Impressive Data from 2011 US Phoenix Installations

TIMS produces absolute isotope ratio values rather than values normalized to a standard as is usual in gas IRMS. There is however always a small difference from machine to machine which explains why although modern TIMS systems can achieve a measurement precision of  less than 5ppm, accuracy specifications are usually of the order of 25 or 30 ppm. Nevertheless we would expect instruments made in the same factory within a few months of each other to achieve broadly similar results.

Phoenix TIMS instruments were delivered into four leading US geological laboratories during 2011. The figures below compare the 87Sr/86Sr (NBS987), and 143Nd/144Nd (JNdi-1) from the sign-off data from these four installations.

NBS987 – Averaged over the four installations, the mean value for 87Sr/86Sr is 2.3ppm away from our accepted value for NBS987. Inter-machine precision is 4.8ppm.

JNdi-1 – Averaged over the four installations, the mean value for143Nd/144Nd is 4.5ppm away from our accepted value for JNdi-1. Inter-machine precision is 4.6ppm.


This comparison highlights the excellent machine to machine consistency of these four Phoenix TIMS systems. Isotopx have worked very hard in recent years to standardize instrument production and work with our suppliers to maximize component quality. The data shown here is testament to that hard work and speaks volumes for the quality of the products we deliver every day to our customers.


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