ガラスコイル管による吸湿性アルカリ金属塩化物微粒子の捕集

抄録

A new sampling method for airbone hygroscopic particulate matter such as alkali metal chlorides (NaCl, KCl, RbCl, and CsCl: called as AX) using water-rinsed and cooled glass coiled tube was developed. Sample gas involving gaseous or fine particulate AX was cooled and moisturized in the glass coiled tube, resulting in water soluble coarse coagulated matter, which are collected on the inside wall of the tubes; afterwards, rinsing with injected water, analytical water sample was obtained. As a preliminary step, AX was vaporized at 1000 ℃ , condensed through 200 ℃, and collected at the cooled tubes. Arrival rate defined as the ratio of collection to vaporization was around 50% for NaCl and KCl, 85% for RbCl, and 96% for CsCl. The order of the arrival rate of AX agrees to the volatility estimated from thermochemical estimation of saturated vapor pressure. Fine particulate matter of AX less than 0.3 µm generated by passing a PTFE thimble filter at 200 ℃ was introduced to the serial glass coiled tubes; sufficient collection was evidenced by the ratio of 80:20 at the 1st and 2nd tubes. Theoretical calculation of two physical processes in the glass coiled tube: diffusive displacement and centrifugal motion proved that only centrifugal mechanism for particulate matter larger than 1 µm is effective but diffusion scarcely function. However, the experimental results gave perfect collection even for fine particulate matter less than 0.3 µm. Comparing the theoretical and experimental discussions, hygroscopic growth enabled all particulate matter to be collected by centrifugal mechanism. This method is suitable for hygroscopic particulate matter as total amount determination.