Certificate of analysis is the document that tells you what is actually in the vial. For research peptides sold as research-use-only (RUO) reagents, the COA is the single most important quality document a supplier provides [9]. Knowing how to read one is one of the few skills that separates a researcher buying reliable reagents from a researcher buying a label.
This guide walks through every section of a credible peptide COA, explains what each test result means in plain English, and lists the red flags that signal a COA is unreliable. It is written for laboratory researchers buying peptides in 2026, with examples drawn from current testing practices at ISO/IEC 17025-accredited laboratories [5] and the major independent peptide testing services researchers actually use [10].
Before You Read Your First COA
- A peptide COA is a batch-specific laboratory report that documents the identity, purity, and contaminant profile of a specific lot of compound. It is not a marketing document.
- A credible COA answers four questions: What is the compound? (mass spectrometry), How pure is it? (HPLC), How much actual peptide is in the powder? (net peptide content), and Is it safe for cell-based work? (endotoxin and contaminant testing).
- The minimum acceptable HPLC purity for most research applications is ≥99%.
- Mass spectrometry confirms identity by measuring molecular weight. Observed mass should match theoretical mass within ±1 Dalton.
- The batch number on the COA must match the lot number printed on the vial you received. If they do not match, the COA does not apply to your material.
- Third-party testing by an ISO/IEC 17025-accredited laboratory is the strongest documentation standard available; in-house COAs without independent verification carry significantly less weight.
- Endotoxin testing by the LAL assay is essential for any peptide used in cell culture, immune cell work, or inflammation research. Acceptable limits for research-grade peptides are typically <0.5 EU/mg.
What is a Certificate of Analysis for a Peptide?
A Certificate of Analysis is a batch-specific laboratory report. It documents the analytical testing performed on a defined lot of a research peptide and reports the results in a standard format that researchers across institutions can read and compare [6, 9].
The COA is not a specification sheet, not a marketing document, and not a generic template applied to every batch. A real COA records what was tested, what method was used, when the test was performed, where the test was performed, and what the result was. It is the primary quality record for the vial in your hand and the document a competent researcher reviews before using a new reagent.
Because research peptides are sold as research-use-only material rather than approved pharmaceutical products, the COA is the only systematic quality assurance you have. The burden of verification sits with the buyer. This is one of the reasons documentation matters so much in peptide sourcing: without a COA, you have no independent record of what was synthesized or what was shipped.
The Four Questions a Credible COA Must Answer
Every COA worth reading answers four core questions:
- Identity – Is this the correct compound? (Mass spectrometry confirms molecular weight matches the expected molecule.)
- Purity – What percentage of the sample is the target peptide versus impurities? (HPLC measures purity.)
- Content – How much actual peptide is in the powder versus water, salts, and counterions? (Net peptide content reports the true mass of peptide per gram of powder.)
- Safety – Is the peptide free of contaminants that would interfere with research? (Endotoxin, heavy metals, and residual solvent testing.)
A COA that cannot answer all four is incomplete. The most common gap in commercial RUO COAs is the absence of endotoxin testing, which matters for cell-based research even when HPLC and mass spec results look perfect.
Section 1: Header and Identification
The header section establishes what the document is and what it applies to. Look for:
- Compound name and synonyms. The peptide name (e.g., Semaglutide, BPC-157, GHK-Cu) plus any synonyms, code names, or CAS numbers. These should match the product page and the vial label exactly.
- Batch or lot number. This is the most important traceability element on the entire document. The lot number must match the vial in your hand. If it does not match, the COA does not apply to your material, regardless of what the other test results say.
- Date of analysis. Recent testing is preferred. COAs older than 12 months on a peptide you just received warrant a question to the supplier about why the testing is so old.
- Manufacturing date. Useful for tracking peptide stability against the storage window.
- Testing laboratory name and address. A real, independent third-party laboratory should be named. If the COA is internally generated by the supplier, this is documented; either is acceptable, but third-party testing carries more weight.
