PeptidePedia The community reference

Topic portal·2 articles

Portal:Analytical chemistry

How a purity number is produced, and what it means

Introduction

Almost every quality dispute in this field reduces to a question about an analytical result: what was measured, against what standard, by what method, and what the number is relative to. This portal covers separation science, mass spectrometry, the compendial water and endotoxin tests, and the validation framework that decides whether a method is fit for the claim being made from it.

The single most useful idea here is the distinction between area percent purity and peptide content: the first is a ratio among the species that eluted, the second is a mass fraction of the vial.

Picture of the month

048121620main peak 12.4 min · 98.7 area%mAUminutes
A reverse-phase chromatogram with a main peak at 12.4 minutes and five resolved impurities. Area percent is a relative measure and says nothing about mass.

Selected article

Karl Fischer titration — Karl Fischer titration is the compendial method for determining water content in lyophilised peptides, and the reason a purity figure alone cannot establish how much peptide a vial holds.

82 revisions since 2 July 2024. Discussion · history

Articles in this portal

Things you can do

  • Source the interference claims in the water-determination articles individually.
  • Add a worked limit-of-detection calculation with real signal-to-noise figures.
  • Reconcile the peak-purity terminology used across the chromatography articles.

Items here are deliberately small enough to finish in one sitting. See Project:Verifiability before adding sources.