Quantitative Production of H₂ by Pyrolysis of Gas Chromatographic Effluents

Abstract

Hydrogen gas can be produced quantitatively from nanomole amounts of organic H in continuously flowing gas streams. The system described here is suitable for use in isotope-ratio-monitoring mass spectrometric systems and is based on a pyrolysis reactor consisting of a graphitized alumina tube heated to 1450 °C. Methane forms as an intermediate product at temperatures above 750 °C, but, for all tested analytes, yields of H 2 were quantitative at temperatures between 1430 and 1460 °C, provided residence times in the reactor were greater than 300 ms. Quantitative yields of H 2 were obtained for all components of a homologous series of n-alkanes (C 15 to C 30 ). Analyses of low-molecular-weight alcohols demonstrated that O-bound H was also quantitatively converted to H 2 and, thus, that H 2 O, if formed, was quantitatively reduced to H 2 .

Isotope‐ratio detection for gas chromatography

“…Pyrolysis over reduced carbon eliminates that problem [29], as well as the possibility of memory effects associated with metal reductants [28], and is now almost ubiquitous in its use. Burgoyne and Hayes [30] were the first to show that quantitative pyrolysis can be achieved without metal reductants by using a carbon-lined reactor heated to >14408C. At this temperature, organic analytes are converted to H 2 and either solid carbon (carbon black) or CO, depending on the presence of oxygen.…”

“…At this temperature, organic analytes are converted to H 2 and either solid carbon (carbon black) or CO, depending on the presence of oxygen. At lower temperatures methane is a significant product, and fractionation is induced by the nonquantitative conversion to H 2 [30]. Nichrome resistance heaters cannot reach such high temperatures, and most pyrolysis interfaces use silicon carbide resistance elements such as those sold by Kanthal-Globar (Amherst, NY).…”

Eastern tropical Pacific hydrologic changes during the past 27,000 years from D/H ratios in alkenones

“…The Trace GC was equipped with a PTV inlet operated in splitless mode, a 30 m DB-5 capillary column with 0.25 mm ID and 0.25 mm film thickness. With helium as carrier gas, the effluent from the GC entered the Combustion III interface, a graphite-lined tube held at 1400°C, where the sample was quantitatively pyrolyzed to graphite, H 2 and CO [Burgoyne and Hayes, 1998]. The hydrogen gas was then introduced to the mass spectrometer through an open split.…”

Interlaboratory comparison of <i>δ</i><sup>13</sup>C and <i>δ</i>D measurements of atmospheric CH<sub>4</sub> for combined use of data sets from different laboratories

“…The number of measurements was limited not only because of laborious and time-consuming laboratory procedures but also because large volumes of air sample were required (> 100 L STP for δD-CH 4 ). Later, a method based on a continuous-flow gas chromatography isotope ratio mass spectrometry (GC-IRMS) technique combined with combustion and pyrolysis furnaces became available (Merritt et al, 1995;Burgoyne and Hayes, 1998;Hilkert et al, 1999), which dramatically reduced time and effort in the laboratory and likewise the amount of sample air required (now typically 100 mL STP ). Such systems are now used in most laboratories worldwide to acquire δ 13 C-CH 4 and δD-CH 4 data in the current and past atmosphere (Rice et al, 2001;Miller et al, 2002;Sowers et al, 2005;Ferretti et al, 2005;Morimoto et al, 2006;Fisher et al, 2006;Umezawa et al, 2009;Brass and Röckmann, 2010;Sperlich et al, 2013;Schmitt et al, 2014;Bock et al, 2014;Brand et al, 2016;Röckmann et al, 2016).…”