Peptide Purity vs Measured Content: What Your Certificate's HPLC Results Mean
Quick answer: purity and measured content answer two different questions. Purity tells you what share of the material is the target compound. Measured content tells you how much compound is actually in the vial. A certificate that reports both gives you a far more complete picture than either figure alone.
Purity: "How pure is it?"
High-performance liquid chromatography (HPLC) dissolves a sample and pumps it through a packed column. Different molecules interact with the column differently, so they come out at different times and register as separate peaks on a chromatogram.
Purity is calculated as the area of the main peak as a share of the total area of all detected peaks. A figure of 99% means the main peak accounts for 99% of what the detector picked up in that sample.
- Good at: detecting and quantifying impurities and degradation products.
- Reported as: a percentage, e.g. "Purity (HPLC): 99%".
Measured content: "How much is in the vial?"
Content is an absolute measurement of how much compound is present. It is what catches the problem a purity figure cannot: a vial that is 99% pure but holds less material than the label states.
That is why ELEVR certificates report both. Every certificate on our certificates page shows the HPLC purity and the measured content, side by side.
Purity vs content, side by side
| Purity (HPLC) | Measured content | |
|---|---|---|
| Question answered | What share of the material is the target compound? | How much compound is in the vial? |
| Type of measure | Relative (a percentage) | Absolute (a mass) |
| Example line on a COA | "Purity (HPLC): 99%" | "Measured content: 10.02mg" |
| Catches | Impurities and degradation products | Under-filled vials |
Worked examples from ELEVR certificates
Our current certificates report both figures for every tested product:
- MOTS-c 10mg: 99% purity by HPLC, measured content 10.24mg.
- BPC-157 10mg: 99% purity by HPLC, measured content 10.02mg.
- NAD+ 500mg: 99% purity by HPLC, measured content 514.46mg.
- 5-Amino-1MQ 5mg: 99% purity by HPLC, measured content 5.02mg.
- GHK-Cu 50mg: 99% purity by HPLC, measured content 53.77mg.
In each case the measured content meets or exceeds the declared amount on the label.
How the analysis is run
Our certificates state the method in full: a BioBasic 8 (Thermo Scientific) column with an H₂O / acetonitrile gradient and 0.1% TFA, carried out by Analiza Białek sp. z o.o., an independent analytical laboratory in Wrocław, Poland. Measurement error is ± 0.05mg, so tiny differences from the label are within normal analytical tolerance.
How to check any purity figure
- Is the method stated? A percentage with no method behind it is just a number.
- Is content measured too? Purity alone can't tell you how much is in the vial.
- Can you verify it? Our reports carry the lab's own order number and password, so you can check the result on the laboratory's portal yourself.
Frequently asked questions
Is 99% purity good?
Suppliers set their own thresholds. ELEVR only lists batches that test at 99% purity by HPLC; any batch that falls short is not sold.
Why is measured content sometimes above the label amount?
Slight overfill is within normal measurement tolerance and is the acceptable direction of variance.
What does ± 0.05mg mean?
Every analytical method has a stated measurement error. Read small differences in that light.
Does a COA prove safety or effect?
No. It records analytical results for a tested sample. Our products are for laboratory research only.
All ELEVR products are supplied strictly for laboratory research use only. They are not medicines and are not for human or veterinary use.
Related guides: How to read a peptide COA · Research peptide supplier checklist