- Supplier name and address. The company supplying the peptide should be clearly identified.
A COA missing any of these basic identifiers is a structural problem. A credible report identifies who tested what, when, and where, without ambiguity [6, 9]. Researchers comparing suppliers should also evaluate broader supplier quality signals beyond the COA itself; for a wider view of how documentation reflects supplier rigor, see Lab Credibility and COA Authority.
Section 2: HPLC Purity Analysis
High-performance liquid chromatography (HPLC) is the standard method for measuring peptide purity. The HPLC section of a COA tells you what fraction of the sample is the target peptide versus everything else.
How HPLC Works (the short version)
In short: HPLC separates the compounds in a sample by their physical and chemical properties, so each one elutes at its own retention time and can be measured individually — for peptides, typically reverse-phase HPLC on a C18 column with UV detection at 214–220 nm. We cover the full mechanics and trade-offs in our dedicated HPLC vs. Mass Spectrometry guide; here the focus is on what the purity number on your COA actually tells you.
What to Look For in the HPLC Section
- Purity percentage. This is the headline number. For research-grade peptides, ≥99% is the accepted standard, including for precision assays [9]. Peptides below 95% contain enough impurity to confound dose-response curves and cell-based assay results.
- The chromatogram image. A credible COA includes the actual HPLC chromatogram, not just a single purity number. A clean chromatogram shows one dominant peak (the target peptide) with only small satellite peaks. Multiple significant peaks indicate impurities or incomplete synthesis.
- Retention time of the main peak. The retention time should match the expected retention time for the target peptide under the stated method conditions.
- Method details. Column type, mobile phase composition, flow rate, gradient program, and detection wavelength. A COA that does not state the method conditions limits your ability to interpret or independently reproduce the analysis.
- Peak area percentages. For each significant peak, the area under the curve as a percentage of total peak area.
Limits of HPLC Purity Alone
A purity number alone tells you how much of the sample is one compound but cannot prove which compound that is. A different molecule with a similar retention time could co-elute and produce the same purity number. This is why HPLC purity must be combined with mass spectrometry identity confirmation, covered in the next section.
A second limitation is that HPLC measures peptide-related substances against each other. A peptide can report 99% pure by HPLC and still contain significant water, salts, or counterions that are not detected at the UV wavelength used. This is what the net peptide content section addresses.
Section 3: Mass Spectrometry Identity Confirmation
Mass spectrometry (MS, often reported as LC-MS in research peptide COAs) confirms the identity of the peptide by measuring its molecular weight. While HPLC tells you how pure the sample is, mass spectrometry tells you what the sample actually is.
How Mass Spectrometry Works (the short version)
In short: the instrument ionizes peptide molecules and sorts them by mass-to-charge ratio (m/z), giving a direct, high-precision molecular-weight readout (typically ±0.1 Da for small to mid-size peptides). For how MS compares with HPLC and when each test matters, see the HPLC vs. Mass Spectrometry guide; on the COA, what matters is whether the measured mass matches the theoretical mass.
What to Look For in the MS Section
- Theoretical molecular weight. The expected mass calculated from the peptide sequence and any modifications (amidation, acetylation, fatty acid side chains, disulfide bonds).
- Observed molecular weight. The mass measured by the instrument.
- Acceptable variance. Differences within ±1 Dalton are normal due to instrument calibration and isotope distribution. Deviations greater than 2 Daltons warrant investigation [9]. A 4 Dalton difference, for example, can indicate an oxidation, a missing residue, or an unrelated compound.
- Ion form. Mass spectra report the molecular ion in different charge states. [M+H]⁺ is the singly protonated form. [M+2H]²⁺ is the doubly charged form, which appears at half the actual molecular weight, common for larger peptides. The COA should specify which ion form is being reported.
Limits of Mass Spectrometry Alone
Mass spectrometry confirms molecular weight but not sequence. Two peptides with the same amino acids in different orders have the same molecular weight, and standard MS cannot distinguish between them. For absolute sequence confirmation, tandem mass spectrometry (MS/MS) with fragmentation is required; this is not standard in commercial research peptide COAs but is available on request from most third-party laboratories.
