COA Methodology: How Research Peptides Are Tested

A number printed on a label is not evidence. A Certificate of Analysis is evidence — but only if you understand exactly what the underlying methods measure, what they cannot see, and how the laboratory workflow connects a specific result to the specific vial in your hand. This page documents the analytical methods Condor Research uses to characterise every batch, what each method proves, and where each stops. Nothing here is promotional. The goal is precision: a researcher working with our materials should be able to read this page and know, technically, what they are holding.

Why methodology matters more than a headline percentage

The research-peptide market prints purity numbers with some enthusiasm and very little explanation of where they come from. The number “99%” — or “≥ 99%” — can mean different things depending on the instrument, the method, the wavelength, the column, and the laboratory. It can be honest analytical data or a reused figure from a generic specification sheet. The only way to judge is to ask about the method: what instrument ran the sample, under what conditions, measured against what standard, on what batch?¹ At Condor Research, every batch is tested by an independent third-party laboratory in Czechia using two complementary analytical techniques. This page describes those techniques, what they establish, and what they leave unaddressed — because that honesty is part of the quality claim, not a footnote to it.

The laboratory workflow: from synthesis to COA

The material does not leave the manufacturer and arrive in a Condor vial unchanged and untested. The flow is: manufacturer produces a batch → a sample from that lot is sent to the independent EU laboratory in Czechia → the laboratory runs the analytical panel described below → results are issued on the lab’s letterhead as a per-lot Certificate of Analysis → the COA lot number is matched against the vials in that shipment → the material is offered only after that confirmation. The lot number is the thread that ties the certificate to the physical material; a COA without a matching lot identifier describes an abstraction, not a vial.¹

The independent-laboratory step is the structural element that separates data from self-declaration. In-house testing by a manufacturer or a seller is not the same as testing by a lab with no commercial stake in the outcome. The independence is auditable: the certificate names the testing laboratory, not Condor, and the data are the laboratory’s data.

Method 1 — HPLC: what it measures and what it does not

High-performance liquid chromatography (HPLC), typically run in reversed-phase mode (RP-HPLC), is the workhorse for purity determination. The dissolved sample is pushed through a column packed with a non-polar stationary phase; molecules bind to that phase with different tenacity and elute at different times. Detection is usually UV at around 214–220 nm, the window where the peptide bond itself absorbs. The purity figure is the area under the main peak expressed as a percentage of the total area of all detected peaks — a relative chromatographic measurement, not an absolute concentration.²

Condor’s specification is ≥ 99% by RP-HPLC for individual compounds. That number means: in the chromatogram for this lot, the dominant peak represents at least 99 of every 100 parts of UV-absorbing material that eluted from the column. It says nothing about anything that did not absorb UV at the measurement wavelength, or that did not elute at all. In practice, the most relevant things HPLC cannot see on its own are: molecular identity (the right peptide versus a differently sequenced one of similar mass), residual water, counter-ion (salt) content, and endotoxins.

What HPLC does reveal, beyond the headline percentage, is the impurity profile. The small peaks beside the main peak are not noise — they are identifiable synthesis by-products: deletion sequences missing one or more residues, truncated chains where elongation stalled, fragments carrying residual protecting groups, and oxidised or deamidated variants of the target.³ These are the predictable debris of solid-phase peptide synthesis (SPPS). A credible COA shows the chromatogram and accounts for these minor peaks; ICH Q3A impurity-reporting logic and the EMA’s synthetic-peptide guidance both require that impurities at or above approximately 0.1% of peak area be reported and, above higher thresholds, identified. A certificate that shows only a headline figure and no chromatogram is giving you less than the method produces.³

Method 2 — Mass spectrometry: confirming identity

HPLC answers “how pure?” It cannot, on its own, answer “pure what?” A clean single peak at high area percentage is evidence of chromatographic homogeneity, not molecular identity. Two peptides with similar hydrophobicity can elute at indistinguishable retention times. The identity question requires a method that weighs the molecule, not one that separates it by polarity.

Mass spectrometry (MS) supplies that orthogonal check. The dissolved peptide is ionised — most often by electrospray ionisation (ESI-MS) for peptides in the 1–5 kDa range — and the instrument measures the mass-to-charge ratio of the resulting ions. The observed molecular mass is then compared against the theoretical mass calculated from the amino-acid sequence stated on the label. A match within instrument tolerance (typically 0.01–0.1% of molecular mass) is strong evidence that the molecule has the backbone the label claims.¹ A mismatch at this step overrides a perfect chromatogram: the correct mass is a necessary condition for identity, and the absence of it is disqualifying regardless of purity.²

MS has its own limits worth stating. Two peptides that happen to share the same molecular mass (isobaric sequences or some isomers) would not be distinguished by a simple intact-mass measurement. For the peptides Condor Research carries — sequences ranging from dipeptides to 30-mers such as BPC-157, Epitalon, and GHK-Cu — the intact mass is sufficiently discriminating for practical identity confirmation. Where there is any ambiguity, the retention time from HPLC provides orthogonal supporting evidence.¹

Method 3 — Water content and physical appearance

The purity and identity data describe the molecular content of the vial. Two additional assessments address the physical state of the material, and both matter for practical research use.

