EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides. II. Effects of chloride and sulfate

Common complexing ligands such as chloride and sulfate can significantly impact the sorption of Hg(II) to particle surfaces in aqueous environmental systems. To examine the effects of these ligands on Hg(II) sorption to mineral sorbents, macroscopic Hg(II) uptake measurements were conducted at pH 6 and [Hg](i)=0.5 mM on goethite (alpha-FeOOH), gamma-alumina (gamma-Al(2)O(3)), and bayerite (beta-Al(OH)(3)) in the presence of chloride or sulfate, and the sorption products were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of chloride resulted in reduced uptake of Hg(II) on all three substrates over the Cl(-) concentration ([Cl(-)]) range 10(-5) to 10(-2) M, lowering Hg surface coverages on goethite, gamma-alumina, and bayerite from 0.42 to 0.07 micromol/m(2), 0.06 to 0.006 micromol/m(2), and 0.55 to 0.39 micromol/m(2) ([Cl(-)]=10(-5) to 10(-3) M only), respectively. This reduction in Hg(II) uptake is primarily a result of the formation of stable, nonsorbing aqueous HgCl(2) complexes in solution, limiting the amount of free Hg(II) available to sorb. At higher [Cl(-)] beam reduction of Hg(II) to Hg(I) was observed, resulting in the possible formation of aqueous Hg(2)Cl(2) species and the precipitation of calomel, Hg(2)Cl(2(s)). The presence of sulfate caused enhanced Hg(II) uptake over the sulfate concentration ([SO(4)(2-)]) range 10(-5) to 0.9 M, increasing Hg surface coverages on goethite, gamma-alumina, and bayerite from 0.39 to 0.45 micromol/m(2), 0.11 to 0.38 micromol/m(2), and 0.36 to 3.33 micromol/m(2), respectively. This effect is likely due to the direct sorption or accumulation of sulfate ions at the substrate interface, effectively reducing the positive surface charge that electrostatically inhibits Hg(II) sorption. Spectroscopic evidence for ternary surface complexation was observed in isolated cases, specifically in the Hg-goethite-sulfate system at high [SO(4)(2-)] and in the Hg-goethite-chloride system.     

Mercury(II) cysteine complexes in alkaline aqueous solution

Mercury(II) complexes with l-cysteine (H(2)Cys) in alkaline aqueous solutions have been structurally characterized by means of extended X-ray absorption fine structure (EXAFS) spectroscopy. The distribution of [Hg(Cys)(n)] (n = 2, 3, and 4) species in approximately 0.09 mol dm(-3) mercury(II) solutions with H(2)Cys/Hg(II) ratios varying from 2.2 to 10.1 has been evaluated by fitting linear combinations of simulated EXAFS functions for the separate complexes to the experimental EXAFS data, aided by (199)Hg NMR and Raman results. For the [Hg(Cys)(2)](2-) and [Hg(Cys)(3)](4-) complexes and the novel four-coordinated Hg(Cys)(4) species that dominates in solutions with excess of cysteine (H(2)Cys/Hg(II) > 5), the mean Hg-S bond distances were found to be 2.35(2), 2.44(2), and 2.52(2) Angstroms, respectively. The minor amount of the linear [Hg(Cys)(2)](2-) complex that can still be discerned in solutions with ratios up to H(2)Cys/Hg(II) = 5 was derived from the distinct S-Hg-S symmetric stretching Raman band at 334 cm(-1). From (199)Hg NMR spectra, the chemical shift of the Hg(Cys)(4) species was estimated to -340 ppm with an amount exceeding 85% in the highest excess of cysteine, consistent with the EXAFS data.     