For practical research purposes, a peptide that passes HPLC purity (correct retention time) and mass spectrometry (correct molecular weight) is considered identity-confirmed. The combination is the standard, and a COA that only reports one of the two is incomplete. This combination becomes especially important when comparing structurally distinct peptides whose mechanisms depend heavily on their exact sequence; for a deeper look at why molecular size and sequence drive completely different pharmacology, see Why BPC-157 Behaves Nothing Like Thymosin Beta-4.
Section 4: Net Peptide Content
Net peptide content is the percentage of the lyophilized powder that is actually peptide, as opposed to water, salts, counterions, and other non-peptide components. It is one of the most commonly misunderstood parameters on a peptide COA.
Why Is Net Peptide Content Important
A peptide synthesized by solid-phase peptide synthesis (SPPS) using TFA in the purification step is typically supplied as a TFA salt. The TFA counterion adds mass to the powder that is not the peptide itself [7]. Other contributors to non-peptide mass include residual water (lyophilized peptides are hygroscopic and absorb water from the air), residual acetate or HCl counterions in non-TFA preparations, and any residual solvents from synthesis.
For accurate dosing in cellular assays or animal work, the researcher needs to know the actual mass of peptide per gram of powder, not just the gross weight of the vial.
How Net Peptide Content Is Calculated
The theoretical net peptide content can be estimated from the peptide molecular weight and the number of counterions required to neutralize the charged residues [7]:
For a peptide with TFA salt (MW of TFA = 114) and two TFA counterions per molecule (one free N-terminal amine plus one Lys side chain):
Net peptide content = MW peptide / (MW peptide + (2 × 114))
So a 1,000 Da peptide with two TFA counterions has a theoretical net peptide content of approximately 81%.
In practice, the measured net peptide content is determined by amino acid analysis (AAA) or quantitative nitrogen analysis, and reported on the COA as a percentage. For TFA-salt peptides, typical net peptide content is 70-90% depending on the number of basic residues. For acetate-salt peptides, net peptide content is generally higher because the acetate counterion is smaller.
What This Means for Dosing
If a researcher dissolves 10 mg of powder from a vial with 80% net peptide content, the actual peptide mass is 8 mg, not 10 mg. For receptor-binding assays, IC₅₀ determinations, and any quantitative work, this distinction matters. A COA that reports net peptide content alongside HPLC purity provides more complete documentation than one that reports purity alone.
The counterion choice also matters for cell-based work. TFA at high concentrations has been reported to affect certain G-protein-coupled receptor assays at supra-physiological levels, which is why some laboratories specifically request acetate-salt or HCl-salt peptides for sensitive applications. The full distinction between research peptides and other biological reagents (including how net peptide content compares with concentration metrics for recombinant proteins) is covered in Synthetic Peptides vs. Biological Reagents: Lab Guide.
Section 5: Endotoxin Testing
Bacterial endotoxins (lipopolysaccharides, or LPS) are byproducts of gram-negative bacterial contamination during synthesis, purification, or handling [8]. They are invisible to HPLC and mass spectrometry and can be present in a peptide that passes all purity and identity tests.
Why Are Endotoxins Important for Research
In cell culture and in vitro research systems, endotoxins trigger inflammatory signaling cascades at concentrations as low as 0.1 ng/mL [1, 8]. LPS activates Toll-like receptor 4 (TLR4), which is expressed on macrophages, dendritic cells, epithelial cells, endothelial cells, and many cell lines commonly used in research. If your work involves immune cells, macrophage activation, cytokine release, NF-κB pathway studies, or any inflammation-sensitive assay, endotoxin contamination is a critical confound.
A peptide with high endotoxin content can produce inflammatory responses in cell models that look like a peptide-driven effect but are actually the LPS contamination. This is one of the most common silent failures in cell-based peptide research, and it is the kind of error that contributes to the broader reproducibility problem in published research. For a broader discussion of how trace contamination drives reproducibility issues across reagent classes, see Endotoxin Contamination in Research Peptides and The Reproducibility Crisis in Research.
