Determining the delay volume

[cottrel]

Hi all,

for delay volume I mean the volume between the detector and the fraction collector.
I would like to measure it precisely as, given the really poor recovery I am getting, I suspect the current value is wrong.
I know one can measure it knowing the internal diameter and length of the tubing between fraction collector and detector but I think it's best to inject only a dye and see if it's really collected properly or it's partially discarded into the waste .

I know the dye method is used, it would be great if someone could tell which dye or suggest another method.

I hope I explained the problem and that you can help,

Thanks

Man

[carls]

I have used an injection of air when using clear tubing between the detector cell outlet and the fraction collector tip. If enough volume is injected (required volume depends on tubing ID) the flow will stop temporarily

[cottrel]

Ok, suppose I inject air, then I will notice a drop in pressure when the bubble gets into the columns but what can I know about the volume between the Uv detector and the tip of the ftaction collector? Am I going to see something in the chromatogram when the bubble goes through the detectror?
Thanks

Man

[carls]

I assumed you were running this test without a column, i.e. with a union in place of the column. You definitely dont want to inject dye onto your column.

Replace the column with a union, set the flow rate to what you will be using when collecting fractions, inject air and measure the time it takes to get from the cell to the tip. If the tubing in not clear and you cannot visually watch the air bubble move from the cell outlet to the tip then start timing when the UV detector spikes and stop when the flow momentarily stops or "spits" at the tip.

[cottrel]

great! I'll give it a go and let you know!

Man

[cottrel]

Thanks a lot for your help, I tried your method and it worked fine! I got consistent result and found the volume.
Unfortunately now the problem is that I can't change the value in the software. I am running Trilution and whenever I change the value the software just won't let me save the method. I am running as admin so permissions shouldn't be a problem.
I have just contacted a guy from Gilson hoping that he gets back to me asap. In case, if you guys know something any suggestion is much appreciated!

Man

It's me again! swift reply from Gilson and the problem is solved, I just had to rename the configuration!