Single-column Separation Of Cu,Fe And Zn From Rock Matrices And Their Isotopic Composition Analysis By MC-ICP-MS

With the development of multi-collector inductively coupled plasma mass spectrometer(MC-ICP-MS),the accurate and precise measurements of the isotopic compositions of Cu,Fe,and Zn isotopes have been materialized for decades.Although domestic and foreign laboratories have focused on the isotopic analysis methods for Cu,Fe,and Zn isotopes,the separation procedures for Cu,Fe,and Zn in different laboratories are manifold.Most of current separation procedures employ single ion exchange resin column only to separate one or two elements in Cu,Fe,and Zn.Therefore,the analysis efficiency for large quantities of geological samples still remains to be improved.Despite individual laboratories have constructed the single-column separation procedure,the efficiency of the present separation procedures needs to be further verificated and optimized.Based on the comprehensive comparison of the analysis methods of various laboratories and the existing ion exchange technology,this study focuses on the verification of the reproducibility,the improvement and the optimization of the single-column separating procedure for Cu,Fe,and Zn elements.This single-column separating procedure employs significantly reduced the acid consumption to lower the whole process blank.In addition,the analysis efficiency has been particularly improved,especially for some precious geological samples which are difficult to collect or with low contents of Cu.Fe and Zn,the isotopic compositions of Cu,Fe,Zn can all be analyzed by MC-ICP-MS only through the single-column separation,which ensures that as much analyzing data can be obtained as possible for a sample,thereby providing more technical support for geological surveys and scientific research.The establishment of this method provides analysis-technical support for Cu,Fe and Zn isotopic tracing the source of metallogenic materials in metal deposits,and shows many potential applications in deposit geochemistry,paleo-redox conditions and pollution source tracing.The main achievements and conclusions are summarized as follows:1.The sample separation and enrichment conditions were experimented,including leaching efficiency,separation effect region,recovery and the whole process blank.The result shows that 1ml AG-MP-1(100-200 mesh)resin has resulted in fast leaching speed,obvious element separation range and high recovery.A mixed standard solution has been used for column recovery analysis,and the experimental results show the recovery of Cu was 97.4±5.7%(2SD,n=4),the recovery rate of Fe was 97.1 ±2.5%(2SD,n=5),the recovery rate of Zn was 96.0±2.3%(2S,n=4).Meanwhile,the process has been optimized to reduce the acid consumption,the process blanks(Cu:5.2±2.3 ng,Fe:14.3± 1.7 ng,Zn:6±3.8 ng)satisfied the blank requirements of the on-line measurements by MC-ICP-MS.By comparing the digestion methods of different samples,the recovery rate of Cu,Fe,and Zn using the steel sleeve is significantly higher than that of the PFA beaker.The average recovery rates of Cu,Fe,and Zn digested in the steel sleeve were 99.8%(n=3),103.1%(n=3),and 101.7%(n=3),respectively.2.The influence of matrix elements Co and Ca on the MC-ICP-MS measurement of Cu isotope composition was discussed.When the ratios of Co/Cu and Ca/Cu are less than 5,0.5,respectively,the interference influence of Co and Ca on Cu could be neglected.After the purification work in this study,Co/Cu and Ca/Cu are less than 0.1 and 0.17,respectively,Therefore,the Co and Ca concentrations satisfied the requirement of matrix content in Cu isotope measurements3.In this study,the standard-sample-bracketing(SSB)method has been used to correct the mass bias effect during the MC-ICP-MS measurements.The isotopic compositions of Cu,Fe,Zn in the standard solutions of CAGS-Cu,CAGS-Fe,CAGS-Zn and the geological standards of AGV-2,BCR-2,BIR-1,BHVO-2 have been measured,respectively,relative to the international standard solutions NIST 3114 Cu,IRMM 524a Fe,IRMM 3702 Zn.The measurement results of Cu,Fe,Zn isotopic compositions are in good agreement with the previous reported values within the error range,indicating that the chemical separation process of Cu,Fe,Zn and their isotopic composition analysis method by MC-ICP-MS established in this study are reliable.