title: Application of gas chromatography with a pulsed discharge helium ionization detector for measurements of molecular hydrogen in the atmosphere.
abstract: The Earth's troposphere contains approximately 160 Tg H2 with an average surface mixing ratio approximately 530 nmole mole(-1) (ppb) and lifetime of 2 years. Atmospheric H2 is typically measured using gas chromatography (GC) followed by hot mercuric oxide reduction detection (GC-HgO). Here we describe an alternate method using GC with a pulsed-discharge helium ionization detector (HePPD). HePPD is a universal detector; when applied to H2, the GC-HePDD provides a wide linear range (0.3% over a range of 2000 ppb), a detection limit of approximately 0.03 pg, high precision (0.12%) and a stable response (+/-1.6% over nearly one year). HePPD is compared to HgO reduction using a suite of gravimetrically prepared reference gases spanning remote to urban concentrations. The method is excellent for atmospheric measurements as it provides a wide linear range with high precision, stability and reproducibility. We suggest these characteristics will improve the ability to maintain reference gases and improve measurements of atmospheric H2, thus providing better constraints on potential future changes in its sources and sinks.
authors.affiliation: Global Monitoring Laboratory, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA. paul.c.novelli@noaa.gov
authors.forename: P C
authors.initials: PC
authors.lastname: Novelli
authors.forename: A M
authors.initials: AM
authors.lastname: Crotwell
authors.forename: B D
authors.initials: BD
authors.lastname: Hall
mesh_terms: D001272:Atmosphere; D002849:Chromatography, Gas / Q000379:methods*; D006371:Helium / Q000737:chemistry*; D006859:Hydrogen / Q000032:analysis*
chemical_list: D006371:Helium; D006859:Hydrogen