US EPA Method TO-17 is one of the most popular standard methods for sampling and analysing sorbent tubes, and is most commonly employed in monitoring programs in urban and industrial environments.
What does Method TO-17 involve?
Method TO‑17 involves pumping the sample atmosphere onto sorbent-packed TD tubes, which are then analysed by two-stage thermal desorption in conjunction with GC–MS. The method leaves open the options for sorbent packing, but in practice a multi-bed tube (and therefore backflush desorption) is essential to achieve the analyte range stipulated for ambient air monitoring.
In addition, Method TO-17 points out that use of sorbent tubes offers several options for handling humid air streams – including hydrophobic sorbents, a post-sampling dry purge and sample splitting during analysis.
What analytes are monitored under Method TO-17?
Method TO-17 is most commonly applied to ambient air monitoring, and in such cases it requires monitoring of the same target compound list as defined in Method TO-15 – namely, a subset of the 97 hazardous pollutants listed in the 1990 Clean Air Act Amendments. Typically, 65 compounds ranging from propene to naphthalene are used to judge compliance, and these include polar species such as ethanol, acetone, isopropanol and p-dioxane.
Method detection limits are stipulated as ≤0.5 ppbv, and Method TO-17 also defines acceptable performance criteria for analytical precision, linearity and reproducibility.
Complying with Method TO-17
From the above summary, it will be clear that Method TO-17 places considerable demands upon the equipment used for sampling and analysis.
Markes’ TD100-xr thermal desorber complies fully with the requirements of US EPA Method TO-17, and we also offer a range of supplies and equipment to assist with this application.