COA and Purity Science

ICH Q3C classes, USP 467 headspace GC, and why a 99% pure peptide can still be several percent solvent by mass. What the certificate omits.

How USP <905> content uniformity, batch sampling, and fill accuracy actually work for lyophilized research peptides — and what a COA does not tell you.

How LAL and recombinant Factor C endotoxin assays actually work, what USP <85> and <86> require, and what a research peptide COA does and does not certify.

Third-party or in-house peptide testing? Eight national metrology labs measured one oxytocin vial and disagreed by 220 mg/g. What that means for a COA.

Reporting, identification and qualification thresholds are three different obligations. Why a single peptide purity percentage satisfies none of them.

Where the 98% peptide purity number comes from, why ICH excludes peptides from its own thresholds, and what a US research COA should report.

MS confirmed is not one claim. What MALDI-TOF and LC-MS/MS each certify about peptide identity, and what a US research COA should state.

HPLC purity is a chromatogram statistic, not a vial inventory. What 99% actually certifies, what it misses, and what to demand on a US batch COA.

HPLC measures purity, MS confirms mass — but both share a blind spot. What each method can and cannot certify on a research peptide COA.

A purity percentage is a chromatogram statistic, not a statement of what is in the vial. How to read a peptide COA line by line, and what it omits.