Water content: Lyophilised peptides are hygroscopic — they attract and retain moisture from the environment. A vial that is 5% water by mass contains 5% less peptide than the label net weight suggests, a systematic error that compounds directly into any concentration calculation. Water is measured by Karl Fischer titration (a direct titration that reacts specifically with water) or by loss on drying (mass lost after heating under defined conditions). Neither HPLC nor mass spectrometry captures water content; it requires its own measurement and is reported separately in the quality record.¹

Physical appearance: A peptide described as a white to off-white lyophilised powder that arrives discoloured, damp, or clumped is signalling that something happened in storage or transit — moisture ingress, temperature excursion, contamination, or degradation. Appearance is a fast, equipment-free first integrity check. It is a specification item, not a subjective judgement, and it is documented in the quality record alongside the instrumental data.

The five analytical parameters in Condor Research’s testing panel. Purity and identity are answered by different methods; neither alone constitutes a complete characterisation. Water content and appearance are assessed separately because neither HPLC nor mass spectrometry captures them. For the interpretation of each parameter in a COA document, see How to Read a Certificate of Analysis.¹²

What the COA does not guarantee

Intellectual honesty about the limits of testing is part of the quality claim, not a detraction from it. There are things a purity-plus-identity COA, run to the standard described above, does not establish.

Endotoxins. Bacterial lipopolysaccharides (endotoxins) are not chromophores at peptide-bond UV wavelengths and carry no peptide-bond signature, so they pass through RP-HPLC and intact-mass MS without leaving a trace. Detecting them requires a dedicated assay — the LAL (Limulus Amebocyte Lysate) test or a recombinant equivalent. A standard peptide COA makes no claim about endotoxin levels unless the certificate explicitly reports a LAL result. For researchers performing in vitro cell-culture assays or any work sensitive to LPS contamination, this is the test to ask about. See our article on endotoxins and sterility for the full discussion.⁴

Counter-ion (salt) content. Synthetic peptides are almost universally isolated as salts — typically trifluoroacetate (TFA) or acetate — and the counter-ion contributes to the mass in the vial. The HPLC purity figure does not factor in the counter-ion fraction; a vial that reads 99% pure by HPLC may be, in practice, closer to 85–90% peptide by weight once the TFA salt content is accounted for. Ion-exchange or ion-pairing HPLC can separate and quantify counter-ions, but this is not always included on a standard COA. Where this matters for stoichiometry in a research assay, the question to ask is whether the supplier can provide counter-ion data alongside the purity figure.¹

Biological activity. A COA characterises a molecule by its physicochemical identity and purity. It says nothing about receptor binding, bioassay potency, or any functional endpoint. Activity is not tested; inferring it from a purity figure is not scientifically supportable. All materials supplied by Condor Research are reference compounds for laboratory research, not assessed for any biological or clinical application.

Stability over time. The COA data reflect the lot at the time of testing. Peptides can degrade — through oxidation, deamidation, hydrolysis, or moisture uptake — during storage, particularly at incorrect temperatures or if a vial is opened and handled improperly. The COA is a snapshot, not a permanent guarantee. Storage conditions (typically −20 °C or −80 °C lyophilised, protected from light and moisture) are specified on the label precisely because the analytical data are time- and condition-dependent.⁴

How this methodology connects to the wider COA ecosystem

The methods described here are not proprietary or unique to Condor. They are the standard analytical tools the field has converged on for characterising synthetic peptides, codified in guidance documents that are publicly available. HPLC purity method conventions draw on ICH Q6A (specifications for new drug substances) and the ICH Q3A impurity-reporting framework, as well as pharmacopoeial general chapters such as USP <621>. Mass spectrometry for intact-peptide identity is embedded in the EMA’s guideline on the development and manufacture of synthetic peptides. The reference-standards literature for synthetic peptide therapeutics — notably the work by McCarthy et al. in Pharmaceutical Research — makes explicit that purity and identity are distinct attributes, each requiring its own method and its own acceptance criterion.¹

Understanding this context is useful because it lets you evaluate any COA, from any supplier, against the same framework. The question is not whether a number is impressive but whether the method behind it answers the question you are asking. A purity figure from a validated RP-HPLC run with chromatogram and impurity profile is analytically meaningful. A purity figure with no named method, no chromatogram, and no batch link is not evidence — it is a label.²

For how to apply this methodology to reading an actual COA document line by line, see How to Read a Certificate of Analysis. For the specific interaction between HPLC purity and mass spectrometry, including the technical limits of each method, see HPLC & Mass Spectrometry: What the COA Purity Number Really Means. For our published quality position and the third-party testing programme as a whole, see Quality & Third-Party Testing.

