Overview. Contaminant testing should be designed as a risk-based programme linked to cultivation, suppliers, process materials, equipment and finished-product release. Testing alone cannot compensate for weak prevention or non-representative sampling.
Map credible hazards
The programme should begin with the actual product and process. Soil, nutrients, water, pesticides, drying, extraction solvents, equipment, cleaning agents and packaging each create different contaminant risks.
Define specifications
Limits should reflect product classification, route of administration, daily dose, pharmacopoeial requirements and market commitments. Reporting limits should sit sufficiently below action limits.
Choose appropriate methods
Pesticides may require LC-MS/MS and GC-MS/MS; metals commonly use ICP-MS; residual solvents use headspace GC; mycotoxins use LC-based methods; microbiology uses compendial or validated alternatives.
Sampling strategy
Contaminants can be localised. Flower batches may require stratified sampling across containers and positions. Composite sampling can improve coverage but may dilute a localised high concentration.
Supplier and reduced testing
Reduced testing requires robust supplier qualification, historical evidence and periodic verification. Certificates of analysis should not be accepted automatically.
Trend review
Results below specification can still reveal deterioration. Site, season, cultivar, supplier and process trends should be reviewed.
Investigation and escalation
Unexpected detections should trigger assessment of source, blank contamination, matrix interference, cross-contamination and upstream controls.
Practical reference table
| Hazard | Likely source | Preferred control | Typical method |
|---|---|---|---|
| Pesticides | Cultivation inputs or drift | Approved-use programme | LC-MS/MS or GC-MS/MS |
| Mycotoxins | Fungal growth | Drying and storage control | LC-MS/MS |
| Heavy metals | Soil, nutrients, equipment | Input and site qualification | ICP-MS |
| Residual solvents | Extraction and cleaning | Validated removal | Headspace GC |
| Microorganisms | Cultivation and handling | Hygiene and moisture control | Compendial microbiology |
Control and decision path
Frequently asked questions
Should every batch be tested for every contaminant?
The requirement depends on law, product risk and approved control strategy.
Can supplier certificates replace testing?
Only within a qualified programme with periodic verification.
Why are trends important below the limit?
They can identify deterioration before a specification failure.
How low should the reporting limit be?
Low enough to support a reliable decision around the specification.
What is matrix effect?
A change in analytical response caused by sample components rather than the analyte.
Primary references and guidance
- ICH Q3D(R2)
- ICH Q3C
- European Pharmacopoeia general chapters
- EU GMP Part I, Chapter 6
- WHO GACP
- ISO 17025
- Applicable national cannabis specifications
Confirm the current effective revision and national applicability before operational or regulatory use.