Combined Isotopic Analysis of Nanogram Quantities of Atmospheric Methane

✍ Scribed by Andrew D. Morse; G. H. Morgan; A. L. Butterworth; I. P. Wright; C. T. Pillinger

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 378 KB
• Volume: 10
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(199611)10:14<1743::aid-rcm762>3.0.co;2-r

✦ Synopsis

Stable isotope measurements are increasingly utilized to constrain global budgets of atmospheric trace gases.

Published analytical techniques for studying the parallel stable isotopic composition of methane (6I3C and SD) require prohibitively large quantities of methane for analysis. In a break from convention, a static mass spectrometer has been developed to use aliquots of methane as the analyte. These measurements yield the relative abundances (6I7M, %o) of the major isotopomers of methane (13CH,' and "CDH,') with "CHI+. Analyses of 0.5 nmol samples of NGS standards have shown that 617M can be determined with a precision of f 0.2960. If the 6°C of the sample is known then 6D may be calculated from the measured 6I7M. Calculations show that a precision of 0.2%0 for Si7M is equivalent to measuring SD with a precision of f 3.6% (cf. f 2 -3 s by conventional means). Where S1'C is not known, then 6"M still provides useful information on methane sources, in effect combining SI3C and SD.