Solid Sorbent Tube Sampling

Sorbent Tubes

1.7.1 Solid Sorbent Tube Sampling

Solid sorbent tubes include large and small charcoal tubes, porous polymer tubes such as XADand XAD-7, large and small silica gel tubes, DNPH (dinitrophenyl hydrazine) tubes, Orbo tubes,Porapak Q, Tenax tubes, Firebrick tubes, Hydrar tubes and Florisil tubes. Sampling should be performed in the following manner:

  1. Calibrate each pump at the recommended flow rate for the analyte of interest, using are presentative solid-sorbent tube in-line. Calibrate each pump with a bubble meter or equivalent flow measuring device.
  2. Break the ends of the solid sorbent tube immediately before sampling. The openings should be at least ½ of the internal diameter of the tube. Use a tube tip breaker or file.
  3. Connect the solid sorbent tube to the tube holder, making sure the smaller sorbent section(backup section) is nearest the pump. The air that is being sampled should not pass through any hose or tubing before entering the solid sorbent tube. To avoid channeling and premature breakthrough, position the tube vertically during sampling.
  4. Prepare field blanks by breaking the ends of tubes from the same lot as the tubes that are being used for sampling. Handle the blanks in the same manner as the samples, but do not draw air through the blanks.
  5. Sample at an accurately known flow rate for the length of time necessary to obtain the specified air volume. Check the pump periodically during sampling to detect any changes inflow rate. If the accurate measurement of volume cannot be determined due to in consistent flow rates, discard the sample.
  6. Be sure to keep an accurate record of sampling data including sample location, beginning and en
    ding times of air sampling, temperature, relative humidity, atmospheric pressure or elevation above sea level, and name of employee.
  7. Seal the ends of the tubes with plastic caps immediately after sampling. Clearly label each sample with an appropriate identification number. Label each blank tube as a blank.
  8. Pack the tubes tightly for shipment to the laboratory, with adequate packing to minimize the possibility of breakage. Enclose a completed sample analytical request form (chain of custody) with each batch.
  9. Bulk samples are recommended when sampling chemical mixtures such as fuel oil,kerosene, etc. When it is necessary to ship a bulk sample along with the air samples, the bulk sample must be shipped in a separate package to avoid possible cross contamination.