Analytical results are useful only when the question, method, sample, and lot are clear. This guide explains common tests used to characterize peptide research materials and how to read a lot-linked report without turning one result into a broader claim.
Primary action: Search certificates and reports by lot Secondary action: Learn how to read a report
Research-use notice: Serum Research materials are sold for laboratory research only. They are not for human or veterinary use. The information below explains analytical documentation; it is not a statement of clinical safety, efficacy, or suitability.
Start with the question being tested
“Tested” is not a complete result. Every analytical method is designed to answer a particular question, within stated conditions and limits.
Identity
An identity test asks whether evidence from the sample is consistent with the expected analyte. Depending on the procedure, that evidence may include molecular mass, fragmentation data, chromatographic behavior compared with a reference material, or another analyte-specific property.
An identity result does not, by itself, establish purity, quantity, sterility, or stability.
Chromatographic purity
A chromatographic purity result describes the relative detector response of components that the method separated and detected. It depends on the column, mobile phase, gradient, detector, wavelength or acquisition settings, integration rules, reference materials, and the sample itself.
A reported peak-area percentage is therefore not automatically the percentage of the vial’s total mass that is the target peptide. Water, counterions, salts, residual solvents, compounds that do not respond equally to the detector, and co-eluting components can require different measurements or may not be represented by a simple area-percent result.
Content or quantity
Content testing asks how much of a defined analyte is present, using a stated quantitative procedure and appropriate reference. It is a different question from relative chromatographic purity. A report should identify the units, calculation basis, reference standard, and method before a content value can be interpreted.
Other attributes
Water, counterion content, residual solvents, elemental impurities, bioburden, sterility, bacterial endotoxins, and stability are separate attributes. None should be inferred from an HPLC or mass-spectrometry result. Each requires its own suitable procedure and an explicit result.
A test that is not listed should be treated as unknown, not as a passing result.
What HPLC can show
High-performance liquid chromatography, or HPLC, separates sample components as they travel through a column. A detector records the resulting signal over time as a chromatogram. When a method resolves components adequately, the chromatogram can help assess relative purity and related substances under that specific procedure.
A useful HPLC report should make the result interpretable. At minimum, look for:
- the sample and lot tested;
- the analytical method or a clear method reference;
- the detector and relevant acquisition conditions;
- a chromatogram with labeled peaks where appropriate;
- the calculation or integration basis;
- the numerical result and units;
- any specification and acceptance criterion applied; and
- the laboratory, report identifier, test date, and authorized review.
HPLC has limits. Components may co-elute, different compounds may produce different detector responses, and some material may not be visible under the chosen detection conditions. FDA analytical guidance therefore emphasizes specificity: a method should distinguish the analyte from likely impurities, degradation products, related substances, and other potential interferences.
What LC–MS can add
Liquid chromatography–mass spectrometry, or LC–MS, combines chromatographic separation with mass measurement. Comparing an observed mass pattern with the expected analyte can support identity. Tandem mass spectrometry, often written LC–MS/MS, can add fragmentation information that strengthens structural or sequence characterization.
Mass agreement is still a bounded result. A matching mass alone does not establish total sample purity, content per container, sterility, stability, or the absence of every possible impurity. Some closely related structures can require better separation, fragmentation evidence, reference comparison, or another orthogonal technique.
For complex analytical questions, one method may not provide enough discrimination. FDA’s current analytical-procedure guidance recommends combining procedures when a single procedure is not sufficiently specific or selective.
Identity and purity are not interchangeable
These two questions complement each other:
- A sample can produce evidence consistent with the expected analyte while also containing other components.
- A sample can show one dominant chromatographic peak without that peak’s identity being established by the chromatogram alone.
That is why a defensible characterization package often uses more than one measurement principle. The conclusion should stay within the scope of the tests actually performed.
What makes a report useful for a specific lot
An analytical document is most useful when a researcher can connect it to the physical item in hand. A lot-linked record should identify:
- The material: exact compound name, form or salt where applicable, labeled amount or configuration, and sample description.
