Chromatography Forum

Does anyone know if the switching valve (used to divert early eluters to waste) on a Varian 1200 LC-MS/MS can be time programmed in addition to the first divert to waste? We would like to be able to time program some diversions into our run (eg. really late eluters during column flush, and to remove some high level matrix which elutes midway through the run).

Yes, the diverter/switching valve can be programmed to turn during an acquisition cycle. Unfortunately, it is not something you can simply program in MS Workstation's method editor... In system control, with your quadrupole tab displayed, select:

Tools --> PML Editor

I would suggest reading the Varian 1200L service manual and familiarize yourself with generating a PML. Once you have developed the PML, it will tell the valve when to switch during a run per your specifications. In method editor, under your 1200L tab, select Advanced MS Options and link your PML so that you have better control of the diverter valve.

Good luck!

I have used the method editor to switch the diverter valve. It is much like the previous response stated. In the quad mass spec control-acquisition method part of method builder, toward the top of the screen there's the option to make a new segment in your method- just select the time of that second segment, then under the 'advanced options' button (near the bottom of the same screen) in the tab "PMLs", you put in LC_valve=0 to divert flow and LC_valve=1 to change it back to flowing into the MS. You would need to make as many segments as needed, and be sure that all the other parameters are correct in each segment (if you, for example, change a mass transition or voltage in one segment, it doesn't change in any other segments). You also need to be sure your timing allows some time for the spray to reestablish before your compounds elute.

Thanks for the suggestions - all too easy once you know how.