Read a peptide certificate from the top: the laboratory, report number, sample and lot identifiers, and dates tie the document to a vial. Then the identity block, purity block and content block, each with its method beside the result and the specification beside that. Finish with the signatures and the route to verify the report with the issuer.
- Read the header first: laboratory, report number, sample and lot identifiers, and test date decide whether the results are evidence of anything.
- The identity block needs theoretical and observed mass on the page, with the instrument and the difference; a bare conforms is not an identity result.
- The purity block needs the method conditions and the chromatogram; the percentage alone is a conclusion without its evidence.
- The content block, often absent, needs net content by a stated method plus water and counterion, and the budget should close near 100 percent.
- Every result should sit beside its specification, and the footer should carry two signatures and a route to verify the report with the issuer.
Read it in order
A certificate of analysis is a form, and forms reward being read in the order they were filled in. The header says whose document it is and what it describes. The results blocks say what was measured. The footer says who stood behind it and how to check. A reader who jumps to the purity figure in the middle has skipped the fields that decide whether the figure is evidence of anything, and that is the reading habit this page is meant to replace.
The fields below are the ones a complete certificate carries. Few certificates in the research peptide category carry all of them, and the absences are as informative as the entries. Where a field is missing, the section says what its absence means, because a certificate is not scored on how it looks but on what it can support. Two habits help. Read every field before any number, and write down what is missing as you go, because the list of absences is the certificate's grade and it is easier to see on paper than to hold in the head while a purity figure is doing its best to distract you. The certificate overview covers what the document proves in principle; this page covers what to look at on the page.
The header: whose document, describing what
Issuing laboratory. Name, address and contact. This is the party whose word the certificate carries. If the field names the supplier rather than a laboratory, the certificate is the supplier's own release testing. If it names no one, the document has no issuer and is evidence of nothing that can be confirmed.
Report number. The laboratory's own identifier for this report. It is what you quote when you ask the laboratory to confirm the document, and it is what an altered certificate cannot survive, because the laboratory's copy under that number will not match. A certificate with no report number cannot be verified.
Sample identifier and description. What the laboratory received, in its own words: a vial, a quantity of powder, a labelled container. And the lot identifier the sample carried. This lot identifier is the join between the certificate and the vial in your hand; if it is missing, or differs from your label, the document describes something else.
Dates. Received, tested and reported. Three dates, ideally. The test date is the one that matters, because the results describe the sample on that day and no other. A certificate dated years before the product it accompanies is describing a sample that has long since become something else.
Client. Who submitted the sample and paid for the test. A certificate whose client is the manufacturer describes bulk before it reached the supplier. One whose client is the supplier describes what the supplier submitted. The field says which stage of the chain was tested.
The identity block
The identity block reports the test that establishes what the material is. For a peptide it should be a mass spectrometry result, and the fields that make it readable are these.
| Field | What it should contain | If missing |
|---|---|---|
| Method and instrument | LC-MS or MS, ionisation mode, instrument class or model | The accuracy of the match cannot be judged |
| Theoretical mass | Monoisotopic or average, computed from the stated sequence and modifications | The observed mass has nothing to be compared to |
| Observed mass | The deconvoluted neutral mass, with charge states or spectrum shown | The result is a number without its evidence |
| Difference and tolerance | Observed minus theoretical, and whether it lies within the instrument's accuracy | Whether the result is a match is left to the reader |
| Result against specification | Conforms or does not, with the criterion stated | A measurement, not a decision |
A certificate whose identity block reads only conforms, or lists a retention-time match on HPLC and nothing else, has not established identity by a method that can. The LC-MS guide explains the measurement and what an observed mass can and cannot rule out. The point here is simpler: if the observed and theoretical masses are not both on the page, identity has not been demonstrated on the page.
The purity block
Purity is nearly always a reversed-phase HPLC result, and its fields describe a separation.
Method conditions. Column, mobile phases, gradient, flow rate, detection wavelength, injection volume. These are what make the result repeatable. A purity figure with a wavelength is interpretable, because the wavelength decides what the detector could see; one without conditions is a number from an unstated experiment.
