Flow injection analysis involves the rapid injection of a sample into a continuously flowing unsegmented carrier stream. If necesaary for detection, one or more reagent solutions are continuously merged with the carrier prior to detection. The injected sample zone undergoes dispersion and is mixed with the carrier and reagent solutions. The resultant product is transported to the detector for measurement.

The dispersion or dilution of the sample zone can be controlled and adapted to the requirements of the analysis, by varying some operational parameters including the injected sample volume, the flow rate of carrier and reagent streams, the reaction coil length, and the inner diameter of the tubing.