Method Develpoment

[RobPelot]

Hello,

I have been working on oil samples from the gulf oil spill. I am extracting beach sand and looking at it with a fluorescence detector. I found the best excietation and emission lambdas (at least best that I am aware of ) and injecting the samples.
I never get the same result twice. I tend to have a large emission pegging out in the beginning and the end of the run. One time, I got a beautiful chromatogram, but I cannot replicate this. I am using a C18 and a guard column.
My books do not say how to resolve these types of groups. Any help anyone can give would be helpful

http://www.facebook.com/photo.php?fbid= ... 09&theater

Here is what I am seeing!

[yanyan]

I can’t see your chromatograms since I don’t have Facebook account. From your description above, it sounds like you have some none polar component(s) retened in the column. If I was you, I would try to re-develop a gradient method with a higher organic ratio at the end and then back to the starting condition with enough equilibrium time in order to eluent all components out of the column.

Hope it helps.

[DR]

apologies if this does not help...

[RobPelot]

Thanks for posting the picture.

I am not really getting any defined peaks. It all comes out as one blob in the beginning and the end, with a large amount of space in between.
I got one chromatogram that looked great, but never reproduced it again.

will switching to a more organic solvent yield better resolution ? Or will it only help the compounds elute off the column completely?

Thanks again!

[yanyan]

[quote]will switching to a more organic solvent yield better resolution ? Or will it only help the compounds elute off the column completely?
[/quote]

It will help the componds eluete off the column. It may or may not increase the resolution depending upon your application.

What gradient was for the third chromatogram you got? And what was the next chromatogram look like? May be you can find some clue and look into it from there...