Mercury(II) penicillamine complex formation in alkaline aqueous solution

The complex formation between mercury(II) and penicillamine (H(2)Pen = 3,3'-dimethyl cysteine) in alkaline aqueous solutions (pH approximately 2) has been investigated with extended X-ray absorption fine structure (EXAFS) and 199Hg NMR spectroscopy. By varying the penicillamine concentration (C(H(2)Pen) = 0.2-1.25 M) in approximately 0.1 M Hg(II) solutions, two coexisting major species [Hg(Pen)2](2-) and [Hg(Pen)3](4-) were characterized with mean Hg-S bond distances 2.34(2) and 2.44(2) A, respectively. The [Hg(Pen)2](2-) complex with two deprotonated penicillamine ligands forms an almost linear S-Hg-S entity with two weak chelating Hg-N interactions at the mean Hg-N distance 2.52(2) A. The same type of coordination is also found for the corresponding [Hg(Cys)2](2-) complex in alkaline aqueous solution with the mean bond distances Hg-S 2.34(2) A and Hg-N 2.56(2) A. The relative amounts of the [Hg(Pen)2](2-) and [Hg(Pen)3](4-) complexes were estimated by fitting linear combinations of the EXAFS oscillations to the experimental spectra. Also their (199)Hg NMR chemical shifts were used to evaluate the complex formation, showing that the [Hg(Pen)3](4-) complex dominates already at moderate excess of the free ligand ([Pen(2-)] > approximately 0.1 M).     

Application of a wool column for flow injection online preconcentration of inorganic mercury(II) and methyl mercury species prior to atomic fluorescence measurement

The use of an unmodified native sheep wool packed minicolumn for the online preconcentration of Hg(II) and methyl mercury species prior to the determination of mercury by atomic fluorescence spectrometry was investigated. Experimental conditions, such as pH, desorbing agents, volume of solution were optimized. 0.5M thioglycolic acid was found to be a successful eluting agent for both mercury species. Breakthrough and total capacities were determined. The method is simple and rapidly applicable for the determination of Hg(II) and methyl mercury in tap water. The accuracy of the method was examined by the analysis of a peach leaves standard reference material. Recoveries of spiked mercury species in tap water were 105.8% for Hg(II) and 98.8% for methyl mercury.     

Test method for the separate determination of mercury(II), cadmium, and lead in one sample on the fibrous sorbent PANV-AV-17

The sorption of Hg(II), Cd(II), and Pb(II) as anionic complexes on the solid phase of polyacrylonitrile fiber filled with the AV-17 anion exchanger from NaCl and KI solutions and their complexation with 4-(2-pyridylazo)resorcinol (PAR) and dithizone were studied. A test method was developed for the individual determination of Hg(II), Cd(II), and Pb(II) from one sample on three support disks. From the same solution, by the successive sorption on two disks from a 0.2 M NaCl solution, mercury was determined with dithizone and cadmium was determined with PAR. After the addition of a KI solution and sorption on the third disk, lead was determined with PAR. Using the added-found method, the procedure was approved in the analysis of natural sodium chloride water. The detection limit was 0.01 mg/L for Hg(II) and 0.02 mg/L for Cd(II) and Pb(II) for a volume of the analyzed sample of 25 mL. The time of the analysis of five or six samples (determination of three elements) is no longer than 50 min.     

Sorption and filtration of Hg(II) ions from aqueous solutions with a membrane containing poly(ethyleneimine) as a complexing polymer

The performances of a PVA/PEI complexing membrane for the removal of Hg(II) from aqueous solutions were investigated by performing sorption and filtration experiments. This membrane, that was previously shown to ensure efficient sorption of the heavy metal ions Pb(II), Cd(II) and Cu(II) at pH 5, presented a higher affinity for Hg(II) at pH 2.5. The sorption equilibrium was satisfactorily represented by the Langmuir model. In view of possible application to the treatment of industrial wastewaters, the effects of parameters such as pH, temperature, water hardness, and the presence of complexing chloride anions were investigated. The effect of increasing temperature was not straightforward: the complexation equilibrium constant decreased, but the mass of mercury sorbed increased, probably due to the higher mobility of the polymer chains that made internal sites available for complexing mercury. The maximum retention capacity of the membrane was 311 mg Hg g⁻¹. Also, operating at large calcium or chloride concentrations was not detrimental to the membrane performances. For regeneration of the membrane, a 0.05 M solution of EDTA is recommended on the basis of limited performance loss. When used in the filtration mode, the elimination ratio of Hg(II) was close to 99%.     

