Method 7C/7D: Determination of Nitrogen Oxide- Colorimetric and Ion Chromatography
Method 7C (Colorimetric) and 7D (Ion Chromatography) are used for the determination of nitrogen oxide emissions.
A sample is passed through a series of specially built impinger that contains an alkaline potassium permanganate solution. The impingers are of standard height with a narrow bottle, which improves the collection efficiency. The sample rate is between 400 and 500 cubic centimeters per minute. Normally, three one-hour samples are collected for the test.
For 7C, an integrated gas sample is extracted from the stack and passed through impingers containing an alkaline potassium permanganate solution; NOX (NO + NO2) emissions are oxidized to NO2 and NO3. Then NO3− is reduced to NO2− with cadmium, and the NO2− is analyzed colorimetrically.
For 7D, an integrated gas sample is extracted from the stack and passed through impingers containing an alkaline-potassium permanganate solution; NOX (NO + NO2) emissions are oxidized to NO3−. Then NO3− is analyzed by ion chromatography.
For more information and documents about Method 7C, please consult the EPA's Method 7C webpage. For more information and documents about Method 7D, please consult the EPA's Method 7D webpage.
Apex Instruments offers a Method 7C/7D Sampling System. If interested in Method 7C/7D sampling, Apex Instruments works with our customers to make sure we are providing the correct products for your project and will provide you with a price quote. For any questions about our sampling system, please contact sales@apexinst.com.