How to read a peptide COA and SDS for cosmetic use

Two documents travel with every lot of peptide raw material: a certificate of analysis for the lot and a safety data sheet for the substance. Most formulators glance at the purity figure on the first and file the second unread. The lines people skip are the ones that decide whether a gram of powder contains the amount of peptide you think it does, whether the material is the molecule you ordered, and whether your laboratory is handling it correctly.

This guide goes through a peptide COA line by line, the chromatogram behind it, the check against a public record and the 16-section SDS, and ends with a worked example on a fictional certificate and a checklist for the incoming-goods bench.

What a COA is, and what it is not

A certificate of analysis is a test report for one lot. It states what the manufacturer's laboratory measured on a sample of that lot, by which methods, against which limits, on which date. Its value is its specificity: a lot number that matches the vial, results produced for that lot, and a method named for every result.

A COA is not any of the following.

• Not a specification sheet. A specification lists the limits a lot must meet; a COA lists what the lot showed.
• Not a regulatory approval. A COA says nothing about whether the substance may be used in a cosmetic in any market. The brand and its safety assessor answer that, with the COA as one input.
• Not a statement about your bottle. The results describe the lot on the test date; storage and shipping since then are why the retest date and the storage statement are on it.
• Not a complete description of the powder. Each line answers one question with one method. What was not tested is not on the certificate.

The lines on a peptide COA and what each one means

Layouts vary, but the lines below appear on most peptide certificates. Read them in this order.

Identity block

• Product name, INCI name and common name. The INCI name is the one for your raw-material file. If the COA carries only a trade name or an abbreviation, ask for the INCI name and CAS number to be added.
• Lot number. Must match the vial exactly.
• Manufacture date and retest date. The retest date is not an expiry: it is the date after which the manufacturer no longer vouches for the results without re-testing, and the date to plan your own re-test around.

Physical block

• Appearance. Colour and form, to compare with what you see when you open the container: white to off-white for most peptides, blue for copper peptides such as Copper Tripeptide-1.
• Water content by Karl Fischer titration. Peptide powders are hygroscopic and can hold a meaningful share of their weight as water. Karl Fischer measures it directly, and the figure is part of the net-peptide arithmetic below.
• Counter-ion. A synthetic peptide is isolated as a salt. If it was purified by reverse-phase HPLC with trifluoroacetic acid in the mobile phase it is a trifluoroacetate (TFA) salt unless the manufacturer exchanged the counter-ion, usually to acetate or hydrochloride. For a cosmetic raw material acetate is the usual request: TFA is a strong-acid residue that lowers the pH of your water phase, adds weight that is not peptide, and does not belong in a finished product. A metal complex such as GHK-Cu may have no counter-ion line.

Cornish and colleagues reported that trifluoroacetate carried over from HPLC purification, at the levels present in TFA salts of peptides, reduced proliferation of osteoblasts and chondrocytes in culture, while the same peptides as hydrochloride salts did not; they recommend converting peptides to a hydrochloride or equivalent salt before biological testing (Cornish J et al. Am J Physiol, 1999).

Purity and content block

• HPLC purity, as area percent. The main peak's area divided by the total area of all peaks, at one detection wavelength. It says how much of what the detector can see is the target peptide, not how much of the powder is peptide: water, counter-ion and inorganic salts have no chromophore and are invisible to a UV detector, so a lot can show a high area-percent purity and still be well below that figure as grams of peptide per gram of powder.
• Peptide content, or net peptide. Grams of peptide per gram of powder, measured by amino acid analysis, nitrogen determination or quantitative UV, or calculated from purity, water and counter-ion. It is the figure you need when a use level is expressed as peptide rather than as powder. If it is missing, ask for it or calculate it.
• Mass-spectrometry identity, expected versus found. The expected molecular weight and the ion observed. A singly charged ion appears near the molecular weight plus one and a doubly charged ion near half that: for Acetyl Octapeptide-3, molecular weight about 1075, that is near m/z 1076 and m/z 538. Agreement confirms that the main peak is the right molecule; it is also the line that separates GHK-Cu from copper-free GHK.

