A new ice mill allows precise concentration determination of methane and most probably also other trace gases in the bubble air of very small ice samples

A new extraction system has been constructed and tested which allows the extraction of gases from air bubbles in ice without melting it. An ice sample of up to 20 g is crushed in a sealed container by a milling cutter and the gas escaping from the opened bubbles is flushed with helium to a Porapak column where it is stored until its injection into the gas Chromatograph. To avoid any contamination with CH 4 produced by friction in the gear section, a helium-flushed rotary feed-through is used. CH 4 analyses on ice samples of about 10 g from the last 1000 years give precise and reproducible results. In the future, it is planned to measure also the CO 2 and N 2 O concentrations on the same sample.