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1.
The molecular-weight distributions of fulvic and humic acids in sediments and their complexes with metal ions (Cu(2+), Zn(2+), Mn(2+)) were investigated by gel filtration. In all cases, metal complexes were found in the fulvic and humic acids. In the complexes the metals were bound to the high molecular-weight fulvic and humic polymers. By use of gel filtration, stability constants for the complexes of copper, zinc and manganese with fulvic acids have been measured. Scatchard plots indicate the presence of two classes of binding site with stability constants of 2.3 x 10(7) and 1.4 x 10(6) for copper, 2.1 x 10(6) and 6.6 x 10(4) for zinc and 1.8 x 10(5) and 7.3 x 10(3) for manganese, respectively. 相似文献
2.
J. Z. Du W. J. Li H. Q. Zhang X. D. Wang Z. J. You C. Y. Zhou W. M. Dong Z. Y. Tao 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(3):651-654
The stability constants for tracer concentrations of Co(II) complexes with both the red earth humic and fulvic acids were
determined at pH 5.9 and ionic strength 0.010 mol/l by using theArdakani-Stevenson cation exchange equilibrium method and the radiotracer60Co. It was found that the 1:1 complexes of Co(II) with the red earth humic and fulvic acids were formed and that the average
values of logβ (stability constant) of humic and fulvic acid complexes were 5.76±0.19 and 4.42±0.03, respectively. 相似文献
3.
A study of antimony complexed to soil-derived humic acids and inorganic antimony species along a Massachusetts highway 总被引:2,自引:0,他引:2
Gabriel Ceriotti 《Microchemical Journal》2009,91(1):85-93
Antimony is a toxic metalloid and is often present in inorganic forms such as more toxic Sb(III) and less toxic Sb(V). Auto brake linings are major contributors to antimony emissions along heavily traveled highways. In this study the distribution of water extractable Sb(III) and Sb(V) species along a Massachusetts highway was investigated. Antimony complexed to roadside soil-derived humic acids was studied by ion chromatography (IC) and size exclusion chromatography (SEC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Thirty surface soil and soil core samples along route 116 in western Massachusetts were collected. Two soil-derived humic acids were extracted from the roadside soils. Elevated levels of nitric acid-extractable Sb (range: 2.9-24.9 µg/kg) and Pb (range: 10.4-2420 mg/kg) were found in the soil along the road and correlated well with highway traffic patterns. Sb(V) was the dominant species present in both surface and soil core samples, and is mostly confined to the top 20-cm layer of soil. HA mediated Sb(III) to Sb(V) oxidation was relatively fast and demonstrated pseudo-first order kinetics, where pseudo rate constant k is 3.033 h-1. Antimony bound to soil-derived humic acid molar mass fractions was identified. 相似文献
4.
A nonionic macroreticular styrene/divnylbenzene copolymer, Amberlite XAD-2 resin is pulverized to 1–10 μm and treated with indium ions to saturate traced of cation exchange sites for the quantitative separation of humic complexes from cations. A 100-ml filtered sample is passed through an indium-treated XAD-2 column (16 diameter, 5 mm tall) at pH 5 at a flow rate of 2 ml min? to sorb heavy metals complexed with humic and fulvic acids. Inorganic cations and anions, EDTA complexes and colloidal hydrated iron(III) oxide are not retained on the column at all. The heavy metals sorbed on the column are then ultrasonically desorbed with 0.5 M nitric acid and determined by graphite-furnace atomic absorption spectrometry. The results fo two river water samples obtained are in good agreement with those obtained when the macroreticular weak-base anion-exchanger DEAE-Sephadex A-25 is used. 相似文献
5.
Liquid-liquid extraction preconcentration technique which allows the achievement of extremely high ratio between the aqueous and organic phase was specified as semi-microextraction. A modified highly effective liquid phase semi-microextraction (LSME) procedure was developed for preconcentration and determination of ultra trace levels of inorganic antimony species in environmental waters using electrothermal atomic absorption spectrometry (ETAAS) for quantification. Antimony(III) species were selectively extracted as dithiocarbamate complexes from 100 mL aqueous phase into 250 μL xylene at pH range of 5-8. Total Sb was determined using the same extraction system over a sample acidity range of pH 0-1.2 without the need for pre-reduction of Sb(V) to Sb(III). The concentration of Sb(V) was obtained as the difference between that of total antimony and Sb(III). With an 8 min extraction an enrichment factor of 400 was achieved. The limit of detection (3 s) was 2 ng L−1 Sb. The method was not affected by the presence of up to 0.01% humic acid, 0.025 mol L−1 EDTA, 0.01 mol L−1 tartaric acid and 0.001 mol L−1 F−. Recoveries of spiked Sb(III) and Sb(V) in river, tap, and sea water samples ranged from 93 to 108%. The results for total antimony concentration in the river water reference material SLRS-5 were in good agreement with the information value. The procedure was applied to the determination and quantification of dissolved antimony species in natural waters. 相似文献
6.
