Performance Characteristics of a PFA Cyclonic Spray Chamber with HR ICP-MS

The Savillex PFA cyclonic spray chamber was used with a Thermo ElementXR HR-ICP-MS for the measurement of trace element/calcium ratios in foraminiferal calcite. The signal stability and washout (particularly for boron which is a "sticky" element) were studied. The spray chamber was found to have excellent sensitivity, good short and long term stability, and fast washout (60 s for B), making it well suited to the application.

Elemental ratio determinations in foraminiferal calcite require the measurement of trace levels of Na, Mg, Sr, and ultra-trace levels of Li, B, Ba, Cd, Mn, U in a calcium rich matrix and ratioed to calcium. Samples are run in an 0.1 M HNO₃/0.3 M HF matrix to prevent boron carryover between samples, so an inert sample introduction system is required. PTFE and PFA inert spray chambers generally have inferior performance to quartz spray chambers. We evaluated the recently introduced Savillex PFA cyclonic spray chamber to see if advancements in technology have improved the performance of inert sample introduction systems for ICP-MS. A Thermo ElementXR HR-ICP-MS was fitted with a Savillex inert kit comprising of an inert torch with platinum injector, PFA cyclonic spray chamber (no surface treatment) with baffle, and a C100 PFA concentric nebulizer.

Figure 1: Savillex PFA cyclonic spray chamber.

An acid blank and three standards (standards 0, 4, and 8) containing 10 ppm Ca and varying ppt–ppb levels of trace elements were run. After the initial data acquisition for all standards, the blank, standard 0, and standard 8 were measured 17 times each in sequence, to check for reproducibility and drift. The spray chamber was found to have good short-term stability with RSDs of 0.5–1%, and good long-term reproducibility RSDs of 1.5–2.9% over 4 h. No drift correction was applied. Washout of B from the high standard (0.74 ppb) to blank levels took <60 s, demonstrating the good washout characteristics of the spray chamber.

Figure 2: Boron signal over 5 h-acid blank and standard 0 (2 ppt B in 10 ppm Ca), showing excellent sensitivity and washout (the higher standards in between have been excluded for clarity). For full details visit www.savillex.com/ICP.

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