A multi-purpose flow system is characterized by a flexible and simple manifold and can be used for different assays after slight modifications. In small laboratories it can be regarded as the main instrument, dedicated to different single-analyte determinations. It is also useful as a secondary instrument in large laboratories, as it can replace an instrument under maintenance, perform urgent analysis and/or assess the laboratory quality, this later aspect often demanding comparative analysis. This was already realized in 1975 when a single-channel segmented-flow analyzer was designed for biologic fluid assays [1]. Calcium, uric acid, glucose, phosphorus, chloride, urea nitrogen and carbon dioxide were determined without the need for manifold changes: only the chromogenic reagent and the monitoring wavelength were modified from one assay to another.