How Endotoxin Testing Works
The standard method is the Limulus Amebocyte Lysate (LAL) assay, which uses a reagent derived from horseshoe crab blood cells that reacts specifically with bacterial endotoxins [8]. The result is reported in Endotoxin Units per milligram of peptide (EU/mg). Modern alternatives include the recombinant Factor C (rFC) assay, an animal-free method that reports in the same units.
What to Look For
- Endotoxin level. Reported in EU/mg of peptide.
- Method used. LAL or rFC.
- Specification limit. A defined threshold the lot must meet to pass.
Acceptable Endotoxin Limits for Research Peptides
For research-grade peptides used in standard cell culture, in vitro receptor assays, and most preclinical work, the typical acceptable limit is <0.5 EU/mg [8]. Some testing laboratories specify ≤0.01 EU/μg (equivalent to ≤10 EU/mg) as the upper limit for routine research grade. For immune cell research, primary macrophage culture, and inflammation studies, low-endotoxin specifications of <0.1 EU/mg are preferred. For comparison, the FDA limit for injectable pharmaceutical peptides like tirzepatide is <10 EU/mg of active pharmaceutical ingredient.
Endotoxin testing is not always included on every commercial research peptide COA, particularly for lower-cost RUO suppliers. If your application is endotoxin-sensitive, request endotoxin documentation specifically before ordering, and treat the absence of endotoxin data as a meaningful gap rather than a minor omission.
Section 6: Heavy Metals and Residual Solvents
Two further classes of contaminant are tested on more complete COAs:
Heavy metals. Trace inorganic elements that can enter the product during synthesis (often from palladium catalysts used in some coupling reactions), purification, or handling. Standard panels screen for lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As). The standard method is inductively coupled plasma mass spectrometry (ICP-MS), which detects metals at parts-per-billion levels. The USP General Chapter ⟨232⟩ provides the reference limits for pharmaceutical-grade products; research-grade peptides should be at or below those limits [2].
Residual solvents. Organic solvents used during synthesis and purification (most often acetonitrile, dichloromethane, methanol, and TFA) should be removed during lyophilization but may be present as trace residuals. The standard method is gas chromatography (GC) or headspace GC-MS following the ICH Q3C guidance [3, 4]. TFA, the most clinically relevant residual for SPPS peptides, is typically reported as a percentage; research-grade specifications cluster around <0.1% TFA residual.
These tests are more common on premium-grade and pharmaceutical-grade COAs than on basic RUO documentation. Their presence on a COA is a quality signal; their absence is acceptable for most research applications but worth knowing if your work is sensitive to trace metals or solvents.
Section 7: Physical Description and Appearance
A short but important section describing the visual characteristics of the lyophilized product:
- Appearance. Typically described as “white to off-white lyophilized powder” or “white to slightly cream lyophilized powder.”
- Form. Lyophilized, crystalline, or solution.
- Solubility observations. Whether the peptide dissolves cleanly in standard solvents such as sterile water or bacteriostatic water.
If the vial you received looks dramatically different from the stated appearance (yellow, brown, wet, oily, crystalline when described as amorphous), this is a quality flag worth investigating with the supplier before use. Minor variations in shade (white to slightly cream) are normal and not cause for concern.
Section 8: Storage and Handling
Standard storage recommendations for lyophilized peptides are -20 °C (desiccated, protected from light), with -80 °C preferred for long-term storage of sensitive peptides such as disulfide-bonded compounds or those prone to oxidation. After reconstitution, peptides should be stored at 2 to 8 °C for short-term use or aliquoted and frozen at -20 °C or below.
The COA should state the recommended storage conditions and any specific cautions (avoid repeated freeze-thaw cycles, protect from light, store under inert atmosphere). Storage information is rarely a quality differentiator between suppliers, but it should match standard peptide handling guidance for the compound class.
