Development of droplet surface applied passive monitoring device for low concentration VOC

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We developed the new environmental monitoring instrument of high performance passive sampling by the droplet method based on the research reports given by Dasgupta, et al. We also improved the instrument for producing large droplets. The pumping method of gas-absorbed solution needed high accuracy at very low flow rates for absorption on a flow droplet surface. We used a plunger pump for the absorbed solution and made the stable continuous flow.On the basic experiment for volatile organic compounds (VOC), especially HCHO, passive sampling instruments, constructed instruments were carried out in the same wind tunnel experiment for nitrogen dioxide, and optimized for sampling conditions, for example, a HCHO-absorbed solution flow rate, droplet diameter, temperature, moisture, wind velocity, and so on.A new, simple, sensitive and in-field fluorimetric method for the determination of formaldehyde is proposed. The reaction of formaldehyde with hydralazine in acidic medium, heating on a boiling water-bath for 25 min, produces s-triazolo [3,4-α] phthalazine (Tri-P). the fluorescence intensity of the product formed (Tei-P) was determined at λ em=389 nm with λ ex=236 nm. The fluorescence intensity is linear over a formaldehyde concentration range of 1.2-33.0 μ gl-1. The proposed method was applied successfully to the determination of formaldehyde sampled from the atmosphere using the liquid droplet technique. Formaldehyde vapor in a wind tunnel and that in the droplet. The detection limit for formaldehyde was 2.0 μ gl-1 with RSDs varying from 3 to 12% in ambient air, using a droplet correction solution (boric acid and hydralazine). The effect of interfering substances on the determination shows that most cations and anions did not interfere. The results obtained were satisfactory compared with a reference method.