Development and Optimization of an Airborne Formaldehyde Microfluidic Analytical Device Based on Passive Uptake through a Microporous Tube

Abstract

This paper describes a compact microfluidic analytical device developed for the detection of low airborne formaldehyde concentrations. This microdevice was based on a three-step analysis, i.e., the passive gaseous formaldehyde uptake using a microporous membrane into an acetylacetone solution, the derivatization with acetylacetone to form 3,5-diacetyl-1,4-dihydrolutidine, and the quantification of the latter using fluorescence detection. For a rapid and easier implementation, a cylindrical geometry of the microporous element was considered to perform laboratory-controlled experiments with known formaldehyde concentrations and to establish the proof of concept. This work reports the evaluation of the uptake performance according to the microporous tube length, the liquid flow rate inside the tube, the gas flow rate outside the tube, and the gaseous formaldehyde concentration. A 10.0 cm microporous tube combined with a gas flow rate of 250 NmL/min (normal milliliters per minute) and a liquid flow rate of 17 µL/min were found to be the optimized conditions. In these experimental conditions, the fluorescence signal increased linearly with the gaseous formaldehyde concentration in the range 0–118 µg/m3, with the detection limit being estimated as 0.13 µg/m3 when considering a signal-to-noise ratio of 3.

Measurement Device for Ambient Carbonyl Sulfide by Means of Catalytic Reduction Followed by Wet Scrubbing/Fluorescence Detection

“…Similar approaches have been carried out by Guglielmino et al for absorbance detection and Ueda et al and Becker et al for fluorescence detection of gaseous HCHO. 57 − 59 An effective enrichment of the analyte gas was achieved by the microchannel scrubber, which could have a high ratio of the gas absorbing area to absorbing solution volume, and a small liquid volume of the scrubber makes the system response faster. However, the previous microchannel scrubber made of poly(dimethylsiloxane) (PDMS) 50 was not robust for long operations.…”

Optofluidic Formaldehyde Sensing: Towards On-Chip Integration

“…Indoor HCHO concentrations are up to fifteen times higher than those measured outdoors [ 6 ] and may have values ranging from 10 to 100 µg/m 3 (1 to 82 parts-per-billion (ppb) at 25 °C and atmospheric pressure) [ 7 ]. The World Health Organization (WHO) standard for a safe daily exposure is set to 100 µg/m 3 (82 ppb) concentration for a maximum period of 30 min.…”

“…These methods rely on bulky instruments that are not or barely portable, and are, therefore, not compatible with indoor air monitoring. A device adapted for this need should be real-time, selective, palm-held, low-noise, battery-operated, and cost-effective [ 7 , 15 ].…”

“…Some works related to on-chip optofluidic integration of HCHO detection in either food [ 18 , 19 , 20 ], Chinese herbs [ 21 ], or indoor air [ 7 , 22 ] have recently been reported. A microfluidic paper-based analytical device (µPAD) was proposed by Guzman et al [ 18 ] for detection of low HCHO concentrations in food.…”

“…Becker et al [ 7 ] developed a microfluidic analytical device (20 cm × 25 cm × 15 cm) dedicated to air analysis based on the Hantzsch reaction, which reached a LOD of 0.13 µg/m 3 (0.1 ppb) for a 17 µL/min reagent flow rate in a microporous tube (10.0 cm length, 0.9 mm internal diameter). The porous tube was placed in a gas microchamber fueled with gaseous HCHO at a flow rate of 250 NmL/min.…”