Humic analysis

The development of methods of analysis of tria2ines and thek hydroxy metabohtes in humic soil samples with combined chromatographic and ms techniques has been described (78). A two-way approach was used for separating interfering humic substances and for performing stmctural elucidation of the herbicide traces. Humic samples were extracted by supercritical fluid extraction and analy2ed by both hplc/particle beam ms and a new ms/ms method. The new ms /ms unit was of the tandem sector field-time-of-flight/ms type. 

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. 

In multiresidue analysis, where more analytes with a wide polarity range need to be determined, large transfer volumes are required, and consequently, the selectivity is lower. However, since the major interferences in water analysis are the polar humic and fulvic acids, removing this early eluting interference in coupled-column RPLC will also be feasible in multiresidue methodology. 

E. A. Hogendoorn, E. Dijkman, B. Baumann, C. Hidalgo, J. V. Sancho and E. Hernandez, Strategies in using analytical restricted access media columns for the removal of humic acid interferences in the trace analysis of acidic herbicides in water... 

Lindberg, W., et al. "Partial Least Squares Method for Spectrofluorimetric Analysis of Mixtures of Humic Acid and Ligninsulfonate , Anal. Chem. 1983, (55)643-648. 

Various destructive and non-destructive methods of analysis have been tested and H-l and C-13 NMR have, among other techniques provided valuable structural information on soluble humic acids and fulvic acids 48, Humin, on the other hand has withstood detailed non-destructive analysis. 

Supercritical fluid extraction (SFE) is generally used for the extraction of selected analytes from solid sample matrices, but applications have been reported for aqueous samples. In one study, recoveries of 87-100% were obtained for simazine, propazine, and trietazine at the 0.05 ug mL concentration level using methanol-modified CO2 (10%, v/v) to extract the analytes, previously preconcentrated on a C-18 Empore extraction disk. The analysis was performed using LC/UV detection. Freeze-dried water samples were subjected to SFE for atrazine and simazine, and the optimum recoveries were obtained using the mildest conditions studied (50 °C, 20 MPa, and 30 mL of CO2). In some cases when using LEE and LC analysis, co-extracted humic substances created interference for the more polar metabolites when compared with SFE for the preparation of the same water sample. ... 

Restricted access phases are another approach to exploiting the differences in characteristics of analytes. Large analytes are excluded from an internal surface on which an adsorptive stationary phase is present. A herbicide analysis for Metsulfuron methyl, Bentazone, Bromoxynil, methylchlorophenoxy acid, and Mecoprop in the presence of humic acid was performed on restricted access reversed phase media.52 The cytostatic compound epirubicin and its metabolites were separated from plasma using a Pinkerton GFF II column.53 Gradient separations of polymers on reversed phase and on normal phase represent an alternative to gel permeation chromatography. Polyesters of noncrystalline materials were separated on a variety of such phases.54... 

Solid state 13C NMR spectroscopy has emerged as a very useful tool for characterizing SOM (Kinchesh et al. 1995 Preston 1996). Several workers have reported that Koc of HOCs was linearly or exponentially related to the aromatic carbon contents of HAs or whole soils as determined by 13C NMR analysis (Ahmad et al. 2001 Chen et al. 1996 Chin et al. 1997 Gauthier et al. 1987 Perminova et al. 1999). The Koc value of humic materials can vary by as much as an order of magnitude, depending upon their origins (Fig. 1). 

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. 

Applications of NMR, ESR, thermal analysis, spectrophotometry, gas chromatography, and GC-MS to humic and fulvic acid analysis have been reviewed by Schnitzer [452]. 

Zwiener C. and Frimmel F., 2004. LC-MS analysis in the aquatic environment and in water treatment-a critical review. Par II Applications for emerging contaminants and related pollutants, microorganisms and humic aicd. Anal Bioanal Chem 378 862. 

Despite the advances made in high-performance liquid chromatography in recent years, there are still occasionally applications in which conventional column chromatography is employed. These methods lack the sensitivity, resolution and automation of HPLC. They include the determination of urea herbicides in soil, polyaromatic hydrocarbons, carbohydrates, chloroaliphatic compounds and humic and fulvic acids in non-saline sediments. The technique has also been applied in sludge analysis, e.g. aliphatic hydrocarbons and carboxylic acids. 

Randle and Hartman [12] used thermal neutron activation in analysis to investigate total bromine in humic compounds in soil. Bromine was extracted from the soil water with sodium hydroxide or sodium pyrophosphate, then the extract dried prior to analysis. 

When environmental water was analyzed with respect to a possible contamination with 4-nitrophenol, it could be shown that by using an MI-SPE polymer selective for 4-nitrophenol the following LC-analysis was much facilitated due to the cleaner matrix and the reduction of interference caused by humic acids [91 ]. 

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