Where to Buy Research Peptides: How to Evaluate a Supplier

What should researchers look for in a research peptide supplier?

The most informative documents are the ones that describe a specific lot: its certificate of analysis, the name of the laboratory that performed each test, and the lot number that links the material to its production and distribution history. ICH Q7 defines a batch number, or lot number, as a unique combination of numbers, letters and/or symbols that identifies a batch and from which the production and distribution history can be determined.^[1]

ICH Q6B groups the tests in a specification under appearance and description, identity, purity and impurities, potency and quantity. A certificate that reports only one of these attributes documents only that attribute.^[2]

Each item can be checked against the lot actually supplied: either the documentation matches that lot or it does not. The criteria below are documentation criteria; they do not rank suppliers.

What makes a peptide supplier's documentation trustworthy?

Documentation is checkable when it identifies who produced it, for which lot and when. Section 11.4 of ICH Q7 states that certificates should be dated and signed by authorized personnel of the quality unit, and that certificates issued by or on behalf of repackers, reprocessors, agents or brokers should show the name, address and telephone number of the laboratory that performed the analysis, with a reference to the original batch certificate.^[1]

A result is also only as informative as the procedure behind it. Under ICH Q2(R2), validation is meant to show that an analytical procedure is fit for its intended purpose, judged on characteristics that include specificity or selectivity, range, accuracy and precision.^[3]

ICH Q6B defines an acceptance criterion as a numerical limit, range or other measure for accepting the results of an analytical procedure. A reported result is read against the criterion stated for that lot.^[2]

Should peptide certificates of analysis be lot specific?

ICH Q7 states that authentic certificates of analysis should be issued for each batch on request, and lists the batch number among the items a certificate should carry.^[1]

ICH Q7 defines a batch, or lot, as a specific quantity of material produced in a process or series of processes so that it is expected to be homogeneous within specified limits. A certificate reports results for samples drawn from that quantity, so a result for one lot says nothing about another lot.^[1]

How can a peptide certificate of analysis be verified?

The first check is the lot number. ICH Q7 states that labels on containers should indicate the name or identifying code and the batch number, so the lot number on the certificate can be compared with the lot number on the container label.^[1]

The second check is the issuer. ICH Q7 states that certificates should be dated and signed and should show the name, address and telephone number of the original manufacturer, or of the laboratory that performed the analysis when a certificate is re-issued. A named laboratory is the party that can confirm whether a report exists for a given sample.^[1]

The third check is the content. ICH Q7 states that a certificate should list each test performed, including the acceptance limits and the numerical results obtained. Each numerical result can then be compared with its stated acceptance criterion.^[1],[2]

Which documents should a buyer check for each research peptide lot?

A short document checklist, applied to one lot at a time. Each line is either present in the paperwork for that lot or it is missing.

• Lot code: the certificate carries a lot or batch number, the identifier ICH Q7 defines as the key to a batch's production and distribution history.^[1]
• Named test and result: every test appears by name next to the numerical result it produced, as ICH Q7 section 11.4 describes for a certificate.^[1]
• Testing laboratory: the certificate names the laboratory that ran the analysis and how to reach it, which ICH Q7 expects on a re-issued certificate.^[1]
• Method limits: each result is shown with its acceptance criterion, and the method behind it is identified, since ICH Q6B regards purity figures as method dependent and ICH Q2(R2) ties a procedure's validity to its intended purpose.^[2],[3]
• Label match: the name or identifying code and the batch number on the container label are the same as those on the certificate; ICH Q7 lists both among the items a container label should show.^[1]

• What a certificate of analysis reports
• How HPLC purity is measured and what it leaves out
• How identity testing confirms which peptide is present
• How lot traceability connects a vial to its records

Does HPLC purity establish peptide identity?

