Abstract
Abstract. Alkali backgrounds in laser ablation ICP-MS analyses can be enhanced by electron-induced ionisation of alkali contamination on the skimmer cone, reducing effective detection limits for these elements. Traditionally, this problem is addressed by isolating analyses of high-alkali materials onto a designated cone set, or by operating the ICP-MS in a "soft extraction" mode, which reduces the energy of electrons repelled into the potentially contaminated sampling cone by the extraction field. Here we present a novel approach, where we replace the traditional alkali glass tuning standards with synthetic low-alkali glass reference materials. Using this vitreous tuning solution, we find that this approach reduces the amount of alkali contamination produced, halving backgrounds for the heavy alkali elements without any change to analytical procedures. Using segregated cones is still the most effective method for reducing lithium backgrounds, but since the procedures are complimentary, both can easily be applied to the routine operations of an analytical lab.
Highlights
In solution ICP-MS, tuning and calibration are performed using carefully selected, high-purity aqueous solutions
In early August, the custom-made Tune-1 glass replaced NIST 612 as the glass used for tuning
Day-to-day background levels in alkali elements were highly variable throughout the study
Summary
In solution ICP-MS, tuning and calibration are performed using carefully selected, high-purity aqueous solutions. Laser ablation ICP-MS (LA-ICP-MS) tuning and calibration are often conducted using natural or multielement glass reference materials such as the NIST 600series glasses, which are generally not chosen or synthesised for the purpose of tuning a plasma source mass spectrometer. This can create a host of contamination issues (Eggins and Shelley, 2002). The LA-ICP-MS Agilent 7500 lab in operation at the Research School of Earth Sciences (RSES), Australian National University (ANU), during 2006, was a general-purpose, multidisciplinary analytical facility. The extensive variety of analytical procedures performed led to a number of potential contamination and cross-contamination issues
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