【讨论】《环境空气 挥发性有机物的测定 吸附管采样热脱附/气相色谱-质谱法》（征求意见稿）

方法基本是参照EPA TO-17做的,细节上的修改,如吸附剂选择,
EPA中规定比较原则性,有较多的种可选择,可以是几种组合用于未知物的监测,而对常规只须选定一种吸附剂,而新标准只规定一种吸附剂(Carbopack B，40/60 目；CarbopackC，40/60 目；Carboxen 1000，45/60目或其它等效吸附剂.)

9.1.3 Three General-Purpose 1/4 Inch or 6 mm O.D. Multi-Bed Tube Types.
[Note: The three general-purpose tubes presented in this section are packed with sorbents in the mesh size
range of 20-80 mesh. The difference in internal diameter between standard glass and stainless steel tubes
will result in different bed volumes (weights) for the same bed length.]
9.1.3.1Tube Style 1 consists of 30 mm Tenax®GR plus 25 mm of Carbopack™ B separated by 3 mm
of unsilanized, preconditioned glass or quartz wool. Suitable for compounds ranging in volatility from n-C to 6n-C for air volumes of 2 L at any humidity. Air volumes may be extended to 5 L or more for compounds 20ranging in volatility from n-C . 7
9.1.3.2Tube Style 2 consists of 35 mm Carbopack™ B plus 10 mm of Carbosieve™ SIII or Carboxen™
1000 separated by glass/quartz wool as above. Suitable for compounds ranging in volatility from n-C to n-C 3 12(such as ?Compendium Method TO-14 air toxics”) for air volumes of 2 L at relative humidities below 65% andtemperatures below 30EC. At humidities above 65% and ambient temperatures above 30EC, air volumes shouldbe reduced to 0.5 L. Air volumes may be extended to 5 L or more for species ranging in volatility from n-C . 4A dry purge procedure or a large split ratio must be used during analysis when humid air has been sampled on
these tubes.
9.1.3.3 Tube Style 3 consists of 13 mm Carbopack™ C, 25 mm Carbopack™ B plus 13 mm of Carbosieve™ SIII or Carboxen™ 1000 all separated by 3 mm plugs of glass/quartz wool as above. Suitable for compounds ranging in volatility from n-C to n-C for air volumes of 2 L at relative humidities below 65 percent 3 16 and temperatures below 30EC. At humidities above 65 percent and ambient temperatures above 30EC, air volumes should be reduced to 0.5 L. Air volumes may be extended to 5 L or more for compounds ranging in volatility from n-C . A dry purge procedure or a large split ratio must be used during analysis when humid air 4 has been sampled on these tubes.

[Note: These multi-bed tubes are commercially available prepacked and preconditioned if required.]
[Note: These general purpose multi-bed tubes are only recommended for monitoring unknown atmospheres or wide volatility range sets of target analytes. Most routine monitoring of industrial air (for example at factory fencelines) only involves monitoring a few specific target analytes such as benzene, toluene,ethylbenzene, and xylenes (BTEX), carbon disulfide (CS2) or 1,1,1-trichloroethane. Single-bed sorbent tubes selected from the options listed in Appendix 1 are typically used in these cases.]