Quality
HPLC vs mass spec: what each assay proves
Jul
Suppliers often quote a single purity figure and leave it there. But two separate questions need answering before you can trust a research peptide: is it the right molecule, and how much of the sample is that molecule. HPLC and mass spectrometry each answer one of those questions. Neither answers both.
What HPLC measures
High performance liquid chromatography separates the components of a sample as it passes through a column. A detector, usually UV, records each component as a peak. The area of the main peak as a percentage of the total gives the purity of the sample.
HPLC is very good at showing how clean a sample is: truncated sequences, deletion products and other synthesis impurities typically appear as separate peaks.
What HPLC cannot do on its own is prove identity. A sharp peak at 99% tells you the sample is mostly one component. It does not tell you that component is the sequence on the label.
What mass spectrometry measures
Mass spectrometry ionises the sample and measures the mass of the molecules present. The observed mass is compared with the theoretical molecular weight of the intended sequence. A match confirms identity.
MS is highly specific for identity, but on its own it is not a reliable purity measure. Different molecules ionise with different efficiency, so the relative size of signals does not map neatly onto how much of each is present.
Why you need both
Consider two failure cases:
- A sample could show 99% by HPLC but be the wrong peptide, or a closely related sequence. HPLC alone would not catch this.
- A sample could show the correct mass by MS but contain significant impurities. MS alone would not catch this.
Only the combination confirms that the material is both the right molecule and present at the stated purity. This is why HPLC-MS, where the two techniques are coupled or run together, is the standard for peptide characterisation.
A quick comparison
| HPLC | Mass spectrometry | |
|---|---|---|
| Answers | How pure is it? | Is it the right molecule? |
| Key result | Purity % and retention time | Observed vs theoretical mass |
| Strength | Separates and quantifies impurities | Highly specific for identity |
| Blind spot | Cannot confirm identity alone | Not a reliable purity measure alone |
What to ask a supplier
- Does the COA report both an HPLC purity result and a mass confirmation?
- Is the COA specific to the lot number on your vial?
- Can they provide the chromatogram and mass spectrum on request?
If a supplier can only answer one of these questions, you only have half the picture.
The TLC Renew standard
Every TLC Renew lot is tested by HPLC and mass spectrometry before release, confirming identity and purity together. Results are published on a lot-specific Certificate of Analysis you can look up using the batch number on your vial.
All TLC Renew products are sold for laboratory research use only. They are not drugs, foods, cosmetics or medical devices, and are not for human or animal use. Nothing in this article is medical advice or dosing guidance.
