Heavy metals are a concentration risk in botanical extracts: a herb that passes a limit can produce an extract that fails. ICP-MS is the usual method because it measures several elements at low limits in one run and reports each element separately.
How the method works
A representative sample is digested, usually with acid and heat or microwave assistance, to bring the metals into solution. The digest is nebulized into an argon plasma at several thousand degrees, where atoms are ionized. A mass spectrometer separates the ions by mass-to-charge ratio and quantifies each element against calibration standards.
Digestion completeness, reagent purity, instrument drift, and matrix effects all influence the result. Laboratories use internal standards, blanks, and certified reference materials to control these factors. The report should state the method, the digestion procedure, and the reporting limit for each element.
What it can prove
- The concentration of each tested element in the sample.
- Whether the lot meets the agreed limit for those elements.
- A traceable analytical record for the batch file.
Where it stops
- Does not identify the chemical form of the element unless speciation is added.
- Result quality depends on sampling and digestion.
- A pass does not cover elements that were not tested.
Why element-specific results matter
A single 'heavy metals: complies' line does not tell you which element was close to the limit, which one failed, or how the result compares with your market's limit. Each element has a different toxicological profile and, in many jurisdictions, a different limit for a given product category.
Arsenic is a good example: total arsenic includes organic forms that are less toxic than inorganic arsenic. If a market or customer requires inorganic arsenic speciation, a total-arsenic result is not enough.
What to check on the report
Check the element list, the result units (mg/kg or ppm), the limit applied, the reporting limit, and the laboratory's accreditation. Ask whether the sample was composited and how many increments were taken; a non-representative sample can make a good lot look bad, or a bad lot look good.
Reading the result on a COA
- Compare each element with the limit for your market and category.
- Check the reporting limit, not only the result.
- Confirm the laboratory's accreditation and method.
What to ask a supplier
Which elements were tested and at what reporting limits?
Was the laboratory accredited for this method?
Can you provide speciation for arsenic if required?
Related terms
References and further reading
External links are provided for orientation. Methods, limits, and acceptance criteria differ by market and product; confirm the applicable requirements with your regulatory advisor.
Cite this page
Rainwood Botanical. "ICP-MS heavy metal testing for botanical extracts." October 2026. https://ingredients.rainwoodbio.com/resources/methods/icp-ms/