What is a COA?
COA stands for certificate of analysis: a document a laboratory issues for one specific lot, or batch, of a material. It names the material and the lot, lists each test with its method, its acceptance criterion (specification) and the result, and records who ran the tests and when.
Quality attributes, procedures and acceptance criteria are the same three parts that drug specifications are built from (Vergote et al., 2009). For a research peptide, the certificate ties a vial to laboratory data on what it contains. The plural is COAs, often written COA's. Outside chemistry, COA can mean certificate of authenticity; on a peptide supplier's site it means certificate of analysis.
What appears on a certificate of analysis
- Product identity: compound name, often the sequence or formula, and the labeled amount.
- Lot or batch number, linking the certificate to the vials from that run.
- Laboratory name and contact details, a certificate number and a signature.
- Dates the sample was received, analyzed and reported.
- For each test, the method, the specification and the result, with a verdict where the lab states one.
- Where offered, a verification code or QR link to the same report on the lab's own system.
Peptide testing on a certificate answers four questions: is it the right molecule, how pure is it, how much is there, and is it contaminated?
What third-party testing means
Third-party testing means a laboratory independent of the manufacturer and the seller did the analysis. ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories, is the standard testing laboratories can be accredited against. Accreditation covers a listed scope of methods, so the useful check is whether the tests on a certificate fall within the named lab's scope.
Identity: is it the right molecule?
Mass spectrometry answers this most directly: it measures the molecular mass, which is compared with the mass calculated from the sequence. Electrospray ionization made this practical for large biomolecules by producing intact, multiply charged ions from solution (Fenn et al., 1989).
Liquid chromatography with high-resolution mass spectrometry can also confirm the sequence and quantify impurities even when they co-elute with the main peak (Zeng et al., 2015), and a single-quadrupole mass detector added to routine HPLC identifies the peptide and its impurities (Stalmans et al., 2016). Identity by HPLC alone rests on retention time matched to a reference standard, which on its own cannot tell apart compounds that elute together.
Purity: what an HPLC percentage means
Peptide purity is routinely measured by reversed-phase HPLC with ultraviolet detection, and the result depends on the chromatographic system, including column, acidic modifier and temperature (Stalmans et al., 2016). Each separated component appears as a peak, and purity is the main peak's share of the total peak area: 99% means the other detected peaks add up to 1% of the area. Those peaks can include related peptides such as deletion and insertion sequences, diastereomers, oxidized forms, dimers and degradation products, and they can distort early functional studies (D'Hondt et al., 2014).
The percentage does not mean that 99% of the powder's mass is peptide. Water, counter-ions and salts are not counted, and anything that co-elutes with the main peak is counted as peptide. Peptides purified by HPLC are often trifluoroacetate (TFA) salts, and in osteoblast cultures the TFA salts of amylin and calcitonin masked a proliferative effect that the hydrochloride salts showed (Cornish et al., 1999). In one analysis, synthetic peptides above 99% purity by reversed-phase HPLC had peptide contents of about 62 to 88% (Wang et al., 2012).
Content: how much peptide is in the vial
Quantity is a separate result, given either as the measured amount in the vial beside the labeled amount or as peptide content, the share of the powder's mass that is peptide. Labs determine it by quantitative HPLC against a reference standard, by amino acid analysis, or by other methods (Cueto Díaz et al., 2014). Many certificates report quantity without a pass or fail limit. For molar calculations, use the measured amount and the formula or salt form the certificate states.
Endotoxin, sterility and heavy metals
Endotoxin testing. The Limulus amebocyte lysate (LAL) test uses a horseshoe crab blood cell lysate that gels on contact with Gram-negative bacterial endotoxin through a protease cascade; a separate (1,3)-beta-D-glucan pathway can also produce a gel (Iwanaga, 2007). USP <85>, Bacterial Endotoxins Test, describes gel-clot, turbidimetric and chromogenic versions, reported in endotoxin units (EU) against a limit. Endotoxin matters in cell work: in one study, a recombinant protein's apparent ability to make macrophages release TNF-alpha was due entirely to contaminating endotoxin (Gao and Tsan, 2003).
Sterility testing and USP <71>. USP <71>, Sterility Tests, is the compendial growth-based method: the sample is membrane-filtered or added directly to two culture media, incubated for at least 14 days and inspected for growth. USP <1223> covers validation of alternative methods such as automated culture and PCR. In a challenge study with 118 organisms, detection differed between the compendial method and two automated systems (England et al., 2019). A PCR result and a USP <71> result come from different tests, so check which one a certificate names.