The chromatogram. The trace itself, or a table of peaks with retention times and areas. A certificate that shows the chromatogram lets a reader see the main peak's shape, the shoulders that might be co-eluting impurities, and the baseline the integration rested on. One that shows only the percentage has kept the evidence and reported the conclusion.
Integration and result. The main peak's area as a percentage of total area, with the integration convention stated where the laboratory has one. This is the purity figure. It is an area percentage, blind to water, salts and counterion, and the purity testing guide explains what that means in full.
Impurity profile. The named or numbered secondary peaks with their areas. A certificate that reports total impurities as one figure has summarised; one that lists them has shown its work, and the pattern of impurities is itself a signature of the synthesis that a knowledgeable reader can recognise.
Reference standard. Some certificates note that the sample was run against a reference standard of the same peptide, with the standard's own lot and source stated. Where present, a matching retention time is a small supporting check on identity and a mismatch is a warning. Where absent, nothing is lost from the purity result, which does not depend on a standard at all.
The content block
The content block reports how much of the sample is peptide, and it is the block most often absent. Where it is present, four fields carry it.
Net peptide content. The fraction of the sample mass that is peptide, with the method stated: amino acid analysis, nitrogen determination, ultraviolet absorbance, or quantitative NMR. This is the number that corrects the label, and the net content guide sets out why it is not the purity figure.
Water. By Karl Fischer titration, as a percentage. Residual water in a lyophilized cake is ordinary and the certificate should state how much.
Counterion. Which salt the peptide is, and how much, by ion chromatography or equivalent. Trifluoroacetate and acetate differ by nearly a factor of two in mass per site, and the identity of the counterion changes the net content arithmetic and belongs in the safety data sheet's composition section as well.
Closure. Peptide, water, counterion and the remainder should approach one hundred percent of the sample mass. A budget that adds to seventy has left something out, and a certificate that reports purity without any of these has reported the peaks and nothing about the mass.
Other tests, and the specification column
Some certificates carry further blocks, and each has its own reading.
Appearance. A description of the material, usually a white to off-white lyophilized solid. Worth checking against the vial before the seal is broken.
Solubility. Observed solubility in water or a stated solvent at a stated concentration. Useful, and easily overstated; a result at 1 mg/mL says nothing about 10.
Endotoxin. By an LAL or recombinant factor C assay, in endotoxin units per milligram. Reported where the laboratory was asked for it and absent otherwise, and absence means unknown rather than zero.
Sterility. Rarely reported for a lyophilized research chemical and not to be assumed from any other result.
Across every block runs the specification column: the acceptance criterion each result was compared against. The pharmaceutical rule on release, 21 CFR 211.165, ties the decision to conformance with a stated specification, and the ICH guidance Q6B defines a specification as the list of tests, methods and criteria a product is held to. On a certificate this means each result should sit beside its limit. A purity of 97.2 percent is a pass against 95 and a failure against 98; a certificate that prints the number without the limit has left the reader to supply the specification, and the reader usually supplies a generous one.
Two certificates side by side
The fields are easiest to see in contrast. Below are two certificates for the same kind of product, described field by field. Both are typical of what circulates in the research peptide category, and only one of them is evidence.
| Field | Certificate A | Certificate B |
|---|---|---|
| Issuing laboratory | A logo, no address | Named laboratory, address, contact |
| Report number | None | Present, quotable to the laboratory |
| Sample and lot | Product name only | Sample identifier, lot identifier matching the vial |
| Dates | One date, unspecified | Received, tested, reported |
| Identity | Conforms | LC-MS, instrument named, theoretical 1418.7, observed 1418.7, within tolerance |
| Purity | 99.2 percent | 99.2 percent by RP-HPLC, column, gradient and 214 nm stated, chromatogram attached |
| Content | Absent | Net peptide 81 percent by amino acid analysis, water 4.1 percent, trifluoroacetate 13 percent |
| Specifications | Absent | Limit printed beside each result |
| Signatures | None | Analyst and reviewer |
| Verification | None | Laboratory portal, report number resolves |
Certificate A reports the same purity as Certificate B, and a buyer comparing headline numbers would see no difference. Everything that makes B evidence is in the rows A leaves blank: A cannot be tied to a vial, cannot be confirmed with anyone, does not say what the material is, and does not say how much of it there is. It is a purity figure with a border, and it would look identical if the number had been changed.
