Category: Analytical Methods

What causes peak tailing in peptide HPLC, how tailing and asymmetry factors are calculated, and how a long tail can hide impurities in a purity result.

N-methylated peptides: +14 Da isobaric traps, cis/trans conformer peaks in HPLC, hindered-coupling impurities and how to tell conformers from impurities.

How capillary zone electrophoresis separates peptides by charge and size, why CE peak areas need migration-time correction, and how it cross-checks HPLC.

What a proton NMR spectrum confirms about peptide identity and what it misses, from residue order to trace impurities, with a worked integral check.

Why polydisperse PEG turns one peptide mass into a 44 Da ladder, broadens HPLC peaks and hides free polymer from UV, plus what a report should show.

How to calculate a peptide extinction coefficient from Trp, Tyr and cystine, and when A205 or A214 replaces A280 for measuring concentration by UV.

Chromatography records audited against ALCOA+: audit trails, manual integration, trial injections and what a complete HPLC record contains.

How ion chromatography and 19F NMR quantify TFA, acetate and chloride in peptide salts, with a stoichiometry example and evidence a TFA exchange worked.

D-amino acid and retro-inverso peptides share their parent’s mass. Why MS and C18 HPLC miss chirality, and which chiral methods can detect it.

How GRAVY scores and HPLC retention coefficients predict where a peptide elutes on reverse phase, with a worked example and the limits of each scale.