Pretreatment Method parameters in Empower

Question

Dear All,

We are having issues with setting Pretreatment Method parameters in Empower 3 with ICF 3.0. When attempting to add the second needle wash, the chromatography shows absolutely no peaks (almost as if it is injection the wash solution instead of sample), and appears as a blank injection. As soon as I removed the wash and only have one time, the chromatography is as expected.

Has anybody experienced same?

Regards,

Weronika

howard_sanford · Accepted Answer

kdales , I can see several potential issues with attempting to perform a post injection needle wash, especially if you are running a gradient LC method. With your current program you perform an injection, which places the needle into the seat and the switches the valve to mainpass. Then you immediately switch the valve back to bypass for the wash, stopping the flow of solvent through the loop, needle, and seat. I suspect that will not be enough time to adequately flush your sample out of the sampler and onto your column. You can add a WAIT command and flush the injection path with however much solvent volume you think will be necessary to get your sample into the flow path. But then you must switch the valve back to bypass during the analytical portion of your run to perform the wash. This will cause a baseline disturbance, though if you can do it before the void volume time it might not affect things too much, but you would have to determine that experimentally. Now you can perform your wash, but your loop, needle, and seat are no longer part of the flow path, and if you are performing a gradient run they will not have their internal volume flushed with your organic phase (assuming you are doing reverse phase work) unless you again switch the valve back, which will cause another baseline disturbance and flush a slug of your starting condition eluent onto your column. Depending on where you are in your gradient this may not be desirable. You could just leave it in bypass until your last peak of interest comes out and then switch the valve back, but then you are mixing your starting condition eluent directly with your end run eluent composition. If you are using buffers that may not be the best thing to do. I would suggest referring to the sampling sequence information that starts on page 10 of the user manual found here to have a full understanding of how an injection sequence normally works to help in making your injection program. As for removing the wash vial I believe you can use the NEEDLE command and tell it to go into the seat. This should return the vial to the tray and lower the needle into the seat. Then you would have to decide if you want to use a VALVE command to switch back to mainpass right away or how you would want to proceed.

Pretreatment Method parameters in Empower

Top Replies