Time-division multiplex technique for producing concentration profiles in flow analysis Original Research Article

A technique is described which uses computer controlled solenoid valves for creating concentration profiles for various flow-based methods of analysis. These profiles can be quickly selected through software and, 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 flow injection but is equally applicable to other methods. In all these methods, only a single channel pump is required to draw the mixed solutions through the detector and individual solutions are introduced into the flowing stream by selection through solenoid operated valves. Results are presented for the determination in water samples of calcium using potentiometric titration and orthophosphate by flow injection using the molybdenum blue method. The technique uses only small volumes of solutions and is fully automated and so is ideal for use in portable instrumentation.