The Stability of 100 ppb Hydrogen Sulfide Standards

Abstract

An experimental study has been performed to determine the factors affecting the stability of hydrogen sulfide calibration mixtures at concentrations below 1 ppm. Quantitative data was obtained that illustrates that material selection and surface treatment are major factors affecting the shelf life of low concentration reactive gas mixtures. With the proper material selection and surface treatment, hydrogen sulfide and carbonyl sulfide standard mixtures on the order of 50-100 ppb can be maintained for at least 18 months.

Measurement of Parts per Million Level Gaseous Concentration of Hydrogen Sulfide by Ultraviolet Spectroscopy using 1,1,1,5,5,5-Hexafluoropentan-2,4-dione as a Derivative by Reaction of Cu(hfac)(1,5-Cyclooctadiene)

“…Results of analyses are given in Table and Table . Benesch et al have discussed the handling of gas mixtures containing trace amounts of H 2 S and concluded that aluminum storage cylinders are the best choice. In this investigation, mixtures were prepared in N 2 or other carrier gases at high pressure in a well aged aluminum cylinder (method HP) and at low pressure in a polypropylene cylinder (method LP).…”

Enhanced Stability of Stable Isotopic Gases

“…Typically, as the cylinder pressure decreases, species which may be present on the surface of the cylinder, such as moisture, can desorb from the cylinder surface. 8 Trace moisture is known to desorb from compressed gas cylinder walls below approximately 4 bar; 11 therefore, if there is any residual moisture remaining in the compressed gas cylinder, the CO 2 –oxygen isotopic ratios will change as the cylinder is depleted, with more pronounced effects below approximately 4 bar.…”

“… 5 They will come in contact with the cylinder material or impurities present in the mixture and react or adsorb, thus forming new compounds. By understanding the factors that affect the stability, those having an impact can be minimized with appropriate material selection, 6 , 7 cylinder treatment, 8 and quality control of the source material used to prepare the mixtures. 5 Stable isotope mixtures used for calibration of analytical equipment have an added degree of complexity: the isotopic composition, in addition to the molecular concentration, must remain stable.…”

“…A previous work by Gonfiantini et al focused on δ 13 C-CO 2 ratios and how they changed with the addition of 13 C-enriched CO 2 into natural-abundance CO 2 . In compressed gas cylinders, moisture is ubiquitous and known to cause stability issues; , therefore, these experiments focused on using added moisture to highlight the 18 O- 16 O exchange between the moisture and CO 2 . Gaseous carbon dioxide was chosen as a proxy for these evaluations as it is known that the oxygen in CO 2 and the oxygen in water (H 2 O) can undergo exchange reactions as illustrated For stable isotope mixtures to be stable (both in composition and isotopic signatures), there must be no residual moisture to participate in exchange reactions .…”

“…cause stability issues;5,8 therefore, these experiments focused on using added moisture to highlight the 18 O-16 O exchange between the moisture and CO 2 . Gaseous carbon dioxide was chosen as a proxy for these evaluations as it is known that the oxygen in CO 2 and the oxygen in water (H 2 O) can undergo exchange reactions 10 as illustrated…”