Development Of Primary Standard Gas Mixtures Of Fourteen Volatile Organic Compounds In Hazardous Air Pollutants For Accurate Ambient Measurements In Korea (At 1 Mu Mol/Mol Levels)

Hazardous air pollutants (HAPs) in the atmosphere are regulated as major air pollutants in Korea by the Air Pollution Control Act. In order to manage and control HAPs, accurate standards, which are traceable to the International System of Units (SI), are required. In this study, primary standard gas mixtures (PSMs) of volatile organic compounds (VOCs) which are specified as HAPs were developed at 1 mu mol/mol levels. The selected fourteen VOCs include Benzene, Toluene, Ethylbenzene, m-Xylene, Styrene, o-Xylene, Chloroform, 1,1,2-Trichloroethane, Trichloroethylene, Tetrachloroethylene, 1,1-Dichloroethane, Carbon tetrachloride, 1,3-Butadiene, and Dichloromethane. The HAPs PSMs were gravimetrically prepared in aluminum cylinders and their consistency was verified within the relative expanded uncertainty of 0.71% (k=2). Potential adsorption loss onto the internal surface of cylinders was estimated by cylinder-to-cylinder division method. No adsorption loss was observed within the uncerainty of 0.53%. The long-term stability of the HAPs PSMs was evaluated comparing with freshly prepared HAPs PSMs. The HAPs PSMs were stable for one year within the uncertainty of 0.38%. The final uncertainty of the PSMs was determined by combining the preparation uncertainty, verification uncertainty, and stability uncertainty Finally, traceable and stable HAPs PSMs at 1 mu mol/mol levels were developed with the uncertainty of less than 0.76% in high-pressure aluminum cylinders.