No. ICH Q6B lists identity and purity and impurities as separate specification items, each with its own tests, and states that purity results are method dependent. A purity result does not establish identity, and an identity result does not establish purity.^[2]

ICH Q2(R2) states that an identification procedure should be able to identify the analyte based on unique aspects of its molecular structure or other specific properties. In its LC/MS example, it combines an accurate m/z value with retention time as the basis for specificity, rather than relying on retention time alone.^[3]

Some synthetic peptide impurities are isomers of the intended peptide. Isomers share a chemical formula and therefore a mass-to-charge ratio, so a mass-based identity result cannot by itself exclude an isomeric impurity such as a peptide epimer.^[4],[5],[6]

What testing do researchers commonly look for?

Each kind of result answers one question and leaves others open:

• Identity: whether the material is the named substance. ICH Q6B states that identity tests should be highly specific and that more than one test may be necessary. Limit: identity tests can be qualitative and do not measure how much is present or how pure it is.^[2]
• Purity: how much of the material is the intended substance rather than other components, usually by HPLC. Limit: ICH Q6B states that purity results are method dependent and are usually estimated by a combination of methods; a purity figure does not establish identity, endotoxin or microbial content.^[2],[7]
• Measured quantity: the amount of each component the laboratory measured. ICH Q6B lists quantity as a separate specification item. Limit: it establishes neither identity nor purity.^[2]
• Endotoxin: bacterial endotoxin measured by a Limulus amebocyte lysate (LAL) method, which FDA guidance associates with USP chapter <85>. Limit: FDA guidance states that endotoxin assays are subject to interference from the test article, and an endotoxin result does not measure other microbial contaminants.^[8],[9]
• Microbial or sterility related screening (PCR): a certificate may report a rapid PCR screen, a compendial test, or both; the compendial chapters named in ICH Q4B annexes cover microbial enumeration (USP <61>), tests for specified microorganisms (USP <62>) and sterility (USP <71>). Limit: a PCR screen is a detection result for the sample tested and does not by itself establish the sterility of every unit or a validated sterility assurance; an FDA inspection technical guide states that a reduction in microbial level is not associated with a similar reduction in endotoxin, so a low microbial result does not predict a low endotoxin result.^{[10],[11],[12],[13],[14],[15],[16]}
• Lot traceability: a lot number that connects the material to its records. ICH Q7 states that a system should be in place by which the distribution of each batch can be readily determined. Limit: a lot number connects material to records; it does not show what those records contain.^[1]

What are documentation red flags?

These are objective problems with the documentation itself, each measured against what ICH Q7 and ICH Q6B describe:^[1],[2]

• A certificate that cannot be matched to a lot: ICH Q7 lists the batch number among the items a certificate should carry.^[1]
• An unidentified laboratory: ICH Q7 states that re-issued certificates should show the name, address and telephone number of the laboratory that performed the analysis.^[1]
• A missing report date: ICH Q7 states that certificates should be dated and signed by authorized personnel.^[1]
• A purity percentage without supporting analytical documentation: ICH Q6B describes purity as method dependent, and ICH Q2(R2) uses representative chromatograms, electropherograms or spectra as supporting data for specificity.^[2],[3]
• One generic certificate presented for multiple lots: ICH Q7 describes certificates as issued for each batch, and a batch as homogeneous only within specified limits.^[1]
• Claims beyond what a test establishes: for example, a purity result presented as proof of identity, when ICH Q6B lists identity and purity as separate items.^[2]

How can research peptide suppliers be compared?

A neutral checklist. It names no supplier and produces no ranking; each row is either documented for the lot supplied or it is not.

How does PepGenex document its research materials?

PepGenex first-party information. Source: PepGenex, as published on its Research Standards page, and written confirmation from the laboratory that prepares its research materials, dated 2026-09-24.

PepGenex research materials undergo independent third-party analytical testing. COA available on request.

Each certificate reports the following items:

• Identity confirmation
• Measured quantity of each component
• HPLC purity, reported against a specification of greater than 98.0%
• Endotoxin by LAL (limit 5.0 EU/mL)
• Rapid Sterility Screening (PCR), result: Not Detected
• The Rapid Sterility Screening (PCR) result is a detection result for the sample tested and does not by itself establish the sterility of every unit or a validated sterility assurance.
• Lot code and sample code
• Date received and date published
• Laboratory review and director certification
• Sample code verification through the laboratory
• The lot code is printed on the vial label.
• Certificates of analysis are available on request. Include the lot code. Requests go to info@pepgenex.com.

