![]() The effect of the adsorption of water vapor on all aspects of the sampling and analysis of polar molecules is of such importance as to require further investigation. Carbosieve S-III has a fine mesh-size, limiting the range of flow-rates that can be used ( OSHA, 1988 NIOSH, 2003). Presently, however, Anasorb CMS (carbon molecular sieve) is no longer commercially available. Carbon molecular sieves (Anasorb CMS and Carbosieve S-III) were evaluated in NMAM 2555, and in the Occupational Safety and Health Administration (OSHA) Analytical Method 69, respectively for the determination of acetone using extraction by carbon disulfide (CS 2) alone or with a cosolvent. As it became obvious that relative humidity had an important effect on the sampling of polar compounds on coconut charcoal, alternatives were sought ( Harper et al., 2000). Thermal desorption has become popular in some countries, but this technique can present problems for the sampling and analysis of highly volatile, reactive or unstable compounds, such as acetone.Ĭoconut shell charcoal was initially recommended by the National Institute for Occupational Safety and Health (NIOSH) Manual of Analytical Methods (NMAM) 1300 for the measurement of acetone, but this was based on preexisting methods where no account had been taken of relative humidity in the sampled air ( NIOSH, 1994). Solvent desorption is the most frequently employed method of sample recovery. At the end of the sampling period the adsorbed VOCs are separated from the solid adsorbent by one of two methods, either through solvent extraction or through thermal desorption. The tube and inner sorbent typically weigh only a few grams and are unobtrusive when clipped to workers’ clothes. The present study confirms not only previous observations but also adds to the literature showing carbonaceous sorbents are not well suited for sampling ketones at high humidity and low concentration.Īcetone, beaded active carbon, carbon molecular sieve, silica gel, sorbent tube sampling IntroductionĪ convenient and popular approach to sampling volatile organic compounds (VOCs) in breathing zones is to draw air through a tube containing a bed of sorbent, most often a porous adsorbent ( Harper et al., 2000). ![]() ![]() The likely cause of mass dependence may arise from the humidity effect on acetone adsorption onto both beaded active carbon and carbon molecular sieve either in sampling or in analysis. Silica gel provided a consistent recovery of acetone at all RHs and in the presence of other chemical interferences at 75% RH. There were significant reductions in the recovery of acetone from both Anasorb 747 and Carbosieve S-III collected from air at 75% RH, relative to collection at 25 or 50% RH at very low loading compared with that of samples collected at mid to high loading. Silica gel sorbent tubes analyzed according to NMAM 2027 were included. Additional extraction procedures with and without 1% dimethylformamide and anhydrous magnesium sulfate were included in the modified NMAM 1501 using Anasorb 747. Both methods were modified to include the additional analytes. ![]() Sorbent samples were analyzed in accordance with OSHA Method 69 (Carbosieve S-III) and NMAM 1501, modified to use Anasorb 747 sorbent. A dynamic atmosphere system produced an acetone alone and a mixture with other analytes containing ~73, 483, and 1898 µg acetone mass loading at 25, 50, and 75% relative humidity (RH) at 25☌. This study experimentally evaluates the performance of different sorbent tubes for sampling acetone vapor in workplace air.
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