Abstract
Ion suppression in analysis of tetracyclines in feed was studied. The conventional analysis consists of a liquid extraction followed by a clean-up step using solid phase extraction (SPE) technique and analysis of the tetracyclines by liquid chromatography and mass spectrometric detection. Various strategies for extraction and cleanup were tested in the present work, and the effectiveness to decrease the ion suppression on the MS/MS signals was evaluated. Four sample treatment methods were tested with five different feed samples. Extraction solvents tested were McIlvaine buffer and a mixture of McIlvaine buffer dichloromethane (3 : 1). SPE cartridges for cleanup were Oasis HLB, Oasis MCX, and Oasis MAX. The effectiveness of the methods was evaluated in terms of decreasing the ion suppression effect but also of decreasing the variability of ion suppression between samples. The method that provided the most satisfactory results involved a clean-up step based on SPE using mixed-mode cation exchange cartridges (Oasis MCX).
Highlights
Tetracyclines are a family of drugs belonging to the group of antibiotics
The conventional analysis consists of a liquid extraction followed by a clean-up step using solid phase extraction (SPE) technique and analysis of the tetracyclines by liquid chromatography and mass spectrometric detection
The method that provided the most satisfactory results involved a clean-up step based on SPE using mixed-mode cation exchange cartridges (Oasis MCX)
Summary
Tetracyclines are a family of drugs belonging to the group of antibiotics. They are widely used in animal husbandry for therapeutic and prophylactic purposes. Oxytetracycline, tetracycline, chlortetracycline, and doxycycline are by far the most used antibiotics from this family. Their main chemical properties are their amphoteric behaviour due to their several acid-base equilibria and the tendency to act as chelating agents in presence of multivalent ions [1, 2]. At pH values below 3 they are positively charged. At pH between pKa1 and pKa2 they are neutral (zwitterionic state), and above pH 8 they are negatively charged
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