TIME-DIVISION MULTIPLEX TECHNIQUE FOR PRODUCING CONCENTRATION PROFILES IN FLOW-ANALYSIS

A technique is described which uses computer controlled solenoid valve s for creating concentration profiles for various flow-based methods o f analysis. These profiles can be quickly selected through software an d, similarly, parameters such as the volume of the sample, carrier and reagents can be set and altered when required with minimal changes to the hardware. The technique has been demonstrated for flow titration and how injection but is equally applicable to other methods. Tn ail t hese methods, only a single channel pump is required to draw the mixed solutions through the detector and individual solutions are introduce d into the flowing stream by selection through solenoid operated valve s. Results are presented for the determination in water samples of cal cium using potentiometric titration and orthophosphate by flow injecti on using the molybdenum blue method. The technique uses only small vol umes of solutions and is fully automated and so is ideal for use in po rtable instrumentation. (C) 1998 Elsevier Science B.V.