Evaluating the use of UV Absorbance for the Differentiation of Humified from Non-humified Materials

Abstract

Background Products containing humic acids (HA) and fulvic acids (FA) have significant commercial potential, however, unknown to the consumer, some products may be mislabeled or contain adulterants. The prevalence of mislabelling and adulterants is primarily found in FA products. Using UV-Vis spectroscopy to differentiate between real and fake FA products is practical and desirable. Objective The objective of this study was to expand the data set generated using a UV-VIS based method proposed by Mayhew et al., 2023. Methods In total, thirty (30) test samples were used to generate ninety test portions (3 replicates per test sample) for analysis using the UV-Vis methodology outlined in Mayhew et al., 2023, which in this study is referred to as the UVAC (UV absorbance confirmation) method. Results None of the thirteen FA test samples investigated were determined as humified using the UVAC method. The FA samples studied comprised of two IHSS standards, five commercial FA products (CFAP) and six full FA fractions (SFA), which were isolated from six known solid humic material sources (SHMS). There was a leonardite, a humalite, and four peat sources used as the SHMS. Analysis of the neutralized extract of the SHMS found only 3/6 SHMS were determined as humified. Six HA (SHA) test samples were also generated by isolating the HA from the SHMS and only 3/6 SHA were determined as humified. Conclusion Given the high prevalence of false determinations more work is needed to improve the method so it can be used by industry or regulators. Highlights The proposed method failed to determine IHSS FA standards as humified. Although the method is practical, it needs improvement and further study before it can be used for reliable differentiation of real from fake FA or HA.