Passive monitoring of VOC in air using ACC.

This project dealt with developing the method of using activated carbon cloth as a sampler for measuring volatile organic compounds (VOC's) in air. Strips of carbon cloth mounted in slide holders were tested as diffusive samplers. These were exposed to known concentrations of standard chemicals in test chambers. The adsorbed chemicals were extracted with sol vents and analyzed. The tests showed that relative humidity has some effect on adsorption, and carbon cloths from different manufacturers showed some variation in their performance. The method of storage of the samplers can lead to some tosses in concentration. Aluminum foil was found to be superior to polyethylene bags in preventing diffusion of gases from the carbon cloth. Two methods of extraction - using a syringe or an ultrasonic technique were compared. Ultrasonic extraction was found to be superior to using a syringe for extraction. lt appeared that the cloths had a different response rate to chemicals of varying molecular weight. Molecules with higher molecular weight are preferentially adsorbed compared to those with lower molecular weight. A correction factor may be necessary. Comparison between the activated carbon cloths and 3M passive samplers gave smaller sampling rates for the carbon cloth. The difference may be due to the effect of humidity. lt would appear that a hydrophobie carbon cloth would be preferable. Field testing using these activated carbon cloths in houses remains to be done. The potential for using these samplers for semi-quantitative analysis also remains.