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Issue 12, 2013
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High-precision helium isotope measurements in air

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Abstract

Helium has two natural isotopes which have contrasted, and variable sources and sinks in the atmosphere (3He/4Heair = 1.382 ± 0.005 × 10−6). Variations in the atmospheric helium isotopic composition may exist below typical measurement precision thresholds (0.2 to 0.5%, 2σ). In order to investigate this possibility, it is necessary to be able to consistently measure helium isotopes in air with high precision (below 0.2% 2σ). We have created an air purification and measurement system that improves the helium isotope measurement precision. By purifying a large quantity of air at the start of a measurement cycle we can make rapid standard-bracketed measurements. Controlling the amount of helium in each measured aliquot minimizes pressure effects. With this method we improve the standard errors by 2× over measuring the same amount of gas in a single step. Individual measurements have standard errors of 0.2 to 0.3% (2σ), with three repeat samples needed to reach 0.1% or better errors. The long-term reproducibility of our calibration sample is 0.033% (2σ).

Graphical abstract: High-precision helium isotope measurements in air

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Publication details

The article was received on 30 Apr 2013, accepted on 13 Sep 2013 and first published on 13 Sep 2013


Article type: Paper
DOI: 10.1039/C3JA50155H
Citation: J. Anal. At. Spectrom., 2013,28, 1903-1910
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    High-precision helium isotope measurements in air

    J. Mabry, T. Lan, P. Burnard and B. Marty, J. Anal. At. Spectrom., 2013, 28, 1903
    DOI: 10.1039/C3JA50155H

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