How to Test Peptide Purity: HPLC vs Mass Spectrometry and Where to Get Peptides Tested

Key takeaways

When a supplier attaches a certificate of analysis to a research peptide, that document almost always rests on two distinct instruments. Understanding HPLC vs mass spectrometry peptide testing is the difference between reading a COA as a marketing artifact and reading it as evidence. The two techniques are frequently named in the same sentence and treated as interchangeable proof of "quality," but they answer separate questions, and a report that leans on one without the other leaves a specific, knowable gap.

This article sets out what each method measures, where each is blind, and why a complete peptide COA generally needs both.

What HPLC actually measures

High-performance liquid chromatography (HPLC) separates the components of a sample by pushing it through a column under pressure. Different molecules travel through the column at different rates, emerge at different times, and are registered by a detector — most commonly a UV detector — as a series of peaks. The area under each peak, expressed as a percentage of total detected area, is what most reports call "purity."

That definition carries two consequences researchers should hold onto:

• HPLC purity is a ratio, not a mass. A 99% area figure describes the composition of the UV-absorbing material in the vial. It says nothing about how much peptide is actually present. A vial can be 99% pure and still be underfilled relative to its labelled quantity.
• HPLC sees what the detector sees. A UV detector responds to species that absorb at the chosen wavelength. Salts, residual water, and certain counter-ions absorb weakly or not at all, so they can be substantially underrepresented in the peak areas. Purity by area-percent is therefore a statement about detectable organic components, not about everything in the vial.

HPLC is the right tool for asking how clean a preparation is relative to related impurities — truncated sequences, deletion products, and other close chromatographic neighbours. It is not, on its own, a tool for confirming what the main peak is.

What mass spectrometry actually measures

Mass spectrometry (MS), usually run downstream of a separation step as LC-MS, measures the mass-to-charge ratio of ionised molecules. For a peptide, the observed mass can be compared against the theoretical mass calculated from the amino acid sequence. When the measured value matches the expected value within instrument tolerance, that is strong evidence the molecule present is the one named on the label.

Mass spectrometry answers the identity question that HPLC cannot: is this actually the compound it claims to be, rather than a different peptide of similar retention behaviour? For a compound like BPC-157 10mg or TB-500 10mg, a matching mass confirms the sequence assembled to the intended target rather than a near-miss.

What MS does not do well on its own is quantify. A confirmed identity tells you the right molecule is present; it does not tell you what proportion of the sample it represents, nor how much sits in the vial.

Why the two are complementary, not redundant

The cleanest way to see the relationship is to line up the questions side by side.

Read together, HPLC and MS establish that a preparation is both clean and correctly identified. Read in isolation, each leaves an opening. A high HPLC figure with no identity confirmation could describe a pure sample of the wrong molecule. An MS match with no purity data confirms the right molecule is present but says nothing about the impurity load surrounding it. Neither, on its own, reports quantity — that requires a dedicated content assay, which is a third measurement entirely.

What this means when you read a COA

When evaluating a certificate, the practical checks follow directly:

1. Confirm the report includes both an HPLC purity chromatogram and a mass spectrometry identity result, not one standing in for the other.
2. Check whether a separate quantity determination is present. Purity and identity together still do not confirm the vial holds the labelled fill.
3. Match the lot number on the report to the lot number on the vial you received. A method is only as useful as its traceability to your specific batch.
4. Verify the document at the issuing laboratory rather than trusting a hosted image. Our approach to independent verification is covered in Janoshik Analytical Explained.

Hermetica Research Labs publishes the third-party HPLC and mass spectrometry certificates tied to each production lot on our COA page, including reports from Janoshik Analytical and Freedom Diagnostics, so the lot number on a vial of TB-500 10mg or any other certified compound in the catalogue can be matched to the specific document that describes it — both the purity chromatogram and the identity confirmation.

A supplier that shows one method but not the other has answered half the question. Knowing which half is missing is the point.

Research use only. All materials described here are supplied strictly for in-vitro laboratory research and analytical use. They are not drugs, foods, cosmetics, or medical devices, are not approved by Health Canada for any therapeutic purpose, and are not intended for human or veterinary consumption or administration. Nothing in this article constitutes medical, clinical, or regulatory advice.

