Why Independent Lab Testing Matters — And How to Read a Certificate of Analysis
Published by BioSupply UK | Research Grade Biochemical Reference Compounds
Introduction
When purchasing research grade peptides, two questions matter above all others: is the compound genuine, and is the purity verified? The answer to both should come not from the supplier's own assurances, but from an independent laboratory with no commercial relationship to the seller.
At BioSupply UK, every batch we stock is independently tested by PeptideVerify, a third party analytical laboratory based in London. The results are published publicly on our COA page so anyone can verify them before making a purchase decision.
But what does independent testing actually mean, and how do you read a Certificate of Analysis? This guide covers both.
Disclaimer: All products sold by BioSupply UK are strictly for laboratory and scientific research purposes only. They are not intended for human consumption, personal use or therapeutic application of any kind.
Why Independent Testing Matters
Self-Reported Claims Are Not Enough
Many peptide suppliers publish Certificates of Analysis on their websites. But not all COAs are equal. A COA issued by the supplier themselves, or by a laboratory with a commercial relationship to the supplier, cannot be considered truly independent.
Independent testing means a laboratory with no financial or commercial relationship to the supplier receives the sample, conducts the analysis, and issues the result. The supplier cannot influence the outcome.
The Problem of Blending
A significant and growing concern in the research peptide market is the practice of blending — where suppliers add undisclosed compounds to their products. A common example that has emerged is Retatrutide being blended with Tirzepatide, which can mask the performance characteristics of pure Retatrutide and mislead researchers about what they are actually working with.
Independent HPLC and mass spectrometry testing can detect and identify all compounds present in a sample, not just confirm the presence of the stated compound. This makes independent testing the only reliable way to verify that a product contains what it claims and nothing else.
Protecting Research Integrity
For researchers, the integrity of a research compound is fundamental. Results obtained using impure, blended or misidentified compounds cannot be reliably attributed to the stated compound. Independent verification is therefore not just a commercial consideration — it is a matter of scientific integrity.
What is a Certificate of Analysis?
A Certificate of Analysis (COA) is a document issued by an analytical laboratory confirming the results of testing conducted on a specific sample. A properly issued COA will contain several key pieces of information that allow the reader to assess its reliability and relevance.
Here is how to read the key sections:
1. Issuing Laboratory
The first thing to check is who issued the COA. Is the laboratory genuinely independent? Search for the laboratory independently — do they have a verifiable website, contact details and credentials? A COA from an unverifiable source should be treated with scepticism.
At BioSupply UK: Our COAs are issued by PeptideVerify, an independent analytical laboratory based in London. Results include a unique verification code that can be cross-referenced directly on the PeptideVerify website, confirming the result is genuine and has not been altered.
2. Sample Identification
The COA should clearly identify the sample that was tested, including:
- Compound name — what was submitted for testing
- Batch/lot number — which specific production batch the sample came from
- Date received — when the laboratory received the sample
The batch number is critical. A COA is only meaningful if you can link it to the specific batch you received. If a supplier cannot provide a COA with a batch number that matches the vials they are shipping, the COA offers no meaningful assurance about your specific product.
At BioSupply UK: Our vials are batch coded (e.g. BSUK003) and each COA specifies the batch tested. Customers can confirm their vial's batch number and cross-reference it with the corresponding COA on our public COA page.
3. Analysis Method
The COA should specify the analytical method used. The two most important methods for peptide verification are:
RP-HPLC (Reverse Phase High Performance Liquid Chromatography) HPLC separates the components of a sample and measures their relative quantities. It is the standard method for determining purity — the percentage of the sample that consists of the target compound versus impurities or degradation products.
ESI-MS or LC-MS (Mass Spectrometry) Mass spectrometry identifies compounds by their molecular weight. A correctly identified compound will show a detected molecular weight that matches its expected theoretical molecular weight within an accepted tolerance.
The combination of HPLC and mass spectrometry is the gold standard for peptide analysis — HPLC confirms purity while mass spectrometry confirms identity.
At BioSupply UK: Our PeptideVerify COAs use both RP-HPLC and ESI-MS analysis, providing both purity and identity confirmation.
4. Purity Result
The purity result is typically expressed as a percentage — for example, 99% or 99.9%. This represents the proportion of the tested sample that consists of the stated compound.
What is a good purity level?
For research grade peptides, a purity of 98% or above is generally considered acceptable, with 99%+ considered high quality. At BioSupply UK our independently verified results have returned 99% for Retatrutide and 99.9% for both GHK-Cu and Melanotan 2.
5. Molecular Weight
For mass spectrometry results, the COA will show:
- Expected molecular weight — the theoretical molecular weight of the compound based on its known chemical structure
- Detected molecular weight — the molecular weight measured in the sample
- Mass accuracy — the difference between expected and detected, expressed in Daltons (Da)
A difference of ±2 Da or less is generally considered within acceptable tolerance for peptide mass spectrometry. A larger discrepancy may indicate the sample is not the stated compound.
Example from our Retatrutide COA:
- Expected MW: 4731.4 Da
- Detected MW: 4730.3 Da
- Mass accuracy: ±1.1 Da ✓
6. Verification Code
The most reliable COAs include a unique verification code that can be independently checked on the issuing laboratory's website. This confirms the COA document itself is genuine and has not been altered or fabricated.
At BioSupply UK: Every PeptideVerify COA includes a verification code (e.g. PV-F01FF8-WRWI for our Retatrutide batch) that can be checked directly at peptideverify.com.
Where to Find Our COAs
All of our independently verified batch results are published live on our COA page at biosupplyuk.com/pages/coa. We add new results as they are received from PeptideVerify, and results remain permanently accessible so customers can verify historical batches.
We believe that genuine transparency means making this information publicly available to anyone — not just sharing it on request. If you cannot find what you need on our COA page, contact us directly at support@biosupplyuk.com and we will provide it.
Summary
Independent lab testing is the only reliable way to verify the purity and identity of a research grade peptide. When evaluating a COA, check that it comes from a genuinely independent laboratory, that it specifies the batch tested, that it uses HPLC and mass spectrometry methodology, and that it includes a verifiable verification code.
At BioSupply UK, we submit every batch to PeptideVerify and publish every result publicly. We believe this is the standard the research peptide industry should be held to — and the standard we hold ourselves to every day.
BioSupply UK — Research Grade Biochemical Reference Compounds BioSupply Group Ltd | Company No: 17152707 | Bournemouth Airport, Christchurch biosupplyuk.com | support@biosupplyuk.com All products are for research purposes only. Not for human consumption.