Validation of an easily-synthesised sorbent-based magnetic dispersive solid phase extraction method for the extraction of fluoroquinolone antibiotics from raw cow milk samples.

In the current work, a sample pre-treatment method based on magnetic dispersive solid phase extraction was developed and validated for the extraction of fluoroquinolone antibiotics from raw cow milk samples before their quantification with HPLC with a diode array detector. A magnetised carbonised cellulose filter paper was synthesised easily and employed as an efficient sorbent in the extraction process. In the proposed method, after precipitating the milk proteins using trichloroacetic acid solution, the magnetic particles were dispersed throughout the pH-adjusted sample solution by vortex agitation. After removing the liquid phase in the presence of an external magnet, the sorbent particles were eluted with acetonitrile along with vortex agitation to desorb the analytes. The liquid phase was put into a vial and evaporated to dryness. The residue was dissolved in the mobile phase, and an aliquot was injected into the analytical instrument for quantitative analysis. Under the optimum conditions, acceptable extraction recoveries (67-76%), low limits of detection (0.21-0.32 ng mL-1) and quantification (0.70-1.07 ng mL-1), and good precision (relative standard deviation ≤ 6.5%) were attained. After optimising and validating the proposed method, it was performed on thirty different raw cow milk samples; none of the antibiotics were detected.