Exploring the interaction of mercury(II) by N(2)S(2) and NS(3) anthracene-containing macrocyclic ligands: photophysical, analytical, and structural studies

The complexation properties toward Hg(II) of six macrocyclic ligands, 3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1), 7-(9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L2), 7-(10-methyl-9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L3), 7,7'-[9,10-anthracenediylbis(methylene)]bis-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L4), 1,4,7-trithia-11-azacyclotetradecane (L5), and 11,-(anthracen-9-ylmethyl)-1,4,7-trithia-11-azacyclotetradecane (L6), were studied. The stoichiometries of the formed species were determined from absorption and fluorescence titrations. In these anthracene-containing macrocycles, a fluorescent quenching of the emission was found upon Hg(II) addition. The X-ray crystal structure of [HgCl2(L2)] x 1/2CH2Cl2 was determined. The asymmetric unit contains two independent [HgCl2(L2)] molecules and one dichloromethane molecule. Each Hg(II) ion is coordinated by the pyridine nitrogen, the two sulfur atoms of one L2 molecule, and two chloride ions. Analytical studies using solvent extraction separation of Hg(II) from aqueous solutions were performed to determine the Hg(II) extraction capability of ligands L1, L2, and L5.     

Living organisms as an alternative to hyphenated techniques for metal speciation. Evaluation of baker's yeast immobilized on silica gel for Hg speciation

The use of living organisms for metal preconcentration and speciation is discussed. Among substrates, Saccharomyces cerevisiae baker's yeast has been successfully used for the speciation of mercury [Hg(II) and CH₃Hg⁺], selenium [Se(IV) and Se(VI)] and antimony [Sb(III) and Sb(V)]. To illustrate the capabilities of these organisms, the analytical performance of baker's yeast immobilized on silica gel for on-line preconcentration and speciation of Hg(II) and methylmercury is reported. The immobilized cells were packed in a PTFE microcolumn, through which mixtures of organic and inorganic mercury solutions were passed. Retention of inorganic and organic mercury solutions took place simultaneously, with the former retained in the silica and the latter on the yeast. The efficiency uptake for both species was higher than 95% over a wide pH range. The speciation was carried out by selective and sequential elution with 0.02 mol L⁻¹ HCl for methylmercury and 0.8 mol L⁻¹ CN⁻ for Hg(II). This method allows both preconcentration and speciation of mercury. The preconcentration factors were around 15 and 100 for methylmercury and mercury(II), respectively. The method has been successfully applied to spiked sea water samples.     

Dual-cloud point extraction as a preconcentration and clean-up technique for capillary electrophoresis speciation analysis of mercury

A novel dual-cloud point extraction (dCPE) technique is proposed in this paper for the sample pretreatment of capillary electrophoresis (CE) speciation analysis of mercury. In dCPE, cloud point was carried out twice in a sample pretreatment. First, four mercury species, methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) formed hydrophobic complexes with 1-(2-pyridylazo)-2-naphthol (PAN). After heating and centrifuging, the complexes were extracted into the formed Triton X-114 surfactant-rich phase. Instead of the direct injection or analysis, the surfactant-rich phase containing the four Hg species was treated with 150 microL 0.1% (m/v) l-cysteine aqueous solution. The four Hg species were then transferred back into aqueous phase by forming hydrophilic Hg-l-cysteine complexes. After dCPE, the aqueous phase containing the Hg-l-cysteine complexes was subjected into electrophoretic capillary for mercury speciation analysis. Because the concentration of Triton X-114 in the extract after dCPE was only around critical micelle concentration, the adsorption of surfactant on the capillary wall and its possible influence on the sample injection and separation in traditional CPE were eliminated. Plus, the hydrophobic interfering species were removed thoroughly by using dCPE resulted in significant improvement in analysis selectivity. Using 10 mL sample, 17, 15, 45, and 52 of preconcentration factors for EtHg, MeHg, PhHg, and Hg(II) were obtained. With CE separation and on-line UV detection, the detection limits were 45.2, 47.5, 4.1, and 10.0 microg L(-1) (as Hg) for EtHg, MeHg, PhHg, and Hg(II), respectively. As an analysis method, the present dCPE-CE with UV detection obtained similar detection limits as of some CE-inductively coupled plasma mass spectrometry (ICPMS) hyphenation technique, but with simple instrumental setup and obviously low costs. Its utilization for Hg speciation was validated by the analysis of the spiked natural water and tilapia muscle samples.     

