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Peptency Academy · Testing

How to read a peptide CoA, line by line, with red flags

What does each line on a peptide certificate of analysis mean, and which gaps are red flags?

A certificate of analysis (CoA) is a document that reports the tests run on one batch of material, with each test's acceptance limit and measured result. Source sentence11.42: "The Certificate should list each test performed in accordance with compendial or customer requirements, including the acceptance limits, and the numerical results obtained (if test results are numerical)."1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000 Each line reads as one test with its acceptance limit and its result; a red flag is a line that is missing, or a test listed without a limit or a numerical result. Source sentenceurl:ich-q7 11.42: "The Certificate should list each test performed in accordance with compendial or customer requirements, including the acceptance limits, and the numerical results obtained (if test results are numerical)."1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000

Version 1Edited 13 sources

Known, not known, contested

Known

  • HPLC purity and peptide content are separate measurements: purity is a share of the chromatogram's peak area, while counterions and water are measured by weight. Source sentence"The equation used to calculate purity separates HPLC impurities, which are measured as a % of the total detected area by chromatography, and counter ion / impurities measured on a weight/weight basis."2 Pharm Res 2023
  • In one purified peptide reference material, the TFA counterion was nearly 25 percent of the mass. Source sentence"a validated 19F-qNMR method to measure the trifluoroacetic acid (TFA) counter-ion, considered an impurity in this case at nearly 25% by mass"3 Anal Bioanal Chem 2018
  • A sterility pass does not rule out endotoxin: in a 2024 test purchase study, no viable microorganisms were found, yet endotoxin was detected in every vial. Source sentence"The lyophilized peptide samples were devoid of viable microorganisms at the time of testing; however, endotoxin was detected in all samples"4 J Med Internet Res 2024
  • Under ICH Q7, a supplier's CoA does not replace an identity test: at least one identity test is run on each incoming batch. Source sentence7.30: "At least one test to verify the identity of each batch of material should be conducted, with the exception of the materials described below in 7.32. A supplier's Certificate of Analysis can be used in place of performing other tests"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000

Not known

Contested

  • Methods for assigning a peptide content value differ: USP authors report the least variation between laboratories with a mass balance approach, while a National Research Council Canada group combines mass balance with qNMR and amino acid analysis. Source sentence36949371: "we found the least inter-laboratory variability when using a mass balance approach"; 30143839: "Ideally, results from these three orthogonal methods can be combined for final purity assignment of peptide reference standards."2 Pharm Res 20233 Anal Bioanal Chem 2018

What is a CoA used for?

A CoA records which tests were run on one batch, against which limits, with which results. Source sentence11.40: "Authentic Certificates of Analysis should be issued for each batch of intermediate or API on request."; 11.42 as above1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000 In pharmaceutical manufacturing a CoA is not taken on trust: buyers run at least one identity test per batch and compare full analyses with the certificates at set intervals. Source sentence7.31: "as a minimum, a full analysis should be performed at appropriate intervals and compared with the Certificates of Analysis. Reliability of Certificates of Analysis should be checked at regular intervals."1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000 A CoA is the issuer's statement about one batch; its weight depends on who tested what, by which method, against which limit. Source sentence11.42 to 11.44: tests with limits and results, signature, and the name of the laboratory that performed the analysis1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000

What a batch certificate carries under ICH Q7

  1. This page reads a peptide CoA against the certificate list in ICH Q7, the international good manufacturing practice guide for active pharmaceutical ingredients. Source sentenceSection 11.4, Certificates of Analysis, paragraphs 11.40 to 11.441 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
  2. The material's name and its batch number. Source sentence11.41: "Information on the name of the intermediate or API including where appropriate its grade, the batch number, and the date of release should be provided"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
  3. The release date, and an expiry or retest date where one applies. Source sentence11.41: "the date of release"; "the expiry date should be provided on the label and Certificate of Analysis"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
  4. Each test performed, with its acceptance limit and the numerical result. Source sentence11.42: "each test performed ... including the acceptance limits, and the numerical results obtained"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
  5. A date and the signature of authorised quality staff. Source sentence11.43: "Certificates should be dated and signed by authorised personnel of the quality unit(s)"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
  6. The original manufacturer's name and address. Source sentence11.43: "should show the name, address and telephone number of the original manufacturer"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
  7. On a reissued certificate: the laboratory that ran the analysis, and a copy of the original batch certificate. Source sentence11.44: "show the name, address and telephone number of the laboratory that performed the analysis ... the original batch Certificate, a copy of which should be attached"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000

What does each line on a peptide CoA mean?

