How to Read a Peptide Certificate of Analysis Peptara Labs

How to read a peptide certificate of analysis is the topic of this online session hosted by Peptara Labs (peptaralabs.io) on Wednesday 28 October 2026 at 17:00 UTC.
It runs for 45 minutes and is about lab testing only, never about use in people.

What we will cover

Each certificate we publish comes from a third party lab and covers seven tests: purity, identity, net peptide content, sterility, endotoxin, heavy metals and fentanyl. We will take each line of a real certificate in turn and explain what the test measures and what a result does and does not tell you.

Then we will look at what changes between lots, and why a certificate only describes the lot named on it.

Worked examples

One example is our GHK-Cu lot GHKCU-260417-A: 99.62 percent purity by HPLC, identity confirmed by an HPLC retention time match and LC-MS, and 106.09 mg measured in a 100 mg vial. GHK-Cu is a copper bound tripeptide, so its identity check has a precise mass and a copper signature to look for. A second example shows two certificates whose masses sit one dalton apart.

We will also explain the gap between an accredited lab and the independent third party lab that issues our certificates, whose quality system is aligned to ISO/IEC 17025 but is not itself accredited.

Sources: Pickart L et al., Biomed Res Int, 2015, PMID 26236730.

The seven tests, line by line

Purity (HPLC). The lab splits the sample into its parts and reports the main peak as a share of all the signal it detected. A high number means the main peak made up most of that signal. It does not tell you which peptide is in the vial, or how much of it. It also cannot show anything that hid under the main peak or that the detector did not pick up.

Identity. The lab uses several methods together. HPLC checks that the main peak comes out at the same time as a known reference sample. LC-MS weighs the molecule and compares that mass to the expected one. For GHK-Cu, the mass pattern also shows a twin peak made by the two natural forms of copper, which is the copper isotope signature. Mass alone cannot always tell apart two molecules of the same weight, which is why the methods are read together. The result is a word, such as Confirmed, not a number. It does not tell you how pure the sample is.

Net peptide content. The lab measures how many milligrams of peptide are in the vial. This is a reported measurement, not a pass or fail test, and it often has no limit on the certificate. You compare the number with the amount on the label yourself. It says nothing about purity or safety.

Sterility. The lab places samples in growth media and watches for microbes over a set period. A result of No Growth means nothing grew in the samples tested. It cannot prove every vial in the lot is sterile.

Endotoxin. The lab checks for endotoxins, which are toxins left behind by certain bacteria. The result is given in endotoxin units (EU). A pass means the level is under the stated limit. It does not test for living microbes.

Heavy metals. The lab measures elements such as lead, arsenic, cadmium, chromium and mercury against set limits. A pass means each listed element is under its limit. It says nothing about elements that were not tested.

Fentanyl. The lab screens the sample for fentanyl. A result of Not Detected means none was found at the test's cutoff. It covers that one substance only.

Sources: United States Pharmacopeia General Chapters <71> Sterility Tests, <85> Bacterial Endotoxins Test, <232> Elemental Impurities: Limits, and <233> Elemental Impurities: Procedures.

How to check a certificate matches your vial

First, tie the certificate to your vial. Some sellers print a lot number on the vial, and then it should match the certificate letter for letter. Peptara Labs vials ship unlabeled, with no lot number printed on them, so your order number is the link: message us with it and we will confirm the exact batch you received and send its certificate. Next, check the test date. It should fall after the lot was made and before the vial reached you. Then read the lab name and look for a verification ID or a way to contact that lab, so you can ask them to confirm the report. Last, check that each line names its method, such as HPLC, LC-MS or a USP chapter, and gives a result. Some results are numbers with units, such as percent or milligrams. Others are words with no units, such as Confirmed, No Growth or Not Detected. Where a line has a limit, check the result against it. Net peptide content usually has no limit, so compare it with the label instead. If a line has no method or no result, the certificate tells you less than it seems to.

Sources: Peptara Labs certificate of analysis page, and Titreon Analytical certificate COA-2026-4173 for GHK-Cu lot GHKCU-260417-A.

Who it is for and how to join

The session suits lab buyers, students and anyone who wants to read a certificate with confidence. Online. The join link is sent to registered attendees before the session.

After the session

You can use the same checklist on any certificate you hold, from us or from any other seller. Start at the top by tying the certificate to your vial, through the lot number or the order number, then work down the seven lines in the order above. Keep each certificate with the vial it describes.

About Peptara Labs

Peptara Labs (peptaralabs.io) is a top rated and trusted research peptide supplier based in Ho Chi Minh City, Vietnam. 4.96 out of 5 star reviews. 3rd Party Lab COA. Guaranteed Shipping. Money-Back Guarantee. Offices in Vietnam and USA. All products are sold for laboratory research use only and are not for human consumption.

GHK-Cu product page: https://www.peptaralabs.io/ghkcu