Issue 6, 2024

Comparison and influence of 1011 and 1013 ohm resistors used for MC-ICP-MS determination of isotope ratios in highly enriched silicon

Abstract

The molar mass M and isotopic composition of a silicon material highly enriched in 28Si were measured for the first time using high ohmic (1013 Ω) resistors in the feedback loop of amplifiers connected to the Faraday detectors of a multicollector-inductively coupled plasma mass spectrometer (MC-ICP-MS). In the context of the realization and dissemination of the SI units kilogram and mole via the X-ray crystal density (XRCD) method, it is of high importance to maintain and improve the state-of-the art technique to determine M with the lowest possible associated uncertainty. The applications and influences of 1011 Ω and 1013 Ω resistors for ion detection were compared using the crystal Si28-33Pr11 exhibiting a large range (≈102) of the ratio 30Si/29Si. The low abundance of 30Si hampers the measurement and thus enlarges the uncertainty. The use of 1013 Ω resistors enables a fourfold dilution of the initial Si sample stock solutions from wx(Si) = 4536 μg g−1 down to 1134 μg g−1 preserving the MS equipment (ion lenses, slits etc.). A lower limit of wx(Si) ≈ 1134 μg g−1 for ion currents I = 3.4 fA (corresponding to U = 0.34 mV: gain corrected for R = 1013 Ω) for 30Si+ was determined still maintaining the ability to yield urel(M) = 4 × 10−9. This will also enable the use of smaller sample sizes, which will considerably reduce costs and time and thus improve this method strongly. Tau correction for 1013 Ω resistors was studied showing no significant influence in case of the continuous beam experiments.

Graphical abstract: Comparison and influence of 1011 and 1013 ohm resistors used for MC-ICP-MS determination of isotope ratios in highly enriched silicon

Supplementary files

Article information

Article type
Paper
Submitted
22 Feb 2024
Accepted
01 May 2024
First published
02 May 2024
This article is Open Access
Creative Commons BY license

J. Anal. At. Spectrom., 2024,39, 1540-1550

Comparison and influence of 1011 and 1013 ohm resistors used for MC-ICP-MS determination of isotope ratios in highly enriched silicon

A. Pramann and O. Rienitz, J. Anal. At. Spectrom., 2024, 39, 1540 DOI: 10.1039/D4JA00066H

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