How to Read a Peptide Certificate of Analysis

Start with the document-to-vial match

The first task is not interpreting a chromatogram. It is confirming that the certificate belongs to the material in front of you. Compare the exact product or material name, presentation, and lot or batch number. A catalog SKU identifies a product listing; a lot number identifies a specific production grouping. They are not interchangeable.

Record the report identifier, test laboratory, sample receipt or test date, and release or approval date when shown. If a certificate is revised, the revision number or superseded-document trail should make that change visible. A polished PDF with no batch connection is weak evidence.

Evidence: [1], [4]

Read specifications and results as different fields

A specification is the pre-established acceptance limit or criterion. A result is what the laboratory measured for that sample. “Purity ≥98%” is a specification; “99.1% by RP-HPLC” is a result. A pass or conforming statement should be traceable to both fields, not presented in place of the numerical result when the test produces a number.

Check the unit and the basis of measurement. Percent peak area, percent by mass, milligrams per vial, water content, and concentration describe different attributes. They should never be treated as synonyms.

Evidence: [1], [3], [4]

Separate the major analytical questions

Identity asks whether the detected material is consistent with the intended analyte. Mass spectrometry commonly supports this by comparing an observed ion or deconvoluted mass with an expected mass. Chromatographic purity asks how much of the detected chromatographic signal is assigned to the main peak under one stated method. Assay or content asks how much analyte is present. Quantity testing asks how much material is in the container.

One result cannot quietly stand in for another. A high HPLC area percentage does not establish vial fill mass, and an expected mass peak does not quantify every impurity. Orthogonal methods are valuable because they answer different questions.

Evidence: [2], [3]

Check the method context

At minimum, the certificate should name the technique used for each reported attribute. More useful packages identify the method or procedure number, detector, reference material, and any relevant sample preparation or acceptance rule. Supporting chromatograms or spectra should carry the same sample or lot identifier as the certificate.

Method suitability matters. ICH Q2(R2) treats specificity or selectivity, range, accuracy, precision, and robustness as performance characteristics chosen according to the procedure’s purpose. A result without enough method context cannot be independently interpreted simply because it has several decimal places.

Evidence: [2]

Recognize what is not established

A COA reports the tests that were performed; it is not a universal quality guarantee. If the certificate does not report microbial limits, endotoxin, residual solvents, water, counterion, or stability, do not infer those results. “Third-party tested” also needs context: identify who tested what, on which lot, using which method, and when.

The FDA and ICH documents cited below apply to regulated drug manufacturing, not automatically to research-material sellers. We use them here as a transparent benchmark for the kinds of fields that make analytical records interpretable. Their inclusion does not claim that a research product is an approved drug or was manufactured under a particular regulatory status.

Evidence: [1], [3]

A practical 60-second COA check

• Match material name, format, and lot number.
• Identify the issuing laboratory and report number.
• Confirm test and approval dates and any revision status.
• For every claim, find the method, specification, result, and unit.
• Confirm supporting traces carry the same sample identifier.
• Note attributes that were not tested instead of assuming they passed.
• Save the certificate with the receiving and inventory record for that lot.

Evidence: [1], [4]