Method For The Determination Of Six Polyether Antibiotics Residues In Dairy By LC-MS-MS

Polyether antibiotics, also known as ionophore antibiotic, was widely used as high- efficiency, broad-spectrum anti-Coccidiostats, can also be used as animal growth-promoting agent. To use this antibiotics excessiveLy will lead to residues in animal food, or even cause animal poisoning or death.In this study, Selected full fat milk, low fat milk, fresh milk, full fat powdered milk, calcification of powdered milk for infant, skimmed fat milk as samples, a sensitive and selective method was developed for determination of six Polyether antibiotics residues in milk and powdered milk. Using external standard method.The results show:First: Dichloromethane, methanol and ethyl acetate as extractions, the average recovery rate of samples between 10.52% and 70.13%, but acetonitrile as the extraction, the average recovery rate of samples was over 70%, so the extraction was acetonitrile. Second: Solid-phase extraction method and gel permeation chromatography as a clean-up method, the average recovery rate of samples between 15.21% and 65.40%, but liquid-liquid extraction as a clean-up method, the average recovery rate of samples was over 71.20%, so liquid-liquid extraction was the clean-up method.Third: Chromatographic conditions: Methanol +Formic acid of 0.1%-Ammonium acetate of 5 mmol/L (90:10,v:v) as its mobile, the flow rate was 0.25 mL/min, column temperature was at 40℃. MS conditions: the capillary cone was 2.8 KV; ion source temperature was 110℃; desolvation temperature was 380℃; desolvation gas flow was 600 L/hr.Fourth: The operating ranges of the chromatographic analysis were determined. Calibration graphs were good linearity over the concentration ranges tested (0.5μg/Kg～100μg/Kg, R>0.99). The average recoveries from spiked milk and powdered milk at the three concentrations of 0.5, 10.0, 20.0μg/Kg ranged from 75.62%～112.55%,78.25%～112.13%,74.89%～108.10%,78.11%～108.94%,74.60%～114.20%,78.70%～115.64% respectively; with relative standard deviation ranged from 4.97%～12.88%,3.91%～13.76%,5.34%～13.68%,4.40%～13.94%,4.19%～13.42%,3.94%～12.59% respectively; and the limits of detection were 0.2μg/Kg,0.1μg/Kg,0.1μg/Kg,0.2μg/Kg,0.1μg/Kg,0.3μg/Kg respectiveLy in milk and powdered milk. Our experiment used liquid chromatography with mass pectrometry was confirmed, it was applied to detect six Polyether antibiotics residual in milk and powdered milk.