Peptide quality is described by separate attributes, each with its own test: identity, purity, and strength (called assay in USP texts). Source sentenceTable II, USP Peptide Quality Attributes and Analytical Methodology: Identity, Purity, Strength; footnote: "Strength is referred to as Assay in USP monographs and general chapters"2 Pharm Res 2023

The lines of a peptide CoA

Illustrative layout, not a Peptency lot

  • Batch and dates
    Method
    Not a test
    Reports
    Material name, batch number, release or test date
  • Identity
    Method
    Mass spectrometry (for example LC-MS)
    Reports
    Observed mass beside the theoretical mass
  • Purity
    Method
    HPLC with UV detection
    Reports
    Main peak as a percent of detected peak area, with the wavelength and chromatogram
  • Content (assay)
    Method
    HPLC against a reference standard, or mass balance
    Reports
    Peptide share by weight, with its basis
  • Counterion
    Method
    HPLC or other validated method
    Reports
    Salt form and TFA or acetate content by weight
  • Water
    Method
    Karl Fischer titration
    Reports
    Residual moisture by weight
  • Endotoxin
    Method
    Pharmacopoeial bacterial endotoxins test
    Reports
    Method and result with units
  • Sterility
    Method
    Pharmacopoeial sterility test
    Reports
    Growth or no growth
  • Sign off
    Method
    Not a test
    Reports
    Date, signature, issuer and testing lab name and address, accreditation and scope
Illustrative layout, not a Peptency lot. Each line names the test, the method and what the line reports; no result values are shown.

What to look for on each line

Batch and dates
The batch number and release date tie the certificate to one batch; the batch number on the certificate matches the one on the container label. Source sentence11.41: "the batch number, and the date of release should be provided on the Certificate of Analysis"; 7.32: "Visual examination of containers, labels, and recording of batch numbers should help in establishing the identity of these materials."1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
Identity
Identity by mass spectrometry compares the measured mass, and with tandem MS the amino acid sequence, with the expected molecule. Source sentenceTable II: "LC-MS/MS Peptide mass and Amino acid sequence" (Identity)2 Pharm Res 2023
Purity
HPLC purity is the main peak as a percent of all detected peak area at a UV wavelength, so the method, wavelength and chromatogram belong beside the number. Source sentence"HPLC impurities, which are measured as a % of the total detected area by chromatography"; "Peptides and impurities were monitored at 220 nm."2 Pharm Res 2023
Content (assay)
Content (assay) is how much of the material, by weight, is the peptide, and it is stated on a basis, for example peptide free base per unit of material on the anhydrous basis. Source sentenceTable VII example: the theoretical example "would have a purity of 0.93" of peptide (free base) relative to material on the anhydrous basis2 Pharm Res 2023
Counterion
Solid phase synthesis and HPLC purification leave most peptides as TFA salts, and USP testing measures acetic acid and TFA content separately. Source sentence40872554: "resulting in peptides being obtained as TFA salts"; 36949371 Table II: "Acetic Acid by HPLC Determine acetic acid content Trifluoroacetic acid by HPLC Determine TFA content"6 Pharmaceuticals (Basel) 20252 Pharm Res 2023
Water
Residual moisture in a freeze dried peptide is measured on its own, for example by coulometric Karl Fischer titration. Source sentence"Residual moisture was determined destructively by coulometric Karl Fischer titration"2 Pharm Res 2023
Endotoxin and sterility
Endotoxin and sterility are separate tests with separate results: one study found endotoxin in every vial that passed for viable microorganisms. Source sentence"devoid of viable microorganisms at the time of testing; however, endotoxin was detected in all samples"4 J Med Internet Res 2024
Sign off
ICH Q7 asks for a dated, signed certificate with the manufacturer's name and address, and a reissued certificate names the laboratory that ran the analysis. Source sentence11.43; 11.44: "these Certificates should show the name, address and telephone number of the laboratory that performed the analysis"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
Accreditation
A lab's accreditation is read from its certificate of accreditation together with the scope, which defines the testing activities covered. Source sentence2.1: "The definitive statement of the accreditation status of a testing laboratory is the certificate of accreditation and the associated scope of accreditation."; 2.3: "The scope of accreditation defines the measurement capabilities, ranges and boundaries of the testing activities for which the organisation holds accreditation."7 INAB PS34, scope format for testing laboratories accredited to ISO/IEC 17025

