Development of microfluidic analytical method for on-line gaseous Formaldehyde detection

Abstract

This paper reports on the development of a novel colorimetric analytical method based on microfluidic technologies for the detection of low airborne Formaldehyde concentrations, representative of those found in indoor air, i.e. 10–100μgm−3. The new analytical technique operates according to 4 distinct steps: 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) colorimetric DDL detection with a liquid-core-waveguide.Laboratory experiments were performed to determine the experimental conditions permitting to obtain a stable annular flow, i.e. a liquid flow rate above 5μLmin−1 and gas to liquid flow rate ratios greater than 1000. Effects of liquid-core-waveguide of internal diameter and length were also investigated.Using liquid and gas flow rates of 35μLmin−1 and 35mLmin−1 respectively, the resulting uptake yield of gaseous Formaldehyde in aqueous solution was around 90% and the detection limit of gaseous Formaldehyde was 0.7μgm−3, which is consistent with the guideline values for indoor air. In addition, the low reagent consumption increases significantly the device autonomy up to 20days with 1L of acetylacetone solution.