Development of low-cost passive sampler from cow bone char for sampling of volatile organic compounds

A simple and low-cost passive sampler for collection of volatile organic compounds, specifically benzene, toluene, ethylbenzene and xylene (BTEX), from the ambient air has been developed by using cow bone char (CBC) as an adsorbent with desorption by solvent extraction prior to analysis by gas chromatography–mass spectrometry (GC–MS). The laboratory-made CBC was prepared by calcination process in a partially oxidative atmosphere. The developed passive sampler was tested for a suitable amount of CBC used, diffusion tube type and size, and sampling duration, in a closed chamber saturated with each of the BTEX vapors. With the optimum amount of 250 mg CBC packed in a glass bottle (82.6 mm height × 11.1 mm i.d.) and the exposure time of 168 h, detection limits (µg/m3) for BTEX determination using this developed sampler together with GC–MS were 0.28 (benzene), 0.79 (toluene), 0.58 (ethylbenzene), 0.28 (p-xylene) and 0.54 (o-xylene). The proposed method was applied to sampling BTEX from selected petrol stations, traffic congestion areas and a rural area in Chiang Mai Province, Thailand. The BTEX concentrations detected were well correlated with their sources as they were the highest at the petrol station sites, lower at the traffic congestion area sites and the lowest at the rural area site. The laboratory-made passive sampler containing CBC has thus opened up a possibility of having a simple and effective device for sampling of BTEX in the ambient air.