Impressive Performance for small Sr loads on Phoenix TIMS

Phoenix has been recognized as the most sensitive TIMS currently available. In order to characterize the system we analyzed small loads of NBS 987 to test Sr ionization efficiency and provide an insight into typical system performance.

Using a modified loading technique with a tantalum activator on a rhenium center filament, very high atom to ion efficiency was observed on small strontium loads. This allowed a 1 ng load of NBS 987 to be analyzed in a three cycle dynamic acquisition with sufficient signal to collect 147 cycles of data (equivalent to 441 static cycles) at an aiming intensity of 2V. This analysis produced a 87Sr/86Sr of 0.710245 +/- 4ppm (1 RSE).

As a comparison, another 1 ng strontium load was run in a static acquisition. Again the aiming intensity was ~2V. 400 cycles of data were acquired before the acquisition was stopped due to time constraints (the acquisition could have continued for some time at this intensity). The analysis produced a 87Sr/86Sr of 0.710240 +/- 5ppm (1 RSE). This was a true static acquisition with no amplifier switching and confirms that amplifier averaging isn’t required to achieve the highest performance in static mode, even on very small sample loads.

We are planning to extend this provisional work by running a series of 1 ng and 5ng Sr loads to quantify the ionization efficiency across replicates and establish sample to sample reproducibility in both static and dynamic mode. This will be published in a future application note.

In summary, Phoenix’s very high sensitivity permits Sr sample loads of 1 ng to be analysed either in dynamic or static mode with long acquisition times leading to very high accuracy and precision.


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