Extraction of metal ions using chemically modified silica gel: a PIXE analysis

Organic ligand with carboxyhydrazide functional group was immobilised on the surface of silica gel and the metal binding capacity of the ligand-embedded silica was investigated. The functional group was covalently bonded to the silica matrix through a spacer of methylene groups by sequential reactions of silica gel with dibromobutane, malonic ester and hydrazine in different media. Surface area value of the modified silica was determined. The changes in surface area were correlated with the structural change of the silica surface due to chemical modifications. A mixture solution of metal ions [K(I),Cr(III),Co(II),Ni(II),Cu(II),Zn(II),Hg(II) and U(VI)] was treated with the ligand-embedded silica in 10(-3) M aqueous solution. The measurement of metal extraction capacity of the silica based ligand was done by multielemental analysis of the metal complexes thus formed by using Proton Induced X-ray Emission (PIXE) technique.     

Poly(acrylamide) grafts on spherical bead polymers for extremely selective removal of mercuric ions from aqueous solutions

Poly(acrylamide) grafted from solid polymer particles provides a simple solution for extremely selective removal of mercuric ions from aqueous solutions. The grafting of polyacrylamide has been performed, in high yields (164%), by redox initiation from iminoacetic acid groups created on crosslinked spherical beads (210–420 μm) of glycidyl methacrylate/methyl methacrylate/ethylene glycol dimethacrylate terpolymer. In the grafting, homopolymer formation has been reduced greatly (22%) by the treatment of the bead polymer with ceric ammonium nitrate before the addition of acrylamide monomer. The mobility of the graft chains provides nearly homogeneous reaction conditions and rapid mercury binding ability, as for low molecular weight amides [mercury sorption by a 0.105‐g polymer sample from 105 mL of a 7.74 × 10^?4 mol L^?1 (～155 ppm) Hg(II) solution shows first‐order kinetics with respect to the Hg(II) concentration, k = 1.1 × 10^?3 s^?1]. The mercury sorption capacity under nonbuffered conditions is around 3.6 mmol g^?1 (i.e., 720 g of mercury/kg) and mostly occurs with the formation of diamido–mercury linkages, which result in the crosslinking of polyacrylamide brushes outside the spherical beads. The crosslinks can be destroyed by treatment with hot acetic acid, without hydrolysis of the amide groups. This process allows a complete elution of the mercury as mercury acetate, and the overall result is reversible crosslinking of the outer shell by mercuric ions. The material presented is efficient in the removal of mercury at concentrations measured in parts per million, and the mercury sorption is extremely selective over some foreign ions, such as Fe(III), Cd(II), Zn(II), and Pb(II). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3068–3078, 2002     

Determination of trace levels of mercury in aqueous solutions by inductively coupled plasma atomic emission spectrometry: Elimination of the ‘memory effect’

The measurement of mercury in aqueous solutions by ICP-AES is adversely affected by the memory effect wherein mercury accumulates within the sample introduction system and is slowly released over time to give increasing response signals at the same initial mercury concentration. The memory effect is obviated by the addition of Hg(II) complexants: thiourea and gold(III) chloride are both effective in preventing mercury sorption and vapor buildup with the latter being preferred because the memory effect vanishes more rapidly. Conditions are described wherein it is possible to quantify low levels of mercury(II) in aqueous solutions by ICP-AES under routine operating conditions that can be applied to other metal ions by adding 1 mg of gold(III) chloride per 3 mg of mercury(II) to those solutions.     

Determination of trace levels of mercury in water samples based on room temperature phosphorescence energy transfer

A novel method has been developed for the sensitive determination of mercury in aqueous media by room temperature phosphorescence (RTP). The measurement principle is based on the energy transfer (ET) from a phosphor molecule (acting as a donor) to a Hg-sensitive dye (acceptor). To our acknowledgment this is the first RTP method for mercury measurement developed so far. α-Bromonaphthalene (BrN) was selected as the phosphorescent donor molecule (BrN can produce significant RTP emission in aqueous media in a β-cyclodextrin rigid microenvironment without deoxygenation).The absorption spectrum of the complex formed between mercury and the dithizone dye possesses a desirable spectral overlap with the RTP emission spectrum of the donor (BrN), giving rise to a nonradiative ET from the phosphor molecules to the mercury complex. An increase in the concentration of Hg(II) causes an increase on the concentration of the dithizone complex (acceptor) with the subsequent increase of the absorbance and, therefore, resulting in a decrease of the RTP emission. Both, RTP intensities and triplet lifetimes of the BrN decreased with increases on the Hg(II) concentration.Possible interferences present in natural waters, including different cations and anions, which could affect the analytical response, were evaluated and the analytical performance characteristics investigated. The use of phosphorescence measurements (low background noise signals) resulted in an improvement on the sensitivity of the Hg(II) detection higher than five times as compared to the molecular absorption spectrophotometric method for Hg(II) detection based on dithizone as Hg-indicator. A detection limit (D.L.) of 14 ng ml⁻¹ of Hg(II) was obtained by RTP with a precision of ±4.8% for five replicates of 300 ng ml⁻¹ of Hg(II). The usefulness of the method was successfully evaluated by the determination of Hg(II) in spiked natural water samples.     

