Graduate Thesis Or Dissertation
 

A comparison of porous polymers used in collecting organic volatiles in foods

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  • Porapak Q, Chromosorb 102, and Tenax GC, three porous polymers commonly used as adsorbents in headspace analyses were investigated. The retention times of various low-boiling compounds relative to water were measured on the collection columns to determine which compounds would be lost during the water removal step employed after sampling aqueous materials. Compounds eluted fastest from Tenax GC precolumns and slowest from Porapak Q, with retention times on Chromosorb 102 generally intermediate. Thus, loss of low-boiling compounds relative to water was greatest on Tenax GC and limited the use of this polymer for quantitative study of samples containing low-boiling volatile compounds. The residual water in Porapak Q precolumns employed in the usual procedure for collection of volatile materials by entrainment from aqueous systems, could be completely eluted in 15 min with a N₂ purge of 30 ml/min at 55°C. without appreciable loss of collected organic compounds. Retention times of high-boiling organic compounds were determined on the precolumns, and those containing Tenax GC had shorter times than Chromosorb 102 or Porapak Q. Under conditions employed for unloading trapped compounds from precolumns, fewer compounds remained on Tenax GC precolumns. Thus, Tenax GC appeared to be the trapping polymer of choice in investigations involving high-boiling compounds. Back flushing of Porapak Q, Chromosorb 102, and Tenax GC precolumns during unloading was essential in order to recover the trapped organics within the time allotted for unloading at 135°C. At 280°C back flushing on Tenax GC was not necessary to insure unloading since retention times were well within the unloading period. The recovery of n-undecane from the precolumns after simulated water removal conditions was found to be 98.5% for Tenax GC, 99.5% for Porapak Q, and 100.0% for Chromosorb 102.
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