Gradient Mystery

[Sallybeetle]

I have a problem with a gradient assay that I have not encountered before.

The last peak at the end of the gradient keeps increasing in peak area and height without changing retention time or symmetry.

A diluent blank injection showed an extremely good baseline with no carryover peaks.

The run contains 4 analytes. 2 of the analytes are before the gradient starts and one is at the beginning of the gradient; but, these show excellent retention time %RSD and peak symmetry.

Any advice would be appreciated.

[AdrianF]

Could you give more details eg nature of gradient, wavelength, type of compound, column and a typical problem chromatogram

[Sallybeetle]

That problem resolved itself mysteriously. After running about 7 injections of standard overnight. The peak heights returned to the typical level, and I was able to run a 15 hour analysis without 'this' problem recurring.

However this is the same method for which I just started a new post titled, "B Vitamins HPLC Analysis." All of the information you requested in this post is included the new post.

I do not think that the two problems are related, since this increasing peak height thing is a first out of many months of runs. However, I could be wrong.

Let me know if enough information is included in that post to help you visualize what is going on.