Supplies and Services for Mass Spectrometers, Gas Chromatographs
and Liquid Chromatographs
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32 | Last Update: 01/31/00 |
INTRODUCTION
Adsorbent resins such as Tenax TA, Tenax GR and a wide variety of activated charcoals are widely used to trap volatile and semi-volatile organics from gas or liquid samples when utilizing purge and trap techniques for the trapping and subsequent analysis of volatiles from gas, liquid or solid matrix samples. Adsorbent resins are specified in several EPA methods for air and water testing. Manufacturers of these resins report the breakthrough volumes for organics on these resins at room temperature. This data is required in order to determine the gas volume which can be sampled in order to efficiently trap the organics on the resin bed without any loss due to elution off the resin bed. However, little data is available on the breakthrough volumes at elevated temperatures. This data is required in order to determine the desorption temperature, gas volumes and desorption times required to thoroughly elute the analytes off the resin bed for quantitative analysis of these analytes.
This paper describes the parameters which must be considered when selecting an adsorbent resin for a particular application. A GC equipped with a FID detector was used to analyze adsorbent traps packed with seven different adsorbent resins (Figure # 1) to determine the breakthrough volumes for a large number of hydrocarbons and alcohols as a function of desorption temperature. A series of Breakthrough Volume charts were developed to permit the proper selection of the adsorbent resin which will permit the accurate and quantitative collection and desorption of analytes off the various resins. Finally, all the data was condensed into histogram bar charts to permit the quick comparison of different adsorbent resins for classes of organic compounds. These charts will aid the analyst in the selection of appropriate resins for a particular application.
