Determination of radiogenic and stable strontium isotope ratios (Sr-87/Sr-86; delta Sr-88/86) by thermal ionization mass spectrometry applying an Sr-87/Sr-84 double spike

Recent findings of natural strontium isotope fractionation have opened up a new field of research in non-traditional stable isotope geochemistry. While previous studies were based on data obtained by MC-ICP-MS we here present a novel approach combining thermal ionization mass spectrometry (TIMS) with the use of an Sr-87/Sr-84 double spike (DS). Our results for the IAPSO sea water and JCp-1 coral standards, respectively, are in accord with previously published data. The strontium isotope composition of the IAPSO sea water standard was determined as delta Sr-88/86 = 0.386(5)parts per thousand (delta values relative to the SRM987), Sr-87/Sr-86* = 0.709312(9) n = 10 and a corresponding conventionally normalized Sr-87/Sr-86 = 0.709168(7) (all uncertainties 2SEM). For the JCp-1 coral standard we obtained delta Sr-88/86 = 0.197(8)parts per thousand, Sr-87/Sr-86* = 0.709237(2) and Sr-87/Sr-86 = 0.709164(5) n = 3. We show that by applying this DS-TIMS method the precision is improved by at least a factor of 2-3 when compared to MC-ICP-MS.