Optimization of the wash-off method for measuring aerosol concentrations

Using the fluorescence-washing technique, oleic acid particles tagged with uranine were extracted and analyzed fluorometrically. The possible sources of errors in the technique were evaluated in this study. First, the sensiti vity of uranine fluorescence in different solutions was compared. The resul ts indicated that uranine in distilled water with pH 10 buffer and in sodiu m hydroxide have high sensitivity, Second, the interference of oleic acid w ith uranine quantification in a variety of media was investigated. It was f ound that there is no interference from oleic acid in distilled water and s odium hydroxide solutions under our operating conditions. However, oleic ac id did significantly quench the uranine fluorescence signal in ethanol. Thi rd, the ability of different solutions to extract uranine from glass fiber and Teflon filters was tested. The results indicated that distilled water a nd sodium hydroxide solutions have the highest extraction ability of the me dia evaluated. Based on the results above, distilled water, 0.001 N sodium hydroxide, and 0,01N sodium hydroxide solutions were the optimal washing so lutions in the fluorescence-washing technique. It was also found that, for inlet washes, distilled water would not be reactive and have high extractio n efficiency.