Short answer: They answer two different questions. HPLC tells you how pure a sample is (what percentage is the target compound vs. impurities). Mass spectrometry tells you what the compound is (confirming its molecular weight and identity). Reputable research peptides are tested with both because purity without identity — or identity without purity — is only half the picture.
TL;DR — HPLC = "how much of this is the real thing?" (purity %). Mass spec = "is this actually the right molecule?" (identity). You want both on a COA.
HPLC — the purity test
High-Performance Liquid Chromatography pushes a dissolved sample through a column that separates its components based on how they interact with the column material. Orthogonal LC approaches and reference-standard frameworks for synthetic peptide quality are active topics in the pharmaceutical analysis literature (e.g. Pharm Res, 2023; J Chromatogr A, 2025). Each component appears as a peak:- The target peptide shows up as the dominant peak.
- Impurities show as smaller peaks.
- The area of the main peak relative to the total gives the purity percentage — e.g., 99% means the target peptide accounts for 99% of the total UV-absorbing peak area. That is not the same as 99% of the vial by weight — water, salts and TFA or acetate counterions do not absorb UV and are not counted at all. The figure that answers "how much of this is peptide" is net peptide content, which is a separate assay.
Mass spectrometry — the identity test
Mass spectrometry (MS) measures the mass-to-charge ratio of the molecule, which reveals its molecular weight. Because each peptide has a known, specific molecular weight, MS confirms that the compound is exactly what it's supposed to be — not a different or mislabeled molecule.HPLC alone can't do this: a sample could be 99% pure but still be the wrong compound. MS closes that gap — LC-HRMS methods have been specifically evaluated for peptide drug impurity detection and identity confirmation (Zeng et al., AAPS J, 2015; follow-on validated LC-HRMS impurity quantitation work in J Pharm Biomed Anal, 2025).
Why both together
- HPLC without MS: you know it's pure, but not what it is.
- MS without HPLC: you know what it is, but not how much impurity is present.
- Both: you know the sample is the correct compound and highly pure — which is why quality research peptides report both on their Certificate of Analysis.
What "99%+ purity, HPLC & mass-spec verified" actually means
It means an independent lab ran HPLC and found the target peptide accounted for ≥99% of the total UV-absorbing peak area, and ran mass spec to confirm the molecule's identity matched the expected molecular weight — for that specific batch. Learn how to read those results in our Certificate of Analysis guide.Every Dynamite Research Peptides compound is verified by HPLC and mass spectrometry, with a batch COA. For in-vitro laboratory research use only — not for human or animal consumption.