Page 188 - Illustrated Pocket Dictionary of Chromatography
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190 SUPERCRITICAL FLUID CHROMATOGRAPHY (SFC)
supercritical fluid chromatography (SFC) Utilizes a super-
critical fluid as the mobile phase and offers a means of effectively
analyzing compounds that are thermally labile and incompatible with
GC or have limited solubility in liquids used as LC mobile phases.
suppressor A component used in an ion-exchange chromato-
graphic system. It is positioned between the column and the detector
and “neutralizes” the effluent before it reaches the detector and
thereby dramatically reduces background noise.
A suppressor is used in conductivity detectors to reduce signal background gen-
erated by the ions in the mobile phase. In the case of a hydrochloric acid eluent,
a tetrabutyl ammonium hydroxide solution is used to exchange in the suppressor
column and produce water in the column (thereby reducing the ion concentration
and signal generated by the mobile phase) and remove the chloride and the
tetrabutyl ammonium chloride. Suppressor column solutions must be replenished
periodically.
surface area The surface area of a porous packing material is com-
monly determined through the calculation of nitrogen isotherms run
at -19°C (see BET test method). Surface area is typically expressed
2
as m /g of packing. High-surface-area packing materials are desirable
because this is where the solute equilibrium occurs. Surface areas