Flow injection analysis (FIA) was developed in the mid-1970s as a highly efficient technique for the automated analyses of samples. Unlike a centrifugal analyzer, in which the number of samples is limited by the transfer disk’s size, FIA allows for the rapid, sequential analysis of an unlimited number of samples. FIA is one example of a continuous-flow analyzer, in which we sequentially introduce samples at regular intervals into a liquid carrier stream that transports them to the detector.
A schematic diagram detailing the basic components of a flow injection analyzer is shown here. The reagent serving as the carrier is stored in a reservoir, and a propelling unit maintains a constant flow of the carrier through a system of tubing that comprises the transport system. We inject the sample directly into the flowing carrier stream, where it travels through one or more mixing and reaction zones before reaching the detector’s flow-cell.
This is the simplest design for a flow injection analyzer, consisting of a single channel and a single reagent reservoir. Multiple channel instruments that merge together separate channels, each introducing a new reagent into the carrier stream, also are possible.