Chemiluminescence, like atomic emission spectroscopy (AES), uses quantitative measurements of the optical emission from excited chemical species to determine analyte concentration. However, unlike AES, chemiluminescence is usually emission from energized molecules instead of simply excited atoms. Chemiluminescence can take place in either the solution or gas phase and is used for quantitative determination of many important inorganic and organic species in trace amounts.
Chemiluminescence is produced when a chemical reaction yields an electronically excited species, which emits light as it returns to its ground state. The excited particle can be the product of a reaction between the analyte and a suitable reagent e.g., ozone or hydrogen peroxide. In other cases the analyte is not directly involved in the chemiluminescence reaction; instead it is the inhibiting effect of the analyte that serves as the analytical parameter.
The instrumentation for chemiluminescence measurements is simple and can consist of only a suitable reaction vessel and a photomultiplier tube.
Analysis of gases
Atmospheric pollutants such as ozone, oxides of nitrogen and sulphur compounds can be determined with chemiluminescence methods. The most widely used of these methods is for the determination of nitrogen monoxide. Ozone from an electrogenerator and the atmospheric sample are drawn continuously into a reaction vessel and the radiation is then monitored by a photomultiplier tube. The reaction of nitrogen monoxide with ozone has also been applied to the determination of the nitrogen dioxide content of automobile exhaust gas. Other important chemiluminescence methods are used for monitoring atmospheric ozone and determination of sulphur-containing air pollutants such as sulphur dioxide and hydrogen sulphide.