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Rodionov, Andrei ; Lehndorff, Eva ; Stremtan, Ciprian C. ; Brand, Willi A. ; Königshoven, Heinz-Peter ; Amelung, Wulf:
Spatial microanalysis of natural ¹³C/¹²C abundance in environmental samples using laser ablation-isotope ratio mass spectrometry.
In: Analytical Chemistry.
Bd. 91
(2019)
Heft 9
.
- S. 6225-6232.
ISSN 1520-6882
DOI: https://doi.org/10.1021/acs.analchem.9b00892
Abstract
The stable 13C/12C isotope composition usually varies among different organic materials due toisotope fractionation during biochemical synthesis anddegradation processes. Here, we introduce a novel laserablation-isotope ratio mass spectrometry (LA-IRMS) methodologythat allows highly resolved spatial analysis of carbon isotope signatures in solid samples down to a spatial resolution of 10 μm. The presented instrumental setupincludes in-house-designed exchangeable ablation cells (3.8and 0.4 mL, respectively) and an improved sample gas transfer, which allow accurate δ13C measurements of an acryl plate standard down to 0.6 and 0.4 ng of ablated carbon, respectively (standard deviation 0.25‰). Initial testing on plant and soil samples confirmed that microheterogeneity of their natural 13C/12C abundance can now be mapped at a spatial resolution down to 10 μm. The respective δ13C values in soils with C3/C4 crop sequence history varied by up to 14‰across a distance of less than 100 μm in soil aggregates, while being partly sorted along rhizosphere gradients of <300 μm from Miscanthus plantroots into the surrounding soil. These very first demonstrations point to the appearance of very small metabolic hotspotsoriginating from different natural isotope discrimination processes, now traceable via LA-IRMS.