Quick Verification Checklist
Before using a new batch of research peptide, walk through this checklist:
- The lot number on the vial matches the lot number on the COA.
- The compound name and CAS number on the COA match the product page and the vial label.
- The COA includes both HPLC purity (≥99% on every batch) and mass spectrometry identity confirmation.
- The HPLC chromatogram shows a single dominant peak (if included on the COA).
- The mass spectrometry section reports both theoretical and observed molecular weight, with the difference within ±1 Dalton.
- The COA names the testing laboratory and is dated within the last 12 months.
- If your application is endotoxin-sensitive, the COA includes endotoxin testing data within acceptable limits.
- The physical appearance of the powder matches the description on the COA.
- The COA is filed with your research records alongside the batch number for traceability.
A peptide that passes this checklist is ready for laboratory use. A peptide that fails on any single item warrants a question to the supplier before use.
Red Flags: Signs a COA Is Unreliable
Not every document presented as a COA is a credible quality record. Watch for:
- Generic or template COAs. A COA that looks identical across multiple lots, with the same retention time, the same purity number, the same chromatogram pattern, is a generic template rather than a real per-batch report. Real testing produces minor lot-to-lot variation.
- Missing batch number or batch mismatch. A COA without a lot number, or with a lot number that does not match your vial, is not documentation for your material. It tells you nothing about what you actually received.
- No testing laboratory named. A COA that does not identify the laboratory that performed the analysis cannot be independently verified [10]. The lab name should be explicit; ideally, you should be able to find that laboratory through an independent search.
- Purity stated without method. A COA that lists “purity 99%” without stating the method (HPLC, with column type and gradient) provides no analytical basis for the number. Some lower-quality suppliers report purity by thin-layer chromatography (TLC) or “by weight,” methods that are far less sensitive and precise than HPLC.
- HPLC without mass spectrometry. HPLC purity alone does not confirm identity. A complete COA includes both. If only one is provided, request the other before relying on the document.
- No chromatogram image. Many credible COAs include the chromatogram image so the researcher can visually verify the purity number against the actual peak pattern. A purity percentage with no underlying chromatogram is less informative; if your supplier does not include the chromatogram by default, ask for it on first order from a new vendor.
- Old test dates on recent inventory. A COA dated 18 months ago on a peptide you just received raises a question about why the testing is so old relative to the shipment date. Stability of lyophilized peptides at -20 °C is generally good, but the COA should be reasonably current.
- Internal supplier testing with no third-party verification. In-house COAs from suppliers without independent verification have no external accountability for the reported numbers. They are not automatically invalid, but they carry less weight than third-party documentation from an ISO/IEC 17025-accredited laboratory [5].
- No raw data behind the report. The strongest documentation chains include raw chromatograms, raw mass spectra, and method files that can be independently reviewed. A summary PDF without underlying raw data is the lower end of acceptable documentation [10].
- Refusal to answer questions. A supplier that cannot or will not answer specific questions about the COA (which laboratory tested the sample, when, with what method) is providing a paper document without a credible chain of custody behind it.
What ISO/IEC 17025 Accreditation Means
ISO/IEC 17025:2017 is the international standard for testing and calibration laboratory competence [5]. Accreditation under this standard means an external accreditation body has formally assessed the laboratory’s methods, documentation, staff training, instrument calibration, and quality systems and confirmed they meet the international standard.
ISO 17025-accredited results are accepted by regulators (FDA, EMA, Health Canada), pharmaceutical purchasers, and court systems for evidentiary purposes [5]. For research peptide work, ISO 17025 documentation is the strongest credibility signal a COA can carry.
A practical reality of the research peptide market is that most independent peptide testing services widely cited in the community (including Janoshik Analytical in Prague, the most commonly referenced lab in vendor COAs) do not currently hold ISO/IEC 17025 accreditation for peptide assays specifically [10]. Their results are widely trusted in the research community, but they would not be accepted for regulatory submissions. Researchers who need accreditation-grade documentation should source from suppliers using ISO/IEC 17025-accredited testing laboratories.
