A certificate of analysis (COA) shows whether one specific lot meets the agreed specification. Reading it well takes five minutes and prevents most quality claims.
1. Identity and traceability
Check the product name, botanical name, plant part, grade or cut, lot number, production or packing date and the issuing laboratory. The lot number on the COA must match the bags and the packing list.
2. Physical tests
- Appearance, colour and odour – compared with the approved sample.
- Cut size / sieve analysis – the share of product within the agreed range and the share of fines.
- Foreign and extraneous matter – other plant parts versus stones, soil and non-plant material.
3. Chemical tests
| Parameter | What it tells you | Common method |
|---|---|---|
| Moisture | Storage stability; high moisture risks mould | ISO 939 (distillation) or oven method |
| Total ash | Mineral content, including soil | ISO 928 |
| Acid-insoluble ash | Sand and silica – the best indicator of cleaning quality | ISO 930 |
| Volatile oil | Aroma strength (seeds, mint, herbs) | ISO 6571 |
Watch the comparator. In many specifications “<12” means strictly less than 12%, while “≤12” allows exactly 12%.
4. Microbiology
Typical parameters are total plate count, yeasts and moulds, E. coli, coagulase-positive staphylococci, sulphite-reducing clostridia and Salmonella (absent in 25 g). Limits depend on whether the product will be heat-treated or sterilised before use.
5. Contaminants
For the EU, the main groups are pesticide residues (Regulation (EC) No 396/2005) and contaminants such as PAHs, pyrrolizidine alkaloids, ochratoxin A and heavy metals (Regulation (EU) 2023/915). These tests are usually reported by an external laboratory and attached to the COA.
Red flags
- No lot number, date or laboratory name.
- Results without methods or units.
- Identical results across different lots.
- Contaminant results from a laboratory that is not ISO/IEC 17025 accredited for that test.
- A “specification” column that differs from what you agreed.
COA, TDS and specification – not the same thing
The specification is the agreed limit; the TDS describes the product grade in general; the COA reports results for one lot. ONIC publishes reference specifications on each product page and provides the COA for each lot on request – see for example chamomile or all herbs.
Quick answers
What does acid-insoluble ash show on a herb COA?
It measures sand and silica that do not dissolve in acid, so it is the best quick indicator of how well the herb was cleaned.
What is the difference between a COA and a specification?
The specification is the agreed set of limits; the COA reports the measured results of one specific lot against those limits.
Source from ONIC
Send your specification, quantity and destination port – we reply with a quotation and can send samples.