Sample scan on VWD

Question

Hello, I have an HPLC system agilent 1260 infinity II series with VWD and RID. I have been having troubles into making a sample scan on VWD. I have read the manual and it needs to be done in a zero flow condition. However, there is a possibility of scheduling on the timetable part of the VWD this event on certain times. 
 I have tried to set it up and it did not work. Is there anyone with experience on this type of scan? Sincerely, Carlos,

gabcaron · Answer

Hello, 
 
 As far as I am aware, there is no way around that. You need to trap the compounds in the flowcell, therefore it will affect your runs. You can try to make a method where you can calculate the time it will take for the scan to complete. So you can stop the flow for that amount of time and then resume the injection and the gradient where it stopped and calculate the new retention time with that method for the next compound and go that way. 
 
 The issue with this though is that you will have some diffusion and your peaks may not be as sharp as the normal runs. If you have peaks that are close in retention time, that may also mean that the compounds will mix with eachother and affect your scans. 
 
 I think best and easiest way is probably to do injection of the compounds one by one and scan them one by one. If you have standards of the different compounds, you can prepare a mix of that and inject it so you have only 1 peak for that injection. You can also prepare a mix the same way and use the syringe that comes with the HPLC and basically inject that sample directly into the flowcell and have a method that simply does a scan. then you flush the flowcell out and inject the same way the next compound and run your scan only method, flush out, etc. 
 
 kind regards