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Hazardous air pollutants (HAPs) in the atmosphere are regulated and monitored in Korea by the Air Pollution Control Act. To manage HAPs, accurate standards, which are traceable to the International System of Units (SI), are required. Primary reference gas mixtures (PRMs) are prepared gravimetrically and their amount fractions (mole fractions) are gravimetrically determined values. However, for reactive gases such as volatile organic compounds (VOCs), the gravimetric values can be changed due to physical adsorption loss onto the internal surface of the cylinder. The loss can result in significant difference between the gravimetric and actual mole fractions, which is crucial for developing accurate PRMs especially for reactive gases. In this study, the physical adsorption loss onto the internal surface of the cylinder was evaluated for developing VOCs at 5 nmol mol. Suites of VOC gas mixtures containing the 18 components at 5 nmol mol were gravimetrically prepared in aluminum cylinders. The potential physical adsorption loss was estimated by the cylinder-to-cylinder division method. The results showed that a significant physical adsorption loss occurred for acrylonitrile while little adsorption loss occurred for the other VOC components. The gravimetrically determined mole fraction for only acrylonitrile was corrected to account for the physical adsorption loss.

Evaluation of Physical Adsorption Loss of Volatile Organic Compounds of Primary Reference Gas Mixtures at 5 nmol mol-1