A suppressor is also a device used in ion chromatography, a specific form of High-Performance Liquid Chromatography. The suppressor is used to decrease the background conductivity of the mobile phase to increase the limit of detection for the ions being separated. The suppressor is placed after the analytical column and before the detector.
The original IC suppressors were made using semi-permeable membranes. The mobile phase (a dilute carbonate solution for example) would be pumped through the suppressor on one side of the membrane, while a solution of counter-ions (dilute sulfuric acid would typically be used in the case of a carbonate mobile phase) was pumped through on the other side of the membrane. If the concentrations of the mobile phase and suppressor ions were balanced properly, their charges would cancel each other, and the ions being separated by the chromatography system would represent the majority of the conductivity measured by the detector.
Dionex Corporation is the leading manufacturer of ion chromatography equipment and supplies. They are now marketing their fifth generation of suppressors. After the original membrane suppressors, the next step was to use semi-permeable fibers instead of membranes. The last two generations have employed electrolysis of water to generate the necessary counter-ions to suppress mobile phase conductivity.