Matt and others,
We (the USGS Energy Resources Program) are currently engaged in a project to develop a suite of natural gas standards to replace the old NGS gases that were formerly distributed by NIST. We are hoping to produce three gas mixtures containing methane, ethane, and propane with d2H and d13C compositions ranging from -50 to -350 and -15 to -85, respectively. Our plan is to start with pure methane, ethane, and propane of intermediate d2H and d13C compositions and spike in small quantities of D and 13C enriched or depleted methane, ethane, propane to achieve the desired range of isotopic compositions. These individual gas components will then be calibrated against primary standards, and then blended together to create the three gas mixes (light C1, C2, C3; intermediate C1, C2, C3; and heavy C1, C2, C3).
Methane, ethane, and propane of intermediate isotopic composition (d2H~-150 and d13C~-40) is readily available from our local gas supplier. Cambridge Isotope Laboratories (http://www.isotope.com) sells 13C and D enriched methane, ethane, and propane as well as 13C depleted methane. They likely sell other gases that would be useful to you.
We are currently searching for a source of 13C depleted ethane and propane, and a source of D depleted methane, ethane, and propane. I would greatly appreciate it if anyone can help us locate a source for these gases. Alternatively, we are considering a number of potential methods for producing these light gases in our laboratory (eg., Fischer-Tropsch synthesis, pyrolysis of carboxylic acids, catalytic isotopic exchange, etc.). If anyone has any ideas for a simple method for generating isotopically light methane, ethane, and propane I would love to hear your suggestions.
Geoffrey S. Ellis, PhD
Energy Resources Program
US Geological Survey