How to read a certificate of analysis (COA) for herbs and spices
The certificate of analysis tells you whether the lot you are buying meets what was agreed. This guide explains each part and the warning signs to check before you accept a shipment.
By Vijay ChoudharyCo-founder & Partner, Customer relations · 4 min read
In short
A certificate of analysis (COA) is the lab report for one lot. To read it well, check five things: that it matches your lot (product, botanical name, lot number and dates), who tested it and whether the lab is accredited, which method was used for each test, whether every result has units and meets the specification, and that it is signed and dated.
1. The header: is it your lot?
Before looking at results, check that the certificate is about the lot you will receive:
- Product and botanical name, for example Withania somnifera root powder. The common name alone is not enough.
- Lot number, the same one on the invoice, the packing list and the bags.
- Dates: sample received, tested and report issued. They should make sense against the production and shipping dates.
- Laboratory: name, address, report number and, if accredited, its accreditation number.
2. Who did the testing
A COA can come from the supplier's in-house lab or from an independent lab. Both are valid as long as you know which and agreed to it. For contaminants such as heavy metals, pesticides and mycotoxins, many buyers ask for an accredited independent lab.
In India, labs are accredited by NABL to the international standard ISO/IEC 17025. Accreditation covers specific tests, so check that the test you care about is within its scope.
3. The results, test by test
| Parameter | What it tells you | Usual unit and method |
|---|---|---|
| Identity | That the plant is the species you ordered | macroscopy, microscopy or HPTLC against a reference |
| Moisture | Storage stability; mould risk | % by loss on drying |
| Total ash | Total mineral content | % |
| Acid-insoluble ash | Sand and soil in the product | % |
| Foreign matter | Stems, stones, other plants | % |
| Mesh or particle size | Whether the powder or cut is as agreed | % passing a set mesh |
| Actives or markers | Curcumin, withanolide, bacoside content, etc. | % by HPLC or spectrophotometry (the method changes the figure) |
| Heavy metals | Lead, arsenic, cadmium and mercury | mg/kg (ppm), usually by ICP-MS |
| Pesticide residues | Traces of agrochemicals | mg/kg, by chromatography with mass spectrometry |
| Aflatoxins and ochratoxin A | Mould toxins | µg/kg (ppb) |
| Ethylene oxide | Traces of a fumigant banned for food in many markets | mg/kg, when the buyer asks for it |
| Microbiology | Total count, yeasts and moulds, E. coli, Salmonella | cfu/g; Salmonella "absent in 25 g" |
4. The method matters as much as the figure
The same lot can give different results depending on the method. The most common case is actives: curcumin measured by spectrophotometry, or withanolides measured gravimetrically, usually come out higher than when measured by HPLC. If your specification asks for "3% curcumin" without naming the method, two labs can both be right and still disagree.
The same goes for "not detected" (ND): it means the result is below the method's limit of quantification (LOQ). If that limit is higher than your market's limit, ND doesn't tell you whether you comply. Ask for the COA to show the LOQ for each test.
5. Warning signs
- No lab name or report number.
- Results that only say "complies", with no figures or units.
- No method given for the important tests.
- A lot number that doesn't match the invoice or the bags.
- Dates that make no sense, such as a test dated before production.
- The same certificate used for different lots.
- A limit of quantification higher than the limit you need.
If in doubt, ask the lab to confirm the report. Many labs verify reports on their website or through a code printed on the document.
How we do it
Every quotation includes a written specification with the test parameters. Each lot is tested against those parameters before shipment, and the test report travels with the documents, together with the phytosanitary certificate and the certificate of origin. If you want a particular lab, or to test the sample yourself before you order, we agree it in the quotation.
To see which tests are usually asked for each product, read the questions on the product pages, for example ashwagandha, turmeric or psyllium, and our registrations and quality page.
Frequently asked questions
What is a certificate of analysis (COA)?
It is the lab report for one specific lot: what was tested, by which method, the result, and whether it meets the agreed specification. It is different from a spec sheet, which describes the product in general.
What does "ND" or "not detected" mean on a COA?
That the result is below the method's limit of quantification (LOQ). Check what that limit is: if it is higher than your market's limit, "not detected" is not enough to know whether you comply.
Why do curcumin or withanolide results differ between labs?
Because the methods measure different things. Spectrophotometric and gravimetric methods usually give higher figures than chromatography (HPLC). That is why the specification should fix the method, not just the figure.
What is NABL?
It is India's laboratory accreditation body. It accredits labs to the international standard ISO/IEC 17025 for specific tests; check that the test you care about is within the scope of the accreditation.
Can I have a lab of my choice test the lot?
Yes. You can name the lab in the specification, or test the sample yourself before you order. We confirm the test plan and the laboratory in the quotation.
Importing from India?
Send us the product, quantity and destination port. We reply with a written specification and price.
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