Tenax® GR is a porous polymer resin based on 2,6-diphenylene-oxide plus 30% Graphite. It is a widely used adsorbent resins for use with Purge and Trap Thermal Desorption for applications such as trapping VOC's in air and liquids. Tenax GR is especially beneficial in trapping volatile organics from high moisture content samples due to its low breakthrough volume for water. It is available from Scientific Instrument Services in 5.0, 10.0 and 25 gram bottles.
Determination of Back Pressure Versus Flow for Adsorbent Resins
A desorption tube filled with adsorbent resin can produce significant back pressures for the sampling pump when collecting a sample. If the back pressure is too high the air sampling pump will fail. For efficient operation the Back Pressure should not exceed 25. inches of water. In order to determine the Back Pressure at the end of the thermal desorption tube with flow at a fixed rate, the above system was set up. Flows were calibrated through the desorption tube packed with the measured amount of resin and the pressures recorded as a function of flow for both 3.0 and 4.0 mm I.D. desorption tubes. From this data it can be seen that for a 3.0 mm I. D. tube packed with 100 milligram of Tenax GR, the sample pump should not exceed 75 ml/minute. For a 4.0 mm I.D. tube packed with 100 milligram of Tenax TA, one can safely collect samples at flows in excess of 200 ml/minute.
Back Pressure expressed in inches of water
Yttria coated filament at start
Yttria coated filament after 16,000 cycles