According to the research of C.E.Ejim et al. , under the same air flow, the particle size of atomized particles will be affected by solution viscosity and surface tension, and the increase of solution viscosity or surface tension will increase the size of atomized particles. DMF has a viscosity of 0.802 mPa•s and a surface tension of 25.7 dyne/cm, while water has a viscosity of 2.98 mPa•s and a surface tension of 72.8 mN/m. The viscosity and surface tension of DMF are both smaller than those of water, which will cause the particle size of the DMF solution to be much smaller than that of the aqueous solution during atomization. Therefore, the 7-(Diethylamino)coumarin-3-carboxylic acid sample has an observability much worse than that of aqueous samples.