(佛山市质量计量监督检测中心, 广东 佛山 528225)
(Foshan Supervision Testing Centre of Quality and Metrology, Foshan 528225, China)
The use of salting-out assisted liquid-liquid extraction (SALLE) combined with UPLC-MS/MS has been evaluated for the determination of tetracyclines in milk powder. The samples were extracted with Na2EDTA-Mcllvaine buffer, and then the target analytes were extracted with acetonitrile assisted with (NH4)2SO4. After concentrated, the target analytes were separated on a BEH C18 column with gradient elution using acetonitrile and water containing volume fraction 0.1% formic acid as mobile phase. MS detection was performed with the positive ion mode in multi-reaction monitoring. The samples were quantified with external standard method. The result showed that, under the assisted with (NH4)2SO4, the extraction and purification effect of acetonitrile was improved. The limit of detection was 0.36μg/kg, which was much lower than 50μg/kg for the solid-phase extraction method. The linear range was from 1 to 100μg /kg with the correlation coefficient R>0.999. The recoveries of the method were ranged from 71.88% to 107.13% at the spiked levels of 1,5, 50μg/kg and the relative standard deviation was less than 8%. This method was simple, sensitive, economical, reliable and environmentally friendly. The method was suitable for the qualitative and quantitative of tetracyclines in milk powder.