While the traditional methods of  “wet chemical analysis” are carried out in batch mode (‘beaker chemistry’) that allows homogeneous and instant mixing of sample with reagents, all flow injection techniques are based on gradual dispersion of the sample zone, that forms a concentration gradient as the sample moves towards a detector.

The response of the Sequential Injection system is the result of two processes, both kinetic in nature, the physical process of dispersion of sample and reagent zones and the chemical process of formation of chemical species at the interface of stacked zones. Therefore, the SI system must be constructed in such a way, that the radial dispersion is maximized, the axial dispersion which determines mutual penetration of sample with reagent zones is optimized and the rate of chemical reactions is maximized in order to achieve a high sampling frequency.

Homogenous Mixing and Concentration Gradients