Flow injection analysis

Flow injection analysis (FIA) is an approach to chemical analysis that is accomplished by injecting a plug of sample into a flowing carrier stream. The principle is similar to that of segmented flow analysis (SFA) but no air is injected into the sample or reagent streams.

FIA is an automated method of chemical analysis in which a sample is injected into a flowing carrier solution that mixes with reagents before reaching a detector. Over past 30 years, FIA techniques developed into a wide array of applications using spectrophotometry, fluorescence spectroscopy, atomic absorption spectroscopy, mass spectrometry, and other methods of instrumental analysis for detection. Based on computer control, FIA evolved into Sequential Injection and Bead Injection which are novel techniques based on flow programming. FIA literature comprises over 22,000 scientific papers and 22 monographs.

A sample (analyte) is injected into a carrier solution which mixes through radial and convection diffusion with a reagent for a period of time (depending on the flow rate, coil length, and coil diameter) before the sample passes through a detector to a waste container. A peristaltic pump is the most commonly used pump in FIA instruments but new variants of FIA technique use computer controlled syringe pumps that generate discontinuous flow precisely choreographed to the needs of assay protocol. The result is dramatic decrease in sample consumption, reagent consumption, and waste generation. The new technologies broadened applicability of FIA techniques from laboratory serial assays to research applications and continuous monitoring of environmental and industrial processes.

A flow-through detector is located downstream from the sample injector and records a chemical physical parameter. Many types of detector can be used such as:

An experiment that is used in analytical chemistry lab courses to familiarize students with FIA is the determination of phosphate by flow injection analysis. The experiment involves calibrating an FIA system, optimizing the system for detection of phosphate and finding the amount of phosphate in an unknown sample.

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