Matrix effects and mass bias caused by inorganic acids on boron isotope determination by multi-collector ICP-MS

Abstract

The influence of inorganic acids (HCl, HNO 3 , and HF) on boron isotope measurement by using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) has been investigated. The acid concentration is in the range of 0-0.2 M. Generally, acids can enhance B signal intensities and reduce isotopic mass bias compared to that of the same B concentration in a H 2 O matrix. The signal enhancement in each acid matrix differs slightly, while B isotopic mass bias is significantly different among them, with the highest 11 B/ 10 B ratio in the HF matrix and the lowest in the HCl matrix. In HCl and HNO 3 matrices, boron isotopic mass bias reduces when the acid concentration goes up. However, such a scenario is not observed in the HF matrix. Furthermore, the 11 B/ 10 B ratio in the HF matrix is the same as that in the H 2 O matrix within the studied acid concentration (up to 0.2 M). This implies that changes in mass bias and the B signal cannot be related to the same process in ICP-MS. We suggest that B signal enhancement in inorganic acids can mainly be attributed to Coulomb fission during aerosol transport towards plasma, while boron ion redistributions in the plasma caused by matrix element (e.g. Cl, N) ionization lead to changes in isotopic mass bias. As acids can cause considerable matrix effects and mass bias for boron, acidity match between samples and standard solutions is imperative for accurate and precise B isotope measurement by MC-ICP-MS.

Fast and precise boron isotopic analysis of carbonates and seawater using Nu Plasma II multi‐collector inductively coupled plasma mass spectrometry and a simple sample introduction system

“…Both results for the processed samples are consistent with reported values ( Figure 7B). This observation that low acid molarity causes higher δ 11 B values was consistent with findings of Chen et al, 31 although the magnitude was greater in our study. It is likely that the droplet size distribution was slightly different under different acid concentration, which causes variable transport efficiency through the spray chamber.…”

“…It is likely that the droplet size distribution was slightly different under different acid concentration, which causes variable transport efficiency through the spray chamber. 31 It is noted that when the sample solution is in 1 M HNO 3 and measured against standard in 0.5 M HNO 3 , there was no observable difference in the δ 11 B values.…”

“…The typical residual 11 Rinsing with various chemical solutions in addition to blank acid (HCl, HNO 3 , HF, ammonia, mannitol, water) has been suggested to be effective in minimizing the B memory effect during MC-ICPMS analysis. [18][19][20][21][22][23][24]31 However, most of these rinsing solutions rely on the F ions to form stable B complexes in solution 27,30 and the strong affinity of B with F could lead to a drop of~10% ionization efficiency. 30 HF readily attacks glass and quartz and can be damaging to the sample introduction system.…”

“…13,14 Over the past two decades, multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) has become the most common approach for B isotopic analysis, owing to its high ionization efficiency, stable instrumental mass bias, fast routine analyses, and high precision ( HF, ammonia, mannitol, water) were also adopted to minimize the B memory effect. [18][19][20][21][22][23][24][25][26][27][28][29][30][31] These efforts all have drawbacks as they require a specialized sample introduction system or the use of toxic chemicals. The sample introduction system is critical for obtaining highprecision B isotopic measurements because it affects the ionization efficiency and instrumental mass fractionation.…”

Atomic spectrometry update – a review of advances in environmental analysis

“…The influence of different inorganic acids on B isotope measurements by MC-ICP-MS was studied 434 using B solutions containing HCl, HNO3 and HF at concentrations up to 0.2M.…”