COA Library

What a batch certificate documents

A Certificate of Analysis is a record of what an analytical laboratory measured in one specific batch of material. It is not a specification sheet and it is not a marketing document. A specification says what a compound is supposed to be; a certificate says what this batch actually was, on a stated date, by a stated method.

That distinction is the whole point. Two vials with the same label can come from different synthesis runs with measurably different purity, different residual solvent content and different counter-ion load. Only a batch-specific certificate tells you which one you are holding.

Reading an HPLC purity result

Purity on a peptide certificate is almost always determined by reverse-phase high-performance liquid chromatography. The sample is separated on a column, and a detector records absorbance as each component elutes. The result is a chromatogram: a baseline with peaks on it. Purity is reported as the area of the target peak as a percentage of the total area of all peaks.

Three things are worth checking on that number. What wavelength was used — 214 nm detects the peptide bond itself and sees essentially everything peptidic; 280 nm detects aromatic residues and will not see fragments that lack them, which flatters the result. Whether the gradient is stated — a purity figure without the method behind it is unverifiable. Whether the chromatogram is shown — a number alone tells you nothing about whether the impurities are one closely-eluting related substance or a dozen scattered peaks.

Purity by area percentage is also not the same as peptide content by mass. See the reconstitution calculator for why nominal vial mass and assayed peptide mass differ, and HPLC and mass spectrometry purity testing for how the two methods complement each other.

Identity confirmation

Purity tells you how much of the material is one thing. It does not tell you that the thing is the compound on the label. That is what mass spectrometry is for: the measured molecular mass is compared against the theoretical mass calculated from the sequence. A certificate that reports purity but never confirms identity has answered only half the question.

The heavy metals panel

Every batch supplied by PerformanceLabsUK is tested for arsenic, cadmium, lead and mercury. These four are the standard elemental impurity panel because they are the elements most likely to be introduced by reagents, catalysts or equipment during synthesis and purification, and they are the four named in the elemental impurity guidance most analytical laboratories work to.

Heavy metals testing is a separate assay from purity, run on a separate instrument, and it is reported on its own certificate. A supplier who says “independently tested” and produces only a purity result has not tested for elemental impurities at all.

How to tell a real certificate from a fabricated one

Fabricated certificates are common in this sector and they are usually easy to spot once you know what to look at.

1. A named laboratory, not just a logo. A real certificate names the testing laboratory and gives a way to reach it. A logo with no address, no contact and no report number is decoration.
2. A batch number that matches your vial. If the certificate cannot be tied to the specific batch you were sent, it is evidence about somebody else's material.
3. A test date. Certificates are dated because material changes. An undated certificate is not a record of anything.
4. The method, not just the result. Column, gradient, detection wavelength, instrument. Results without methods cannot be checked or reproduced.
5. The chromatogram itself. A typed percentage is trivial to alter. A chromatogram is much harder to fake convincingly, and it shows you the shape of the impurity profile.
6. Purity figures that are not suspiciously round. Real analytical results land on numbers like 98.4% or 99.2%. A catalogue where every compound is exactly “99%” is quoting a specification, not reporting measurements.
7. Separate reports for separate assays. Identity, purity and elemental impurities are different tests. One page claiming all three with a single result line is not how analytical laboratories report.

For the wider question of how independent testing is arranged and what accreditation actually certifies, see how independent lab testing works and third-party accreditation of a testing laboratory.

Requesting the certificate for your batch

Certificates for individual batches are issued against the batch number printed on your vial. Email support@performancelabsuk.com with your order number and we will send the identity, purity and heavy metals reports for the batch you were supplied. Sample certificates are published on this page as batches are released.

Reference materials by research area

Every compound below ships with its own batch certificate.

Frequently asked questions

Why is the certificate specific to a batch rather than the product?

What does a purity percentage on a peptide certificate actually measure?

Which heavy metals are tested for?

Can I get the certificate before ordering?

Does a certificate mean the material is safe for any use in humans or animals?

Research use only. All materials referred to on this page are supplied for in vitro laboratory and scientific research use only. They are not medicines, are not for human or veterinary use, and are not for use in diagnosis or treatment.