Quick answer
HPLC separates a sample and usually produces the result figure. Mass spectrometry measures molecular mass and is the usual way identity is checked. Each method has limits, so read every result together with the method behind it.
A COA rarely shows a number on its own. Next to each result, it names the method used to get it. On peptide COAs, two methods come up often: high-performance liquid chromatography (HPLC) and mass spectrometry. Mass spec may appear as "MS", "LC-MS" or "LC-MS/MS".
This guide explains what each method reports, and why the method matters as much as the number. It sticks to what the methods show on paper, not how any material is used. If COAs are new to you, How to Read a Peptide COA is a good place to start.
Why a COA names its methods
A COA is a record of measurements. A number only means something when you know how it was measured. Naming the method tells you which instrument produced the result, and so which question that result actually answers.
That matters because different methods answer different questions. One may show how much of the sample is the intended material. Another may show whether the material is what the label says. These are separate questions, so a complete record usually reports more than one method.
When HPLC and mass spectrometry are listed together, the COA is answering two of the most important questions a reader can ask.
HPLC: the method behind the result figure
High-performance liquid chromatography (HPLC) separates a sample into its components and measures how much of each is there. The sample travels through a column that pulls its components apart in time. Each one comes out at a different moment, so the detector sees it on its own.
The instrument records each component as a peak. The relative size of those peaks is then summarized as a result figure, often called purity.
For peptides, the detector usually reads ultraviolet (UV) light at around 214 to 220 nm. The purity figure is typically the main peak's share of the total peak area at that wavelength.
This can be confusing, because "purity" can sound like a measure of the whole vial. It isn't. It's a relative figure that only covers what the method separates and the detector can see.
So HPLC is the method behind the result figure on a COA. It answers one question: of everything detected in this sample, what share is the main component? The answer is a proportion, shown as a percentage.
A real record shows why the method name matters. The published PolarLabs record for BPC-157 covers lot PL-BPC10-0826-01. It was tested by Freedom Diagnostics (certificate ID POLA2608310062, test date September 2, 2026; net content 11.91 mg). On that record, the published test result is 99.62%.
The record's on-page summary calls this a "test result" and does not name the method. So before reading it as an HPLC purity value, check the laboratory's full report to see what the figure measures.
Mass spectrometry: the method behind identity
Mass spectrometry measures the mass of the components in a sample. Each compound has a characteristic mass. By measuring mass, an analyst can check whether the material present matches the expected material.
Put another way, HPLC asks "how much?" while mass spec asks "is this what it's supposed to be?"
Two related setups are worth knowing. In LC-MS, the HPLC column feeds straight into the mass spectrometer. Each separated component is weighed as it comes off the column.
LC-MS/MS (tandem mass spectrometry) goes a step further. The instrument picks one ion, breaks it into fragments and measures those too. The fragment pattern carries the information that confirms the amino-acid sequence, not just the overall mass.
This is why mass spectrometry is tied to identity on a COA. An identity result confirms, or fails to confirm, that the compound in the sample is the one named on the label. The identity line usually says the measured mass is consistent with the expected compound. The COA reports this as a confirmation, not as a percentage.
On a record that reports it, the mass spec result is usually the main identity evidence. Because identity is a confirmation and not a figure, there's no number to look for. What you read is the confirmation statement itself, wherever the COA presents it.
The published BPC-157 record does not show an identity line in its on-page summary. So treat identity as confirmed only where a record states it directly.
Read the method and the value together
Each method result on a COA has two parts, and they make the most sense side by side:
- The method name: what was measured (HPLC for the result figure, mass spec for identity).
- The reported value: the outcome of that measurement (a percentage for the result figure, a confirmation for identity).
| Method | Question it answers | Form of the result | On the BPC-157 record |
|---|---|---|---|
| HPLC | How much of the sample is the main component? | A percentage | Published test result: 99.62% (method not named on the on-page summary) |
| Mass spectrometry | Is the material what the label says? | A confirmation | Not shown on the on-page summary. Where a record reports it, read the confirmation statement. |
Reading both parts keeps you from taking one method's result as an answer to the other's question. A high percentage does not confirm identity by itself. Identity is a separate line, produced by a separate method.
What two methods tell you that one can't
Used together, HPLC and mass spectrometry let a record answer both questions. One is how much of the intended material is present. The other is whether that material is what the label says.
A record that reports only one method leaves the other question open. A record with both a result figure and an identity confirmation is more complete, because it answers both.
That's why careful readers look for method names, not just numbers. The methods are the evidence behind the numbers. A COA that names them is showing its work.
Where each method falls short
No method sees everything. Each one answers its own question and has its own blind spots:
- HPLC can miss things. An impurity that comes off the column at the same moment as the main peak can hide under it. A component that absorbs little UV light can be under-counted. Water, salts and counter-ions aren't counted at all, so an HPLC percentage is not the amount of peptide in the vial.
- Mass alone can't spot same-mass changes. Some changes leave the mass the same. Examples are swapping an amino acid for its mirror-image (D) form, or leucine for isoleucine. Telling these apart needs other methods.
- A strong signal isn't a large amount. The strength of a mass spec signal doesn't reliably tell you how much of something is there, unless reference standards are used.
- Very small amounts can go unseen. Every method has a smallest amount it can detect. Anything present below that level goes unreported.
This is why quality guidance recommends combining independent methods. It's also why a result describes only the sample tested, by that method, at that time.
Finding the full lab report
The method results in a summary come from a full laboratory report. That's the document the testing lab issued for that specific lot.
On the BPC-157 record, that report is identified by certificate ID POLA2608310062 and tied to lot PL-BPC10-0826-01. The laboratory hosts it, and it opens on the lab's own website. The summary is there to help you read. The report is the record.
You can reach these records through the Verification Center, which sorts published records by product and lot.
Sources
- Journal articleHoofnagle AN, et al. Recommendations for the generation, quantification, storage, and handling of peptides used for mass spectrometry-based assays
- Journal articleNeagu A-N, et al. Applications of tandem mass spectrometry (MS/MS) in protein analysis for biomedical research
- Journal articleTao Y, Julian RR. Identification of amino acid epimerization and isomerization in crystallin proteins by tandem LC-MS
- FDAICH Q2(R2) Validation of Analytical Procedures
- EMA guidelineGuideline on the Development and Manufacture of Synthetic Peptides
These sources explain how the test methods work in general. None of them is evidence about any PolarLabs material.