SD flowpath selectors select one of 4 to 16 dead-ended streams. This example illustrates a method for sampling non-pressurized containers which eliminates any possible effect from pressure differences among the containers, providing accurate and repeatable results.
In step 1, a vacuum pump moves sample from the container selected by the SD valve to a 6 port sampling valve. In step 2, the 3 port valve blocks the vacuum flow through the sampling valve to allow the sample within the loop to equilibrate at atmospheric pressure. Then in step 3, the 6 port valve is switched, injecting the sample.
All three valves can be automated with air or electric actuators for unattended operation.
Step 1:
Sample pulled from selected container into the sample loop of the injector
Step 2:
Vacuum blocked, loop contents equilibrate
Step 3:
Contents of the sample loop injected onto the column