Frequently asked questions

Why can’t HPLC purity alone confirm what peptide is in the vial?

HPLC separates molecules by hydrophobicity and reports the area under the main peak as a percentage of all UV-absorbing peaks that eluted under the method conditions. Two different peptides with similar hydrophobicity can elute at the same retention time, making the chromatogram indistinguishable. A clean single peak is evidence of chromatographic homogeneity; it is not evidence of molecular identity. That is the role of mass spectrometry, which compares observed and theoretical molecular masses independently of retention time.²

What is the ≥ 99% HPLC specification, exactly?

It means the main peak accounts for at least 99% of the total UV-absorbing peak area detected in the chromatogram, run under the laboratory’s validated RP-HPLC conditions (column type, mobile phase, gradient, detection wavelength). It is a relative chromatographic measurement, not an absolute concentration by weight. The figure does not include anything that does not absorb UV at the measurement wavelength, or that does not elute from the column under those conditions.²

What do the small peaks beside the main peak on the chromatogram mean?

They represent related impurities — synthesis by-products predictable in solid-phase peptide synthesis: deletion sequences (missing one or more residues), truncated chains where coupling failed, incompletely deprotected fragments, and oxidised or deamidated variants of the target. A credible COA reports these rather than burying them in the baseline; impurity-reporting logic from ICH Q3A and the EMA synthetic-peptide guideline requires peaks at or above approximately 0.1% to be documented and assessed.³

Why is water content measured separately?

Lyophilised peptides are hygroscopic: the powder in the vial can hold adsorbed water. If a batch is 5% water by mass, the effective peptide content is 5% lower than the label net weight implies, introducing a systematic error into any concentration preparation. Neither HPLC nor mass spectrometry detects water; Karl Fischer titration or loss on drying is required. The result appears in the quality record separately from the chromatographic and MS data.¹

Does the COA cover endotoxins?

Standard RP-HPLC and intact-mass MS are blind to endotoxins. Bacterial lipopolysaccharides have no chromophore at the UV wavelength used for peptide-bond detection and carry no relevant MS signature. Endotoxin testing (LAL assay or recombinant equivalent) is a separate, dedicated analysis. A standard peptide purity COA does not claim anything about endotoxin unless a LAL result is explicitly included on the certificate. Researchers performing cell-culture or receptor assays should check this point specifically. See Endotoxins & Sterility in COAs.⁴

What does “independent EU laboratory in Czechia” mean in practice?

Testing is carried out by a third-party analytical laboratory located in Czechia — an entity separate from Condor Research and from the manufacturer. The laboratory issues results on its own letterhead, tied to the batch lot number. This structure is the same independence standard referenced in quality guidance for pharmaceutical reference materials and is what makes the data independently verifiable rather than self-declared.¹

Research Use Only. All compounds supplied by Condor Research (operated by Atrio Sciences s.r.o., IČO 57 669 651, Nitra, Slovakia) are reference materials for in vitro laboratory research exclusively. They are not medicines, not assessed for human or veterinary use, and not intended for administration to any living organism. The analytical methodology described on this page characterises physicochemical identity and purity for research purposes only. Nothing here constitutes a clinical, therapeutic, or safety claim. — Condor Research · Scientific desk

1. McCarthy D, Han Y, Carrick K. Reference Standards to Support Quality of Synthetic Peptide Therapeutics. Pharm Res. 2023;40(6):1345–1360. PMID: 36949371. https://pubmed.ncbi.nlm.nih.gov/36949371/
2. Stoll DR, Sylvester M, Euerby MR. A Strategy for assessing peak purity of pharmaceutical peptides in reversed-phase chromatography methods using two-dimensional liquid chromatography coupled to mass spectrometry. Part II: Development of second-dimension gradient conditions. J Chromatogr A. 2023;1693:463873. PMID: 36871316. https://pubmed.ncbi.nlm.nih.gov/36871316/
3. Roberts BJ, Mattei AE, Howard KE. Assessing the immunogenicity risk of salmon calcitonin peptide impurities using in silico and in vitro methods. Front Pharmacol. 2024;15:1363139. PMID: 39185315. https://pubmed.ncbi.nlm.nih.gov/39185315/
4. Mateescu DM, Gavrilescu DM, Constantinescu FE, et al. BPC-157 as an Investigational Peptide Therapeutic: Biopharmaceutical Challenges, Formulation Strategies, and Translational Development Barriers. Pharmaceutics. 2026;18(5):625. PMID: 42198317. https://pubmed.ncbi.nlm.nih.gov/42198317/