Optimization of the composition and pH of the mobile phase used for separation and determination of a series of quinolone antibacterials regulated by the European Union

To ensure the safety of human food the European Union (EU) has set tolerance levels for quinolone compounds in animal products, so screening and confirmatory analytical methods are required for monitoring of these drugs. In this work, the proportion of organic modifier and the pH of acetonitrile-water mixtures used as mobile phases were optimized for separation of a group of quinolones. Linear solvation energy relationship (LSER) formalism based on the single solvent polarity parameter E-T(N) was used to predict the chromatographic behaviour of the compounds as a function of the amount of acetonitrile in the mobile phase. Correlation between retention and the pH of aqueous-organic mobile phases has also been used to optimize mobile-phase pH. The optimized mobile phase was a linear gradient starting from 18:82 (v/v) acetonitrile-acetate + formate buffer, pH 2.5. Quality data were determined and were satisfactory The method detection limit was approximately 10 ng mL(-1) for most of the quinolones studied. The proposed mobile phase is compatible with mass spectrometric detection of the substances.