Purity by reversed-phase HPLC
A sample of the lot is dissolved and injected onto a C18 column. A gradient of water and acetonitrile, each with 0.1 % trifluoroacetic acid, carries the components through the column at different rates; the peptide bond absorbs ultraviolet light at 214–220 nm, so a detector at that wavelength records a chromatogram of absorbance against time. Purity is the area of the main peak as a percentage of the area of all peaks.
Our criterion is a main peak of 99.0 % or more. A clean batch shows one dominant peak and a flat baseline. Small late-eluting peaks are usually oxidised or deamidated forms of the peptide; a shoulder before the main peak is more often a deletion sequence. The chromatogram itself is in the signed report, so a reader can judge the trace rather than trust a number. HPLC and LC-MS explained covers the method in plain language.
Identity by LC-MS
Purity says how much of the sample is one substance; it does not say which substance. Identity is confirmed by liquid chromatography coupled to electrospray mass spectrometry. The main peak is ionised and its mass-to-charge ratios are measured; peptides carry several charges, so the instrument records a series of peaks that deconvolute to the neutral molecular mass. That observed mass is compared with the theoretical mass of the compound. Our criterion is agreement within 1.0 Da for peptides above 2,000 Da and within 0.5 Da below that. The certificate reports both the observed and the expected figures and says whether the result is a monoisotopic or an average mass.
Endotoxin by LAL
Bacterial endotoxin is measured with a limulus amoebocyte lysate assay and reported in endotoxin units per milligram. It matters for cell-based assays, where endotoxin contamination can confound inflammatory readouts. Not every compound is tested for endotoxin; where it is, the result is on the certificate and in the register, and our criterion is 1.0 EU/mg or less.
Net peptide content
A lyophilised peptide is not 100 % peptide by mass. It carries bound water and the counter-ion from purification, typically trifluoroacetate, which together can account for 10–25 % of the powder. Net peptide content, measured by amino acid analysis or by ultraviolet absorbance against a standard, expresses the peptide fraction. Where it is reported, use it to correct concentrations; the reconstitution calculator explains how.
What the register shows
The certificate register lists every batch with its purity, identity result, endotoxin where tested, laboratory and test date, and links to the signed PDF. The product page shows the same figures for the batch currently shipping for each vial size. The figures on the site are transcribed from the report by hand and checked against it; the report is the primary record.
Independence
The laboratory that tests our lots is independent of us and of the manufacturer, is named on every certificate, and is paid per analysis regardless of the result. We do not select which lots to publish. The laboratory page describes who they are.