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Differentiation Between Humic and Non-Humic Substances Using Alkaline Extraction and Ultraviolet Spectroscopy

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 convent...

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Detalles Bibliográficos
Autores principales: Mayhew, Lawrence, Singh, Amit Pratap, Li, Peng, Perdue, E Michael
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10156414/
https://www.ncbi.nlm.nih.gov/pubmed/36610457
http://dx.doi.org/10.1093/jaoacint/qsad001
Descripción
Sumario: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.