"[2D301F01C975]" . "A bulk humic acid (HA) extracted from a South Moravian lignite was further fractionated by sequential extraction in buffers at different pHs. All samples were analyzed by high performance size exclusion chromatography (HPSEC) and elemental analysis. Weight-averaged molecular weights (Mw) of fractions dissolved at pH 7, 8, and 9 were larger than for the parent bulk HA, thereby indicating that Mw of humic matter is related only to molecular size as affected by sample hydration rather than its molecular maass. Moreover, hydration radius was a function of the specific chemical properties of humic fractions. Addition of small amount of either mineral (HCl) or organic acid (formic, acetic, propionic) to humic solutions induced significant changes in conformational arrangements of the treated sample in respect to control. Also the conformational changes among humic fractions depended on their different molecular composition and suggested a weakly-bound supramolecular association of different humic molecules"@en . "683-689" . "humic substances, lignite, HPSEC"@en . . . "RIV/00216305:26310/03:PU38208!RIV/2004/MSM/263104/N" . . . "Conformational behavior of lignite humic fractions separated by sequential pH-extractions" . "Peka\u0159, Miloslav" . . . "2"^^ . . . "Conformational behavior of lignite humic fractions separated by sequential pH-extractions"@en . . . "DE - Spolkov\u00E1 republika N\u011Bmecko" . . . "0"^^ . "4"^^ . "12" . "0"^^ . . "Conformational behavior of lignite humic fractions separated by sequential pH-extractions" . "RIV/00216305:26310/03:PU38208" . . . "602014" . "Ku\u010Der\u00EDk, Ji\u0159\u00ED" . "Z(MSM 263100019)" . "Conformational behavior of lignite humic fractions separated by sequential pH-extractions"@en . . "7"^^ . "Fresenius Environmental Bulletin" . "1018-4619" . "26310" . "A bulk humic acid (HA) extracted from a South Moravian lignite was further fractionated by sequential extraction in buffers at different pHs. All samples were analyzed by high performance size exclusion chromatography (HPSEC) and elemental analysis. Weight-averaged molecular weights (Mw) of fractions dissolved at pH 7, 8, and 9 were larger than for the parent bulk HA, thereby indicating that Mw of humic matter is related only to molecular size as affected by sample hydration rather than its molecular maass. Moreover, hydration radius was a function of the specific chemical properties of humic fractions. Addition of small amount of either mineral (HCl) or organic acid (formic, acetic, propionic) to humic solutions induced significant changes in conformational arrangements of the treated sample in respect to control. Also the conformational changes among humic fractions depended on their different molecular composition and suggested a weakly-bound supramolecular association of different humic molecules" . "7" .