COA and Purity Science

A purity percentage counts molecules. A bioassay measures function. Why ICH Q6B treats potency as a separate specification, and what our COA omits.

Capillary electrophoresis separates peptides by charge, not hydrophobicity — and catches the impurities an HPLC-UV purity number cannot see.

A purity percentage is the output of a procedure. ICH Q2(R2), adopted by FDA in 2024, defines what makes that output worth believing.

A purity figure is a comparison, and comparisons need a standard. What happens when national metrology labs measure the same peptide batch.

Amino acid analysis takes the peptide apart and counts the residues. What net peptide content measures that purity and fill weight cannot.

HPLC purity is a ratio; qNMR is a count. What quantitative NMR measures that a purity percentage cannot, and what our COAs report instead.

Why water content is the one certificate value that changes after the certificate is issued, what Karl Fischer titration measures, and what our COAs omit.

A peptide can be 99% pure and still be one-fifth trifluoroacetate by weight. What the counterion is, why HPLC misses it, and why it is not inert.

Why HPLC purity is blind to metals, what ICH Q3D actually requires, how ICP-MS works, and why a copper peptide inverts the whole question.

Sterility and bioburden are different questions with different compendial tests. What each one proves, and what a peptide COA actually carries.