Sample with 8-channel 16-port valve

Figure 4.5 shows clearly how a loop valve operates. The loop is filled with sample solution and the internal channelled rotor seal is then turned to bring the loop within the eluent flux. These valves are known as six-port valves as they have six connections. 

Fig. 6 Diagram of the injector with a mobile container in position for application of a sample with a micro-syringe. 1 - container, 6 -mandrel, 7 - quartz tube, 8 - magnet, 9 - lower housing, 10 - upper housing, 11, 15 - ball valve, 12 -injecting chamber, 13, 14 - electrically heated chamber, 16, 17, 18 -radiator, 19 - solenoid, 20, 26, 27 -solenoid valve, 21 - carrier gas inlet, 22 - chromatographic column port, 23 - six-way valve, 24, 25 - needle valve, 28, 29 - auxiliary gas inlet, 30 - connecting pipe for sample introduction, 31 -micro-syringe needle channel, 32 - membrane, 33 - auxiliary gas outlet.

An integrated mixer/valve with a cantilever-plate flapper valve allows for non-continuous mixing by diffusion [49]. The mixer/valve consists of two wafers (i) a lower silicon wafer with a cantilever-plate flapper valve and fluid ports and (ii) an upper glass wafer that contains the fluidic channel. Initially the sample flows down the channel. When it is time to mix a reagent with the sample, the reagent is injected into the sample stream, and the two mix diffusively in a few seconds. After the desired section of sample is prepared, the reagent is shut off and the mixed... 

In a theoretical SIA system using a single reagent, the central port of the switching valve would connect to the sample channel and the pump would be set to aspirate a preset volume of sample at a fairly low flow rate in order to avoid bubbles formation. Then, the central port would connect to the appropriate side port in order to aspirate a preset voliune of reagent. Next, the valve would be acmated to connect its central port with the channel leading to the detector and an appropriate voliune of carrier would be dispensed to drive the sample and reagent to the detector in flow reversal mode. 

The microchips are coupled to an SIA system for fully automated determination of MSG. The system is constructed with a syringe pump, a 10-multiposition valve, an enzymatic microchip, and a fluorescence detector. The inlet capillary of the single-channel microchip is connected to a 10-position valve, but in this case, only four ports are used (only beads, sample, waste, and microchip position). The whole system is controlled by a computer using software developed in-house. The fluorescence of the NADH peak is recorded by a chart recorder. 

---