Matrix Solid-Phase Dispersion Extraction and Capillary Electrophoresis Determination of Tetracycline Residues in Milk

A capillary zone electrophoresis method was proposed for simultaneous detection and quantification of three tetracycline antibiotics in commercial milk samples, i.e., tetracycline, oxytetracycline, and doxycycline. The influences of the electrolyte composition, pH, as well as temperature and applied voltage on separation were investigated. The optimal running buffer was 30 mM Na2HPO4 and 1 mM EDTA at pH 11.5, with 3 s hydrodynamic injection, 25 kV applied voltage, and UV detection at 268 nm. Matrix solid-phase dispersion procedure was used for sample pretreatment. Several solid support materials were investigated, and silica with bonded C-18 chains (C-18) was used as sorbent. Electrophoretic analysis was completed in less than 6 min, with LODs ranging from 0.0745 mu g/mL for oxytetracycline to 0.0808 mu g/mL for doxycycline. The recoveries obtained were between 93.4% and 102%.