Chromatography Forum

I am attempting to quantify ergosterol using HPLC. The standards I am running produce a peak with a shoulder. is this a problem

If your standards have a shoulder, in a word, yes, it is a problem. First off, what is the purity of your standard? If it is supposed to be 100% pure, then you have a dirty column I would guess. If it is significantly less than 100%, I would suspect you have a co-elution issue and need to continue development to separate the second peak.

You could have other problems, but this is I would start if I were you.

Ergosterol might be difficult to dissolve in aqueous mobile phases, and you may have dissolved it in 100% organic. This can create peak distortion in aqueous mobile phases if you inject a large sample volume.

To see if this is the problem, inject less sample.