High Precision 3ppm (2RSD) Strontium isotope ratio data produced during instrument test

Introduction

The information below shows the most recent factory test data on replicate measurements of 150ng Sr NBS987 demonstrating the exceptionally high precision 87Sr/86Sr reproducibility that can be achieved on the Phoenix TIMS during regular multidynamic analysis. Normal sample loading techniques were utilised; 1µl of TaF solution was initially dried down on degassed Rhenium filaments with 1µl of 150ng Sr NBS987 loaded on top. These were both dried down at 0.5A and then glowed in air at around 2.1A.

The complete analysis was ran overnight, fully automatically, without any user intervention. A “sample preparation method” was used to adjust and maintain the filament current at around 2.9A to give a stable 6V 88Sr ion beam. A multidynamic 3 jump analysis was employed with 10 second on peak integration times. 40 second baselines were taken at + and – 0.5AMU between each jump. Each analysis consisted of 10 blocks of 16 cycles amounting to 160 ratios in total with a measurement duration of ~ 2 hours.

Multidynamic 3 jump Sr sequence

Table 1. Multidynamic 3 jump analysis

Results

The results are shown in table 2. 87Sr/86Sr is fractionation corrected using the exponential fractionation law and an 86Sr/88Sr ratio of 0.1194.

Table 2. 87Sr/86Sr internal and external precision

Table 2. 87Sr/86Sr of 10 automatic measurements of 150ng NBS987

87Sr/86Sr 150ng NBS987

Figure 1. Graphical representation of the data in table 2. The individual error bars are 2 standard errors and the dotted lines represent +/- 2RSD of the data.

 Summary

A standard Strontium isotope test measurement of NBS987 produces an 87Sr/86Sr ratio of 0.710254 with a reproducibility of 3ppm 2RSD. Note the ion beam used was only 6e-11 amp for the 88Sr. The high precision on a relatively small ion beam reflects the low noise and high stability of the Phoenix ion detection system even in a non- temperature controlled test environment.

 

 

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Category: Geology, Customer News, Applications, Publications
Published: Tuesday, May 16th, 2017 at 10:36 am

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