What a certificate of analysis is, and is not
A certificate of analysis (COA) is a report issued by a laboratory that tested a specific sample. It states what was submitted, which methods were run, and what those methods measured. It describes one sample from one lot on one date. It is not a general product specification, not a statement about every vial ever sold under that name, and not evidence of any property the report does not list.
The most useful habit when reading a COA is to ask, for every line, which sample, which method, which date. If any of the three is missing, the line cannot be tied to the material a laboratory received. The sections below take each field in turn. Terms are defined in the certificate of analysis glossary.
Identity: how the main peak is identified
Identity answers whether the main peak is the compound named on the label. On the reports Arctic Lab Supply publishes, identity is confirmed by HPLC retention-time match (HPLC-RTM) against a reference standard: the sample's main peak is compared with a reference standard run under the same chromatographic conditions. Mass spectrometry is not part of these reports, so there is no observed-mass value to look for on them.
What it must say. The method used (for example HPLC-RTM), the reference standard the sample was matched against, and the result of that match under the stated conditions.
What a weak or missing entry looks like. "Identity: conforms" with no method and no reference. A retention-time match with no reference standard named. A formula or identity reference that does not match the one printed elsewhere on the page. Or no identity line at all, which means the purity figure describes a peak nobody identified.
Purity: HPLC area percent and the method line
A result such as "99.59% (HPLC)" means that, under the stated chromatographic conditions, the main peak accounted for that share of the total detected peak area. It is a relative measurement within that method. It does not by itself establish the identity of the main peak, the absence of substances the method cannot detect, water content, residual solvents, sterility, or endotoxin.
What it must say. The technique (HPLC, usually with a UV detector), the column and mobile phase or a reference to the laboratory's method, the detection wavelength, and the value in area percent. A chromatogram attached to the report lets the reader see the main peak and the minor peaks the percentage was calculated from; how to read an HPLC chromatogram covers that trace.
What a weak or missing entry looks like. A percentage with no method beside it. "Purity: 99%" with no decimal and no chromatogram. A figure of exactly 100%, which no chromatographic integration produces in practice. And a purity figure presented as if it answered the identity question.
Net peptide content versus gross weight
A vial labelled 5mg contains roughly 5mg of solid. That solid is peptide plus counterion plus residual water. Net peptide content is the line that quantifies how much of the solid is peptide at all.
What it must say. The measured figure, its unit (milligrams per vial, or a percentage of gross weight), and the method, such as amino acid analysis, nitrogen determination or quantitative absorbance. On the lots published here the figure is stated in milligrams per vial. Net peptide content: why the label weight is not the peptide weight explains the arithmetic.
What a weak or missing entry looks like. No net peptide line, which leaves the reader with only the label weight. A figure that equals the label weight exactly, which would mean zero counterion and zero water. A percentage with no statement of whether it is by weight or by peak area.
Appearance
Appearance is a visual description of the sample as received: form and colour, for example "white lyophilized powder" or, for a copper complex such as GHK-Cu, a blue to blue-violet solid.
What it must say. A physical form and a colour, as the laboratory observed them for that sample, and whether the sample met the specification if one exists.
What a weak or missing entry looks like. "Appearance: pass" with no description. A description that does not fit the compound.
Counterion and the TFA note
Peptides are purified by chromatography that uses an acid in the mobile phase, and the peptide comes out of that step paired with the acid's counterion. The two common forms are acetate and trifluoroacetate (TFA). The salt form affects the net peptide figure, because the counterion has mass, and residual trifluoroacetate is a known source of interference in certain downstream assays.
What it must say. The salt form of the material and, where the laboratory measured it, the residual TFA content with its unit and method.
What a weak or missing entry looks like. No mention of salt form on the report or the label. A "TFA-free" claim with no measurement behind it. A counterion named on the label that contradicts the one on the report.
Water content, when it is reported
Lyophilized solids hold residual water, and hygroscopic sequences gain more whenever a vial is exposed to air. Water content is measured directly (Karl Fischer analysis is the standard method) or inferred from the gap between gross weight and the sum of peptide and counterion. It is not on every report.
