Abstract: Apparatus, and components for use in apparatus, for changing the concentration of a selected gas in a liquid, for example for degassing liquids. In one apparatus, the apparatus has a flow channel (a) through which the liquid is passed, and (b) which comprises a wall comprising a planar separation membrane, and (c) has a height of 0.00025-0.01 and an aspect ratio (width to height) of at least 25:1. One component, which can be used to support a separation membrane, comprises (a) an inner selection plate surface which comprises (i) a selection plate base and (ii) selection plate elements which (a) extend from the base, (b) are separated by intercommunicating selection areas, and (c) have outer surfaces remote from the selection plate base.

Abstract: A planar degasser comprises (1) a flow plate comprising a flow channel, (2) a planar separation membrane comprising a membrane transmission section which has a first major surface and a second major surface, the flow channel being at least in part bounded by the first major surface of the membrane transmission section, (3) a supporting member which supports the second major surface of the membrane transmission section when the pressure on the first major surface is greater than the pressure on the second major surface, and (4) structural features which enable liquid to flow through the flow channel when the pressure on the first major surface is equal to or less than the pressure on the second major surface, for example when there is no longer a vacuum on the second major surface of the membrane transmission section.

Abstract: Apparatus for changing the concentration of a selected gas in a liquid, the apparatus comprising a flow chamber through which the liquid is passed and which comprises a wall comprising a planar separation membrane, the separation membrane being substantially impermeable to the liquid and permeable to the selected gas, characterized in that the separation member extends beyond the flow chamber and provides a seal between components of the apparatus. The apparatus is particularly useful for degassing liquids, for example HPLC eluents and analysis samples.