For most preclinical and in vitro research, a third-party COA from a reputable laboratory (accredited or not) is sufficient documentation. For pharmaceutical, clinical, or regulatory-track work, ISO 17025-accredited testing is the standard.
How COAs Connect to Research Reproducibility
Reagent quality is one of the central factors in the broader reproducibility problem documented across biological research over the last decade. A research study using a peptide of unknown purity, unknown counterion content, and unknown endotoxin load cannot be reliably reproduced by another laboratory using a different lot, even when the published methods are identical. COA documentation is the mechanism by which lot-to-lot consistency is established and verified, and reagent traceability is what allows other research groups to source comparable material when replicating published work.
In practice, this means:
- Citing the supplier, lot number, and COA reference in published methods sections improves reproducibility.
- Keeping the COA filed alongside the experimental records for each lot used in a study is a basic good-practice habit.
- Storing the COA digitally with the lot number searchable allows years-later verification when reviewers or co-authors ask about reagent provenance.
Frequently Asked Questions About Peptide COAs
What purity should a research peptide COA show?
For most research applications, ≥99% HPLC purity is the accepted research-grade standard [9]. For precision assays, comparative pharmacology, and structure-activity work, ≥99% is preferred. Peptides below 95% contain enough impurity that experimental results can be confounded by truncated sequences, deletion peptides, or oxidation products.
Should a peptide COA include both HPLC and mass spectrometry?
Yes. HPLC measures purity but cannot confirm identity. Mass spectrometry measures molecular weight to confirm identity but cannot measure purity. A complete COA includes both. If a supplier provides only one, request the other before use.
What is the difference between HPLC purity and net peptide content?
HPLC purity measures the percentage of the sample that is the target peptide versus other peptide-related impurities (deletion sequences, oxidized residues, byproducts). Net peptide content measures the percentage of the powder that is peptide at all, versus water, salts, and counterions [7]. A peptide can be 99% pure by HPLC but only 80% net peptide content because of TFA salt and residual water. Both numbers matter for accurate dosing in quantitative work.
What endotoxin level is acceptable for research peptides?
For routine research use in cell culture, in vitro receptor assays, and standard preclinical work, the typical acceptable limit is <0.5 EU/mg [8]. For immune cell research, primary macrophage culture, or inflammation studies, <0.1 EU/mg is preferred. For comparison, FDA limits for injectable pharmaceutical peptides are <10 EU/mg of active pharmaceutical ingredient.
Does the batch number on the vial really need to match the COA?
Yes. The batch number is the traceability link between the document and the physical vial. If they do not match, the COA describes a different lot of material and does not apply to what you received. This is the single most common COA verification step and the easiest to skip.
What if my mass spectrometry result shows half the expected molecular weight?
This typically indicates a doubly-charged ion ([M+2H]²⁺). In electrospray ionization, peptides can acquire multiple protons and appear at m/z values that are fractions of the actual molecular weight. The COA should specify which ion form is reported. For peptides above ~2,000 Da, doubly and triply charged ions are common; check the reported m/z value against (MW + 2H)/2 or (MW + 3H)/3 rather than the molecular ion.
How long is a COA valid?
For properly stored lyophilized peptides (frozen, desiccated, protected from light), the analytical data remains valid for the duration of the labeled storage window, typically 1 to 2 years from synthesis. After reconstitution, the analytical data on the COA describes the lyophilized powder, not the solution; reconstituted peptides should be used within their in-use stability window (typically 2 to 4 weeks at 2 to 8 °C) and may not match the original COA specifications after extended storage.
Is a COA from the supplier as credible as a third-party COA?
A third-party COA from an independent laboratory carries more weight because it removes the conflict of interest inherent in self-testing [5, 10]. In-house supplier COAs are not automatically invalid, but they depend on the supplier’s quality systems and have less external accountability. For most research applications, a credible third-party COA from a recognized laboratory is the practical standard. For regulatory or clinical-track work, ISO/IEC 17025-accredited third-party testing is required.
