Dear Keisuke and all

Much field collection of gases, and, as far as i'm aware, the global networks for atmoshperic sampling, use glass flasks with teflon taps (or vacuum grease taps), for 0.1 to 3 litres of sample - with impeccable results. But if your samples will be fairly numerous, the cost of such flasks can be considerable. I've also used the exetainers (volume 13 ml) commonly used in breath tests on CF-IRMS, and they can be adeqately used for air of ambient CO2 concentration. Delta-13C results are good, s.d within 0.2 per mil, with room for improvement. A few samples showed leakage, but because the ppm of air was measured at the time of measurement, these samples could be excluded later by comparing the measured value with the sample size as measured by the mass spec. Samples were analysed after three months, which included 24hrs in air freight. Delta-18O values were not possible due to some exchange occurring (not with water vpaour, the samples were dried). The samples were analysed on a Europa ANCA 20/20, in tracer gas mode.

I'm aware that there are other labs which do analyses similar or smaller volumes, with better precisions, and would also be interested to hear of any other methods/ variations on the same theme.

I hope this helps.

Jim Gillon
Dept of Environmental and Energy Research
Weizmann Institute of Science
76100 Rehovot
Israel

Tel: 972-8-9344227
Fax: 972-8-9344124
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