In sequential injection manifolds, a stack of well-defined unsegmented zones is assembled in a holding coil using a pump or liquid driver and a selection device. On transporting this stack of zones to the detector, the zones penetrate one another and mixing between their components gives rise to one or more detectable species. These products are measured as the zone stack reaches a suitable (flow-through) detector. The multiposition selection valve allows sequential injection analytical systems to be extremely versatile with many changes to the methodology being achievable through software control of the system parameters rather than actual physical changes to the hardware. Each port of the valve can be dedicated to a specific purpose, and the combinations of sample, standards, reagents, and detectors around the valve are easily modified to suit a particular analysis.

Since the system works sequential, the drawback of such versatility is a reduced sample throughput.