spectrometry

An ultra-high-performance liquid chromatography tandem mass spectrometry method to detect residues of tetracycline (TC), epi-tetracycline (eTC) and oxytetracycline (OTC) in animal hair was developed. Hair samples were washed with water, extracted with NH₄OH 0.1 M, purified by SPE-C₁₈ cartridge and analyzed by tandem mass spectrometry (ESI⁺, MRM mode) with satisfactory results. For the first time, accumulation of TC, eTC and OTC was confirmed in livestock hairs after a therapeutic treatment with TC and OTC, respectively. Administered drug residues were detectable in hair samples up to 2 months after the last treatment, providing a retrospective evidence of TC and OTC administration. Hair analysis seems to offer a wider window of detection than edible tissues.