Fundamentals of sinusoidal flow sequential injection spectrophotometry

A rational design of the sequential injection analyzer is based on description of the mutual penetration of sample and reagent zones, which are sequentially stacked into a tubular conduit and then injected into a reactor and transported toward the detector by means of a carrier stream, flowing at a preprogrammed rate. Variables governing zone penetration have been identified by a series of dispersion experiments, for sequential injection of two and three zones, thus outlining the conditions for performing single- and double-reagent-based assays. A parallel is drawn between conventional flow injection and corresponding sequential injection colorimetric determinations of chloride and phosphate, with the aim of suggesting guidelines for the development of spectrophotometric- and fluorescence-based sequential injection methods.