Purity
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LC-MS Peptide Testing & Identity Assessment
PeptideValidation · Testing knowledge base
Mass evidence needs an identity question.
Understand the difference between a matching molecular mass and the evidence needed for a more detailed structural conclusion.
Quick answer
What does LC-MS peptide testing establish?
LC-MS combines separation with mass-spectrometric detection to provide evidence relevant to a defined identity question. An interpreted mass result can support a claimed molecular identity, but a mass match alone does not resolve every sequence, isomeric or structural distinction. The necessary evidence depends on the material and the conclusion being requested.
From ion signals to a reported conclusion
The laboratory interprets signals in the context of the expected material and method. Ask how charge states, adducts and target-peak assignment are handled, and whether the report supplies the relevant spectrum and interpretation rather than an isolated mass number.
When is additional characterization needed?
| Question | What to discuss |
|---|---|
| Does observed mass support the stated target? | Theoretical identity specification, observed result and the stated comparison basis. |
| Is the complete sequence or modification pattern established? | Whether sequence-level information or another complementary method is required. |
| Are structurally related materials distinguished? | Which distinctions the selected method resolves and which remain open. |
| Is a protein, fragment or conjugate involved? | Whether intact analysis, peptide mapping or other characterization suits the objective. |
| Is the sample a blend or formulation? | Whether each claimed component can be assigned in the actual matrix. |
ICH Q6B describes multiple approaches to molecular characterization, including peptide mapping and other techniques. The relevant approach should follow the actual identity question, not a universal instrument claim.
What should an LC-MS report connect?
- The submitted sample and lot identifier.
- The exact claimed identity specification used for comparison.
- Method and instrument information relevant to interpretation.
- The assigned signal, interpreted result and comparison basis.
- Available supporting spectrum or other agreed data output.
- Any unresolved identity questions and method limitations.
Identity is one part of the picture.
Content
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Microbiological scope
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Provide a precise target specification
Describe your material
Share the exact claimed identity, formulation, physical form, labeled amount and lot identifier. Include existing documentation if available.
Agree on the testing scope
Confirm methods, sample requirements, pricing, timing, report outputs and submission instructions before sending material.
Read the results in context
Check the sample identifier, method, units, reporting limits and any agreed specification. Ask about unexplained or unresolved findings.
From a question to a testing scope
Tell us what you need to learn.
PeptideValidation.com sells laboratory testing services for client-supplied samples. Share the material description and your testing question so method suitability and submission requirements can be confirmed.
Frequently asked questions
Does matching mass prove the complete peptide sequence?
Not by itself. Some distinct structures can remain unresolved by an intact-mass comparison. Ask what evidence is needed for your specific sequence or modification question.
Does LC-MS measure purity or amount automatically?
No. The output depends on the agreed analytical procedure. An identity-focused mass result should not be reinterpreted as a purity or quantitative content result.
What if my sample has a modification or conjugate?
Provide the full claimed specification. Confirm whether the method addresses the complete material and any relevant heterogeneous or related species.
Can LC-MS analyze a blend?
A blend requires component-specific planning and matrix assessment. Confirm whether the intended components can be separated, assigned and, if requested, quantified.
What should I send with my request?
The sample label, lot reference, exact claimed identity, formulation details and the question you need answered. Existing COAs or spectra can help define unresolved questions.