An optical sensor for the sensitive determination of formaldehyde gas based on chromotropic acid and 4-aminoazobenzene immobilized in a hydrophilic membrane
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AuthorFernández Ramos, María Dolores; Moraga Cabezas, Ángela; Medina Castillo, Antonio L.; Capitán Vallvey, Luis Fermín
Royal Society of Chemistry
Formaldehyde gas sensor; Colour measurements; Chromotropic acid; 4-Aminoazobenzene
Analyst, 148 (2023) 4533-4538. DOI:10.1039/d3an01056b
SponsorshipSpanish “Ministerio de Ciencia e Innovación/Agencia Estatal de Innovación” Project: PID2019-103938RB-I00; Spanish “Ministerio de Ciencia e Innovación/Agencia Estatal de Innovación” Project: PID 2021-126579OB-C31; Junta de Andalucía Projects: B-FQM-243-UGR18 and P18-RT-2961
Formaldehyde is a common contaminant in occupational and environmental atmospheres, prolonged exposure leads to health risks, and its determination is necessary to protect health. There is a great demand for portable, rapid, and sensitive methods that can be used in resource-limited settings. In this respect, a colorimetric sensor has been developed based on the colour change from pink to purple of co-immobilized chromotropic acid and 4-aminoazobenzene in hydroxypropyl methylcellulose when it is exposed to different concentrations of formaldehyde. The concentration of formaldehyde in the gas phase was quantified by measuring the change of the appropriate colour coordinates in response to the concentration of formaldehyde. A calibration curve was obtained for formaldehyde, with a useful concentration range from 0.08 to 0.6 ppmv. The detection limit was 0.016 ppmv, which is lower than the maximum exposure concentrations recommended by both the World Health Organization (WHO) and the Occupational Safety and Health Administration (OSHA). The optical sensor was found to have good reproducibility, with a relative standard deviation of 2.3 and 1.7% at 0.08 and 0.25 ppmv, respectively. The sensor can operate at room temperature and environmental humidity, 25 °C, and 50% RH, respectively. In addition, a study of interferents (acetaldehyde, toluene, methanol, ethyl acetate, acetone, acetic acid, carbon dioxide and ammonia) showed high selectivity for formaldehyde, which indicates that this membrane is a simple, fast, and economical alternative for quantifying the concentration of formaldehyde in different environments.