Measurement of Atmospheric Hydroxyacetone, Glycolaldehyde, and Formaldehyde

A method has been modified and optimized for the measurements of hydroxyacetone as well as formaldehyde and glycolaldehyde, based on aqueous scrubbing using a coil sampler followed by DNPH derivatization and HPLC analysis. Derivatization equilibrium and kinetics were studied to optimize the hydroxyacetone-DNPH derivative yield. It was found that the low sensitivity of hydroxyacetone by this method is due to a relatively small equilibrium constant for the hydroxyacetone-DNPH derivatization reaction, and thus it can be improved by increasing DNPH reagent concentration. In a medium containing 500 μM DNPH and 50 mM HCl, the derivatization reaches equilibrium within 30 min. An online reagent purification procedure using a DNPH-saturated Sep-Pak C-18 cartridge effectively removed hydrazone impurities in the DNPH reagent solution, and a sample preconcentration procedure using a C-18 guard column greatly enhanced the sensitivity and lowered the detection limits. The lower detection limits of the system under opti...