《Journal of Coordination Chemistry》2012,65(1-2):81-96
Abstract In order to assess the aluminium binding ability of humic and fulvic acids, important organic soil constituents, a pH-potentiometric study was made of the proton and aluminium(III) complexes of various bi-, tri- and tetradentate catechol and salicylic acid derivatives at 25°C and at an ionic strength of 0.20moldm?3 (KC1). The stability data revealed that at low pH the salicylate function, and at high pH the catecholate function, is preferentially bound to the aluminium ion. In the intermediate pH range, mixed hydroxo complexes and other di/oligomeric species are also formed. With an increase of the number of available coordinating sites in the molecule, the tendency to oligomeric complex formation increases, while the tendency to metal ion hydrolysis decreases. 相似文献
7.
Alexandra C. Stenson 《Rapid communications in mass spectrometry : RCM》2009,23(4):465-476
The interaction between metals and naturally occurring humic substances and the thereby induced issues of bioavailability and hydrogeochemical turnover of metal ions in natural waters have been the subject of intense study for decades. Traditional bulk techniques to investigate metal‐humic binding (e.g. potentiometry and inductively coupled plasma mass spectrometry (ICP‐MS)) can provide quantitative results for the relative abundance and distribution of metal species in humic samples and/or overall binding constants. The shortcoming of these bulk techniques is the absence of structural detail. Ultra‐high‐resolution mass spectrometry, currently the only technique demonstrated to resolve individual humic ions, is not generally employed to provide the missing qualitative information primarily because the identification of metal complexes within the already complex mixtures of humic substances is non‐trivial and time‐consuming to the extent of eliminating any possibility for real‐time manipulation of chelated analytes. Here, it is demonstrated that with tailored selection of the metal ion, it is possible to visually identify large numbers of metal‐humic complexes (~500 for Be2+, ~1100 for Mn2+, and ~1500 for Cr3+) in real‐time as the spectra are being acquired. Metal ions are chosen so that they form primarily even‐m/z complexes with humic ions. These even‐m/z complexes stand out in the spectrum and can readily be characterized based on molecular formulae, which here revealed for example that Suwannee River fulvic acid (SRFA) complexes encompassed primarily highly oxygenated fulvic acids of relatively low double‐bond equivalence. Facile, real‐time identification of even‐m/z metal‐humic complexes additionally allows for the specific selection of metal‐humic complexes for MSn analysis and in‐trap ion‐neutral reactions enabling investigation of metal‐humic complex structure. MS/MS data were collected to demonstrate the potential of the technique as well as highlight some of the remaining challenges. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
8.
A. A. Helal Aly A. Helal N. Z. Salim S. M. Khalifa 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(2):369-375
Summary In a previous paper we studied the interaction of the radionuclides 110mAg, 60Co and 65Zn with peat humin. These nuclides are among the fission or corrosion products in nuclear reactors. The aim of this paper
is to study the effect of certain ligands, which are present in the environment, such as humic acid, fulvic acid, EDTA and
urea, on the sorption of these radionuclides by humin. The obtained results indicated that urea has no effect on the sorption
of Co and Zn by humin, and only a little in case of Ag. However, the presence of the other ligands (humic acid, fulvic acid
or EDTA) leads to different decreases in the sorption of the three nuclides by humin. The results are interpreted in the light
of the complex formation between ligands and the metal cations and of the strength of binding of these cations to the humin
sorbent. The release of Ag+in the presence of different ligands was found to follow the order: humic acid>EDTA>fulvic acid>urea. In the case of both
Co2+and Zn2+, the sequence is changed to be: EDTA>humic acid>fulvic acid>urea, with a higher release in the case of Zn2+. The results showed that cobalt is bound more strongly to humin than silver and zinc. The sulphur content of the humic fractions
plays a significant role in the competition for silver and zinc. 相似文献
9.
