Volatile Organic Compounds from Tenax® Tubes (VOST) by USEPA Method 30.
This methods describe the sampling, desorption and analysis of volatile organic compounds collected from stack gas effluents using volatile organic sampling train (VOST) methodology. Volatile organic compounds are collected on paired sets of sorbent traps (Tenax®/Tenax®-Charcoal). A total number of sorbent tube sets to encompass a total sampling time of 2 hours (one ‘run’) is collected: i.e., if a sampling rate of 1L/min for 20 minutes is used, a total of six sorbent tube sets will be collected in 2 hours of sampling. One condensate sample per run is typically collected and analyzed. One field blank and one trip blank per sampling event are also typically collected and analyzed.

A 20-liter sample of effluent gas is withdrawn from a gaseous effluent source at a flow rate of 1 L/min, using a glass-lined probe and a volatile organic sampling train (VOST). (Operation of the VOST under these conditions has been called FAST-VOST.) The gas stream is cooled to 20EC by passage through a water-cooled condenser and volatiles are collected on a pair of sorbent resin traps. Liquid condensate is collected in an impinger placed between the two resin traps. The first resin trap (front trap) contains approximately 1.6 g Tenax and the second trap (back trap) contains approximately 1 g each of Tenax and petroleum-based charcoal (SKC Lot 104 or equivalent), 3:1 by volume. A total of six pairs of sorbent traps may be used to collect volatile POHCs from the effluent gas stream.

Compliance sampling will usually consist of three runs as described above and require that the Tenax® and Tenax®-Charcoal tubes be analyzed separately to check for breakthrough (must recover <30% of the volatile principal organic hazardous constituents on the Tenax®-Charcoal (back-half) tube as was found on the Tenax® (front-half) tube if >75 ng is detected on the Tenax®-Charcoal trap).

Analysis of the traps is carried out by thermal desorption purge-and-trap by gas chromatography/mass spectrometry (see Method 5041A)

NOTE: SW-846 Method 5040 has been replaced by SW-846 Method 5041A, and SW-846 Method 8240 has been replaced by SW-846 Method 8260B.