Certificate of analysis (COA): the foundational document of trust

Structure of a genuine COA

A professional certificate of analysis always contains these essential elements:

1. Product identification

• IUPAC or trade name: "Methylene blue" or "Methylthioninium chloride" or "C.I. 52015".
• CAS number: 61-73-4 (the universal code for the chemical compound).
• Molecular weight: 319.85 g/mol (allows the ppm conversions to be checked).
• Molecular formula: C₁₆H₁₈ClN₃S.

2. Batch information

• Batch number: identifies the production batch (crucial for traceability).
• Date of manufacture and Expiry date: allow the age of the product to be checked.
• Batch weight: the quantity produced.
• Supplier/Manufacturer: address, licence number.

3. Analytical results

See laboratory analyses for the methods. The COA should include:

• Purity (HPLC): X.X% ± standard deviation. Should be > 98% for USP grade.
• Moisture (Karl Fischer or TGA): < 5% for USP.
• Heavy metals (ICP-AES): Pb, As, Hg, Cd in ppm with limits.
• Residual solvents (GC-MS): for pharmaceutical grades only.
• Azure A and B (HPLC): < 1% ideally.

4. Conformity standards

• Pharmacopoeia: USP, Ph. Eur., BP, or JP (Japan).
• Industrial standards: ISO 9001, ISO 17025 for the analytical laboratory.

5. Signatures and dates

• Signature of the quality manager: a personal commitment.
• Official laboratory stamp: authentication.
• Date of the certificate: the official date of issue.

Verifying the authenticity of a COA

Many counterfeit certificates circulate online. Here is how to spot them:

Major warning signs (probable forgery)

1. No address or contact details for the manufacturer/laboratory: a genuine COA always names the laboratory that carried out the analyses.
2. No batch number: this is indispensable for traceability. A generic counterfeit COA applies to "any batch whatsoever".
3. Suspiciously perfect data: "100% purity", "0 ppm of every heavy metal". Nature never produces 100%. A genuine COA states uncertainties (± 0.5%).
4. Non-existent laboratory: check the name of the laboratory online, look up its ISO 17025 accreditation.
5. No signature or date: these are imperative in official documents.
6. Vague language: phrases such as "the product conforms to the standards" with no numerical data.

Verification by direct contact

The best approach: contact the manufacturer or the analytical laboratory named on the document directly.

• Provide the batch number from the COA.
• Request an authenticated copy of the certificate (genuine laboratories keep archives).
• Check that the data match.

Reputable manufacturers (Sigma-Aldrich, Merck, Fisher Scientific) maintain public databases where you can search for your batch numbers and download the authentic COAs directly.

What to expect from a good COA according to use

For pharmaceutical/humanitarian use

• Grade: USP or Ph. Eur. mandatory.
• Purity: > 98.5%.
• Heavy metals: Pb < 10 ppm, As < 3 ppm, Hg < 1 ppm, Cd < 0.2 ppm.
• Residual solvents: analysed and < 50 ppm each.
• Identity: confirmed by IR or UV-Vis.

For aquarium use (fish)

• Grade: at least "Reagent/Analytical Grade".
• Purity: > 98%.
• Heavy metals: at least Pb and As checked.
• Azure: < 1% acceptable.
• Solvents: not imperative, but desirable.

For textile/artistic use (dyeing paper)

• Grade: technical grade acceptable.
• Purity: > 95%.
• Heavy metals: less critical, but to be checked.
• Azure: acceptable up to 2-3% (slightly affects the shade).

Critical interpretation

A good COA does not say "the product is pure"; it gives exact figures:

• "Purity: 98.7 ± 0.3%" = a reliable product.
• "Contains > 98% methylene blue" = vague, potentially 97.5%.

Demanding quantified evidence

When you buy methylene blue, systematically insist on:

1. A COA in official format (not a screenshot of a web page).
2. An identified batch number (not a "generic" COA).
3. Precise analytical data in figures (not promises).
4. Authenticity verification with the supplier if in doubt.

A seller who refuses to provide a verifiable COA is a poor-quality seller.