• What the research use only (RUO) label means for research materials

Where can researchers access PepGenex research materials?

Research materials are available through Research Access.

Limitations

The scope of any certificate is the tests printed on it, run on the samples that were tested, by the methods named. A test that was not run has no result, and one lot's certificate is silent about every other lot.^[1],[2]

The checklist on this page is a list of documentation criteria. It does not rank suppliers, and it does not establish the regulatory status of any material or its suitability for any use.

The section on PepGenex is first-party information from PepGenex. It has not been independently verified.

This page describes what the cited documents say. It is not a statement that any PepGenex material, or any other supplier's material, has been manufactured, tested or released under any of them.

Frequently asked questions

References

1. ICH Q7 Good Manufacturing Practice Guidance for Active Pharmaceutical Ingredients. U.S. FDA guidance for industry, September 2016. FDA docket FDA-1995-D-0288
2. ICH Q6B Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products. U.S. FDA guidance for industry, August 1999. FDA docket FDA-1998-D-0003
3. ICH Q2(R2) Validation of Analytical Procedures. U.S. FDA guidance for industry, March 2024. FDA docket FDA-2022-D-1503
4. D'Hondt M, Bracke N, Taevernier L, et al. Related impurities in peptide medicines. J Pharm Biomed Anal. 2014;101:2-30. PMID 25044089 · DOI 10.1016/j.jpba.2014.06.012
5. Rathahao-Paris E, Abdoun S, Paris A, et al. Innovative direct introduction-ion mobility-mass spectrometry (DI-IM-MS) approach for fast and robust isomer-specific quantification in a complex matrix. J Mass Spectrom. 2024;59(5):e5026. PMID 38656572 · DOI 10.1002/jms.5026
6. Lian Z, Wang N, Tian Y, Huang L. Characterization of Synthetic Peptide Therapeutics Using Liquid Chromatography-Mass Spectrometry: Challenges, Solutions, Pitfalls, and Future Perspectives. J Am Soc Mass Spectrom. 2021;32(8):1852-1860. PMID 34110145 · DOI 10.1021/jasms.0c00479
7. Mant CT, Chen Y, Yan Z, et al. HPLC analysis and purification of peptides. Methods Mol Biol. 2007;386:3-55. PMID 18604941 · DOI 10.1007/978-1-59745-430-8_1 · PMC7119934
8. U.S. FDA. Pyrogen and Endotoxins Testing: Questions and Answers. Guidance for industry. FDA docket FDA-2013-S-0610
9. United States Pharmacopeia, General Chapter <85> Bacterial Endotoxins Test (as named in FDA, Pyrogen and Endotoxins Testing: Questions and Answers). USP <85>
10. ICH Q4B Annex 4A(R1) Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests General Chapter. U.S. FDA guidance for industry, September 2010. FDA docket FDA-2008-D-0396
11. ICH Q4B Annex 4B(R1) Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms General Chapter. U.S. FDA guidance for industry, September 2017. FDA docket FDA-2008-D-0398
12. ICH Q4B Annex 8(R1) Sterility Test General Chapter. U.S. FDA guidance for industry, September 2017. FDA docket FDA-2009-D-0013
13. United States Pharmacopeia, General Chapter <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests (as named in ICH Q4B Annex 4A(R1), FDA guidance). USP <61>
14. United States Pharmacopeia, General Chapter <62> Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms (as named in ICH Q4B Annex 4B(R1), FDA guidance). USP <62>
15. United States Pharmacopeia, General Chapter <71> Sterility Tests (as named in ICH Q4B Annex 8(R1), FDA guidance). USP <71>
16. U.S. FDA. Inspection Technical Guide No. 40: Bacterial Endotoxins/Pyrogens (March 20, 1985). FDA ITG No. 40