For research & educational purposes only. This article is a neutral, procedural reference for laboratory / in-vitro research handling — not medical advice or a usage recommendation. These materials are not for human or animal consumption.
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What a Certificate of Analysis is
A COA is an analytical record produced by testing a sample drawn from one specific manufacturing lot. The key word is batch-specific: a certificate that is not tied to the lot number printed on your vial describes some other batch, not the material in your hand. A legitimate COA names the compound, the lot, the tests run, and the laboratory that ran them.
HPLC purity — what the percentage means
High-Performance Liquid Chromatography (HPLC) separates the target peptide from related impurities and reports purity as the target peak's area as a percentage of the total. Research-grade material is typically 98% or higher. Look for the actual chromatogram, not just a number: one clean dominant peak tells a very different story than a dominant peak surrounded by a forest of smaller ones.
Mass spectrometry — confirming identity
HPLC tells you how pure the sample is; mass spectrometry tells you what it is. The COA should report an observed molecular weight that matches the theoretical mass of the intended sequence. Purity without an identity confirmation is only half a test — a sample can be 99% pure and still be the wrong molecule.
Net peptide content vs. purity
These two numbers are constantly confused. Peptides are supplied as salts (acetate or TFA) with some bound water, so net peptide content — often around 80% — is how much of the vial's mass is actually peptide. Purity is how much of that peptide is the correct one. A thorough COA reports both, and knowing the difference keeps your concentration math honest.
Red flags on a weak or fake COA
- No lot or batch number, so it cannot be matched to your vial
- No test methods named (no mention of HPLC or mass spectrometry)
- A purity figure with no chromatogram to back it up
- An image-only PDF with no identifiable laboratory
- A certificate that does not name the specific compound on your vial
A quick verification checklist
- 1Match the lot number on the COA to the lot printed on your vial.
- 2Confirm HPLC purity is reported with a visible chromatogram, not just a number.
- 3Confirm the mass-spectrometry result matches the sequence's expected molecular weight.
- 4Check that net peptide content is reported separately from purity.
- 5Confirm an identifiable, independent laboratory produced the certificate.
Every VNG Labs reference material ships with a lot-matched COA, independently tested by Vanguard, documenting identity and purity for the exact batch you receive. This is educational information for laboratory evaluation, not medical advice.
Frequently asked questions
What purity should a research peptide be?
For most in-vitro work, 98% or higher by HPLC is the working standard. Lower purity introduces impurities you cannot control for, which is a common hidden source of irreproducible results.
What is the difference between HPLC purity and net peptide content?
Purity is the fraction of the material that is the correct peptide. Net peptide content is the fraction of the vial's total mass that is peptide at all — the remainder is counter-ions (acetate or TFA salt) and bound water. A good COA reports both.
How do I know a peptide COA is genuine?
A genuine COA is batch-specific, names its test methods (HPLC and mass spectrometry), shows the actual chromatogram and spectrum, and comes from a named independent laboratory. Match the lot number on the certificate to the lot on your vial.
Should every batch have its own COA?
Yes. A COA is only valid for the specific lot it was generated from, because purity and identity are properties of that production run. A single certificate reused across many batches is a red flag.
Why does research-use material need testing at all?
Reproducibility. Misidentified or impure compounds are a leading, easily overlooked cause of experiments that cannot be repeated. Verified identity and purity mean the concentration you calculate reflects what is actually in the vial.
References & resources
Related reference materials
VNG Research Team
VNG Labs supplies analytical-grade reference materials with lot-matched Certificates of Analysis. Our write-ups are neutral, source-cited references for qualified and independent researchers.
More from LearnResearch use only. Not for human consumption or veterinary use. Sold exclusively to qualified researchers for in vitro and laboratory research. These statements have not been evaluated by the FDA. Not intended to diagnose, treat, cure, or prevent any disease. Refrigerate upon receipt. Keep in dark environment.