Sequential-Injection Analysis: Principles, Instrument Construction, and Demonstration by a Simple Experiment

This article is a brief introduction to sequential-injection analysis (SIA), a novel automated analytical technique devised to replace flow-injection analysis (FIA). The principles and requirements of SIA are explained and the different components of a generic SIA apparatus are described. The construction of a simple SIA analyzer from commercially available components is reported together with the control and acquisition software developed in LabVIEW. The typical chemical and instrumental parameters to be considered in a typical SIA experiment and the analytical utility of the technique are demonstrated by using the photometric determination of phosphates in urine by means of the "molybdenum blue" reaction. This experiment is intended to form part of the laboratory coursework in the course of Instrumental Chemical Analysis.