COA Explained
Every line on the certificate, and what it actually measures
A certificate of analysis is only useful if you can read it. This page walks each test we run, what it tells you, what a normal result looks like, and what it does not cover.
Appearance
A visual check against the expected form. Most peptides are a white to off-white lyophilised cake; GHK-Cu is deep blue because of the copper(II) centre. A collapsed, sticky or discoloured cake indicates a problem with the drying cycle or with moisture ingress, and is a reason to reject a lot before any instrument is involved.
Purity by RP-HPLC
The headline number. Material is separated on a C18 column under an acetonitrile gradient and detected by ultraviolet absorbance at 214 nm, which responds to the peptide bond itself. Purity is reported as the area of the main peak divided by the total integrated area.
What it does not tell you: area percent is a relative measure. It says the main peak is 99.4% of what the detector saw - not that the vial is 99.4% peptide by mass. Anything that does not absorb at 214 nm, including water and residual salts, is invisible to it.
We publish the full chromatogram with every lot. A single sharp peak on a flat baseline and a 99.2% result is a different material from a peak with a pronounced shoulder and a 99.2% result. The number is identical; the material is not.
Identity by LC-MS
Confirms the molecule is the one on the label. The sample is ionised by electrospray and the observed mass compared against the calculated value for the sequence, within a stated tolerance - typically ±1 Da for smaller peptides and ±2 Da for polypeptides above 4 kDa.
Purity without identity is close to meaningless: a lot can be 99.5% pure and be 99.5% of the wrong compound. Both tests belong on the same certificate.
Net peptide content by amino acid analysis
The number most often missing elsewhere, and the one you need for a concentration calculation. The sample is hydrolysed and the constituent amino acids quantified, giving the mass of peptide actually in the vial, reported in milligrams against the label claim. The remainder of the fill is counter-ion, residual water and trace solvent.
A 10 mg vial will typically read a little either side of 10 mg, for example 9.8 mg or 10.4 mg. The specification is 90–110% of the label claim. Use the certificate figure, not the label, when the calculation has to be exact.
Heavy metals by ICP-MS
Elemental impurities screened by inductively coupled plasma mass spectrometry against the USP ⟨232⟩ panel: lead, cadmium, arsenic, mercury and the catalytic metals used in synthesis. The specification is ≤ 10 ppm total; a typical lot reads below 1 ppm. Reported as a limit, not a zero, because the instrument has one.
Water by Karl Fischer
Residual moisture after lyophilisation, measured by coulometric titration. Specification is ≤ 8.0%. High water content shortens shelf life and, in a hygroscopic peptide, indicates the vial was exposed before sealing.
Counter-ion by ion chromatography
Peptides are purified against an acid and isolated as a salt. We supply acetate rather than trifluoroacetate because TFA interferes with a range of cell-based assays. Acetate content is reported and specified at ≤ 15.0%.
Endotoxin by USP ⟨85⟩ LAL
Bacterial endotoxin, measured by limulus amoebocyte lysate assay and reported per milligram of peptide. Relevant to any cell culture or in-vivo research model, where endotoxin contamination produces effects easily mistaken for the compound under study.
What no certificate covers
A certificate describes the lot as it was assayed, on the date it was assayed. It does not describe what happened to the vial afterwards, and it makes no statement about biological activity, suitability for any purpose, or safety in any organism.