Separation of isotopic methanes by gas chromatography

Abstract

under these conditions a chemical reaction takes place between H?O?, H+, and NO?-(the radiation yield of NOz-was higher than that of H?Od and all the hydrogen peroxide was consumed. In the absence of NOn-the peak height of HzOn peaks was always proportional to the H202 concentration, obtained when NH4HS04 was used as the eluent.The elution curves of reference solutions of NaNOn, H202, and CH3NOr in N a N 0 3 obtained with 0.1M ("&SO4 are shown in Figure 2. Corresponding curves with 0.1M NH4HS04 are shown in Figure 3.The data obtained indicate that NOn-ions are sorbed only after neutralization to undissociated "02 molecules. The radiolytic products-Hz02, NO*-(in the form of "02) and CH3NOz-are sorbed on strongly acid Dowex 50 W-X8 (cationite), and their desorption proceeds in the order of increasing molecular weights as in the case of homologous series of nitroparaffins.The results indicate that chromatopolarography is applicable for the determination of radiolytic products.

Separation of Carbon Isotopes in Methane with Nanoporous Materials

“…The isotopic effect on carbon-substituted methanes 13 CH 4 , 14 CH 4 , and 12 CH 4 is even more diminutive in comparison with that introduced by isotopic hydrogen substitutions. Especially, the molar volumes of hydrocarbon compounds with peripheral deuterium atoms are substantially smaller than those with skeletal 13 C or 14 C atoms of the same molecular weight. ,, Conventional methods for isotopic separation are mostly based on macroscopic processes that utilize small differences in the thermodynamic or transport properties of bulk systems. ,− Whereas processes such as thermal diffusion, gas–liquid chromatography, or cryogenic distillation have been well-established for industrial production of carbon isotopes, these traditional techniques have extremely low overall separation efficiency and often entail intensive energy consumption and high operation cost. ,,, Relatively inexpensive methods such as chemical isotope exchange are not suitable for industrial-scale applications due to extra energy and material costs affiliated with the recovery of the isotopic products. − Despite its superior separation efficiency, the laser-induced plasma method cannot be scaled up to industrial operations because of high cost and technical difficulties related to the conversion of the direct chemical products to those widely used isotopic carbon compounds …”

“…Naturally occurring carbon consists of two stable isotopes, 12 C (98.89%) and 13 C (1.11%), and a minuscule amount of radioactive carbon 14 C (e.g., 1 part per trillion in the atmosphere). Among different molecular forms of carbon isotopes, labeled methane isotopes 13 CH 4 and 14 CH 4 are widely used in organic and analytical chemistry as a powerful agent to detect trace compounds in various chemical and biochemical systems.…”

Nitrogen Isotopic Fractionation in Ammonia during Adsorption on Silicate Surfaces

“…There is a lack of studies characterizing the isotopic fractionation associated with adsorption, although the gas chromatographic separation of isotopologues in adsorption–desorption processes has been frequently investigated in analytical chemistry. Bruner and Cartoni and Bruner et al showed that methane (e.g., CD 4 , 13 CH 4 , and CH 3 D) and oxygen isotopologues (e.g., 16 O 2 and 18 O 16 O) can be separated by gas chromatography using an adsorption glass capillary column. Van Hook later attempted to provide theoretical and statistical explanations of the reported gas chromatographic separation between the CH 4 and CD 4 systems. , There are several reports of other deuterated small-molecular-weight hydrocarbons , and molecular dinitrogen; however, methane and its deuterated isotopologues have been investigated most extensively.…”

“…Bruner and Cartoni and Bruner et al showed that methane (e.g., CD 4 , 13 CH 4 , and CH 3 D) and oxygen isotopologues (e.g., 16 O 2 and 18 O 16 O) can be separated by gas chromatography using an adsorption glass capillary column. Van Hook later attempted to provide theoretical and statistical explanations of the reported gas chromatographic separation between the CH 4 and CD 4 systems. , There are several reports of other deuterated small-molecular-weight hydrocarbons , and molecular dinitrogen; however, methane and its deuterated isotopologues have been investigated most extensively. In addition, adsorption isotopic fractionation is of interest in geological studies.…”

“…Van Hook 3 later attempted to provide theoretical and statistical explanations of the reported gas chromatographic separation between the CH 4 and CD 4 systems. 1,2 There are several reports of other deuterated small-molecular-weight hydrocarbons 4,5 and molecular dinitrogen; 6 however, methane and its deuterated isotopologues have been investigated most extensively. In addition, adsorption isotopic fractionation is of interest in geological studies.…”