Humic acid samples analysis

Soil extracts are usually very complex. In water samples, humic and fulvic acids make analysis difficult, especially when polar substances are to be determined. Multidimensional chromatography can also make a significant contribution here to this type of analysis. 

Hogendoorn, E.A., Dijkmann, E., Baumann, B., Hidalgo, C., Sancho, J.-V., and Hernandez, F., Strategies in using analytical restricted access media columns for the removal of humic acid interferences in the trace analysis of acidic herbicides in water samples by coupled column liquid chromatography with UV detection, Anal. Chem., 71, 1111, 1999. 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

Elemental Analysis. The elemental analyses are presented in Table IV. The atomic ratios H/C for all drinking water samples (nos. 1-10) were between 1.28 and 1.39. These values were comparable to humic acid derived from lake sediments. However, H/C ratios were much lower when compared to the chlorinated model humic substances (e.g., 1.04-1.08 for CFH-1 and CFH-2). Bromine was present in almost negligible quantities, whereas Cl varied between 0.3 and 2.4, and S varied between 0.9 and 2.7 in the drinking water organic matter. All fractions from drinking water showed similar elemental composition. However, they differed from the elemental composition of the CFH samples in all respects, especially in chlorine content. 

Figure 4.5. Fluorescence excitation-emission matrix spectra of humic acids (HAs) isolated from sewage sludge (B) and two soils either unamended (TH1 and TH2, respectively) or amended with 3901 ha-1 of sewage sludge (THB1 and THB2, respectively) sampled from the surface (s, 0-25cm) and subsurface (ss, 25-50cm) layers. Reprinted from Bertoncini, E. I., D Orazio, V., Senesi, N., and Mattiazzo, M. E. (2005). Fluorescence analysis of humic and fulvic acids from two Brazilian oxisols as affected by biosolid amendment. Anal. Bioanal. Chem. 381,1281-1288, with permission from Springer.

Lignin Analysis. Lignin present in fulvic and humic acids from stream, foam, and foam-extract samples from Como Creek and the Suwannee River were oxidized to phenolic oxidation products by copper oxide oxidation via the method described by Hedges and Ertel (24). These phenolic oxidation products then were derivatized to trimethyl silyl derivatives for GC/MS analysis. 

Table Vn. Concentrations (in meq/g) of oxygen-containing functional groups in fulvic and humic acids from stream and foam samples from Como Creek and the Suwannee River, using a combination of C NMR data, elemental analysis, and potentiometric titration data.

Reaction of Fulvic and Humic Acids with 0 NH2. The H -saturated fulvic or humic acids (400-500 mg) were added to 150-200 ml of H2O, dissolved by raising the pH to 6 with 1 N NaOH, and charged with 200 il of 0 NH2. The reaction solutions were stirred at room temperature for 4-5 days. The samples were then resaturated with H" by passing the solutions through a Dowex MSC-1 cation exchange resin, and freeze dried. The freeze dried powders were redissolved in 2-3 ml DMSO-d6 for NMR analysis. 

SPE methods for organic environmental pollutants, including PAA (Table 1) and HA A (Table 2.B), coupled with electrophoresis end analysis were reviewed126. Analysis of PAA in environmental waters requires preconcentration and cleanup to remove interfering substances such as humic acids from the samples. This may be accomplished by several methods, for example (a) derivatization of the PAA by the Bratton-Marshall method followed by HPLC-UVD measuring at 460 nm (Section III.B.2) (b) flocculation of the water sample with Al3+ ions to selectively remove humic compounds before SPE (c) a... 

The sources and handling of samples chosen for this study were known to be carefully and accurately documented. They include one aquatic fulvic acid with a low ash content, one high ash aquatic humic acid, and one low ash soil humic acid. The laboratories chosen include three widely known commercial laboratories in the United States which specialize in organic elemental analysis and one government laboratory with extensive experience in elemental analysis of humic substances. 

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