What are the red flags on a peptide CoA?

Each flag below is a gap against the ICH Q7 certificate list or a published analytical finding; a flag is a reason to ask the issuer for the missing record, not proof that the material is wrong. Source sentenceSection 11.4, paragraphs 11.40 to 11.441 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 20004 J Med Internet Res 2024

Ten red flags

1. Batch number missing or mismatched
No batch number, or one that differs from the vial label: the certificate cannot be tied to the vial. Source sentence11.41 batch number; 7.32 "recording of batch numbers"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
2. One certificate, several batches
One certificate shown for several batches: ICH Q7 issues a certificate for each batch. Source sentence11.40: "Authentic Certificates of Analysis should be issued for each batch"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
3. No method or no limit
A number with no method or no acceptance limit: a result is read against its limit. Source sentence11.42: "including the acceptance limits, and the numerical results obtained"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
4. Purity only
A purity figure with no identity and no content result: purity, identity and strength are separate tests. Source sentenceTable II: Identity, Purity, Strength listed as separate quality attributes with separate methods2 Pharm Res 2023
5. No mass, or the wrong mass
Identity stated with no measured mass, or a mass that does not match the expected sequence. Source sentenceTable II: "LC-MS/MS Peptide mass and Amino acid sequence"2 Pharm Res 2023
6. No date, signature or issuer
No date, no signature, or no name and address of the issuer. Source sentence11.43: "Certificates should be dated and signed"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
7. Retyped, no original attached
A retyped or rebranded certificate with no copy of the original: a reissued certificate refers to the original batch certificate and attaches a copy. Source sentence11.44: "They should also contain a reference to the name and address of the original manufacturer and to the original batch Certificate, a copy of which should be attached."1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000
8. Accreditation without scope
"Accredited" with no accreditation body, number or scope, or a scope that does not list the method used. Source sentence2.1 and 2.3, scope of accreditation7 INAB PS34, scope format for testing laboratories accredited to ISO/IEC 17025
9. Sterile read as endotoxin free
"Sterile" read as "endotoxin free": endotoxin was found in vials with no viable microorganisms. Source sentence"devoid of viable microorganisms at the time of testing; however, endotoxin was detected in all samples"4 J Med Internet Res 2024
10. Label figure with no lab result
A label figure with no lab result behind it: purchased vials labelled 99 percent purity measured 7.7 to 14.37 percent. Source sentence"the measured semaglutide purity was significantly low, ranging between 7.7% and 14.37% and deviating from the 99% claimed on product labels"4 J Med Internet Res 2024

How does a lab confirm a peptide is the right molecule?

A lab checks identity with mass spectrometry: the measured mass, and with tandem MS the sequence, is compared with the expected molecule. Source sentenceTable II: "LC-MS/MS Peptide mass and Amino acid sequence"2 Pharm Res 2023 Mass alone cannot tell leucine from isoleucine, which have the same mass, so USP authors add amino acid analysis for that. Source sentenceTable II: "AAA Distinguish Ile vs. Leu"; "Some peptide features, such as chiral or isobaric amino acids, may require additional techniques"2 Pharm Res 2023

What mass spectrometry has found in products

  • Published analyses of seized products have used high resolution mass spectrometry to find molecules other than the expected one, such as a glycine analogue of GHRP-2 in one vial and a GHRH analogue with an incomplete C terminal amidation in another. Source sentencePMID 30051972: "to identify a new heptapeptide (MW = 874.02 Da) - a glycine analogue of GHRP-2"; PMID 25283153: "identified in a confiscated product by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Investigation of the product suggests also an incomplete C-term amidation."8 Drug Test Anal 20199 Drug Test Anal 2014

What is a good purity level for a peptide?

