A Rapid and High-Sensitive Determination of Low Molecular Weight Carbonyl Compounds in River Water and Seawater and Photochemical Formation Mechanism

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The aims of this research are high-sensitive determination for low molecular weight carbonyl compounds (LMW-CC) in natural water and investigation of photochemical formation of LMW-CC. We employed an on-line preconcentration HPLC system with 2,4-dinitorphenylhydrazine for determination of LMW-CC in natural water. A C-18 reverse-phase preconcentration column was used instead of a sample loop at the sample injection valve. A 100-5000 ul portion of the derivatized sample solution was injected with a gas-tight syringe. Peak areas for the each carbonyl compounds increased linearly with an increase in injection volume up to 5000 ul. However, the large volume injection caused an unacceptable large peak of non-reacted excess DNPH, which overlapped with the peak of formaldehyde-DNPH and caused a serious interference in determination of formaldehyde. To remove the non-reacted excess DNPH peak, 15% acetonitrile aquatic solution was pushed through the preconcentration column after injection of der … More ivatized sample solution. The detection limits for LMW-CCs were less than 0.1 nM by this system.Distributions and diurnal changes in river water, pond water and seawater were investigated. These results indicated that the concentrations of LMW-CC in natural waters might depend on 1)the photochemical formation, 2)the exchange with air phase (atmosphere) and 3)bio-degradation. Formaldehyde shows the highest concentration in LMW-CCs investigated in this study. For formaldehyde, important sources in natural water might be the photochemical formation and dissolving from atmosphere, and bio-degradation rate of formaldehyde was medium The source of acetaldehyde in natural water might be photochemical formation, and the biodegradation rate was very fast. The faster biodegradation tare and lower photochemical formation rate of propionaldehyde caused the lower concentration of propionaldehyde in natural water. On the other hand, the photochemical formation rate of glyoxal was lower, but bio- degradation rate was also lower. Less