Colorimetric Determination of Sulfur Dioxide in Air Using a Droplet Collector of Malachite Green Solution

• Published in: Microchemical journal Vol. 62; no. 2; pp. 273 - 281
• Main Authors: Milani, Márcio Raimundo, Gomes Neto, José Anchieta, Cardoso, Arnaldo Alves
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier B.V 01-06-1999; Elsevier
• Subjects: air analysis; Analysis methods; Analytical chemistry; Applied sciences; Atmospheric pollution; Chemistry; colorimetry; droplet sensor; Exact sciences and technology; Pollution; Spectrometric and optical methods; sulfur dioxide; colorimetry; sulfur dioxide; droplet sensor; air analysis; Trace analysis; Chemical analysis; Visual colorimetry; Triarylmethane dye; Air pollution; Visible spectrometry; Air; Aqueous solution; Sulfur dioxide; Environmental control
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1006/mchj.1999.1729

The measurement of sulfur dioxide in air at the parts-per-billion level is described. The experimental arrangement consists of two optical fibers placed on opposite sides of a liquid droplet of malachite green solution. After light has been passed through the droplet, the transmitted light is measured by a referenced photodetection arrangement. The light used in this absorption process is from a monochromatic source (λ
max625 nm). This arrangement permits the variation of color in the droplet to be measured. The sulfur dioxide in the sample is collected by the droplet; it reacts with malachite green resulting in a colorless dye. The decoloration of the solution is proportional to the concentration of sulfur dioxide sampled. The signal depends on the sample flow rate. The present technique is simple, inexpensive, and permits a fast and near real time measurement while consuming very little reagent.