Determination of Rare Earth Elements in Fresh Milk,Yogurt and Milk Powder by Inductively Coupled Plasma Mass Spectrometry

A method for determination of 16 rare earth elements in milk and dairy products was developed by inductively coupled plasma mass spectrometry(ICP-MS). Samples were digested by the pretreatment technique of microwave digestion,and the operating parameters of the instrument were optimized,then ¹⁰³Rh,¹¹⁵ In and ²⁰⁹Bi were selected as internal standard elements to correct matrix interference. The results showed that the mass concentration range of 0.2~5 ng/mL for 16 rare earth elements had good linearity with r≥0.9995,the detection limits were 0.03~0.52 μg/kg,the average recoveries were between 92.3% and 109.0%,and the relative standard deviations(RSDs)were 2.21%~5.36%. The method was applied to determine the national standard reference material of citrus leaf(GBW10014),and the determined values were all in the range of the recommended values. The rare earth elements were detected in fresh milk,yogurt and milk powder in the market.The results showed that the contents of rare earth elements were 0.04~19.3 μg/kg in all three kinds of dariy products.The method was rapid,accurate,easy and convenient to operation,and could be used for the determination of rare earth elements in fresh milk,yogurt and milk powder.