Relationship between ethylene adsorption isotherms and GC retention on Carbowax-coated porous graphite

The objective of this work was to correlate adsorption isotherms of ethylene at −78°C on porous graphitic carbon (PGC) with gas chromatographic performance, the intention being that such isotherms could be used as a quality control test for PGC's in general, whether used for GC, HPLC or other adsorptive purposes. GC of test solutes shows that severe peak tailing on bare PGC is removed almost totally by a coating PGC with as little as 0.05% by weight of Carbowax 1500. Surprisingly there is little corresponding change in the ethylene adsorption isotherms, although it is possible to distinguish small differences at surface coverages below 5% of a monolayer of ethylene. Further work is required to establish a useful QC test.