T01_08

Direct Radiocarbon Analysis of Methane by Positive Ion Mass Spectrometry

Mcintyre C¹,  Shanks R¹, Gulliver P¹, Dolan M², Freeman S¹

¹SUERC, East Kilbride, UK, ²GENeco, Avonmouth, UK

After carbon dioxide (CO₂), methane is the second most abundant anthropogenic atmospheric green house gas and it has a warming potential 25 times that of CO₂. Radiocarbon (¹⁴C) is useful for tracking the source, fate and quantity of methane within the atmosphere however, current techniques for its analysis are lengthy and use multiple preparative steps for concentration, combustion and purification.

Positive ion mass spectrometry (PIMS) can directly analyse the ¹⁴C content of gases without the need for graphitization. It uses a plasma-based ion source to produce a positively charged carbon beam and a simple reaction cell to supress ¹⁴C interferences. This plasma-based ion source typically operates on carbon dioxide  but initial experiments have shown that methane analysis is also possible. Initial data from analysis of contemporary and fossil methane using PIMS will be presented and the performance compared with CO₂ PIMS and conventional AMS will be discussed. This new method opens up new areas of application, such as rapid biogas analysis.

In addition, the current status of the integration of automatic sample introduction to the PIMS system and its performance will be presented.