Chromatography Forum

Hi everyone,

I’m using a UPLC amino acid analyser with a 17-amino-acid standard, and I’ve recently encountered a problem with my latest runs. In the last few standards, two amino acid peaks are completely missing, while the neighboring peaks appear distorted (“rough-shaped”) and show almost double the expected peak area.

Has anyone experienced something similar? What could be causing this, and how should I troubleshoot it?

Thank you in advance.

The more you don't tell us the more we can't help you. There are no fortune tellers on this forum.

two amino acid peaks are completely missing, while the neighboring peaks appear distorted (“rough-shaped”) and show almost double the expected peak area.

The "missing peaks" could overlap with the "neighboring peaks". This could double the areas of the "neighboring peaks".

two amino acid peaks are completely missing, while the neighboring peaks appear distorted (“rough-shaped”) and show almost double the expected peak area.

The "missing peaks" could overlap with the "neighboring peaks". This could double the areas of the "neighboring peaks".

Thank you for your answer.

Ι am using a reversed-phase HPLC with a gradient elution. From one day to the next, in the same vial (standard), without any changes to the system, Ι observed this change in the chromatogram.

Again, as vmu prompted, we can't really help without more details. Many of us here routinely do AA analysis, but I have no idea what method you're using. It being 'reversed phase' doesn't really help much; all the varying methods I've ever used are reversed phase.