Abstract:

 A highyield lithium separation technique for rock samples has been established together with precise Li isotope analysis by MCICPMS. The solutions with different concentration of lithium element standard reference materials and single element standard samples of potassium, calcium, sodium, magnesium and iron were used to evaluate the analytical methods applied. Three separate stages of ionexchange chromatography were carried out using organic cation exchange resin (AG 50WX8,200—400 mesh). Lithium was enriched in different eluants for the different stages. 28 mol/L HCl, 015 mol/L HCl and 05 mol/L HCl in 30% ethanol were used for the different three stages. Two kinds of columns which are made of polypropylene for the first and second stages and quartz for the third stage were used, which is different from those used abroad. Total reagent volume for the entire chemical process was reduced to 38 mL for the rock samples and the recovery is more than 976%. The precision of this technique is conservatively estimated to be ±060‰—094‰ (2σ population), which is similar to the precision of other methods used abroad. The δ7Li value (7Li/6Li relative to the IRMM016 standard) determined for AGV2 is 513‰. The δ7Li values determined for BHVO2 (7Li/6Li relative to the IRMM016 standard) and IRMM016 (7Li/6Li relative to the LSVEC standard) are 408‰ and 0038‰, respectively. In addition, the results for the same kinds of samples analyzed by my lab are the same as those by isotope lab of Maryland University. All the analytical results are consistent with those reported by others. Moreover, the δ7Li value (7Li/6Li relative to the IRMM016 standard) determined for substandard NKT1 nephelinite obtained from the United States Geological Survey (USGS) is 871‰ and its precision is ±046‰. According to the experiments, it is concluded that this proposed procedure is a suitable method for determining the lithium isotopic composition of natural samples.

Key words:  lithium isotope analytical method, international standard samples AGV2, BHVO2, IRMM016, multicollector magnetic sector inductively coupled plasmasource mass spectrometer