Project Vienna: A Novel Precell Mass Filter for Collision/Reaction Cell MC-ICPMS/MS.

Grant Craig,Tim Elliott,Markus Pfeifer,Johannes B Schwieters,Henning Wehrs,Nicholas S Lloyd,Dan G Bevan,Chao Huang,Christopher D Coath,Jamie Lewis

doi:10.1021/acs.analchem.1c01475

Abstract

The last decade has seen widespread adoption of triple quadrupole-based inductively coupled plasma-tandem mass spectrometry (ICPMS/MS) technique using a collision/reaction cell in combination with a precell bandpass mass analyzer to measure isotopes otherwise masked by spectral interferences. High-precision isotope ratio analysis containing such isotopes would benefit from a similar capability on a multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) platform, but using a quadrupole-based precell mass analyzer for MC-ICPMS/MS has several limitations. To overcome these limitations, we developed a novel precell mass analyzer for MC-ICPMS/MS using sector field technology. The new precell mass analyzer, comprising two Wien filters and a selection aperture, and a hexapole collision/reaction cell were integrated together in a single module and added to the commercially available Thermo Scientific Neptune XT MC-ICPMS to create a prototype MC-ICPMS/MS we named Vienna. Vienna was proven to retain the same performance of the base MC-ICPMS in terms of sensitivity, accuracy, and precision. Using the Vienna mass filter to eliminate Ar-based species, the abundance sensitivity achievable was equivalent to TIMS at mass 237.05, which was used to accurately determine the low 236U/238U isotope ratio of the uranium reference material IRMM184 (certified value, 1.2446 × 10-7). The performance of Vienna was then tested for a variety of geoscience applications that were expected to benefit from MC-ICPMS/MS technique, including Ca, K, Si, and in situ Rb/Sr dating by laser ablation.

Highlights

The last decade has seen widespread adoption of triple quadrupole-based inductively coupled plasma−tandem mass spectrometry (ICPMS/MS) technique using a collision/reaction cell in combination with a precell bandpass mass analyzer to measure isotopes otherwise masked by spectral interferences
The performance of Vienna was tested for a variety of geoscience applications that were expected to benefit from MC-ICPMS/MS technique, including Ca, K, Si, and in situ Rb/Sr dating by laser ablation
New sample interface designs allowed for greatly improved sensitivity, especially in dry plasma.[12−14] The introduction of multi-ion counting to MC-ICPMS, using compact discrete dynodes (CDD)[15] or Daly detectors,[16] has been extremely beneficial for sample-limited analysis such as in situ U/Pb dating with laser ablation (LA)

Summary

■ RESULTS

Determined at ±1 and ±2 amu from 238U using a 20 ppb IRMM184 standard solution. Measurement conditions were identical to the high-sensitivity dry plasma mode used for testing exponential mass bias, except 1 mL/min of He was added to the collision cell. We need to use the precell mass filter to permit the stable transmission of a window of masses centered on 88Sr.Without the mass window, a multitude of undesirable ion-gas reactions involving matrix elements and SF6 proceed This results in an abundance of secondary interferences being produced, which compromises the accuracy and precision of the radiogenic Sr isotope ratios measured.[41]. The accurate and precise age calculated for SG-1 demonstrated that the nonquadrupole-based precell mass filter of Vienna was capable of producing a stable, flat transmission window sufficient for LA-MC-ICPMS/MS Rb/Sr dating. Advanced triple quadrupole ICPMS/MS instruments have been commercialized and applied to a continually increasing variety of research fields, quadrupole-based ICPMS/MS are unable to offer highly precise isotopic measurements due to intrinsic limitations of quadrupole mass spectrometry, nonsimultaneous detection, mass bias, and detector linearity.[48,49] MC-ICPMS integrating a CRC, specially equipped with a bandpass mass analyzer prior to the cell, has been demanded for high-precision isotope analyses. More future work to further evaluate and demonstrate the powerful capability of Vienna is desirable

■ CONCLUSIONS

Findings

■ REFERENCES