No single figure answers this: a CoA result is read against the acceptance limit printed beside it, set by the specification for that material. Source sentence11.42: "including the acceptance limits, and the numerical results obtained"1 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000 An HPLC purity figure is a share of detected peak area, so it does not say how much of the powder is peptide. Source sentence"measured as a % of the total detected area by chromatography"2 Pharm Res 20233 Anal Bioanal Chem 2018 A printed figure is a claim until a lab result backs it: in one test purchase study, vials labelled 99 percent purity measured 7.7 to 14.37 percent. Source sentence"ranging between 7.7% and 14.37% and deviating from the 99% claimed on product labels"4 J Med Internet Res 2024

Where can a peptide be tested?

Testing laboratories are accredited to ISO/IEC 17025 by an accreditation body. Source sentence"testing laboratories (using ISO/IEC 17025)"10 ILAC, MRA and signatories The certificate of accreditation and its scope state which tests a lab is accredited for. Source sentence2.1: "The definitive statement of the accreditation status of a testing laboratory is the certificate of accreditation and the associated scope of accreditation."; 2.3: "The scope of accreditation defines the measurement capabilities, ranges and boundaries of the testing activities for which the organisation holds accreditation."7 INAB PS34, scope format for testing laboratories accredited to ISO/IEC 17025

What a CoA cannot show

  • A CoA reports the results of the tests listed on it, so a defect that no listed test looks for does not show: a 2019 study traced fast breakdown of one vendor's glucagon to a heat stable high molecular weight contaminant from manufacturing. Source sentence"Contamination by a thermostable high molecular impurity (such as a peptidase with molecular weight between 10 and 30 KDa) during the manufacturing process was the main reason for this interesting phenomenon."11 Pharm Res 2019
  • Its authors proposed adding stability test criteria to CoAs; the ICH Q7 certificate list does not include a stability test. Source sentence"inclusion of the 'accelerated stability criteria' in the Certificate of Analysis (CoAs)"; ICH Q7 11.40 to 11.4411 Pharm Res 20191 ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000

Pharmacopoeia chapters for endotoxin and sterility

Sources

  1. 1ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, Step 4, 10 Nov 2000 accessed 13 Oct 2026
  2. 2Pharm Res 2023 accessed 13 Oct 2026
  3. 3Anal Bioanal Chem 2018 accessed 13 Oct 2026
  4. 4J Med Internet Res 2024 accessed 13 Oct 2026
  5. 5PubMed search for certificate of analysis and peptide, 13 October 2026 accessed 13 Oct 2026
  6. 6Pharmaceuticals (Basel) 2025 accessed 13 Oct 2026
  7. 7INAB PS34, scope format for testing laboratories accredited to ISO/IEC 17025 accessed 13 Oct 2026
  8. 8Drug Test Anal 2019 accessed 13 Oct 2026
  9. 9Drug Test Anal 2014 accessed 13 Oct 2026
  10. 10ILAC, MRA and signatories accessed 13 Oct 2026
  11. 11Pharm Res 2019 accessed 13 Oct 2026
  12. 12ICH Q4B Annex 14, Bacterial Endotoxins Test, Step 4, 18 Oct 2012 accessed 13 Oct 2026
  13. 13ICH Q4B Annex 8(R1), Sterility Test, Step 4, 27 Sep 2010 accessed 13 Oct 2026

About this page

Research-use information. This library summarises published literature and regulator records. It is not guidance for use, not medical advice, and not a statement that any material is suitable for use in people or animals.

Reviewed by the Peptency editorial process. Version 1, last edited 13 October 2026, 13 sources.

Cite this page: Peptency Academy. How to read a peptide certificate of analysis (CoA). Version 1./us/academy/testing/how-to-read-a-coa/