What does a third-party testing laboratory actually do?
A third-party peptide testing laboratory receives a sample (typically 1-5 mg of lyophilized powder), runs HPLC purity analysis and mass spectrometry identity confirmation on the sample, and issues a report documenting the methods and results. The report is the COA. Independent laboratories cited in the research community include Janoshik Analytical (Prague, Czech Republic), Testides (Canada), and a number of US-based and EU-based testing services with varying accreditation status and test menus [10].
Can a COA be faked?
Yes. Fake COAs exist in the research peptide market, typically generated by copying real templates and substituting different batch numbers or purity figures. Defenses against fake COAs include: verifying the lot number on the vial matches the COA; calling or emailing the named laboratory to verify the report number exists in their system; looking for QR codes or unique verification IDs that link to a public verification page; and checking for formatting consistency (real COAs have lab letterhead, authorized signatures, and detailed methodology). A COA that cannot be independently verified should be treated with caution.
What should I do if a new batch fails any COA criterion?
Stop using the lot for any experimental work and contact the supplier. A reputable supplier will investigate the discrepancy, provide replacement material, or refund the order depending on the issue. A supplier that cannot or will not investigate a COA inconsistency is providing the answer you need about the documentation chain behind their products.
Putting It All Together
A peptide Certificate of Analysis is the single most important document in research peptide quality verification. A complete COA includes HPLC purity ≥99%, mass spectrometry identity confirmation within ±1 Dalton of theoretical molecular weight, net peptide content data, endotoxin testing (for cell-based applications), and clear batch traceability between the document and the vial.
A credible COA names the testing laboratory, dates the analysis recently, includes the actual chromatogram and mass spectrum where possible, and links to a system the researcher can verify independently. The strongest documentation chains use ISO/IEC 17025-accredited testing laboratories [5]; the practical research peptide market uses a mix of accredited and non-accredited third-party services, with the latter widely trusted for in vitro and preclinical work even though they would not be accepted for regulatory submissions [10].
For Koi Peptides US, every lot is released against independent ISO/IEC 17025-accredited testing for HPLC purity, LC-MS identity, endotoxin (LPS), water content, and TFA residual. The lot ID printed on each vial corresponds to a publicly hosted COA, so researchers can verify documentation before they order and after delivery. This is the documentation standard the rest of this guide describes; it is the documentation researchers should expect from any peptide supplier they buy from in 2026.
References
- United States Pharmacopeia. (2024). General Chapter ⟨1043⟩ Ancillary Materials for Cell, Gene, and Tissue-Engineered Products. USP-NF.
- United States Pharmacopeia. (2024). General Chapter ⟨232⟩ Elemental Impurities – Limits. USP-NF.
- United States Pharmacopeia. (2024). General Chapter ⟨467⟩ Residual Solvents. USP-NF.
- International Council for Harmonisation. (2021). ICH Q3C(R8) Guideline on Residual Solvents. https://www.ich.org/page/quality-guidelines
- International Organization for Standardization. (2017). ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories. https://www.iso.org/standard/66912.html
- Bachem. (2025). Quality Control of Amino Acids and Peptides: A Guide. https://www.bachem.com/knowledge-center/peptide-quality-control/
- AmbioPharm. (2022). How is Theoretical Net Peptide Content Calculated? https://www.ambiopharm.com/faq/how-is-theoretical-net-peptide-content-calculated/
- Novum Pharmaceutical Research Services. (2024). Limulus Amebocyte Lysate (LAL) assay for bacterial endotoxin testing. USP General Chapter ⟨85⟩ Bacterial Endotoxins Test.
- Apex Laboratory. (2026). How to Read a Peptide COA (Certificate of Analysis). https://apexlaboratory.org/how-to-read-coa-peptide/
- Janoshik Analytical. (2026). Independent Third-Party Peptide Testing: HPLC Purity, Mass-Spectrometry Identity, and Endotoxin Analysis. https://janoshik.com/
