In plain English
A certificate of analysis (COA) is a lab report about one batch of a product. For peptides (short chains of amino acids, the building blocks of proteins), a good COA answers three questions. Is it the right molecule? How pure is it? How much is actually in the vial? [4, 5]
HPLC (a method that separates molecules) measures purity. Mass spectrometry (a method that weighs molecules) checks identity. A separate test is needed to measure the amount [4, 5].
In one 2024 study, vials sold online as 99% pure semaglutide were only 7.7–14.4% pure, and all contained endotoxin (a bacterial contaminant) [3].
A COA describes only the batch that was tested. It cannot prove that a different batch, or a different vial size, is the same. A purity number with no batch link, method or lab name cannot be checked.
The short version
- A COA describes one batch only.
- Identity, purity and amount are separate tests [4, 5].
- A COA does not change a product’s legal status [7].
Why COAs matter for research peptides
Synthetic peptides can contain several kinds of related impurity, from deletion sequences and incomplete deprotection to oxidation products, aggregates and leftover counter-ions such as trifluoroacetate. Regulators note that these impurities can affect experimental results as well as safety [1, 2].
Labels alone are not reliable. In a 2024 study, researchers bought semaglutide vials online that were labelled 99% pure. Laboratory analysis found purity of only 7.7–14.4%, peptide content 28–39% above the label claim, and bacterial endotoxin in every sample [3]. Problems like these are detected by independent, batch-specific analysis.
Anatomy of a peptide COA
| Section | What it should state | Why it matters |
|---|---|---|
| Laboratory | Name, address and contact details of the testing lab; ideally its accreditation (for example ISO/IEC 17025) | Lets you confirm the report is genuine with the lab itself |
| Client and manufacturer | Who submitted the sample and who made it | Shows the supply chain |
| Product and batch/lot number | Compound name, labelled amount (e.g. 10 mg), and a batch or lot number that matches the vial label | Without a matching batch number, the COA could belong to any batch |
| Dates | Date tested, date issued, and ideally manufacture and retest/expiry dates | Peptides degrade, so old results may not reflect current material |
| Identity | Mass spectrometry (MS or LC-MS) showing the observed molecular mass against the theoretical mass | Confirms the molecule is the right one |
| Purity | Usually HPLC (high-performance liquid chromatography), reported as % main peak area, with the chromatogram attached | Shows how much of the peptide material is the target sequence rather than related impurities |
| Assay / peptide content | The measured amount of peptide per vial (mg), against the label claim | Purity and quantity are different questions (see below) |
| Appearance | e.g. “white lyophilised powder” | A basic consistency check |
| Optional but valuable | Water content (Karl Fischer), counter-ion content, endotoxin (LAL test), sterility or microbial counts, heavy metals | Each one can affect experiments independently of purity |
| Signature | Named analyst or approver, with a signature | Accountability |
International guidelines for specifications and analytical method validation (ICH Q6B and ICH Q2(R2)) describe these categories of testing: identity, purity, quantity and impurities. They are a useful benchmark even for research-grade material [4, 5].
Purity and content are different numbers
Two figures on a COA are often confused:
- Purity (%) answers: of the peptide material present, how much is the correct sequence? HPLC separates the target peptide from closely related impurities and reports the main peak as a share of the total.
- Assay or content (mg) answers: how much peptide is actually in the vial? A lyophilised powder also contains water and counter-ions, so a vial can be “99% pure” and still hold less (or more) peptide than its label says [1, 3].
A good COA reports both. For a deeper explanation, see Purity vs Peptide Content.
Testing methods: what each one can and can’t tell you
| Method | Can tell you | Can’t tell you |
|---|---|---|
| HPLC (UV detection) | Purity by separating the target peptide from related substances | The identity of each peak, on its own |
| Mass spectrometry (MS / LC-MS) | Molecular mass, so it confirms identity and can identify impurity peaks | Precise quantity, unless specifically calibrated |
| UV-Vis spectrophotometry (no separation) | Total absorbance compared with a reference standard; a quick estimate of quantity and identity | It can’t separate the target peptide from closely related impurities that absorb light in the same way, so it is a weaker test of purity |
| Amino acid analysis | Accurate peptide content (net peptide) | Sequence order or purity |
| LAL endotoxin test | Bacterial endotoxin levels | Living microbes (that needs separate sterility testing) |
For more detail, see HPLC, LC-MS and UV-Vis: How Peptide Purity Is Measured.
10 red flags on a peptide COA
- No batch or lot number, or one that doesn’t match the vial.
- Wrong size or wrong compound. For example, a 20 mg COA shown for a 10 mg product, or a single-peptide COA shown for a blend.
- The same purity figure on every product. Real batch data varies.
- No laboratory name or contact details, or a lab that can’t be found or contacted.
- No method stated for purity, or purity measured without a separating technique.
- No identity test (no mass spectrometry data).
- No chromatogram attached to an HPLC purity claim.
- An assay result far from the label claim, yet marked “Pass”. The pass criterion should be consistent with the stated specification.
- Out-of-date results for material sold long after testing.
- Signs of editing: mismatched fonts, missing pages, cropped headers, or image files instead of the original PDF.