《Journal of Coordination Chemistry》2012,65(1-4):173-186
Abstract Stability constants for the complexation of zinc(II), lead(II), and bismuth(III) by the vicinal dithiolate chelating agent meso-dimercaptosuccinic acid (DMSA) have been determined by a combination of potentiometric titration and spectrophotometric competition at 25°C and 0.1 M ionic strength. The spectrophotometric studies use the shifts in the ultraviolet bands of the thiol groups to quantitate metal binding to DMSA in the presence of competitive aminocarboxylic acids. Bismuth(III) forms a bis(DMSA) chelate with an exceptionally high stability constant of 1043,87. This complex undergoes a series of protonations over the pH range 10 to 2, but there appears to be no measurable dissociation of ligand over this pH range. The zinc-DMSA system is dominated by a Zn2(DMSA)2 dimer, which has a protonation constant of 106 and dissociates completely at lower pH. No more than 20% of total zinc exists as a monomeric complex at any pH. Lead forms a 1:1 complex with a stability constant of 1017,4. Insoluble protonated lead complexes precipitate at pH < 6.5. Speciation calculations have been used to evaluate the potential competition from serum zinc to the binding of Pb2+ and Bi3+ by DMSA. The results indicate that DMSA should be relatively effective for the in vivo chelation of both Bi3+ and Pb2 +. 相似文献
10.
Distribution of humic and fulvic acids in participate or dissolved form is studied by using simple leaching and sorption techniques. After filtration of water sample (100–200 ml), the filter along with suspended particles is treated with 5 ml of chloroform and 3 ml of 0.1 mol/l sodium hydroxide solution. The filter dissolves completely in the organic phase, while the suspended particles remain in the aqueous phase enabling a leaching of humic substances. The leaching is repeated once more with 2 ml of 0.1 mol/l sodium hydroxide solution. The humic and fulvic acids in the combined solution are fractionated at pH l by filtration, where the membrane filter is preliminarily coated with sodium dodecyl sulfate. On the other hand, dissolved humic substances are concentrated from a 50-ml filtered sample by sorption on a DEAE-cellulose column. They are desorbed with 5 ml of 0.1 mol/l sodium hydroxide solution and fractionated at pH 1. The spectrophotometric analysis of river water reveals that fulvic acid is predominant in suspended particles as well as in filtered samples. The concentration of dissolved humic and fulvic acids is approximately ten times that of suspended particles. 相似文献
11.
We have developed a concise tool for the investigation of the transition of humic substances in environmental water. The separation
of water-soluble humic substances was achieved rapidly and effectively by capillary electrophoresis using a polyacrylamide-coated
capillary and a phosphate electrophoretic buffer solution (pH 7.0) containing hydroxyethyl cellulose. The separation mechanism
was assessed using the ultrafiltration technique. The effect of the complexation of humic substances with metal ions was studied
by using the proposed method. When Fe(III) ions or EDTA was added to the sample solution of fulvic acid, a distinct change
in the electropherogram pattern based on the conformational change of fulvic acid was observed. The successful application
of the proposed method to the characterization of humic substances in a river water sample was also demonstrated.
Figure Addition of Fe(III) ions or EDTA to a solution containing fulvic acid (FA) results in a distinct change in the electropherogram
pattern, which reflects the conformational change of FA: this forms the basis for the characterization of humic substances
in river water samples 相似文献
12.
The effects of pH and light on the interaction between fulvic acid and iron have been investigated through studies of the kinetics of exchange of iron between fulvic acid and 1,10-pehnanthroline(a strong iron(II) complexing agent), and of the quenching of intrinsic fulvic acid fluorescence by iron in solutions of pH 4.0 and 6.5 containing an excess of fulvic acid. The results enable the iron-fulvic acid interaction to be described in terms of operationally defined iron-fulvic acid groupings, the proportions of which are markedly dependent on pH and light conditions. At pH 4.0 fulvic acid exhibits considerable reducing ability with the result that a substantial portion of iron is present in reduced, unbound form. Irradiation of fulvic acids at this pH markedly increases their reducing ability. Iron that is not reduced is present as small (ultrafilterable), strongly bound iron(III) complexes. Iron bound in this form is an effective quencher of intrinsic fulvic acid fluorescence. At higher pH, essentially all of the iron is relatively strongly bound, with most being in the form of large (non-ultrafilterable) iron(III)—fulvic acid groupings. These groupings are not altered significantly by irradiation and iron bound in this form is not a very effective quencher of intrinsic fulvic acid fluorescence. 相似文献
13.
14.
