Simultaneous determination of formic acid and lower carbonyls in air samples by DNPH derivatization

The classical derivatization method of carbonyls based on 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges was tested to concurrently measure lower carbonyls and carboxylic acids in air samples. The performance of these cartridges with respect to formic and acetic acids was evaluated in a number of laboratory measurements on collection and reaction efficiencies. The results showed that HCOOH appeared to have been efficiently collected and derivatized (at 80°C for 8 h) up to air-flow rates of 350 mL/min, while CH3COOH was almost completely lost from the cartridge above 100 mL/min. Also due to the high LOD of HCOOH (0.8 μg/m3) for 120 L of air sampled during 8 h, the DNPH method might be used only in indoor environments polluted by formic acid as well as carbonyls.