Analytics · HPLC & UHPLC

Second pass at: What a reversed-phase purity number actually is

Analytics › HPLC & UHPLC peak integration UV & DAD detection system suitability

j.teixeiraTL225 Jan 2025#1

On the subject in the title: Second pass at: What a reversed-phase purity number actually is Working notes rather than a conclusion.

I would like to understand what this number means before I repeat it anywhere.

A VendorInvestigate report on a semaglutide lot gives 97.5% purity. The supplier certificate for the same lot states 97.8%. Both documents name a reversed-phase method; neither states the same gradient.

My question is not "who is right". It is: given that those two figures were produced by different methods, what is the largest difference I should expect from method alone, and at what point does a gap stop being explainable that way?

53 likes 18mo

s.poulsenTL3Regular22 May 2025#2

The opening post and I disagree about the size of the effect, not about the direction.

This is why a purity figure without the underlying chromatogram is weaker evidence than it appears. It is also why two competent laboratories can report different numbers on the same vial without either being wrong.

0 likes 14mo

ni.stanescuTL215 Aug 2025#3

Nothing to add on the substance. Thank you for taking the question at face value.

2 likes 11mo

This topic was referenced in

Injection volume, overload, and peak distortion — one year onAnalytics › HPLC & UHPLC · 8 replies

Promoted into the documentation commons. The content of this topic is maintained at Reversed-phase HPLC for peptides, with named maintainers and a review date. The promotion was discussed in doc review. Corrections are best raised against the document, which is the version that gets kept current.

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