[Determination of 11 nutrients in liquid milk by ultra-performance liquid chromatography-tandem mass spectrometry].

ABSTRACT

OBJECTIVE: To establish an ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) method for simultaneous determination of 11 nutritional components(thiamine, riboflavin, nicotinamide, nicotinic acid, pantothenic acid, pyridoxine, pyridoxal, pyridoxamine, biotin, choline, L-carnitine) in liquid milk. METHODS: Milk samples were shaken with 20 mmol/L ammonium formate solution and heated in a water bath at 100 ℃ for 30 min, then incubated with papain and acid phosphatase at 45 ℃ for 16 h, the lower liquid was collected after centrifugation for analysis. UPLC separation was performed on an ACQUITY~(TM) HSS T3(3.0 mm×150 mm, 1.8 µm) column, 2 mmol/L ammonium formate(containing 0.1% formic acid) solution and acetonitrile(containing 0.1% formic acid) were used as mobile phase. Quantitative detection was performed by internal standard method. RESULTS: 11 nutritional components can be effectively separated and detected in 12 min, and the linear correlation coefficients(R~2) were all above 0.995. The limits of detection(LODs) were between 0.05 and 0.50 µg/L, and the limits of quantification(LOQs) were between 0.20 and 1.25 µg/L. The recovery rates of three-level addition were 85.6%-119.3%, and the precision RSDs were between 3.68% and 7.82%(n=6). Based on the detection of 60 liquid milk samples from 5 different animals, it was found that the contents of 11 nutrients in liquid milk from different milk sources were significantly different, but pyridoxine could not be detected. CONCLUSION: The method can quantitatively detect 11 water-soluble nutrients, including free and bound forms, by effective enzymolysis. It is sensitive, reproducible and can meet the needs of quantitative detection.