Optional lines

• Residual solvents. Acetonitrile from purification and the solvents of synthesis, by headspace gas chromatography, reported against limits or as not detected. If the line is absent the solvents were not tested, not absent.
• Microbial limits. Total aerobic count, yeasts and moulds, absence of specified organisms. On some powder COAs and not others.
• Heavy metals. Lead, arsenic, mercury and cadmium by ICP-MS, when tested. For a copper peptide a line that includes copper is reporting the molecule, not a contaminant.

ICH's Q3C(R8) guideline, Impurities: Guideline for Residual Solvents, dated April 2021, is the reference most laboratories use to sort solvents into classes and to set the limits printed on a residual-solvent line, although it was written for another industry (ICH Q3C(R8), 2021).

How to read the HPLC chromatogram

Ask for the chromatogram, not only the figure. It is a plot of detector signal against time, and five things on it deserve attention.

1. The header. Column, mobile phases, gradient, flow, detection wavelength, sample volume and concentration. Without it nobody else can reproduce the picture.
2. The main peak. One dominant peak at the retention time the manufacturer reports for this peptide. A shift between lots run by the same method is a question.
3. The impurity peaks. Small peaks before and after the main peak. Sequences missing a residue or carrying an oxidised methionine usually elute earlier; sequences with a protecting group still attached or a hydrophobic adduct usually elute later. The purity figure is the main peak as a share of all of them.
4. The baseline and integration. A rising baseline during a gradient is normal. Peaks cut off, a baseline drawn to shrink an impurity, or an integration table that does not add up to the printed figure are not.
5. The blank. A good report includes a run of mobile phase alone, so that system peaks are neither counted as impurities nor hidden among them.

One method cannot see everything. Reverse-phase HPLC at one wavelength separates by hydrophobicity and detects by UV absorbance. It does not see water, salts or counter-ions. It can place two closely related sequences under one peak, and a diastereomer from racemisation may or may not separate. That is why the water, counter-ion and mass-spectrometry lines sit beside it.

D'Hondt and colleagues reviewed the impurity classes found in synthetic peptides: deletion and insertion sequences, diastereomers from racemisation, incompletely removed protecting groups, oxidation products, dimers and oligomers, residual counter-ions such as trifluoroacetate, and degradation products from diketopiperazine, pyroglutamate and succinimide formation; they note that unidentified impurities can distort experimental results (D'Hondt M et al. J Pharm Biomed Anal, 2014).

Cross-checking a COA against a public record

A certificate in an envelope can be edited by anyone between the laboratory and you; a record the manufacturer publishes in its own library cannot be changed quietly, which makes it the quickest honesty check available. Pepti, Guangzhou keeps its batch records public at peptioem.com/coa: each entry lists the product, the lot code, the HPLC purity figure, the test date and the certificate PDF, and the published figures currently fall between 98.4% and 99.8%.

1. Find the lot code from your vial in the library.
2. Compare product name, purity figure and test date with the paper you received. They should be identical, not similar.
3. Open the published PDF and compare the chromatogram and the mass-spectrometry line with yours.
4. If the lot is not there, ask why. An unpublished bulk lot is not a problem in itself; a lot the manufacturer does not recognise is.

Keep a screenshot of the record in the lot folder.

The SDS: 16 sections, and the seven you actually need

A safety data sheet describes the substance, not the lot. It follows the same 16-section structure in every market that has adopted the UN Globally Harmonized System, so a sheet from any manufacturer reads the same way.

OSHA's Hazard Communication Standard brief on safety data sheets sets out the 16 sections and their minimum contents, notes that sections 1 to 8 carry what is needed quickly in an emergency while 9 to 11 and 16 carry technical data, and explains that sections 12 to 15 are included for consistency with the UN GHS (OSHA Brief 3514; overview at osha.gov/hazcom).