- The lot: a unique lot or batch code that matches the product label and the report.
- The issuer: laboratory name and address, report number, and authorized signatory or reviewer.
- The timing: sample receipt date, test date, and report date where available.
- The method: test name, method identifier or reference, relevant conditions, and reference material where applicable.
- The result: numerical result, units, calculation basis, and supporting chromatogram or spectrum where supplied.
- The decision rule: the specification or acceptance criterion, its source, and the report’s stated conclusion, if a conformance decision was made.
- The record status: current, superseded, corrected, or withdrawn.
A report for one lot should not be presented as evidence for another lot. A report also reflects the sample submitted and the tests requested; it should not be described as testing every individual container unless the sampling record actually supports that statement.
Lot traceability and measurement traceability are different
These terms are often confused.
Lot or chain-of-custody traceability concerns the identity, handling, transfer, storage, and analysis of the physical sample. It helps show how the tested sample relates to the labeled lot.
Metrological traceability concerns the measurement result. NIST describes it as a documented chain of calibrations or comparisons linking a result to a stated reference, with each step contributing to measurement uncertainty. NIST also makes clear that metrological traceability is not the same as chain of custody and does not automatically make a result fit for every purpose.
The phrase “NIST traceable” should not be used merely because an instrument was calibrated or a reference material was purchased. Any such claim needs documentation for the specific measurement result, its reference chain, and its uncertainty.
Our publication standard
[BUSINESS APPROVAL REQUIRED: the following section creates an ongoing public commitment. Publish only if Serum Research adopts and can maintain the workflow.]
For every analytical document published in our certificate library, we will:
- display the compound and lot code associated with the document;
- identify the issuing laboratory and report date as shown on the original record;
- name the tests that were actually reported;
- preserve the result, units, and stated acceptance criteria without rewriting them into a broader claim;
- label corrected, superseded, or withdrawn records clearly; and
- avoid applying one lot’s result to a different lot.
If a lot-linked document is not available, we will say that it is not published. We will not substitute a generic “tested” badge for a report or infer an unreported result.
What an analytical report does not establish
Unless the document explicitly contains a suitable test for the named attribute, it does not establish:
- clinical safety or efficacy;
- suitability for human or veterinary use;
- sterility or bacterial-endotoxin status;
- absence of all contaminants or degradation products;
- content per container;
- stability through a future date;
- compliance with a specification that is not identified in the report;
- the condition of every container in a lot; or
- results for any other lot.
The correct conclusion is the narrowest conclusion supported by the method, sample, and report.
Find a lot-linked record
Use the certificate library to search by the lot code printed on the product label. Match the code exactly before relying on a document.
Button: Search certificates by lot
If a record cannot be located, contact Serum Research with the exact product name, labeled configuration, and lot code. Do not send sensitive personal or medical information.
Button: Ask about a record
Frequently asked questions
Does HPLC purity prove peptide identity?
Not by itself. HPLC can separate and compare components under a defined method, but an identity conclusion should rely on analyte-specific evidence, such as comparison with a suitable reference or mass-spectrometric data. The report should state what its method was designed to establish.
Does an LC–MS identity result prove that a sample is pure?
No. LC–MS evidence may support the presence or identity of an expected analyte, but purity is a separate analytical question. The method’s selectivity, separation, detection, and reporting scope all matter.
Is HPLC area percent the same as peptide content by mass?
Not automatically. Area percent is based on detector response among peaks detected and integrated under the method. Quantitative content requires a suitable assay, calculation basis, and reference. Water, salts, counterions, solvents, and detector-response differences may need separate consideration.
Does a purity or identity report show sterility?
No. Sterility and bacterial endotoxins are separate attributes with separate methods. They should be treated as unknown unless an applicable lot-specific report explicitly names the test and result.
Can one lot’s report be used for another lot of the same compound?
No. A report should be matched to the exact lot code on the product label. The same compound name does not make two lots analytically identical.