Development of a microfluidic analytical method for a continuous real-time monitoring of airborne formaldehyde concentrations: application to field measurements

International audienceFormaldehyde is a major and harmful pollutant of indoor air due to its multiple sources and its carcinogenic effect. This work reports the development of a novel analytical method based on microfluidic technologies for the detection of low airborne Formaldehyde concentrations, representative of those found in indoor air, i.e. 10-100 µg.m-3. The new analytical technique operates as follows: 1) gas sampling, 2) gaseous Formaldehyde uptake into the aqueous solution using an annular gas/liquid flow at room temperature, 3) derivatization reaction with acetylacetone solution at 65°C producing 3,5-Diacetyl-1,4-dihydrolutidine (DDL) and 4) fluorimetric DDL detection. Laboratory experiments were performed to determine the experimental conditions permitting to obtain a stable annular flow, i.e. gas to liquid flow rate ratios greater than 1000. From liquid and gas calibrations, an uptake yield of 102% and a detection limit of 1 µg m-3 were determined. Finally, our 4 kg instrument fully controlled by homemade software has a response time of 10 min, a temporal resolution of 2 seconds and an autonomy of 98 hours with 100 mL reagent. This formaldehyde micro-analyser was then deployed during several field campaigns and compared with the ISO 16000-3 reference method (active sampling on DNPH cartridges)