Ethylene Glycol Solution of 2,4-Dinitrophenylhydrazine for the Determination of Formaldehyde in Air Using a Miniaturized Liquid Absorption Cartridge

I This study employs ethylene glycol (EG) as a solvent for dissolving 2,4-dinitrophenylhydrazine (DNPH) in the collection and derivatization of gaseous formaldehyde using a miniaturized liquid absorption cartridge comprising a polypropylene cartridge and a functional polytetrafluoroethylene (PTFE) membrane, which permits the passage of gas and blocks the flow of liquid. DNPH dissolved in 400 μL EG was used as the absorption solvent in the cartridge. The gas sample was collected at 50 mL/min through the PTFE membrane, and the analyte formaldehyde was derivatized and collected in the solvent. After air collection, the absorption solution was heated at 80 °C for 5 min to enhance the derivatization reaction. Thereafter, the absorption solvent was injected into a high-performance liquid chromatography system for the determination of formaldehyde. EG has a considerably higher viscosity than acetonitrile, which enables a high flow rate during sample gas collection. Additionally, the loss of absorption solvent during sample collection and heating due to solvent evaporation is prevented. The limit of detection of the proposed method is 2.5 ng/L, and the relative standard deviation of the peak area for the standard formaldehyde gas sample (10 ng/L) is less than 7 %.