Miniaturization of colorimetric and fluorimetric analyzers for the gaseous formaldehyde detection

Abstract

Formaldehyde is a major pollutant of indoor air owing to its multiple sources (materials, combustion, painting, etc.). Based on a former in-house formaldehyde analyzer, two new miniaturized analyzers are being developped. The former analyzer was based on the reaction of formaldehyde with a selective derivative agent (fluoral-P) to form a fluorescent species (DDL). The analyzer measured concentrations of formaldehyde in 3 steps strongly coupled to each other: 1) the uptake of gaseous formaldehyde into an aqueous solution, 2) the selective derivatization of formaldehyde by reaction with fluoral-P, 3) the analysis of the reaction product by fluorescence spectroscopy. [1] For the next generation devices, new technologies are used for the uptake of gaseous formaldehyde and the detection. However, the reaction step remains unchanged. New molecules are in development in order to obtain better quantum efficiency. In one case, the detection is realized by colorimetry with the major benefit of no calibration requirement. In the other case, the detection is realized by fluorescence spectroscopy, the major advantage being a better and higher sensitivity than colorimetric detection. The former analyzer weighted 8 kg while future miniaturized analyzers will weigh less than 2 kg making them suitable for field analyses. These new analyzers will combine precision, selectivity towards formaldehyde, high speed analysis, information processing and communication into a single much smaller device. Finally, it will be necessary to validate the smooth running and the precision of these devices by comparison with the conventional technique of derivatization by DNPH coupled to analysis by HPLC/UV on synthetic air samples generated by a calibrated source of gaseous formaldehyde and also in real indoor atmospheres under various scenarios.