Gas-Solid or PLOT Columns


PLOT (Porous Layer Open Tubular) columns are intended for the separation of very volatile solutes (primarily gases) without the need for cryogenic or sub-ambient cooling of the oven. Separations that would require column temperatures below 35°C, even with thick film liquid stationary phase can be obtained at temperatures above 35°C with PLOT columns.


Gas-solid or PLOT column stationary phases are physically different than polysiloxanes and polyethylene glycols. Gas-solid stationary phase are small, porous particles. The particles are stuck to the inner wall of the capillary tubing using a binder or similar means. Solutes are separated based on differences in their adsorption properties. Since the particles are porous, size and shape differentiation occurs also.


GS-Alumina columns are well suited for the separation of C1-C10 hydrocarbons and small aromatics. The KCl version of the GS-Alumina column changes the retention order for some


of the hydrocarbons. The HP-PLOT Q column provides slightly better separation for C1-C3 hydrocarbons, but C4 and higher hydrocarbons are better separated with a GS-Alumina column. HP-PLOT Q exhibits extremely long retention times and very broad peaks for C6 and higher hydrocarbons and aromatics. HP-PLOT Q separates sulfur gases from each other


and form most light hydrocarbons. HP-PLOT Molesieve is used to separate many noble and permanent gases. GS-GasPro columns combine many of the features of the various other PLOT columns. Light hydrocarbons, inorganic gases and solvents are some of the samples suitable for GS-GasPro.


Primary Selectivity Interactions in PLOT Phases Dispersive


Shape/Size Zeolites


Dispersive Shape/Size


Bonded Graphitized Carbon Molecular Sieves


Zeolite/Molesieve: HP-PLOT Molesieve


Graphitized Bonded Carbon: GS-CarbonPLOT Porous Ploymers: Bonded Silica:


Alumina/Al2O3: Proprietary Phase:


HP-PLOT Q, HP-PLOT U GS-GasPro


GS-Alumina, GS-Alumina KCl, HP-PLOT Al2O3 KCl, HP-PLOT Al2O3 “S”, HP-PLOT Al2O3 “M” GS-OxyPLOT


Porous Polymers PLOT Column Examples


Ionic Surface Bonded Silica


Ionic Surface


Alumina/Al2O3 GS-OxyPLOT


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