Chromatographiebedarf

Anwendungsbeispiele für Säulenschaltungen mit Cheminert Ventilen

Applications
 These illustrations show basic sample injection techniques using Cheminert two position valves. With rare exceptions, there is no difference between switching valves and external volume sampling valves, so the same valve can be used for either function.
The unique advantage of 8 and 10 port valves is that they reduce extra column volume by combining sampling and switching functions in a single valve. This minimizes expense, maintenance, service, and risk of leaks as compared to multiple 6 port valve systems.

4 Port Internal Sample Injector

Microvolume Sample Injection

The internal sample (fixed volume) flowpath is used when very small sample volumes are required. The sample size is determined by a passage engraved on the valve rotor, allowing precise, repeatable injections. In Position A, the sampleflows through the sample passage while the mobile phase flows through to the column. The third passage is inactive. In Position B,the sample passage is in line with the column and the mobile phase injects the contents of the sample passage into the column.The passage which was inactive in Position A allows the sample to continue flowing without interruption.

 

4 Port Internal Switching Valve

Detector Selection from Two Columns or One Column and Auxiliary Carrier

This unique configuration allows analysis of different parts of one analysis with two different detectors, without splitting or multiple injections. For example, fixed gases can be analyzed with a thermal conductivity detector, followed by the analysis of a hydrocarbon fraction with a flame ionization detector.

 

 

6 PORT EXTERNAL SAMPLE INJECTOR

Sample Injection

With the valve in Position A, sample flows through the external loop while the mobile phase flows directly through to the column. When the valve is switched to Position B, the sample contained in the sample loop and valve flow passage is displaced by the mobile phase and is carried into the column.Note: Especially for partial-filled loops, the flow direction of the mobile phase through the loop should be opposite (backflush) to the flow direction during the loading of the loop.

 

8 PORT SAMPLING / SWITCHING

Loop Sampling with Backflush to Detector

One valve functions as sampling and backflush valve, simplifying operation and reducing cost. When components of interest are detected, the strongly retained components are backflushed and removed from the column without temperature programming.

 

10 PORT SAMPLING / SWITCHING

Alternate Column Regeneration

When columns must be regenerated following each analysis, this technique permits automation of the process. While one column performs the analysis, the second column undergoes regeneration by use of an auxiliary pump. Once the first analysis is complete, the valve is switched and the regenerated column is now ready for analytical use.