Separation of fulvic acid from soil extracts based on ion-pair formation with a cationic surfactant.
A novel method for separating fulvic acid (FA) from soil extracts is proposed. The FA, defined as the acid-soluble fraction of an alkaline extract of soil, was separated based on the precipitation of an ion-pair with a cationic surfactant, such as domiphen bromide. The precipitate was dissolved in aqueous HCl to produce H+ -type FA and a surfactant chloride (SUR-Cl). SUR-Cl, in the aqueous solution, was removed by extraction with CHCl3. After the aqueous phase was passed through a cation-exchanger (H+ -type), H+ -type FA (FA-SUR) was obtained as a powder by lyophylization. The chemical characteristics of FA-SUR were compared with an FA sample separated according to the method of the International Humic Substances Society using a DAX-8 resin (FA-DAX). The oxygen content, O/C atomic ratio and total acidity of the FA-SUR were significantly larger than the corresponding values for FA-DAX. The solid-state CPMS 13C NMR spectra indicated that the higher oxygen content of the FA-SUR could be due to alcoholic hydroxyl groups and polysaccharides as well as carboxylic groups. These results show that FA-SUR is more polar and hydrophilic than FA-DAX.
Fukushima
Masami
M
National Institute of Advanced Industrial Science and Technology, 16-1 Onogawa, Tsukuba-West, Tsukuba 305-8569, Japan. m-fukushima@aist.go.jp
Kikuchi
Atsunori
A
Tatsumi
Kenji
K
Tanaka
Fumiko
F
D000438:Alcohols / Q000737:chemistry; D000838:Anions; D001578:Benzopyrans / Q000032:analysis* / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D002412:Cations; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D002852:Chromatography, Ion Exchange; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D011134:Polysaccharides / Q000737:chemistry; D012987:Soil / Q000032:analysis*; D013501:Surface-Active Agents / Q000737:chemistry*
D000438:Alcohols; D000838:Anions; D001578:Benzopyrans; D002412:Cations; D006812:Humic Substances; D007477:Ions; D011134:Polysaccharides; D012987:Soil; D013501:Surface-Active Agents; D002244:Carbon; C005023:fulvic acid