TRAPPING EFFICIENCIES OF CAPILLARY COLD TRAPS FOR C2-C10 HYDROCARBONS

The trapping performance of four different capillary cold traps (deactivated, coated. Tenax-TA and Chromosorb 101 packed traps) for C2-C5 n-alkenes, isoprene, benzene, toluene, p-xylene, o-xylene, mesitylene, alpha-pinene, beta-pinene, 1,2,4-trimethylbenzene and 1,2,3-trimethylbenzene were determined over the temperature range -20 to -180-degrees-C. All the hydrocarbons except ethylene were found to be retained by all the traps at different temperatures, but only the Chromosorb 101 capillary trap retained ethylene, and then not completely. The coatings were found to increase the trapping efficiency for the higher hydrocarbons (greater-than-or-equal-to C6), whereas the packings increased the trapping efficiency for all compounds (C2-C10). A linear relationship was found between the boiling point of the compound and its maximum trapping temperature. The flow-rate of the carrier gas (10-60 ml/min) was found to affect the trapping efficiency of the C2-C4 hydrocarbons.