Certificates of Analysis

How to read one of these reports

A certificate of analysis records one production lot. It names the tests run on that lot, the methods used, and the numbers that came back. It says nothing about the next lot, and nothing about the company that sold it. Two minutes spent reading one removes most of the guesswork from buying research peptides in the United States.

What the mass tells you

Mass spectrometry answers a different question than purity does. It compares the mass actually observed against the mass calculated for the intended sequence, which is how you learn the vial holds the compound named on the label. Skip that step and a high purity figure only means the contents are consistent — consistent with something you have not identified.

Why two laboratories can print different purity figures

RP-HPLC purity is an area-percent figure, and the conditions move it. Run a steep gradient and the peaks compress, so deletion sequences eluting close to the target hide beneath the main peak. Run a shallow one and they separate, and the same vial reports lower. Wavelength matters as much: 214 nm reads the peptide bond and catches nearly everything, while 280 nm registers only aromatic residues. A percentage quoted without the column, gradient and wavelength beside it cannot be reproduced, which is why two honest laboratories can disagree about one vial.

What a standard report does not cover

Identity and purity work says nothing about sterility, endotoxin load or residual solvents. Each of those needs its own test, and a report that does not list them did not run them. Anything with an immune or inflammatory readout is worth checking on this point before ordering.

How we handle certificates here

• Reports are posted openly rather than emailed on request. Anyone can read them before ordering, including people who never order. Not every lot has a report published here — when yours is not shown, ask and we will send what we hold for it.
• Cap and crimp colour is the matching mechanism. Our vials carry no printed batch number, so a vial is tied to its certificate by the colour combination, checked against the photographs on the certificate itself.
• Third-party and in-house work are labelled separately. Each report states which methods were applied to that batch and who applied them.
• The claim is falsifiable. Have a compound analysed independently, and if it misses the specification on its certificate we refund the product and what the analysis cost you. A published number means little without a penalty for publishing a flattering one.

Five checks before you trust a number

• Look at the chromatogram before the headline figure. One sharp peak on a flat baseline earns the number; a cluster of unresolved shoulders swept into a single integration does not. Walkthrough: reading an HPLC chromatogram.
• Recalculate the mass from the sequence, acyl groups, bridges and modifications included. Modified analogs are where the arithmetic slips.
• Find the net peptide content. Lyophilised powder carries counterions and water, so the mass in the vial overstates the peptide in it, commonly by fifteen to twenty-five percent. Without that figure your concentrations are estimates. See net peptide content explained.
• Identify the counterion. Trifluoroacetate left over from purification has activity of its own in some cell assays. See counterions and salt form.
• Match the date and batch to the vial in front of you, since the report describes that lot and not the product line.

Longer treatments: how to read a peptide certificate of analysis, why certificates disagree on purity, HPLC and mass spectrometry verification and third-party versus in-house testing.

Questions that separate one US supplier from another

Six of them, and most can be answered from a supplier’s own website in a few minutes:

• Are reports published for anyone to read, or produced only after you ask?
• Can the vial you receive be tied back to a specific report?
• Are the analytical conditions — column, gradient, wavelength — written down?
• Is independent testing separated from testing done in-house?
• Does anything happen if an independent result contradicts the report?
• Is the price comparable per milligram of net peptide rather than per vial?

The last question catches the most people. A cheaper vial holding less peptide is not cheaper. See comparing prices per milligram and choosing a research peptide supplier in the USA.

What we do not claim

• Nothing supplied here is approved or cleared by the FDA, and nothing here is a drug, dietary supplement, food, cosmetic or medical device.
• Not produced under GMP, and we do not represent that it is.
• No sterility or endotoxin assurance unless a specific batch certificate records that those tests were run.
• No dosing, administration or protocol guidance, in any channel, requested or not.
• Supplied for laboratory research use only — not for human consumption, and not for clinical, veterinary, cosmetic or household use.

The regulatory position is set out in buying research peptides in the USA, and the guarantee in full at purity guarantee and independent testing.