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- Posts: 145
- Joined: Sat Sep 25, 2004 3:09 pm
In normal operation, the sample cell is filled with solvent and placed inside the oven. When the fill pressure of 10.34 MPa (1500 psi) is reached, the pump is turned off. The cell (and solvent) are heated at the extraction temperature for a set time. When the pressure reaches 11.72 MPa (1700 psi) during the set time, the static valve opens to relieve pressure by dispensing some of the solvent out of the cell and into the collection vessel. A small amount of solvent is pumped each time the static valve opens to compensate the solvent out of the cell. It so happens that the static valve only opens one or two times for most of the organic solvents. However, when DCM (or a mixture of DCM with other solvents) is used, we find that the pressure shortly reaches 1700psi, causing the static valve to open every 5-10 seconds during the static extraction. This significiantly increases the solvent volume and also causes variation of heated solvent/sample contact time.
Did anyone come across this before? Is it inherent for ASE350 when DCM is used? Any remedial action? We don't have such problem in ASE200 with DCM.
Thanks for your advice in advance.