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Chemiluminescence Detection: NO2 Content Measurement in Sample Gas

Chemiluminescence method using ozone-mixed dry air to measure NO2 content in sample gas. Reaction chamber converts NO to NO2, detected via infrared radiation. Quenching effects addressed through reduced pressure and optimized wavelength range.

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Chemiluminescence Detection: NO2 Content Measurement in Sample Gas

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  1. CLD

  2. With dry air produced ozone is mixed with sample gas. • The mixture enters the reaction chamber, while the NO of the sample gas reacts to NO2 : • NO + O3 NO2 + O2 + h • A proportion of the reaction energy is emitted as infrared radiation(h). • The infrared radiation is detected, enhanced and transformed into the detector signal by the photomultiplier. • The NO2 of the sample gas is converted into NO by the integrated converter and then measured in a separate reaction chamber. • The difference between both measurements corresponds to the NO2 content of the sample gas.

  3. CLD - Measuring Principle The chemiluminescence is disturbed by “Quenching” effects. They are caused by absorption of the emitted radiation by other components and by radiation-free energy loss due to collision processes. Remedy: Reduced pressure (35 mbar)  reduction of collision processes. Selection of a measuring range (650-850 nm) with low foreign absorption. Due to the high amplification factor of the photomultiplier (1:100.000) emission flanks can be used.

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