Category: Analytical Methods

How tandem mass spectrometry reads peptide sequence from b and y fragment ions, where MS/MS is ambiguous, and why sequence is not purity.

Why one analytical report cannot show lot-to-lot variation in a peptide, what trending reveals, and how a lab can build its own consistency record.

How significant figures and rounding shape a peptide purity result: trailing zeros, spec limits, exact fives, and when extra digits mean nothing.

How size exclusion chromatography reveals peptide dimers and aggregates that a reverse-phase purity trace misses, and where SEC results go wrong.

What the mg on a peptide vial means: nominal fill mass vs net peptide content, counter-ion and water. Why two 10mg vials differ, and how to compare price.

How multi-peptide blends are analysed: separating co-eluting components on HPLC, per-component purity and mass. What a blend certificate should list.

A purity percentage without a method is an assertion. The questions that separate a supplier who ran an analysis from one who bought a number.

Bacteriostatic water is sterile water with 0.9% benzyl alcohol; sterile water has no additive. What each label means and where it matters.

Plain definitions of the terms that appear on specifications and certificates, written for people evaluating a supplier rather than writing a synthesis.

The appearance of a lyophilized peptide is weak evidence about quality and strong evidence about process. Here is how to read it, and how not to over-read it.