Tandem Probe Analysis Mode for Synchrotron XFM: Doubling Throughput Capacity

Casey L. Doolette, Daryl L. Howard, Nader Afshar, Cameron M. Kewish, David J. Paterson, Jianyin Huang, Stefan Wagner, Jakob Santner, Walter W. Wenzel, Tom Raimondo, Alexander T. De Vries Van Leeuwen, Lei Hou, Frederik van der Bom, Han Weng, Peter M. Kopittke, Enzo Lombi

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


Synchrotron-based X-ray fluorescence microscopy (XFM) analysis is a powerful technique that can be used to visualize elemental distributions across a broad range of sample types. Compared to conventional mapping techniques such as laser ablation inductively coupled plasma mass spectrometry or benchtop XFM, synchrotron-based XFM provides faster and more sensitive analyses. However, access to synchrotron XFM beamlines is highly competitive, and as a result, these beamlines are often oversubscribed. Therefore, XFM experiments that require many large samples to be scanned can penalize beamline throughput. Our study was largely driven by the need to scan large gels (170 cm2) using XFM without decreasing beamline throughput. We describe a novel approach for acquiring two sets of XFM data using two fluorescence detectors in tandem; essentially performing two separate experiments simultaneously. We measured the effects of tandem scanning on beam quality by analyzing a range of contrasting samples downstream while simultaneously scanning different gel materials upstream. The upstream gels were thin (<200 μm) diffusive gradients in thin-film (DGT) binding gels. DGTs are passive samplers that are deployed in water, soil, and sediment to measure the concentration and distribution of potentially bioavailable nutrients and contaminants. When deployed on soil, DGTs are typically small (2.5 cm2), so we developed large DGTs (170 cm2), which can be used to provide extensive maps to visualize the diffusion of fertilizers in soil. Of the DGT gel materials tested (bis-acrylamide, polyacrylamide, and polyurethane), polyurethane gels were most suitable for XFM analysis, having favorable handling, drying, and analytical properties. This gel type enabled quantitative (>99%) transmittance with minimal (<3%) flux variation during raster scanning, whereas the other gels had a substantial effect on the beam focus. For the first time, we have (1) used XFM for mapping analytes in large DGTs and (2) developed a tandem probe analysis mode for synchrotron-based XFM, effectively doubling throughput. The novel tandem probe analysis mode described here is of broad applicability across many XFM beamlines as it could be used for future experiments where any uniform, highly transmissive sample could be analyzed upstream in the "background"of downstream samples.

Seiten (von - bis)4584-4593
FachzeitschriftAnalytical chemistry
PublikationsstatusVeröffentlicht - 11 März 2022

Bibliographische Notiz

Funding Information:
This research was performed on the XFM beamline at the Australian Synchrotron, part of ANSTO. This work was supported by the Grains Research and Development Corporation (GRDC), Australia (project USA1910-001RTX). We also acknowledge funding provided to S.W. by the Austrian Science Fund (FWF, P30085-N28, project lead: Thomas Prohaska) and to J.S. by FWF and the Federal State of Lower Austria (P27571-BBL). We thank Dr Peter Self (CSIRO) for XRD analysis and interpretation, Adelaide Petrographics for preparation of mineral and wheat thin sections and Prof. Martin Hand for providing mineral sample RB 9B. We acknowledge the late Professor Peter Teasdale and deeply appreciate the invaluable advice, expertise, enthusiasm, and optimism he provided.

Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society.

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