Purity and testing
A purity number you cannot verify is a marketing claim. This is what the tests behind the number actually measure.
- What does 99% HPLC purity actually mean?
- What is HPLC testing?
- What is mass spectrometry?
- What is the difference between HPLC and mass spectrometry?
- What is quality control testing?
- Why does batch consistency matter?
- What counts as third-party testing?
- What is endotoxin testing?
- How do you read an HPLC chromatogram?
- How do you verify peptide purity?
- What does research grade actually mean?
What does 99% HPLC purity actually mean?
It means that in a chromatographic separation, 99% of the detected material eluted as the target peak. It is a statement about relative peak area, not absolute composition — it says nothing about water content, residual salts, or whether the peak is the molecule you wanted. Identity is a separate test.
Full guide: What Does 99% Peptide Purity Mean? HPLC & Mass Spec Explained →
What is HPLC testing?
High-performance liquid chromatography pushes a sample through a packed column under pressure. Components travel at different speeds depending on how strongly they interact with the column, so they separate and exit at different times. A detector records each as a peak, and the relative peak areas give the purity figure.
Full guide: What Does 99% Peptide Purity Mean? HPLC & Mass Spec Explained →
What is mass spectrometry?
Mass spectrometry ionises a sample and measures the mass-to-charge ratio of the resulting ions. For a peptide it answers the identity question: does the observed mass match the mass calculated from the intended sequence? HPLC tells you how pure the sample is; mass spec tells you what it is.
Full guide: What Does 99% Peptide Purity Mean? HPLC & Mass Spec Explained →
What is the difference between HPLC and mass spectrometry?
They answer different questions and neither replaces the other. HPLC separates a mixture and reports how much of it is the main component — purity. Mass spectrometry measures molecular mass and confirms the compound is the one intended — identity. A sample can be 99% pure and still be 99% the wrong molecule.
Full guide: What Does 99% Peptide Purity Mean? HPLC & Mass Spec Explained →
What is quality control testing?
Quality control is the set of checks run on a batch before release: identity, purity, appearance, and where relevant sterility and endotoxin. The important part is that results are recorded per batch and tied to a lot number, so a specific vial can be traced back to the specific data that released it.
Why does batch consistency matter?
Because a result you cannot reproduce is not a result. If material varies between batches, any difference you observe might be the batch rather than the variable you were testing. Lot-specific documentation exists so that batch identity is a recorded fact rather than an assumption.
What counts as third-party testing?
Testing performed by a laboratory with no commercial interest in the outcome, reported directly by that laboratory. A certificate carrying an independent lab's own name and reference is third-party. A supplier's internal result reformatted onto a branded template is not, however similar it looks.
Full guide: How to Read a Peptide Certificate of Analysis (CoA) →
What is endotoxin testing?
Endotoxins are fragments of bacterial cell walls that survive sterilisation and can interfere with biological assays. Testing is usually done by LAL assay and reported in endotoxin units. It is a distinct question from sterility: material can contain no living organisms and still carry endotoxin from bacteria killed earlier.
Full guide: Endotoxin & Sterility Testing in Research Peptides →
How do you read an HPLC chromatogram?
The x-axis is retention time, the y-axis detector response. Your compound is the large peak; the retention time should match the reference. Look at the baseline between peaks, whether small peaks sit close to the main one, and whether the main peak is symmetrical — shoulders and tailing suggest co-eluting impurities.
Full guide: What Does 99% Peptide Purity Mean? HPLC & Mass Spec Explained →
How do you verify peptide purity?
Match the certificate to the vial first: the lot number printed on the label must appear on the certificate. Then check the certificate names an independent laboratory, reports both an HPLC purity figure and a mass spectrometry identity confirmation, and carries a test date. Any of those missing, the number is unverified.
Full guide: How to Read a Peptide Certificate of Analysis (CoA) →
What does research grade actually mean?
It should mean a documented paper trail: identity confirmed, purity measured, results tied to a specific lot, and material supplied for laboratory use only. It is not a regulated term, so it carries no guarantee on its own. What makes it meaningful is the documentation behind it, not the phrase.