On-Line Gaseous Formaldehyde Detection Based on a Closed-Microfluidic-Circuit Analysis

Anaïs Becker,Christina Andrikopoulou,Stéphane Le Calvé,Pierre Bernhardt,Claire Trocquet

doi:10.3390/chemosensors8030057

Abstract

This paper describes a compact microfluidic analytical device in a closed-circuit developed for the detection of low airborne formaldehyde levels. The detection is based on the passive trapping of gaseous formaldehyde through a microporous tube into the acetylacetone solution, the derivative reaction of formaldehyde with acetylacetone to form 3,5-Diacetyl-1,4-dihydrolutidine (DDL) and the detection of DDL by fluorescence. The recirculation mode of the analytical device means that the concentration measurement is carried out by quantification of the signal increase in the liquid mixture over time, the instantaneous signal increase rate being proportional to the surrounding gaseous formaldehyde concentration. The response of this novel microdevice is found to be linear in the range 0–278 µg m−3. The reagent volume needed is flexible and depends on the desired analytical resolution time and the concentration of gaseous formaldehyde in the environment. Indeed, if either the gaseous concentration of formaldehyde is high or the reagent volume is low, the fluorescence signal of this recirculating liquid solution will increase very rapidly. Consequently, the sensitivity simultaneously depends on both the reagent volume and the temporal resolution. Considering a reagent volume of 6 mL, the hourly and daily detection limits are 2 and 0.08 µg m−3, respectively, while the reagent autonomy is more than 4 days the airborne formaldehyde concentration does not exceed 50 µg m−3 as it is usually the case in domestic or public indoor environments.

Highlights

While most scientific studies in the past century were focused on the quality of outdoor air, the quality of indoor air is nowadays the subject of growing interest in the scientific community, such as attests the numerous studies of the two last decades [1,2,3,4,5]
European and French formaldehyde concentrations in indoor air typically vary between 10 μg m−3 and 100 μg m−3 [6,8,9,10], much higher than those found in the corresponding outdoor environments, which are of the order of 1 μg m−3 to 10 μg m−3 in most cases [11]
This study reports the implementation of this analytical method under controlled laboratory conditions for formaldehyde concentrations varying between 0 μg m−3 and nearly 300 μg m−3

Summary

Introduction

While most scientific studies in the past century were focused on the quality of outdoor air, the quality of indoor air is nowadays the subject of growing interest in the scientific community, such as attests the numerous studies of the two last decades [1,2,3,4,5]. Formaldehyde is considered as a major indoor air pollutant due to its many emission sources such as construction materials, furniture, glues and paints, etc. European and French formaldehyde concentrations in indoor air typically vary between 10 μg m−3 and 100 μg m−3 [6,8,9,10], much higher than those found in the corresponding outdoor environments, which are of the order of 1 μg m−3 to 10 μg m−3 in most cases [11]. Several studies have reported that formaldehyde is always present in indoor environments, such as in homes [7,12] or in schools [13,14]. In 2004, the International Agency for Research on Cancer classified formaldehyde as a Chemosensors 2020, 8, 57; doi:10.3390/chemosensors8030057 www.mdpi.com/journal/chemosensors

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