Heavy metals. Elemental impurities such as lead, arsenic, cadmium and mercury are measured by ICP-MS or ICP-OES under USP <233> and compared with limits such as USP <232> or ICH Q3D.
How to match a certificate to your vial
- Find the lot or batch number on the vial label and open the certificate for that exact lot.
- Check that the compound name and labeled amount also match: a lot code alone may not be unique across a catalog.
- Where the lab offers a verification code or QR link, use it to open the report on the lab's own system.
Red flags on a peptide COA
- No lot number, or a lot that does not match the vial.
- No laboratory name, contact details or test dates.
- A compound, sequence or molecular weight that does not match the product.
- Results with no method or no specification.
- Signs of editing: inconsistent fonts or alignment, one certificate number reused for different products or lots, or a verification code that does not open the same report at the lab.
How Disguised Alpha publishes certificates
The COA portal lists published certificates by product and can be searched by compound name or by the batch number printed on a vial; each card opens the lab's certificate and links to the product page. Each product page shows the batch assigned to the selected size and an "Every batch on record" list grouped by testing laboratory. Batch pages, such as the one for L-Glutathione lot GLU03, list the product, lot, certificate number, laboratory, test date and labeled amount, each test with its method, result and specification where printed, the lab's verdict and the original report.
The portal states that ILS Laboratories is ISO/IEC 17025 accredited and that ILS reports carry a QR code and access code for checking a report with the lab, and notes that most certificates report sterility by PCR and a few by USP growth-based methods. For older lots or full multi-page reports, it asks researchers to contact support with the order number.
Key sources
- Vergote V, et al. "Quality specifications for peptide drugs: a regulatory-pharmaceutical approach." J Pept Sci. 2009. PMID 19750489. DOI 10.1002/psc.1167. Review of peptide specifications.
- D'Hondt M, et al. "Related impurities in peptide medicines." J Pharm Biomed Anal. 2014. PMID 25044089. DOI 10.1016/j.jpba.2014.06.012. Review of peptide impurities.
- Stalmans S, et al. "Quality control of cationic cell-penetrating peptides." J Pharm Biomed Anal. 2016. PMID 26397208. DOI 10.1016/j.jpba.2015.09.011. HPLC and mass detection in peptide QC.
- Zeng K, et al. "Liquid Chromatography-High Resolution Mass Spectrometry for Peptide Drug Quality Control." AAPS J. 2015. PMID 25716148. DOI 10.1208/s12248-015-9730-z. Identity and co-eluting impurities.
- Wang X, et al. "[Accurate quantification of synthetic peptides by amino acid-stable isotope dilution mass spectrometry]." Se Pu. 2012. PMID 22715687. DOI 10.3724/sp.j.1123.2012.01035. In Chinese, English abstract: purity versus content.
- Cornish J, et al. "Trifluoroacetate, a contaminant in purified proteins, inhibits proliferation of osteoblasts and chondrocytes." Am J Physiol. 1999. PMID 10567002. DOI 10.1152/ajpendo.1999.277.5.E779. Counter-ion effects in cell culture.
- Standards named on this page: USP <71> Sterility Tests; USP <85> Bacterial Endotoxins Test; USP <232> and <233> Elemental Impurities; USP <1223> Validation of Alternative Microbiological Methods; ISO/IEC 17025.
Frequently asked questions
What does COA mean?
Certificate of analysis: a laboratory's report on one lot of a material, listing each test, its method, its specification and the result. COAs, or COA's, is the plural.
Is HPLC purity the same as peptide content?
No. HPLC purity is the main peak's share of the detected peak area; peptide content is the share of the powder's mass that is peptide, which also reflects water and counter-ions (Wang et al., 2012).
What is USP 71?
USP <71> is the United States Pharmacopeia chapter on sterility tests, a growth-based method with at least 14 days of incubation. A PCR sterility result comes from a different method.
Related links
- COA portal: published certificates, by lot
- Lab testing overview
- HPLC purity testing
- Identity testing
- Endotoxin testing
- Sterility testing
- Research hub
Disguised Alpha products are for research use only. They have not been evaluated for safety or effectiveness in humans. Not for human consumption. All products are intended for laboratory research purposes only.