How to verify a COA
- Match the batch number on the COA to the vial label.
- Contact the laboratory named on the report and ask whether it issued that report number.
- Check that the reported molecular mass matches the theoretical mass, for example from PubChem.
- Read the specification alongside each result, not just the word “Pass”.
What this means in Australia
Accredited laboratories. In Australia, the National Association of Testing Authorities (NATA) accredits testing laboratories to ISO/IEC 17025, the international standard for the competence of testing and calibration laboratories [6]. Accreditation is a useful signal of method control when judging who produced a COA.
What the TGA says about labelling. The TGA warns that the labelling of unapproved peptide products may be inaccurate or misleading [7]. It also states that a “research use only” disclaimer does not make supply lawful, and does not change a product’s regulatory status, permit importation, or remove advertising or supply obligations [7]. The TGA has said that “manufacture” includes applying a label to a blank vial [9].
A COA does not change regulatory status. A COA is evidence about quality. A well-documented batch is still not entered on the Australian Register of Therapeutic Goods (ARTG), and a compound’s Poisons Standard status depends on the substance itself. Several peptides, for example, are named in Schedule 4 (prescription only) and Appendix D, clause 5 (possession without authority is illegal) of the current Poisons Standard (October 2026) [8]. See Are Peptides Legal in Australia?.
This is general information, not legal advice. Laws change; check the current Poisons Standard and TGA guidance.
Frequently asked questions
What is a peptide COA?
A Certificate of Analysis is a laboratory report on one batch of peptide material. It documents identity, purity, quantity and, sometimes, contaminants such as endotoxin [4, 5].
What purity should a research peptide have?
That depends on the experiment, but research suppliers commonly specify ≥98% by HPLC. Whatever purity is claimed, it should be backed by a batch-specific HPLC result with the chromatogram attached.
Is HPLC or mass spectrometry better?
They answer different questions. HPLC measures purity, and mass spectrometry confirms identity. A reliable COA usually includes both, often combined as LC-MS.
Can a COA be faked?
Yes. To check one, match the batch number, check that the lab exists, and confirm the report directly with the laboratory.
Why does peptide content matter if purity is high?
Purity describes the peptide fraction only. Water and counter-ions add weight, so a vial’s actual peptide content can differ from the label even when purity is high [1, 3].
References
- D’Hondt M, Bracke N, Taevernier L, et al. Related impurities in peptide medicines. J Pharm Biomed Anal. 2014;101:2–30. doi:10.1016/j.jpba.2014.06.012. PMID: 25044089
- Colalto C. Aspects of complexity in quality and safety assessment of peptide therapeutics and peptide-related impurities: a regulatory perspective. Regul Toxicol Pharmacol. 2024;153:105699. doi:10.1016/j.yrtph.2024.105699. PMID: 39243929
- Ashraf AR, Mackey TK, Vida RG, et al. Multifactor quality and safety analysis of semaglutide products sold by online sellers without a prescription: market surveillance, content analysis, and product purchase evaluation study. J Med Internet Res. 2024;26:e65440. doi:10.2196/65440. PMID: 39509151
- International Council for Harmonisation. ICH Q6B: Specifications: test procedures and acceptance criteria for biotechnological/biological products. database.ich.org
- International Council for Harmonisation. ICH Q2(R2): Validation of analytical procedures. 2023. database.ich.org
- National Association of Testing Authorities, Australia (NATA). Accreditation programs, including ISO/IEC 17025 testing and calibration. nata.com.au. Accessed 11 October 2026.
- Therapeutic Goods Administration. Understanding your responsibilities when importing, compounding and supplying unapproved peptide products. Safety advisory, 13 April 2026. tga.gov.au. Accessed 11 October 2026.
- Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026 (F2026L01327). Federal Register of Legislation. legislation.gov.au/F2026L01327/latest/text. Accessed 11 October 2026.
- Therapeutic Goods Administration. Unapproved peptide product promoters and suppliers are put on notice. Media release, 20 July 2026. tga.gov.au. Accessed 11 October 2026.
Important information and disclaimer
General information only. This article is published for general educational and informational purposes. It summarises published scientific literature and public regulatory information as at the “last reviewed” date shown above. It is not medical, health, pharmaceutical, veterinary or legal advice, and it must not be relied on as a substitute for advice from a qualified professional about your circumstances.
Not for human or animal use. Nothing in this article recommends, endorses or describes the use of any substance in humans or animals. Findings from cell, animal or early human studies cannot be assumed to apply to people. The compounds discussed have not been evaluated by the Therapeutic Goods Administration (TGA) for safety, quality or efficacy unless the article expressly states otherwise. Any research materials offered by Iconic Peptides are supplied solely for in vitro and laboratory research.
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Regulatory status. Many peptides are scheduled substances under the Poisons Standard. Some are prescription-only (Schedule 4), and some may not be possessed without authority (Appendix D). The TGA has stated that a “research use only” label does not make supply lawful, change a product’s regulatory status, or remove advertising or supply obligations. State and territory laws may also apply. You are responsible for knowing and complying with all laws that apply to you. Regulatory information in this article may change after the review date.
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