How to read a peptide Certificate of Analysis (COA)

A Certificate of Analysis (COA) is the laboratory document that carries the results of the tests run on a sample. Bachem, a peptide manufacturer, says a selection of the obtained results can be found on the Analytical Data Sheet or Certificate of Analysis. The laboratory that ran the tests issues the report and names itself on it, so that laboratory is the one to ask about the report.

The header of a COA says who ran the tests, for whom and on what. It lists the testing laboratory, the client or customer, the sample or compound name, the lot field, and the received, tested and reported dates.

The header also carries the reference the laboratory uses to find the report again, such as a search code or a certificate ID. Note it, because verifying the report with the laboratory starts from it.

The purity result on a COA is the HPLC result: the main peak's share of the total peak area. Bachem describes the same calculation: the area of the main peak in relation to the total area of all peaks reflects the peptide purity. It shows how much of the detected material is the target compound rather than related impurities such as truncated or deletion sequences.

The chromatogram is the trace behind that result. A column maker's guide describes a plot of detector signal versus time in which every peak corresponds to a different component. On a COA, find the main peak first. The smaller peaks are the rest of what the detector recorded.

The identity result on a COA says whether the sample is the intended compound, and it names the method used. A mass spectrometry result compares the measured molecular mass with the mass calculated for the compound. Bachem notes that the molecular weight is determined by mass spectrometry.

In LC-MS, liquid chromatography separates the sample before the mass spectrometer measures it. A peer-reviewed review describes a mass spectrum as a graphical display of the relative abundance of ion signals against the m/z ratios, where m/z is the mass-to-charge ratio. Some reports confirm identity by FTIR (Fourier-transform infrared spectroscopy) instead, which compares the sample's infrared spectrum with a reference.

Purity and identity are separate results. Purity without a confirmation of identity does not show that the main peak is the intended compound, so a report should give both.

Net content is the amount of compound the laboratory measured in the tested sample, in mg. Purity does not give it, because purity compares peaks within what the detector records and does not cover substances the method does not detect, such as water, salts or excipients.

Bachem defines net peptide content as the share of peptide relative to non-peptide material, and says it is not equivalent to purity. It lists nitrogen content from elemental analysis as a measure of the peptide content, and water content by Karl Fischer titration as a separate measurement.

A COA is a record of what the laboratory measured in the sample it tested. It describes that sample and the tests named on the report, so read the sample name, the lot field and the dates as the description of what was tested. It does not describe any other sample.

Each part of a COA answers one question, and each has one thing to check.

Read a COA in six steps, from the header to the reference.

1. Read the header: the laboratory, the client and the sample name.
2. Note the lot field and the dates.
3. Find the purity result, then open the chromatogram behind it.
4. Find the identity result and the method named for it.
5. Find the net content, in mg.
6. Copy the reference so you can confirm the report with the laboratory.

After reading a COA, confirm it with the laboratory that issued it. How to verify a peptide COA explains how. The COA page describes the testing behind Excalibur Peptides products and where its reports can be opened.