A punch assembly for releasing individual samples contained in metallic capsules into an analytical instrument includes a punch for piercing the capsule. The punch has a generally cylindrical piercing front end having a chamfered front surface formed by a plane cutting the front surface at an oblique angle and a central longitudinal channel extending from the front surface through the length of the punch. The cylindrical front end has a diameter which is only moderately smaller than the interior diameter of the capsule, so that the punch acts at least in part as a piston to push the sample material into the longitudinal channel which is connected to the analytical instrument. A relatively rapid flow of transfer gas is caused to flow around the surface of the punch into the capsule to both avoid sample loss and to carry the rest of the sample into the longitudinal channel. The punch assembly thus tends to inject all of the sample into the analytical instrument (e.g., a gas chromatograph) rapidly as a discrete relatively compact "packet" or "slug" of sample material.
