Fiberoptic colorimetric sensor for in situ measurements of airborne formaldehyde in workplace environments

An optical sensor for the sensitive determination of formaldehyde gas based on chromotropic acid and 4-aminoazobenzene immobilized in a hydrophilic membrane

“…20 Examples include FA determination based on the nucleophilic addition of an amine through a reaction with an aldehyde by a dehydration reaction that induces a change in the chromophores of the dyes 21 or using Leuco Fuchsin immobilized in a Nafion® polymer in a fibre optic, which has good selectivity and reproducibility, although it is very sensitive to variations in humidity. 22 The reason for the low number of colorimetric sensors could lie in the interactions that occur between the colorimetric indicator and the polymeric matrix that involves recognition chemistry, which considerably reduces the interaction with FA. 23 This study is based on a hydrophilic membrane that allows the solubility of the reagents used to prepare the sensor: chromotropic acid and 4-aminoazobenzene.…”

3D Printing Filaments Facilitate the Development of Evanescent Wave Plastic Optical Fiber (POF) Chemosensors

“…Once dried, the OFS shows a strong yellow color. Finally, 37.5 cm of the manufactured FA-sensitive optical fiber is cut out (discarding the two final sections), its two ends connectorized, polished, and fitted into an opaque, tubular fiber chamber designed in our research group [19].…”

“…The analytical response of each EWOFS is evaluated by exposing it to different concentrations of formaldehyde in air ranging from 0.6 to 7.0 ppmv in a dedicated test rig previously described with a white LED excitation and the above-mentioned FLAME spectrometer [19]. Measurements are carried out at atmospheric pressure, (25 ± 1) • C, constant flow rate and relative humidity (75 mL min −1 , 50% RH).…”

“…Many analytical methods and sensing devices have been described to monitor formaldehyde due to the toxicity of this widespread chemical [19]. We have recently reported a deployable sensor to monitor in situ the levels of airborne FA in industrial environments.…”