What it must say. If reported: the value as a percentage of gross weight, the method, and the date. If not reported: nothing, and the reader notes that net peptide content is then the only line that accounts for it.
What a weak or missing entry looks like. "Water: n/a" on a lyophilized peptide. A water figure that, added to the net peptide and counterion figures, exceeds the gross weight.
Issuing laboratory and verification route
A third-party report carries the laboratory's name, its certificate number, and a way to confirm that the number refers to this sample, lot and date. In-house testing, where the supplier grades its own material, does not offer that independence; see third-party versus in-house testing.
What it must say. Laboratory name and location, a certificate number, and a verification route hosted by the laboratory: a lookup page, a contact address, or both. Reports published on this site link to the testing laboratory's own verification page for the exact certificate number, on the portal at ils-lab.com.
What a weak or missing entry looks like. A laboratory name with no certificate number. A verification page hosted by the seller rather than the laboratory. A certificate number the laboratory cannot find.
Lot number and dates
The lot identifier ties the report to a specific production batch, and it is the field the receiving laboratory checks first: the lot on the report must be the lot printed on the vial. Dates put the analysis in order: when the sample was received, analysed, and reported.
What it must say. One lot identifier, matching the label character for character, and at least an analysis date; received and issued dates are better. Lot traceability: matching a vial to its record covers the receiving side of this check.
What a weak or missing entry looks like. No lot number. A lot number on the report that appears on no vial. One report presented for several lots or strengths. A blank date, or a date earlier than the lot's production.
Signature and authorization
A finished report is released by a named person at the laboratory, usually an analyst and a reviewer.
What it must say. The name and role of the person who authorized the report, a signature or electronic signature, and the release date.
What a weak or missing entry looks like. No signature block. A signature image identical, pixel for pixel, across reports from different dates. A signatory with no stated role.
Expiry or retest date
Some reports state a retest or expiry date, the point after which the laboratory no longer stands behind the result without re-analysis. Not every report carries this field, and its absence is not a defect in itself.
What it must say. If present: the date, the storage condition it assumes, and ideally the data that supports it. If absent: the analysis date is the only anchor, and the receiving laboratory applies its own retest policy. See storing lyophilized research materials.
What a weak or missing entry looks like. A retest date years out with no storage condition. An expiry on the label that is absent from the report, or the reverse.
Worked examples from published lots
Arctic Lab Supply publishes lot-matched third-party reports for its core products in the batch COA library. The table lists the fields shown on each lot's page on this site; identity on these reports is confirmed by HPLC retention-time match (HPLC-RTM) against a reference standard, and mass spectrometry is not part of them, so there is no observed-mass figure to look for.
| Product and lot | Purity (HPLC, area %) | Test date | Certificate number | Lot page |
|---|---|---|---|---|
| BPC-157 5mg, lot BCP-2502-B | 99.59% | Aug 25, 2026 | COA-2026-Q53ZYU | /coa/bpc-157-5mg/bcp-2502-b |
| GHK-Cu 50mg, lot GHK-2501-B | 99.03% | Aug 10, 2026 | COA-2026-8T-M1B | /coa/ghk-cu-50mg/ghk-2501-b |
| GLOW 70mg, lot GLOW-2502-B | 99.53% | Aug 25, 2026 | COA-2026-7J5N9U | /coa/glow-70mg/glow-2502-b |
| Melanotan I 10mg, lot MT1-2502-B | 99.83% | Aug 8, 2026 | COA-2026-XAJZYM | /coa/melanotan-1-10mg/mt1-2502-b |
| Melanotan II 10mg, lot MT2-2502-B | 98.07% | Aug 19, 2026 | COA-2026-TUFEKC | /coa/melanotan-ii-10mg/mt2-2502-b |
BPC-157 5mg, lot BCP-2502-B
The lot page for BPC-157 5mg lists 99.59% by HPLC, tested Aug 25, 2026, certificate COA-2026-Q53ZYU, with the PDF and the laboratory's verification link. The identity reference is CAS 137525-51-0, formula C62H98N16O22, theoretical mass 1419.5 g/mol; the lot report confirms identity by HPLC retention-time match against a reference standard and does not include mass spectrometry. Reported net peptide content is 5.27 mg against a 5mg label, which is the counterion-and-water arithmetic made concrete: the fill was set so that the peptide fraction meets the label.
