Dataset Information

Managing argon interference during measurements of ¹⁸O/¹⁶O ratios in O₂ by continuous-flow isotope ratio mass spectrometry.

ABSTRACT: Monitoring changes in stable oxygen isotope ratios in molecular oxygen allows for studying many fundamental processes in bio(geo)chemistry and environmental sciences. While the measurement of [Formula: see text]O/[Formula: see text]O ratios of [Formula: see text] in gaseous samples can be carried out conveniently and from extracting moderately small aqueous samples for analyses by continuous-flow isotope ratio mass spectrometry (CF-IRMS), oxygen isotope signatures, [Formula: see text]O, could be overestimated by more than 6[Formula: see text] because of interferences from argon in air. Here, we systematically evaluated the extent of such Ar interferences on [Formula: see text]O/[Formula: see text]O ratios of [Formula: see text] for measurements by gas chromatography/IRMS and GasBench/IRMS and propose simple instrumental modifications for improved Ar and [Formula: see text] separation as well as post-measurement correction procedures for obtaining accurate [Formula: see text]O. We subsequently evaluated the consequences of Ar interferences for the quantification of O isotope fractionation in terms of isotope enrichment factors, [Formula: see text], and [Formula: see text]O kinetic isotope effects ([Formula: see text]O KIEs) in samples where [Formula: see text] is consumed and Ar:[Formula: see text] ratios increase steadily and substantially over the course of a reaction. We show that the extent of O isotope fractionation is overestimated only slightly and that this effect is typically smaller than uncertainties originating from the precision of [Formula: see text]O measurements and experimental variability. Ar interferences can become more relevant and bias [Formula: see text] values by more than [Formula: see text] in aqueous samples where fractional [Formula: see text] conversion exceeds 90%. Practically, however, such samples would typically contain less than 25 [Formula: see text]M of [Formula: see text] at ambient temperature, an amount that is close to the method detection limit of [Formula: see text]O/[Formula: see text]O ratio measurement by CF-IRMS.

SUBMITTER: Bopp CE

PROVIDER: S-EPMC9314310 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Publications

Managing argon interference during measurements of 18O/16O ratios in O2 by continuous-flow isotope ratio mass spectrometry.

Bopp Charlotte E CE Bolotin Jakov J Pati Sarah G SG Hofstetter Thomas B TB

Analytical and bioanalytical chemistry 20220716 20

Monitoring changes in stable oxygen isotope ratios in molecular oxygen allows for studying many fundamental processes in bio(geo)chemistry and environmental sciences. While the measurement of [Formula: see text]O/[Formula: see text]O ratios of [Formula: see text] in gaseous samples can be carried out conveniently and from extracting moderately small aqueous samples for analyses by continuous-flow isotope ratio mass spectrometry (CF-IRMS), oxygen isotope signatures, [Formula: see text]O, could be ...[more]

PMID: 35841416

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Project description:Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations (e.g., drought) that impact water availability. However, relatively few studies have examined variation in the sources of water animals use to maintain water balance, and even fewer have focused on the role of metabolic water. A key reason is methodological limitations. Here, we applied a new method that measures the triple oxygen isotopic composition of a single blood sample to estimate the contribution of metabolic water to the body water pool of three passerine species. This approach relies on Δ'17O, defined as the residual from the tight linear correlation that naturally exists between δ17O and δ18O values. Importantly, Δ'17O is relatively insensitive to key fractionation processes, such as Rayleigh distillation in the water cycle that have hindered previous isotope-based assessments of animal water balance. We evaluated the effects of changes in metabolic rate and water intake on Δ'17O values of captive rufous-collared sparrows (Zonotrichia capensis) and two invertivorous passerine species in the genus Cinclodes from the field. As predicted, colder acclimation temperatures induced increases in metabolic rate, decreases in water intake, and increases in the contribution of metabolic water to the body water pool of Z. capensis, causing a consistent change in Δ'17O. Measurement of Δ'17O also provides an estimate of the δ18O composition of ingested pre-formed (drinking/food) water. Estimated δ18O values of drinking/food water for captive Z. capensis were ~ -11‰, which is consistent with that of tap water in Santiago, Chile. In contrast, δ18O values of drinking/food water ingested by wild-caught Cinclodes were similar to that of seawater, which is consistent with their reliance on marine resources. Our results confirm the utility of this method for quantifying the relative contribution of metabolic versus pre-formed drinking/food water to the body water pool in birds.

Dataset Information

Managing argon interference during measurements of ¹⁸O/¹⁶O ratios in O₂ by continuous-flow isotope ratio mass spectrometry.

Publications

Managing argon interference during measurements of <sup>18</sup>O/<sup>16</sup>O ratios in O<sub>2</sub> by continuous-flow isotope ratio mass spectrometry.

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