Development and optimization of an ultra-fast microextraction followed by HPLC-UV of tetracycline residues in milk products

The present study developed a new ultra-fast microextraction (within 8 min) with acetonitrile followed by gradient reversed-phase HPLC-UV method to determinate six tetracyclines simultaneously in various milk products with HPLC analysis time of 9 min. Chromatographic separations were achieved with a phenomenex (TM) Synergi 4 mu m Fusion-RP (150 x 4.60 mm) column at 220 nm, using acetonitrile/KH2PO4 buffer (4 mmol.L-1, pH 2.5) as mobile phase. The HPLC method showed excellent peak resolutions (3.3-8.8) and peak symmetry (0.99-1.11) inspite of short analysis time. The extraction rates from milk products showed consistently very good values over all tetracyclines (milk 80.58 +/- 5.39 %, yoghurt 82.61 +/- 5.63 %, cream cheese 80.13 +/- 6.32 %, buttermilk 81.07 +/- 6.49 %, kefir 79.69 +/- 6.51 %, skyr 78.12 +/- 5.22 %, quark 65.37 +/- 4.72 %). The optimized method was found to be specific, reproducible, robust. This study combines for the first time a fast, cheap quantification of six tetracyclines via HPLC-UV with a reliable microextraction applicable to various milk products using only standard laboratory equipment.

Automated summary

This study developed a new ultra-fast microextraction method for simultaneous determination of six tetracyclines in milk products. The method showed excellent separation and high extraction rates, and it was found to be specific, reproducible, and robust.