Determination Of Rare Earth Impurities In High Purity Cerium By Inductively Coupled Plasma-Tandem Mass Spectrometry

Analytical and testing workers are committed to developing simple,rapid and accurate analytical methods to determine the contents of other trace rare earths in high purity rare earths.In this paper,inductively coupled plasma tandem mass spectrometer(ICP-MS/MS)was used to compare the elimination effects of three methods,namely the conventional standard curve method,the matrix matching standard curve method and the standard addition standard curve method,on the determination of 14 rare earth elements in high purity cerium sample under different gas collision pool modes.The influences of acidity,matrix concentration and internal standard elements on the determination results were investigated.A method for the direct determination of trace rare earth elrments such as yttrium,lanthanum,praseodymium,neodymium,samarium,europium,gadolinium,terbium,dysprosium,holmium,erbium,thum,ytterbium and lutetiumin in high purity cerium by inductively coupled plasmatandem mass spectrometry was established.The interference caused by matrix and other coexisting elements was eliminated by oxygen and ammonia gas collision reaction mode(MS/MS),and the internal standard element was used to correct the interference,so that the samples could be directly dissolved without separation.Terbium in high purity cerium samples was determined by ammonia mass shift model in a gas collision reaction cell with a mixture of ammonia and helium at a volume ratio of 1 : 9.Oxygen was passed through a gas collision reaction cell and the oxygen mass shift model was used to determine yttrium,lanthanum,praseodymium,neodymium,samarium,europium,gadolinium,dysprosium,holmium,erbium,thum,ytterbium and lutetium in high purity cerium samples.The internal standard element Cs was used to correct the determination interference of yttrium,lanthanum,praseodymium,neodymium,samarium and europium,and the internal standard element Tl was used to correct the determination interference of gadolinium,terbium,dysprosium,holmium,erbium,thulium,ytterbium and lutetium.The recoveries of each elements in high purity cerium sample were 85% ～ 115%.The detection limits of trace rare earth elements in high purity cerium sample calculated in the form of oxide were 0.001 ～ 0.03 μg/L,the lower limit of praseodymium,neodymium,gadolinium and terbium calculated in the form of oxide were 0.2 μg/g.The lower limit of yttrium,lanthanum,samarium,europium,dysprosium,holmium,erbium,thulium,ytterbium and lutetium calculated in the form of oxide were 0.1 μg/g.High purity cerium samples were determined 11 times in parallel and the relative standard deviations of parallel samples were lower than 5%.This method was simple,rapid,accurate and sensitive,and can satisfy the determination of other 14 trace rare earth impurities in high purity cerium with purity of 99.999% and above.