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Updated: Aug 15, 2025

Quantification of Humic and Fulvic Acids in Humate Ores, DOC, Humified Materials and Humic Substance-Containing Commercial Products
Published on: March 18, 2022
Differentiation Between Humic and Non-Humic Substances Using Alkaline Extraction and Ultraviolet Spectroscopy
Lawrence Mayhew1, Amit Pratap Singh2, Peng Li3
1Independent Researcher, Spring Green, WI 53588, USA.
Background:
Although humic substances are the principal ingredients in processed humic products, there has been no practical way to determine if a material is humified, allowing fake products to be used by farmers instead of genuine humic substances.
Objective:
To develop a test method using conventional laboratory techniques to determine if a material is humified.
Method:
A neutralized extract is prepared using the standardized extraction protocols specified in ISO 19822:2018(E). A portion of the extract is used to determine the concentration of dissolved organic matter on an ash-free basis. A portion of the remaining neutralized extract is diluted to a concentration of 30 mg/kg of dissolved organic matter and transferred to a quartz UV cuvette for ultraviolet-visible (UV-Vis) spectroscopy. UV-Vis absorbance is recorded over a wavelength range of 220-500 nm at 5 nm intervals. The absorbance data are normalized by conversion to scaled absorbance, which is compared to a reference scaled absorbance spectral curve for humic substances to determine if the tested material is humic or non-humic.
Results:
This method was able to differentiate legitimate humic substances from non-humic adulterants in a multiple-laboratory validation study (P ≤ 0.05).
Conclusion:
This method can differentiate humic from non-humic substances in materials intended to be used as ingredients in commercial humic products or for research.
Highlights:
This method uses common laboratory procedures and equipment.
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