Two smaller reading points. Units and formats should be consistent and stated: purity as area percent, content as percent by mass, water as percent, endotoxin in endotoxin units per milligram, dates in an unambiguous form. And a certificate should distinguish not tested from not applicable from not detected, because they mean three different things: the first is an absence of evidence, the second a test that does not apply to the material, and the third a result. A certificate that uses one dash for all three has hidden which it means.
The footer: who stood behind it, and how to check
Analyst and reviewer. Two names or two signatures, the person who ran the tests and the person who checked them. The pharmaceutical laboratory-records rule, 21 CFR 211.194, requires both. A certificate with one signature has been checked by no one; one with none has been checked by no one who will say so.
Statement of scope. Many laboratories add a sentence stating that the results relate only to the sample tested, which is true of every certificate and worth being reminded of.
Verification route. A portal address, a code that resolves on the laboratory's own domain, or an email address, by which a reader can ask the laboratory to confirm that a report with this number and these results was issued for this sample on this date. This is the one field the party presenting the certificate cannot fake, and its absence means the document rests on that party's word. The Verify a COA page describes how to use it.
Read in this order, a certificate answers a fixed set of questions or visibly fails to. Who tested what, when. What the material is, by a method that can say. How pure, under stated conditions. How much, by a method that measures mass. Against what limits. Signed by whom. Checkable where. A document that answers all of them is worth the paper; one that answers the middle two and none of the rest is a purity figure with a border around it.
How our certificates are presented
Each LabFirst product record links the issuing laboratory's certificate for the lot currently shipping where that certificate has landed, unedited, together with the laboratory's verification route. The record's own fields state the sequence, theoretical mass, salt form and labelled-mass convention that the certificate's identity, content and purity blocks are read against, so the comparison this page describes can be made without a second document. Fields the laboratory did not report are shown as not reported. The certificate overview sets out what the document proves in principle, and the compliance page states what LabFirst is and is not.
A certificate reports what a sample was found to be. It reports nothing about what the substance is for. FOR LABORATORY AND IN-VITRO RESEARCH USE ONLY. NOT FOR HUMAN OR ANIMAL CONSUMPTION. Analytical documentation exists so that a laboratory can confirm what it received, and for no other purpose.
Common questions
What is the first thing to check on a peptide COA?
Which fields does the identity block need?
Why should a COA show the chromatogram and not just the purity percentage?
What does the specification column tell me?
How do I verify a COA once I have read it?
What does a certificate of analysis actually prove?
Is a manufacturer's certificate the same as third-party testing?
Why does a certificate need a lot number?
Can a certificate be genuine and still be misleading?
How can I tell if a certificate has been altered?
Sources
- 21 CFR 211.194, Laboratory records. The record behind each certificate field: sample description, method, measurements, calculations, results, and the analyst and reviewer signatures.
- 21 CFR 211.165, Testing and release for distribution. Release tied to conformance with specifications; the basis for reading each result beside its limit.
- FDA / ICH Q6B, Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products. The definition of a specification as tests, methods and acceptance criteria, and identity, purity and quantity as separate categories.
- FDA / ICH Q2(R1), Validation of Analytical Procedures: Text and Methodology. Why method conditions belong on the certificate: a procedure is only interpretable and repeatable when it is stated.
- FDA, Guidance for Industry: Pyrogen and Endotoxins Testing: Questions and Answers. Background for the endotoxin field, including the assay types a certificate may name.
- ISO/IEC 17025:2017, General requirements for the competence of testing and calibration laboratories. The standard behind an issuing laboratory's accreditation and reporting requirements, including the statement of scope many certificates carry.