Fulvic materials

Landrum, PE, Reinhold, M.D., Nihart, S.R., Eadie, B.J. (1985) Predicting the bioavailability of organic xenobiotics to Pontoporeia hoyi in the presence of humic and fulvic materials and natural dissolved organic matter. Environ. Toxicol. Chem. 4,459—167. 

Other pathways to better resolution and enhanced sensitivity may involve methods used in NMR studies of cellular phosphorus dynamics and humic and fulvic materials of water, soil, and sediments. These techniques include a variety of extractions, ion-pairing reagents, adsorption techniques, and lanthanide-shift reagents. For example, an extraction technique that has greatly enhanced the resolution and sensitivity of 31P FT-NMR spectra of Ehrlich ascites tumor cells (53) and HeLa cells (54) is the addition of 35% perchloric acid and removal of acid-insoluble material, followed by filtration and neutralization with K.2C03 or NaOH. 

In the recent years, the occurrence of anilines, chloroanilmes, and benzidines in environmental waters has started to be of concern due to their widespread use in various industrial processes. Detection of these compounds is generally carried out with LC-ECD working in the amperometric mode using a glassy-carbon electrode. Problems encountered are similar to those for phenolic compounds and, therefore, confirmation is always necessary by UV, DAD, or, preferably, MS detection [6]. These compounds are also CE amenable and this approach is really promising in the sense of sensitivity and selectivity because humic and fulvic material can be separated from the analytes due to their different migration kinetics. 

Characterization of Aquatic Humic and Fulvic Materials by Cylindrical Internal Reflectance Infrared Spectroscopy... 

For this study, humic and fulvic materials obtained from a small glaciated bog were separated into five size fractions by using hollow-fiber ultrafiltration techniques. The major cations associated with these organics are reported as a measure of the natural binding capacity of each size range. The structural characteristics and carboxylate content of each group were studied by CIR spectroscopy the results are compared with those obtained by traditional Fourier transform infrared techniques. To aid in spectral interpretation, results were compared to those for selected model polyelectrolytes and simple acids. 

Detailed experimental procedures for obtaining infrared spectra on humic and fulvic acids have been reported previously 9,22,25-26) and will be briefly described here. Infrared spectra were taken on the size-fractionated samples by using a Fourier transform infrared spectrometer (Mattson, Polaris) with a cooled Hg/Cd/Te detector. Dried humic and fulvic materials were studied by diffuse reflectance infrared spectroscopy (Spectra Tech DRIFT accessory) and reported in K-M units, as well as by transmission absorbance in a KBr pellet. Infrared absorption spectra were obtained directly on the aqueous size-fractioned concentrates with CIR (Spectra Tech CIRCLE accessory). Raman spectra were taken by using an argon ion laser (Spectra-Physics Model 2025-05), a triple-grating monochromator (Spex Triplemate Model 1877), and a photodiode array detector system (Princeton Applied Research Model 1420). All Raman and infrared spectra were taken at 2 cm resolution. 

Cylindrical internal reflectance infrared spectroscopy presents many advantages over conventional infrared techniques for the study of aquatic humic and fulvic materials. Samples can be studied in their natural state and in the aqueous environment from which they are isolated. Sample alterations due to drying and exposure to high pressures in the pellet forming process are avoided. In addition. 

Little has been published in this area in relation to humic substances. Humates tend to have retention times close to, or before, the solvent front in most reverse-phase columns. In one report (Rodgers et al., 1981), a fulvic material was separated into seven fractions on a silanized BioSil column. The fractions were analyzed by infrared spectroscopy. One of the fractions was patently not a fulvic acid, although it co-precipitated with fulvic acid. 

A study of the bulk properties of seawater humic substances was carried out by Kerr and Quinn (1975), while a detailed structural analysis was undertaken by Stuermer (1975) and Stuermer jmd Harvey (1978). Stuermer discussed the structural features in terms of origin, chemical and physical properties, interaction in the sea and eventual fate. As an example of the formation of a humic substance in seawater, we will discuss Stuermer s proposed structure of seawater fulvic material (Gagosian and Stuermer, 1977), the precursor compounds to its formation, and the condensation and polymerization reactions responsible for its synthesis. Although the material isolated by Stuermer represents only a small portion of the total hiunic material, it serves as an example of a possible condensation product. 

By reviewing microscopic observations, physicochemical properties and numerical simulations of colloid dynamics, BufQe et al. [24] have developed a three-component picture of the heteroaggregation of colloids. In marine systems the three components are inorganic colloids (IC), refractory organic matter (ROM) with characteristics similar to freshwater fulvic material, and fibrillar polymers (FP). 

Thermal quenching appears to increase the deactivation of the excited state by internal conversion (Senesi, 1990). Indeed this effect was observed from 10°C to 45°C by Baker (2005) on examining several riverine and wastewater DOM samples and humic standards. Interestingly, protein fluorescence appeared most susceptible to thermal quenching in several instances as compared to fulvic material fluorescence. As thermal quenching is sensitive to the fluorophores exposure to the energy supplied by increasingtemperature, these results imply that some species may be more easily perturbed than others and can provide information on DOM sources (Baker, 2005). 

Humic and fulvic acids (or their spectra within natural DOM) have been the primary focus of studies assessing optical property changes with respect to pH. Ma et al. (2010) found no significant changes in the optical properties of humic and fulvic material as pH was increased from 7 to 10. Several recent studies have assessed changes in amino acid... 

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