An Improved Faraday Cup Configuration and Its Applying in Sr Isotopic Analysis of Rich-REE Apatite by LA-MC-ICP-MS
It is still difficult to accurately correct the interferences of REE2+in Sr isotopic analysis by LA-MC-ICP-MS.In this study,we corrected the interferences of REE2+by RPSM(Routine Peak Stripping Method)combining use of an improved cup configuration of MC-ICP-MS allowing for synchronic detection of REE2+signals.The effectiveness of IFCC(Improved Faraday Cup Configuration)was evaluated with respect to both the synchrony and the ratios of REE2+signals.With IFCC,no decoupling of REE2+signals was observed.This finding indicates that IFCC is well suited for RPSM to correct the interferences of REE2+.The ratios of REE2+signals(r:166,168,170Er2+/167Er2+和 170,172,174,176Yb2+/173Yb2+)are approximately equal to(r/R≈1)the natural isotopic abundant ratios of Er an Yb(R:166,168,170Er/167Er 和 170,172,174,176Yb/173Yb).This property cause IFCC to be well suited to correct interferences of REE2+with the R and the measured signals of 167Er2+and 173Yb2+.We also determined the Sr isotopic compositions of the Er and Yb-spiked 0.1 μg/g NBS987 Sr solutions by SN-MC-ICP-MS with IFCC,and the results attest that the interferences of REE2+in the solutions with Sr/Er≥3 can be corrected using the RPSM(R as the interference correction factor),and those in the solutions with Sr/Er≥1 can be corrected using the EPSM(Enhanced Peak Stripping Method,measured r as the interference correction factor).Sr isotopic compositions of two rich-REE reference materials(Durango with Sr/Er=7.4,and UWA-1 with Sr/Er=2.8)were determined by LA-MC-ICP-MS with IFCC,and the determined 87Sr/86Sr of the two reference materials are 0.706 27±0.000 14(2SD,n=19)and 0.704 76±0.000 19(2SD,n=20),respectively,both of which agree with previously published values(determined by TIMS or MC-ICP-MS)within uncertainties.
SrisotopesLA-MC-ICP-MSdouble-charged ions of rare earth elements(REE2+)apatitegeochemistry
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