Masataka Hiraide Hiroshi Hommi Hiroshi Kawaguchi 《Fresenius' Journal of Analytical Chemistry》1992,342(4-5):387-390
Summary The extraction behaviour of copper(II) and iron(III) was studied in the presence of humic substances (humic and fulvic acids) by using DDTC and chloroform. Copper-humic complexes were nearly completely extracted over the pH range 3–9, indicating that DDTC reacted with copper more strongly than humic substances. Iron-humic substances, mainly existing as hydrated iron(III) oxide covered with humic substances, were not extracted quantitatively (recovery <70%), though hydrated iron(III) oxide itself was extracted with greater than 93% yields at pH 5–9. For complete extraction of the humic species, ammonium pyrrolidinedithiocarbamate (APDC) was useful, because it allowed extraction from slightly acidic solutions where the binding of iron-humic substances became weak. 相似文献
15.
The speciation of inorganic Sb(III) and Sb(V) ions in aqueous solution was studied. The adsorption behavior of Sb(III) and Sb(V) ions were investigated as iodo and ammonium pyrollidine dithiocarbamate (APDC) complexes on a column filled with Amberlite XAD-8 resin. Sb(III) and Sb(V) ions were recovered quantitatively and simultaneously from a solution containing 0.8 M NaI and 0.2 M H2SO4 by the XAD-8 column. Sb(III) ions were also adsorbed quantitatively as an APDC complex, but the recovery of the Sb(V)-APDC complex was found to be <10% at pH 5. According to these data, the concentrations of total antimony as Sb(III)+Sb(V) ions and Sb(III) ion were determined with XAD-8/NaI+H2SO4 and XAD-8/APDC systems, respectively. The Sb(V) ion concentration was calculated by subtracting the Sb(III) concentration found with XAD-8/APDC system from the total antimony concentration found with XAD-8/NaI+H2SO4 system. The developed method was applied to determine Sb(III) and Sb(V) ions in samples of artificial seawater and wastewater. 相似文献
16.
The H-point standard addition method (HPSAM) was applied to kinetic data for simultaneous determination of Sb(V) and Sb(III) and also selectively determines Sb(V) in the presence of Sb(III). The method is based on the differences between rate of complexation of pyrogallol red with Sb(V) and Sb(III) at pH=2. Sb(V) can be determined in the range of 0.3-2.0 μg ml−1 with satisfactory accuracy and precision in the presence of excess Sb(III). Good selectivity was obtained over the variety of metal ions. The proposed method was used for determination of Sb(V) and Sb(III) in river and spring water samples. 相似文献
17.
P. Schmitt A. Kettrup D. Freitag A. W. Garrison 《Fresenius' Journal of Analytical Chemistry》1996,354(7-8):915-920
Humic and fulvic acids from various sources have been shown to give different electropherograms by capillary zone electrophoresis (CZE), depending on the pH of the electrolyte. This CZE work is extended here through investigations involving the titration of humic and fulvic acids with Fe(III) and Cu(II) cations. As increasing amounts of these cations were added to the humic substances (HUS), flocculation of metal-humic complexes occurred. This is believed to be caused by binding of the metal cations with negative carboxyl and phenolic sites on the HUS, resulting in a decrease of the repulsive forces that keep the HUS in a conformation more suitable for water solubility. The flocculated complexes were separated from the supernatant by centrifugation, and the supernatants were characterized as to total organic carbon (TOC) content, molecular weight (MW) using gel permeation chromatography, and average electrophoretic mobility (AEM) using CZE. The extent of flocculation correlated with both TOC and quantitative CZE measurements. The MW of the HUS remaining in solution actually decreased, presumably because of precipitation of larger molecules as they became insoluble because of reactions with the metals. Humic acids showed total precipitation of TOC with both metals at a concentration equivalent to their measured acidity. CZE demonstrated that certain fulvic acid fractions (low molecular weight phenolic acids) remained in solution even at high metal concentrations. In summary, changes in electrophoretic behavior of the soluble HUS could be related to changes in charge-to-mass ratios (charge densities) of both humic and fulvic acids with increasing metal cation concentration (neutralization). The copper treated HUS showed changes in their electrophoretic behavior even at low metal concentrations before flocculation, whereas the iron treated HUS flocculated uniformally over the range of added iron without significant changes in AEM. Thus these changes in CZE patterns illustrate different specific binding sites of the HUS for each metal. 相似文献
18.