For live examples, the certificates behind our GHK-Cu peptide Canada and BPC-157 Canada pages report purity by HPLC-MS alongside the lot and test references.

Both analyses appear on the certificates we publish, which is why we post the underlying reports rather than a purity figure. The full set is in the COA library; see BPC-157 or GHK-Cu for lot-matched examples.

How to test peptide purity, step by step

1. Pick an independent analytical laboratory that runs HPLC and mass spectrometry and issues numbered reports that can be looked up later. Hermetica's current lots were tested by Janoshik Analytical; Freedom Diagnostics is another lab seen in this space.
2. Submit a sealed sample from a known batch. The report will describe that batch only.
3. Request HPLC purity and MS identity together. One without the other answers half the question.
4. Ask separately for counter-ion or net peptide content if the work needs a mass figure. Peptides from solid-phase synthesis are mainly obtained as trifluoroacetate salts (Roux et al. 2008), and Erckes et al. (2025) describe TFA analysis as a distinct measurement.
5. File the report number with the lot record, and check it on the lab's own system.

What a purity test is looking for

D'Hondt et al. (2014) group peptide-related impurities into synthesis-related types (deletion and insertion sequences, racemised residues, incompletely deprotected side chains, oxidation, dimers and counter-ions such as trifluoroacetate) and degradation-related types (for example diketopiperazine, pyroglutamate and succinimide formation). HPLC is the method used to resolve related impurities from the main peak, which is why a purity figure is an area ratio.

Can you test peptide purity at home?

No. Colour, clarity or how a powder dissolves cannot measure purity or identity. Both need laboratory chromatography and mass spectrometry with calibrated methods. The practical route for a laboratory is an independent test report it can verify.

Worked example

Related: how to read a peptide COA, what 99% purity means, third-party tested peptides Canada.

FAQ

How are peptides tested for purity?

By reversed-phase HPLC, which separates the target peptide from related impurities and reports the main peak's share of total UV-detected area. Mass spectrometry is run alongside to confirm the main peak's identity.

Where can peptides be tested for purity?

At an independent analytical laboratory that runs HPLC and mass spectrometry and issues a numbered report. Hermetica's current lots were tested by Janoshik Analytical, and each test number can be looked up on that lab's system.

Can peptide purity be tested at home?

Not in any meaningful way. Purity and identity need HPLC and mass spectrometry instruments with calibrated methods; visual checks of colour or dissolution cannot measure either.

How do you get a peptide tested?

Send a sealed sample from a known batch to an analytical laboratory, request HPLC purity plus MS identity, and keep the report number. The report then describes that batch only.

Does HPLC purity include TFA or water?

No. Counter-ions such as trifluoroacetate, salts and water are poorly seen by HPLC-UV. Roux et al. (2008) and Erckes et al. (2025) describe measuring TFA separately, for example by 19F-NMR or ion chromatography.

References

1. D'Hondt M, Bracke N, Taevernier L, Gevaert B, Verbeke F, Wynendaele E, De Spiegeleer B. (2014). Related impurities in peptide medicines. Journal of Pharmaceutical and Biomedical Analysis, 101, 2–30. doi:10.1016/j.jpba.2014.06.012 · PubMed 25044089
2. Roux S, Zékri E, Rousseau B, Paternostre M, Cintrat JC, Fay N. (2008). Elimination and exchange of trifluoroacetate counter-ion from cationic peptides: a critical evaluation of different approaches. Journal of Peptide Science, 14(3), 354–359. doi:10.1002/psc.951
3. Erckes V, Streuli A, Chamera Rendueles L, Krämer SD, Steuer C. (2025). Towards a Consensus for the Analysis and Exchange of TFA as a Counterion in Synthetic Peptides and Its Influence on Membrane Permeation. Pharmaceuticals, 18(8), 1163. doi:10.3390/ph18081163 · PMC12389442

Research Use Only. Hermetica Research Labs supplies laboratory reagents for in-vitro research. Not for human or veterinary use. Buyers must be 21 or older.