Analytical performance assessment of LMS-GT, a newly-developed laboratory-scale Laser Ablation Ionization Mass Spectrometry instrument, in the context of geo- and planetary sciences

Direct analysis of micrometer-scale features embedded in solid samples of a wide chemical variety is an integral part of many fields in geo-, geobio-, and planetary sciences. Examples range from microscopic mineral inclusions in meteoritic material, (e.g., zircons, CAIs, chondrules, etc.) to biological inclusions in a variety of mineralogical host materials, e.g., (putative) fossils of microbial species. In many of these use-cases, the determination of the element and/or isotope composition, specifically those of minor or trace abundance, is of prime interest, meaning mass spectrometry is typically the preferred analysis technique.

As a result, a growing group of instruments has been (and are being) developed specifically with the purpose of element and/or isotope analysis of microscale features in solid hosts, each with its specific advantages and limitations. Perhaps the most well-known technique is (nano)SIMS, which boasts analysis spot sizes down to the nanometer level as well as ppm to ppb detection limits, but struggles with quantitativeness and capital and operating expenses. In the field of laser-based solid sampling mass spectrometric techniques, LA-ICP-MS has become a well-established technique, mainly due to its reproducibility and ease of operation. However, due to necessity to transport particles from the ablation plume to the ICP, this technique is inherently limited through fractionation effects and isobaric interferences with the plasma and carrier gas. Furthermore, sample dilution in the plasma and the subsequent loss of sample at the ICP-MS interface result in diminished limits of detection.

Another member of the laser-based solid sampling techniques is Laser Ablation Ionization Mass Spectrometry (LIMS), in which the ions present in the ablation plume are directly introduced into the mass spectrometer. This direct sampling of the ablation plume results in both a significant advantage over LA-ICP-MS (high sensitivity) and a challenge (mass resolution). The limited mass resolution of typical LIMS instruments often makes (quantitative) analysis challenging due to isobaric interferences, especially when applied to more complex materials. To solve this issue, the Laser Mass Spectrometer – Gran Turismo (LMS-GT) was developed at the University of Bern with the aim of achieving mass resolutions sufficient to resolve the most common isobaric interferences (M/ΔM = 10.000).

Over the last years, commissioning and continuous improvement of the instrument has been ongoing, which has led to a set of analytical performance characteristics which highlight the potential complementary value of LMS-GT. In this talk, we will discuss the latest technological developments¹, latest analytical performance metrics (mass resolution, mass accuracy, limits of detection, etc.), and element and isotope ratio accuracies^2,3. We will also discuss a case-study in which LMS-GT was used to study fossilized microbial inclusions in Gunflint chert⁴, highlighting both the potential strength and challenges for LMS-GT in a geo- and geobiosciences context.

1. Gruchola, S. et al., Int. J. Mass Spectrom. 474, 116803 (2022).

2. Wiesendanger, R. et al.,  J. Anal. At. Spectrom. 34, 2061–2073 (2019).

3. de Koning, C. P. et al.,  Int. J. Mass Spectrom. 470, 116662 (2021).

4. Lukmanov, R. A. et al., Front. Space Technol. 3, (2022).