Glass jars with powder samples and laboratory flasks

How to read a certificate of analysis (CoA) when buying supplements in bulk

Short answer: a certificate of analysis (CoA) reports the test results of one batch against the product specification. Read it in four steps: check that it belongs to your batch, compare every result with the limit in the specification, check the test methods and the laboratory, and compare contaminants and microbiology with the limits that apply to your product. A CoA only means something together with the specification it refers to.

What is a certificate of analysis?

A CoA is a batch document. The manufacturer's quality control laboratory or an external laboratory tests a sample of one production batch and lists the results next to the specification limits. The specification describes what every batch must meet; the CoA shows what this batch actually measured. That is why a CoA without a batch number, or without the specification next to it, tells a buyer very little.

For a food business, the CoA is also part of traceability. Regulation (EC) No 178/2002 requires food businesses to identify who supplied them and whom they supplied, and batch documents make that much easier. Keep the CoA with your purchase records and with the batch number on your own products.

The sections of a CoA and what to check

Section Typical content What to check
Header Product name, botanical name and plant part, batch or lot number, production date, best-before or retest date Batch number matches your delivery; name and part match the specification and your label
Identification Appearance, colour, odour, identity test For botanicals, an identity test that confirms the species and part
Assay or standardisation Content of a marker, for example withanolides or fulvic acid, or an extract ratio Marker and test method are named; result meets the minimum in the specification
Physical parameters Particle size (for example ≥ 95% through 80 mesh), moisture or loss on drying, ash, bulk density Suits your capsule filling, tableting or blending process
Contaminants Lead, cadmium, mercury, arsenic, pesticide residues and other contaminants where relevant Results below the specification and the EU maximum levels for your product
Microbiology Total plate count, yeasts and moulds, E. coli, Salmonella Results within the specification limits
Release Laboratory, date, name or signature of the responsible person Who tested, when, and whether the laboratory is accredited

Step 1: does the CoA belong to your batch and your product?

Start with the header. The batch number on the CoA must match the batch number on the bags, drums or cartons you receive. Then check that the CoA describes exactly the material you buy:

  • Species and part: a CoA for ashwagandha leaf does not cover ashwagandha root, and a CoA for mushroom mycelium does not cover the fruiting body.
  • Form: a CoA for an extract does not cover a ground powder of the same plant, and the other way round.
  • Standardisation: a 5% extract and a 50% extract of the same raw material are different products with different CoAs.

Also look at the dates. A production date and a best-before or retest date tell you how much shelf life is left when the goods arrive.

Step 2: compare every result with the specification

Most CoAs have a column with the specification limit and a column with the result. Read them line by line. Watch out for three things:

  • "Complies" without a number. For assay, contaminants and microbiology, ask for the measured value. A figure lets you compare batches over time.
  • "< LOQ" or "not detected". This means the result is below the limit of quantification or detection of the method. Ask what that limit is: "not detected" with a high detection limit says less than it seems.
  • Different units. mg/kg and ppm are the same; µg/kg is a thousand times smaller. Make sure the limit and the result use the same unit.

For standardised extracts, the assay line is the core of the CoA. Examples from our own range are organic ashwagandha KSM-66 powder (withanolides > 5%), shilajit 50% extract powder (fulvic acid ≥ 50%) and ginkgo biloba extract powder (leaf extract 50:1, ≥ 95% through 80 mesh). For mushroom extracts, read our article on mushroom extract specifications: a polysaccharide figure and a beta-glucan figure are not the same thing.

Step 3: check the test methods and the laboratory

A result is only as good as the method behind it. A good CoA names the method for each line, for example HPLC or UV spectrophotometry for a marker compound, ICP-MS for heavy metals, or a reference to a pharmacopoeia or standard method. If no method is given, ask for it, especially for the assay.

Then look at who tested. Many CoAs come from the manufacturer's own laboratory. That is normal, but for important parameters you can ask for results from an independent laboratory. Laboratories can be accredited to ISO/IEC 17025, the international standard for the competence of testing and calibration laboratories. Accreditation applies to specific methods, so check that the method you rely on falls within the laboratory's scope.

Step 4: contaminants and microbiology

For heavy metals, Regulation (EU) 2023/915 sets maximum levels for food supplements: 3.0 mg/kg for lead, 1.0 mg/kg for cadmium (3.0 mg/kg for supplements that consist of at least 80% dried seaweed) and 0.10 mg/kg for mercury. These limits apply to the food supplement, so think about what a raw material result means for your finished capsule, tablet or powder. Pesticide residues fall under Regulation (EC) No 396/2005 on maximum residue levels.

For microbiology, the limits in your specification are the reference. Check that the CoA reports each parameter in the specification, with a value, and that pathogens such as Salmonella are reported for a stated sample quantity.

Red flags on a certificate of analysis

  • No batch number, or a batch number that does not match the goods.
  • Identical results on CoAs for different batches.
  • Only "complies" for every line, without values or methods.
  • A CoA for a different form, part or standardisation than the product you buy.
  • No date, no laboratory name and no responsible person.
  • Results outside the specification without an explanation.

None of these automatically means the product is wrong, but each one is a reason to ask questions before you accept the batch.

CoA and documentation at GOA Supply

For every product we supply a product specification and a certificate of analysis on request. Our product pages list key specifications where available, such as botanical name, extract ratio or standardisation, particle size and country of origin. GOA Supply is organic certified (NL-BIO-01). Our capsules are filled by an external Dutch contract manufacturer, whose organic certificate is available on request.

Standard order tiers are 20,000, 50,000 or 100,000 capsules and 10, 50 or 100 kg for powders, tablets and salts. Smaller quantities are possible on request. Prices exclude shipping, and we can arrange transport. Orders are usually shipped within 1–2 weeks, depending on stock. See our wholesale page for the full overview, and our checklist for buying supplements in bulk for the other documents to request. All products are also available as private label; as the brand owner, you are responsible for your label and for any claims on it, in line with Regulation (EC) No 1924/2006. To request a CoA for a specific product, contact us.

FAQ

What is the difference between a specification and a CoA?
The specification sets the limits that every batch must meet. The CoA reports the measured results of one batch against those limits.

Should a CoA come from an independent laboratory?
Not necessarily. Most CoAs come from the manufacturer's laboratory. For critical parameters you can ask for independent results, preferably from a laboratory accredited to ISO/IEC 17025 for that method.

What does "< LOQ" mean on a CoA?
The result is below the limit of quantification, the lowest level the method can measure reliably. Ask what that limit is.

Which heavy metal limits apply to food supplements in the EU?
Regulation (EU) 2023/915 sets 3.0 mg/kg for lead, 1.0 mg/kg for cadmium (3.0 mg/kg for supplements of at least 80% dried seaweed) and 0.10 mg/kg for mercury.

Do you send a CoA with every order?
The specification and a certificate of analysis are available on request for every product. Ask for them with your quote or order.

Sources

Written by Florian Fermin, co-owner of GOA Supply.

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