Methods for Sampling and Analyzing Atmospheric Pollutants

Environmental Protection Agency specifies reference methods of analysis for selected air pollutants to determine compliance with the primary and secondary national ambient air quality standards for those pollutants. These methods are published annually in the Code of Federal Regulations These methods are not necessarily state of the art and are, in some cases, outdated and cumbersome. However, they provide proven reliable measurements for regulatory and legal purposes. 

2 Determination of Atmospheric Sulfur Dioxide by the West-Caeke Method 

The reference method for the analysis of sulfur dioxide is the spectrophotometric West-Gaeke para-rosaniline method. This somewhat involved method uses a collecting solution of 0.04-M potassium tetrachloromercurate to collect sulfur dioxide according to the following reaction  

The HgCljSOj complex stabilizes the readily oxidized sulfur dioxide from the reaction with oxidants such as ozone and nitrogen oxides. For analysis, sulfur dioxide in the scrubbing medium is reacted with formaldehyde  

The adduct formed is then reacted with uncolored organic pararosaniline hydrochloride to produce a red-violet dye that is measured spectrophotometrically. 

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