Section	Title	Formulator's use
1	Identification	Must match the COA
2	Hazard identification	Read
3	Composition and ingredients	Read
4	First-aid measures	Post in the laboratory
5	Fire-fighting measures	Facilities file
6	Accidental release measures	Spill procedure
7	Handling and storage	Read
8	Exposure controls and personal protection	Read
9	Physical and chemical properties	Read
10	Stability and reactivity	Read
11	Toxicological information	Safety assessor
12	Ecological information	Waste and effluent
13	Disposal considerations	Waste contractor
14	Transport information	Read
15	Regulatory information	Safety assessor
16	Other information	Revision date

The seven sections to read before the material goes on the bench:

• Section 2 gives the GHS classification, or states that the substance is not classified. It sets what your laboratory container label must say.
• Section 3 must agree with the COA: same chemical or INCI name, same CAS number, and a concentration that makes sense for a powder.
• Section 7 gives handling and storage. Compare with the COA storage statement, which for the peptides on this site is 2–8 °C for working stock and −20 °C long-term.
• Section 8 tells you what to wear and whether weighing needs local exhaust. For a fine hygroscopic powder the dust statement matters most.
• Section 9 lists appearance, solubility and, where known, pH in solution and decomposition behaviour. It should match the bench and the COA appearance line.
• Section 10 names incompatible materials: for a copper peptide, chelating agents, strong reducing agents and strongly acidic or alkaline conditions; for other peptides, oxidisers and strong acids or bases.
• Section 14 gives the transport classification, or states that the substance is not regulated for transport, and is where a cold-chain requirement is usually noted.

Powder, solution, missing and generic sheets

A powder SDS is not a solution SDS

A sheet written for the peptide in solution describes a liquid: its section 2 classification is driven by the solvent and any preservative, section 3 lists the peptide at a low concentration beside water and glycerin, section 9 gives density and the pH of the solution, and section 8 says nothing about dust. If you buy powder, you need the sheet for the powder.

What a missing or generic SDS tells you

Some suppliers send no SDS, or a template in which the substance is named only as "peptide", section 3 has no CAS number, most sections read "no data available" and section 1 names a reseller rather than a manufacturer. Nobody in the chain has classified the substance, so the classification for your laboratory label and transport paperwork falls to you or your safety assessor. And the supplier has not done the work a manufacturer does routinely. Take it as a reason to ask who made the material, and to ask that manufacturer for its own sheet.

A worked example: reading a fictional certificate

The certificate below is invented for illustration: the lot number is not real, the product is a generic cosmetic peptide, and the results are described in words rather than figures so that nothing here reads as a specification.

Line	What the example certificate shows	How you read it
Product	Trade name, INCI name and CAS number printed together	Check the CAS in PubChem
Lot number	EXAMPLE-LOT-001	Compare with the vial label
Dates	Manufacture date; retest date later	Diary the retest date
Appearance	White to off-white powder, "conforms"	Open the container and look
HPLC purity	Area-percent figure above the limit, method named, chromatogram attached	Read the chromatogram as above
Water content	Karl Fischer figure below the limit	Part of the net-peptide arithmetic
Counter-ion	Acetate, with a figure	TFA would be a question
Peptide content	Net figure, lower than the area-percent purity	Use when the use level is expressed as peptide
MS identity	Expected weight and found ion agree	Main peak is the right molecule
Residual solvents	Acetonitrile not detected; others below limit	Tested; note the method
Microbial limits	Line absent	Not tested; record the gap
Storage	2–8 °C short-term, −20 °C long-term, protect from light	Compare with SDS section 7

Read in order: the identity block is complete and can be cross-checked; the physical block lets you calculate what fraction of the powder is peptide; the purity block confirms the peptide is clean and is the right molecule; the optional block shows what was and was not tested. The one gap, microbial limits, is recorded as a gap rather than assumed.

Checklist for every incoming lot

• Lot number on COA matches the vial.
• INCI name and CAS number printed; CAS resolves to the form ordered.
• HPLC purity as area percent with method and chromatogram; retention time consistent with earlier lots.
• Water content and counter-ion stated; net peptide stated or calculated.
• Mass-spectrometry expected and found values agree.
• Residual solvents, microbial limits and heavy metals: tested, or recorded as not tested.
• Retest date diarised; storage statement matches SDS section 7.
• COA checked against the manufacturer's public record where one exists; screenshot filed.
• SDS is for the powder, names the same manufacturer as the COA, and sections 2, 3, 7, 8, 9, 10 and 14 have been read.
• Decision recorded with a name and a date.

None of this makes an ingredient permissible in a market. It makes the lot traceable, the identity certain and the handling safe, which is what the brand's safety assessor needs.

Maintained by Pepti, a Guangzhou peptide manufacturer. Batch records referenced on this site are published at peptioem.com/coa. Last reviewed 2026-10-19.