New Alumina Column Shows Promise for Analysing Chlorofluorocarbons

A unique deactivation for alumina PLOT columns has recently been developed to control the high activity of alumina surfaces. Rt®-Alumina BOND/CFC columns utilize this deactivation and provide high retention and high selectivity for volatile halogenated hydrocarbons, without the activity that is usually observed with alumina adsorbents. Chlorofluorocarbon analysis, in particular, can benefit from this new technology.

Chlorofluorocarbons (CFCs) are a group of halogenated hydrocarbons that were heavily used as refrigerants and propellants, until their role in the depletion of the earth’s ozone layer became known. In addition to being active ozone depleting substances, CFCs are also greenhouse gases that contribute to global warming. Now, the manufacture of CFCs is prohibited in most countries and the use of recycled material is restricted. Because of this, CFC analysis has become a priority,

particularly in the environmental field and for industry as companies develop alternative compounds. CFCs are highly volatile and amenable to gas chromatography, but an extremely retentive GC column is needed for successful analysis. Thick film nonpolar capillaries can be used, but these are low in efficiency and generally do not perform optimally. Separations of CFCs have also been done with packed columns, as they can be made with adsorbents or liquid phases with a low phase ratio which allows the resolution of volatile compounds with very specific selectivity. Separations on packed columns are mainly possible due to selectivity combined with high k values; efficiency is still relatively poor as the number of theoretical plates is very low.

The introduction of chemically bonded phases and porous layer open tubular (PLOT) capillary columns allowed selectivity to be combined with a high number of theoretical plates, which provided more opportunity for resolution. Alumina, in particular, offers high retention and good selectivity for a large range of CFCs, but historically these columns have been limited by high activity. Restek recently developed the Rt®-Alumina BOND/CFC column, a new alumina PLOT column which uses a unique deactivation that is quite promising for CFC analysis.