Flow injection

The other type of automated wet-chemistry analysis is flow injection analysis (FIA), which was first described by Ruzicka and Hansen (1975). This is a non-segmented continuous flow method - i.e. no air bubbles are introduced to aid mixing and to separate sample and wash segments. The small diameter of the tubing and the optimized flow rate, together with precise electronic control, enable sufficient separation of samples and wash. By allowing col-orimetric reactions to go only partially to completion, high throughput rates are possible, up to 300 h-1. Although reagent consumption is low compared with the older segmented flow methods, the newer systems are even more economical than FIA. Two areas particularly suited to FIA are stopped-flow analysis as used in some immunoassays, and enzymatic analyses. FIA systems are manufactured by:

• Burkard Scientific: http://www.burkardscientific.co.uk/Analytical/Systems_ Analysers_FIAflo2000.htm

• ChemLab Instruments Ltd: http://home-1.worldonline.nl/~chemlab/

(The ChemLab instrument is in use at the Department of Soil Science, the University of Reading: http://www.rdg.ac.uk/soil/SoilSci/FACILITIES/analytical. html)

• Foss Tecator: the FIAstar® 5012 System: http://www.foss.dk/foss.asp

• Note: a useful list of scientific equipment suppliers is available at:

http://chem.yonsei.ac.kr/~lsk/company.html

We will only be dealing with segmented-flow methodology in this manual, but there are sure to be equivalent FIA methods available.

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