Short-column anion-exchange chromatography for soil and peat humic substances profiling by step-wise gradient of high pH aqueous sodium ethylenediaminetetraacetate

Novel anion-exchange liquid chromatographic method with step gradient of aqueous EDTA4− based mobile phase elution has been developed to profile available Slovak soil humic substances and alkaline extracts of various soils. The method utilize short glass column (30 mm × 3 mm) filled in with hydrolytically stable particles (60 μm diameter) Separon HEMA-BIO 1000 having (diethylamino)ethyl functional groups. Step gradient was programmed by mixing mobile phase composed of aqueous solution of sodium EDTA (pH 12.0; 5 mmol L−1) and mobile phase constituted of aqueous solution of sodium EDTA (pH 12.0, 500 mmol L−1). The FLD of HSs was set to excitation wavelength 480 nm and emission wavelength 530 nm (λem). Separation mechanism was studied by use of selected aromatic acids related to humic acids with the aid of UV spectrophotometric detection at 280 nm. The proposed method benefits from high ionic strength (I = 5 mol L−1) of the end mobile phase buffer and provides high recovery of humic acids (98%). Accurate and reproducible profiling of studied humic substances, alkaline extracts of various types of soils enables straightforward characterization and differentiation of HSs in arable and forest soils. Selected model aromatic acids were used for separation mechanism elucidation.