UV-VIS is fast, inexpensive, and widely used for family totals such as silymarin, total polyphenols, and flavonoids. It is a legitimate method when the market convention accepts it — provided the certificate states the method, the wavelength, the reference standard, and the calculation basis.
How the method works
The sample is dissolved or extracted in a suitable solvent and placed in a spectrophotometer. Compounds absorb light at characteristic wavelengths; the absorbance is proportional to concentration under the Beer–Lambert relationship. A calibration curve built from a reference standard converts absorbance into a percentage.
Because UV does not separate individual compounds, the result is a family estimate. Colour, turbidity, and co-extracted substances can interfere. Sample preparation and the choice of reference standard therefore have a large effect on the reported value.
What it can prove
- An estimate of a marker family total under a stated method.
- Consistency with the reference standard and wavelength used.
- Suitability for release when the buyer has agreed to a UV specification.
Where it stops
- Non-specific: unrelated compounds can absorb at the same wavelength.
- Colour and turbidity can bias the result.
- Not a substitute for a specific-compound HPLC assay.
Where UV is appropriate
UV is appropriate when the buyer and supplier agree that a family total is the specification — for example, 80% silymarin in milk thistle or 95% OPC in grape seed. It is also useful for rapid screening and for routine release where the method has been validated for the matrix.
UV is less appropriate when the label names a specific compound. If a label says silybin, a UV silymarin result does not support that claim. Ask for the HPLC figure for the named compound.
Comparing UV and HPLC results
A UV result can be higher or lower than an HPLC result depending on what the method counts and which standard is used. The numbers are not interchangeable, and a buyer should never compare a UV value from one supplier with an HPLC value from another as if they were the same specification.
Reading the result on a COA
- Confirm the wavelength and reference standard.
- Check whether the result is as-is or dry basis.
- Ask what the method actually counts.
What to ask a supplier
What exactly does the UV method measure?
Which reference standard and wavelength were used?
Do you have an HPLC result for the compound named on our label?
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. "Ultraviolet-visible spectroscopy (UV-VIS) for botanical extracts." October 2026. https://ingredients.rainwoodbio.com/resources/methods/uv-vis/