Colorimetric determination of formaldehyde in air using a hanging drop of chromotropic acid.
A simple and sensitive method to determine parts per billion (ppb) of atmospheric formaldehyde in situ, using chromotropic acid, is described. A colorimetric sensor, coupled to a droplet of 15.5 microL chromotropic acid, was constructed and used to sample and quantify formaldehyde. The sensor was set up with two optical fibers, a light emitting diode (LED) and two photodiodes. The reference and transmitted light were measured by a photodetection arrangement that converts the signals into units of absorbance. Air was sampled around the chromotropic acid droplet. A purple product was formed and measured after the sampling terminated (typically 7 min). The response is proportional to the sampling period, analyte concentration and sample flow rate. The detection limit is approximately 2 ppb and can be improved by using longer sampling times and/or a sampling flow rate higher than that used in this work, 200 mL min-1. The present technique affords a simple, inexpensive near real-time measurement with very little reagent consumption. The method is selective and highly sensitive. This sensor could be used either for outdoor or indoor atmospheres.
Pretto
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Instituto de Química-UNESP, Dep. Quím. Analítica, C. Postal 355, CEP 14800-900, Araraquara, SP, Brazil.
Milani
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Cardoso
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D016902:Air Pollution, Indoor / Q000032:analysis*; D003124:Colorimetry / Q000379:methods; D004202:Disinfectants / Q000032:analysis*; D005557:Formaldehyde / Q000032:analysis*; D008027:Light; D009282:Naphthalenesulfonates / Q000737:chemistry; D012680:Sensitivity and Specificity
D004202:Disinfectants; D009282:Naphthalenesulfonates; D005557:Formaldehyde; C020996:chromotropic acid