Comparison of methodologies for determination of carboxylic and phenolic groups in humic acids

被引：107

作者：

Masini, JC ^{[1
]}

Abate, G ^{[1
]}

Lima, EC ^{[1
]}

Hahn, LC ^{[1
]}

Nakamura, MS ^{[1
]}

Lichtig, J ^{[1
]}

Nagatomy, HR ^{[1
]}

机构：

[1] Univ Sao Paulo, Inst Quim, BR-05599970 Sao Paulo, Brazil

来源：

ANALYTICA CHIMICA ACTA | 1998年 / 364卷 / 1-3期

基金：

巴西圣保罗研究基金会;

关键词：

humic acids; acid-base titrimetry; nonlinear regression; ionizable sites;

D O I：

10.1016/S0003-2670(98)00045-2

中图分类号：

O65 [分析化学];

学科分类号：

070302 ; 081704 ;

摘要：

A nonlinear method for fitting acid-base potentiometric titration data was applied to commercial and vermicompost humic acids in order to determine the concentration and conditional pK(a)'s of the ionizable sites. Data was also treated by a linear method based on modified Gran functions. In both cases the discrete site model was adopted, which means that the humic acid was treated as a mixture of monoprotic acids. Electrostatic effects were evaluated by performing titrations in media of 0.010, 0.10, and 1.0 mol l(-1) NaCl. Results were compared with those obtained by conductimetric titration with NaOH and Ba(OH)(2), infrared spectra of humic acid with different grades of protonation, and classical Ca-acetate and Ba(OH)2 exchange methods. Models with five and six binding sites were the best to represent experimental data of potentiometric titration using both the linear and nonlinear techniques. (C) 1998 Elsevier Science B.V.

引用

页码：223 / 233

页数：11