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Gas analysis, volatile organic, solvent analysis, indoor air quality

TO-15 is a recently written method (but not a new method) for volatile organics which offers more options than the older method TO-14. From our perspective, the main advantage of TO-15 is its applicability to water soluble compounds such as alcohols, ketones, and other small polar organic compounds. This difference is due to the differences in sample concentration steps for each method. TO-14 uses cryogenic preconcentration while TO-15 uses an adsorbent trap. 

The adsorbent trap is the same trap used in the volatile organics analysis of water and soil samples (EPA 502, 601/602, 8240, 8260, etc.) which retains organics while passing water. This is not a new approach, since we and probably others have been using it for many years. This is just the first time EPA has put it in writing. 

TO-15 also allows ambient air to be sampled onto solid adsorbent tubes in the field. This is not a procedure that we can recommend because we feel the negative aspects outweigh the potential gain in detection limits. Most analytical instruments (GC and GCMS with volatile organic concentrators) have limited dynamic ranges (approximately 1-200 ppb for ambient air). If the sample is not in this range and you have used the entire sample tube for the first analysis, the option of taking a portion of the sample or diluting the sample is not available. High level samples can cause the systems to become contaminated. At least with samples in canisters, samples can be screened for high levels prior to low level analysis. 

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