Abstract: An analysis device for mass discrimination is disclosed. The analysis device comprises: a sample chamber for holding a gaseous sample; an analysis chamber arranged to receive sample gas from the sample chamber; a mass discriminator arranged to discriminate in the analysis chamber between ion species generated from the sample gas; and a wall separating the sample chamber from the analysis chamber, the wall comprising a rupture zone controllable to rupture and thereby release sample gas from the sample chamber into the analysis chamber. In one embodiment the rupture zone is adapted to rupture on application of an electric current or mechanical force. The wall may be micromachined. A method of mass discrimination is also disclosed.