Schmitt P Kettrup A Freitag D Garrison AW 《Analytical and bioanalytical chemistry》1996,354(7-8):915-920
Humic and fulvic acids from various sources have been shown to give different electropherograms by capillary zone electrophoresis (CZE), depending on the pH of the electrolyte. This CZE work is extended here through investigations involving the titration of humic and fulvic acids with Fe(III) and Cu(II) cations. As increasing amounts of these cations were added to the humic substances (HUS), flocculation of metal-humic complexes occurred. This is believed to be caused by binding of the metal cations with negative carboxyl and phenolic sites on the HUS, resulting in a decrease of the repulsive forces that keep the HUS in a conformation more suitable for water solubility. The flocculated complexes were separated from the supernatant by centrifugation, and the supernatants were characterized as to total organic carbon (TOC) content, molecular weight (MW) using gel permeation chromatography, and average electrophoretic mobility (AEM) using CZE. The extent of flocculation correlated with both TOC and quantitative CZE measurements. The MW of the HUS remaining in solution actually decreased, presumably because of precipitation of larger molecules as they became insoluble because of reactions with the metals. Humic acids showed total precipitation of TOC with both metals at a concentration equivalent to their measured acidity. CZE demonstrated that certain fulvic acid fractions (low molecular weight phenolic acids) remained in solution even at high metal concentrations. In summary, changes in electrophoretic behavior of the soluble HUS could be related to changes in charge-to-mass ratios (charge densities) of both humic and fulvic acids with increasing metal cation concentration (neutralization). The copper treated HUS showed changes in their electrophoretic behavior even at low metal concentrations before flocculation, whereas the iron treated HUS flocculated uniformally over the range of added iron without significant changes in AEM. Thus these changes in CZE patterns illustrate different specific binding sites of the HUS for each metal. 相似文献
19.
Kelly M ElkinsDonald J Nelson 《Coordination chemistry reviews》2002,228(2):205-225
Aluminum ion (Al3+) in the ‘free’ (aquo) state is becoming increasingly prevalent in environmental waters, especially fresh waters, as a consequence of acid rain and other environmental processes. As Al3+ ion is known to affect markedly a wide range of biological systems, and since the presence of Al3+ in humans has been linked to a number of human diseases, it is important to understand the speciation of Al3+ ion in natural waters. Since some of the most important complexation agents for Al3+ in both fresh and sea waters are members of the complex humic substances group, it is important to understand the manner in which Al3+ interacts with this class of molecules, especially since binding of Al3+ to these molecules can effectively increase the bioavailability of this toxic metal ion to biological systems. The objective of this review is to present the current state of our understanding of aqueous aluminum complexation with the most acidic members (and therefore the most likely candidates for serving as Al3+ complexing agents) of the humic substances group, the fulvic acids. Much of the current knowledge has been revealed by comprehensive fluorescence titration analyses. Some additional information has come from other experimental approaches, including infrared spectroscopy, nuclear magnetic resonance spectroscopy, and a variety of electrochemical approaches. In this review, we also report on the results of our recent fluorescence and IR spectroscopy survey of the interaction of metals from of all three Nieboer and Richardson categories of environmental metals (Class A, Class B and Intermediate Class) with the fulvic acid sub-group of the humic substances. This has proven helpful in understanding some of the unique spectral behaviors of the Al3+-fulvic acid complex vis-a-vis fulvic acid complexes with many other metal ions. The results of our fluorescence and IR experiments with the model compounds, such as salicylic and phthalic acids, have allowed confirmation of the important roles played by both salicylic acid-like sites and phthalic acid-like sites in the unique complexation of Al3+ to humic substances, and help to explain some of the observed spectroscopic changes associated with Al3+ ion complexation to humic material. From the current work, it seems clear that major sources of the deviation in spectral properties between Al3+ and many other metal ions (across all three Nieboer and Richardson categories) are the unusually high value of its charge density and relatively low propensity for involvement in covalent bonding interactions (i.e. a very high ionic index combined with a relatively low covalent index in the Nieboer and Richardson classification of environmental metals), as well as affinity for certain functional groups. 相似文献
20.
T. Sakuragi S. Sawa S. Sato T. Kozaki T. Mitsugashira M. Hara Y. Suzuki 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(3):349-353
Summary In the wide pH range of 4 to 10, distribution ratios of Am(III)-humate species to free Am(III) ions (DAmHA = [Am(III)HA]/[Am(III)]free) were determined at 10 ppm (4.7 . 10-5 eq/dm3) of humic acid and 0.1M NaClO4 by a cation-exchange equilibrium method under N2 atmosphere. The DAmHA was insensitive to an increase in pH (logDAmHA ≈ 2.6-2.8), which indicates the formation of mixed hydroxo-humate complexes. The present DAmHA value is larger than the estimated value from available stability constants for ternary complexations by spectroscopic analysis (1.4-2.1) and is markedly smaller than that of Eu(III) obtained by the dialysis method (3.7-8.0) reported in the literatures. The DAmHA obtained in the present study is widely applicable to estimate the actinide(III) and lanthanide(III) sorption on minerals in the presence of humic and fulvic acids. 相似文献