GHK-Cu 50mg, lot GHK-2501-B
The lot page for GHK-Cu 50mg lists 99.03% by HPLC, tested Aug 10, 2026, certificate COA-2026-8T-M1B. The identity reference is CAS 49557-75-7, formula C14H24CuN6O4, theoretical mass 403.9 g/mol, which is the copper complex rather than the free tripeptide; a report for this material should make clear which of the two it describes. Reported net peptide content is 52.49 mg against a 50mg label. Because the compound contains a metal by design, the heavy-metals panel on the report carries more weight than usual. An earlier lot, GHK-2501-A, was reported at 99.285% by a different laboratory in Feb 2026; the GHK-Cu article explains why a quarter of a point between two laboratories is method variation, not a quality ranking.
Complete versus incomplete: a checklist
Use this table against any report, from any supplier.
| Field | Complete | Incomplete or weak |
|---|---|---|
| Sample identity | Name and labelled strength match the vial exactly | Name only, or a strength that differs from the label |
| Lot identifier | One lot, identical to the vial label | Missing, or one report covering several lots |
| Analysis date | Received, analysed and issued dates in order | No date, or a date that predates the lot |
| Identity | Method named, such as HPLC retention-time match (HPLC-RTM) against a stated reference standard | "Conforms" with no method or reference |
| Purity | HPLC area % with method conditions and a chromatogram | A percentage with no method, or exactly 100% |
| Net peptide content | Value, unit and method stated | Absent, or equal to the label weight |
| Appearance | Form and colour described | "Pass" with no description |
| Counterion | Salt form named; TFA measured where relevant | Not mentioned anywhere |
| Water content | Reported with method, or clearly not tested | "n/a" on a lyophilized solid |
| Issuing laboratory | Named, with certificate number and a laboratory-hosted verification route | Unnamed, or verifiable only through the seller |
| Authorization | Named signatory with role and release date | No signature block |
| Retest or expiry | Date with storage condition, or clearly absent | Date with no condition or supporting data |
Verifying the document with the issuing laboratory
Verification is the step that catches a copied or edited document. Every published report on this site links directly to the testing laboratory's verification page for its certificate number: open the link, compare sample identity, strength, lot, date and result with the PDF, and record the outcome in the receiving log. The full procedure, including what a failed lookup means, is in how to verify a certificate of analysis with the issuing laboratory.
Frequently asked questions
What is the difference between purity and identity on a COA?
Purity is the share of total detected peak area attributable to the main peak under the stated HPLC method. Identity is whether that main peak is the named compound. On the reports Arctic Lab Supply publishes, identity is confirmed by HPLC retention-time match (HPLC-RTM) against a reference standard; mass spectrometry is not part of these reports. A high purity figure with no identity line describes a peak nobody identified.
Why is net peptide content different from the label weight?
The label weight is the mass of solid in the vial: peptide plus counterion plus residual water. Net peptide content is the measured peptide fraction. On the published BPC-157 lot BCP-2502-B it is 5.27 mg against a 5mg label; on GHK-Cu lot GHK-2501-B it is 52.49 mg against 50mg.
How is identity confirmed on these reports?
By HPLC retention-time match (HPLC-RTM): the sample's main peak is compared against a reference standard run under the same chromatographic conditions. Mass spectrometry is not part of these reports, so there is no observed-mass value to check.
Does a 99% purity result mean the vial contains what the label says?
No. It means 99% of what the HPLC method detected was one peak. Whether that peak is the named compound is the identity question, and how much of the vial's mass is peptide is the net peptide question.
How do I verify a certificate with the laboratory?
Find the certificate number on the report, open the issuing laboratory's verification page, and compare sample identity, strength, lot, date and result against the PDF. Published lots on this site link straight to that page; the procedure is in the verification guide.
What if the report has no lot number or no date?
Then it cannot be tied to the vial in front of you. Treat it as a general document rather than a record of the material received, and ask the supplier for the lot-specific report.