Evaluation of a new graphitized carbon black employed in sampling volatile organic compounds

Evaluation of three types of passive samplers for measuring 1,3-butadiene and benzene at workplaces

1,3-Butadiene and benzene are common pollutants in both workplace and ambient air and have received attention for their adverse effects on human health. In exposure studies, simple and sensitive personal monitoring methods are preferable. Thermal desorption passive samplers seem optimal for this purpose, although in occupational studies chemical desorption samplers have been used more often. This may be because their utility for monitoring occupational atmospheres has not been thoroughly validated. Therefore, we evaluated thermal desorption passive samplers containing Carbopack X adsorbent from three manufacturers: Perkin Elmer, SKC-Ultra and Radiello. The uptake rates of benzene and 1,3-butadiene by these samplers were determined over 4 h or 8 h in exposure chamber studies at three concentrations likely to be found in occupational air. The samplers were also tested in a field study, at a petroleum refinery. The results were analyzed using multiple linear regression, and intra-class correlation coefficients (ICCs) were calculated to compare uptake rates of the three passive samplers to those of an active sampler. The three samplers had similar and acceptable accuracy (ICC≥0.9) for measuring benzene concentrations in the field environments, but only the Perkin Elmer sampler gave acceptable ICC values (∼0.85) for 1,3-butadiene over a full 8 h working shift in the field test. The results indicate that passive thermal desorption monitors can provide considerably lower limits of detection than chemical desorption monitors after 4-8 h sampling time, even down to environmental background concentrations, enabling comparison with measurements in ambient air.

Evaluation of multi-walled carbon nanotubes as an adsorbent for trapping volatile organic compounds from environmental samples

A type of purified multi-walled carbon nanotubes (PMWCNTs) prepared by catalytic decomposition of methane, with a surface area of 98 m2/g, was evaluated as an adsorbent used for tapping volatile organic compounds (VOCs). The performance in evaluation was based on breakthrough volumes (BTVs) and recoveries of selected VOCs. PMWCNTs were also used as a trap packing material to adsorb VOCs purged from spiked water sample. Due to their porous structure, PMWCNTs were found to have much higher BTVs than that of Carbopack B, a graphitized carbon black with the same surface area as PMWCNTs. The recoveries of the tested VOCs trapped on PMWCNTs ranged from 80 to 110%, and not affected by the humidity of purge gas. The results indicate that PMWCNTs are a potential useful adsorbent for direct trapping VOCs from air samples and may be a supplement to VOCARB 3000, a commercially available trap, in purge-and-trap system to preconcentrate VOCs from water samples.

Evaluation of multi-walled carbon nanotubes as gas chromatographic column packing

Purified multi-walled carbon nanotubes (PMWCNTs), activated charcoal and graphitized carbon black (Carbopack B) were used as column packing materials to compare their separation ability and other gas chromatographic behavior for aromatic hydrocarbons, alkanes, halogenated hydrocarbons, alcohols, ketones, esters, and ethers. The results show that PMWCNTs can be an excellent gas chromatographic packing material. Compared to Carbopack B with the same surface area, PMWCNTs had a stronger retention ability, a more homogenous surface and smaller theoretical plate numbers. Polar compounds can present symmetric peaks on PMWCNTs. PMWCNTs were found to be an interesting alternative adsorbent to activated charcoal and Carbopack B as gas chromatographic column packing material for volatile compounds, especially those with relatively low boiling points.

Evaluation of a dual-sorbent trap for monitoring organic compounds in air

The performance of a new kind of multi-sorbent trap for use in the simultaneous determination of compounds of different volatility and polarity was investigated. The adsorbents employed for this purpose were Carbograph 2 and Carbograph 5. The performance of this trap was evaluated in terms of thermal desorption and solvent extraction recoveries of substances belonging to the main classes of organic compounds, at different amounts and volumes of air sampled corresponding to concentrations ranging from 0.1 to 1000 mg/m3. The tubes examined allowed the trapping of the compounds used and their complete desorption with the procedure best suited to the analytical problem.