BOOK OF ABSTRACTS 257 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Technologies and Applications P5.1 MSZ 1129:2026: A New Hungarian Standard for the Quantitative Determination of Humic and Fulvic Acids in Humus-Rich Matrices János Csicsor1, Attila Csicsor1, Petra Csicsor-Kulcsár2 1 Biopol Development and Trading Ltd., Munkás tér 1, H-8184 Balatonfűzfő, Hungary, e-mail: info@hymato.hu 2 Research Group of Environmental and Inorganic Photochemistry, Center for Natural Sciences, University of Pannonia, Veszprém, Hungary Reliable quantification of humic acid and fulvic acid remains a critical analytical challenge in the characterization, quality control and regulatory assessment of humic-substance-containing materials. This work presents the Csicsor method, recently published as the Hungarian national standard MSZ 1129:2026 and submitted for international standardization. The method was developed for the determination of humic and fulvic acid fractions in natural humus-bearing materials and artificial growing media, including peats, sapropelic muds, lignites/leonardites, coals, soils, organic manures, sewage sludges, composts, potting soils, vermicomposts and other humic-substance-containing matrices. Its practical significance lies in providing industrial producers, distributors and control laboratories with a relatively simple, transparent and reproducible analytical procedure for the quantitative evaluation of humic materials. A key feature of the method is that it does not only determine the free humic and fulvic acid fractions, but also enables the quantification of extractable humic substances. Free humic substances are extracted with potassium hydroxide at 60–70 °C, followed by acid precipitation of humic acid and gravimetric determination of the humic and fulvic acid fractions after correction for reagent-derived solids. The extractable, or total, fractions are determined after oxidative alkaline extraction using hydrogen peroxide, allowing the quantification of humic substances that can be mobilized from the matrix under controlled oxidative extraction conditions. The protocol also includes the determination of dry matter, moisture, organic matter and ash content, and recommends ash correction of isolated fractions when inorganic components are present in significant amounts. Method performance was evaluated in a 2024 interlaboratory study involving six laboratories using a leonardite sample. Mean values were 3.88% free fulvic acid, 71.4% free humic acid, 5.06% total fulvic acid and 83.4% total humic acid. Repeatability coefficients of variation were 16.3%, 5.67%, 16.9% and 3.78%, respectively, while reproducibility
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