Selective Pre-concentration and Solid Phase Extraction of Mercury（Ⅱ） from Natural Water by Silica Gel-loaded （E）-N-（1-Thien-2＇-ylethylidene）-1,2-phenylenediamine Phase

Silica gel-loaded （E）-N-（1-thien-2＇-ylethylidene）-1,2-phenylenediamine （TEPDA） phase was synthesized based on physical adsorption approaches. The stability of a chemically modified TEPDA especially in concentrated hydrochloric acid that was then used as a recycling and preconcentration reagent allowed the further uses of silica gel-loaded immobilized TEPDA phase. The application of this silica gel-loaded phase to sorption of a series of metal ions was performed by using different controlling factors such as the pH of the metal ion solution and the equilibration shaking time by the static technique. This difference was interpreted on the basis of selectivity incorporated in these sulfur containing silica gel-loaded TEPDA phases. Hg（Ⅱ） was found to exhibit the highest affinity towards extraction by these silica gel-loaded TEPDA phases. The pronounced selectivity was also confirmed by the determined distribution coefficients （Kd） of all the metal ions, showing the highest value reported for mercury（Ⅱ） extraction by the silica gel immobilized TEPDA phase. The potential applications of the silica gel immobilized TEPDA phase to selective extraction of mercury（Ⅱ） from aqueous solution were successfully accomplished and preconcentration of low concentration of Hg（Ⅱ） （30 pg·mL^-1） from natural tap water with a preconcentration factor of 200 for Hg（Ⅱ） off-line analysis was conducted by cold vapor atomic absorption analysis.     

Sorption isotherms of Nickel(II), Cobalt(II), Mercury(II), and Lead(II) ions on a phosphorus-containing polymeric sorbent

The influence of the concentration of a complexing ion on the sorption recovery of nickel, cobalt, mercury, and lead ions from aqueous solutions by a phosphorus-containing polymeric polybutadiene-based sorbent was studied. Sorption isotherms of the studied metal ions were processed by the Langmuir and Freindlich models. The affinity of metal ions to the functional groups of a sorbent and the stability of complexes were established to decrease in the order Hg(II) > Pb(II) > Co(II) > Ni(II).     

EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides. I. Effects of pH

The study of mercury sorption products in model systems using appropriate in situ molecular-scale probes can provide detailed information on the modes of sorption at mineral/water interfaces. Such studies are essential for assessing the influence of sorption processes on the transport of Hg in contaminated natural systems. Macroscopic uptake of Hg(II) on goethite (alpha-FeOOH), gamma-alumina (gamma-Al(2)O(3)), and bayerite (beta-Al(OH)(3)) as a function of pH has been combined with Hg L(III)-edge EXAFS spectroscopy, FTIR spectroscopy, and bond valence analysis of possible sorption products to provide this type of information. Macroscopic uptake measurements show that Hg(II) sorbs strongly to fine-grained powders of synthetic goethite (Hg sorption density Gamma=0.39-0.42 micromol/m(2)) and bayerite (Gamma=0.39-0.44 micromol/m(2)), while sorbing more weakly to gamma-alumina (Gamma=0.04-0.13 micromol/m(2)). EXAFS spectroscopy on the sorption samples shows that the dominant mode of Hg sorption on these phases is as monodentate and bidentate inner-sphere complexes. The mode of Hg(II) sorption to goethite was similar over the pH range 4.3-7.4, as were those of Hg(II) sorption to bayerite over the pH range 5.1-7.9. Conversion of the gamma-Al(2)O(3) sorbent to a bayerite-like phase in addition to the apparent reduction of Hg(II) to Hg(I), possibly by photoreduction during EXAFS data collection, resulted in enhanced Hg uptake from pH 5.2-7.8 and changes in the modes of sorption that correlate with the formation of the bayerite-like phase. Bond valence calculations are consistent with the sorption modes proposed from EXAFS analysis. EXAFS analysis of Hg(II) sorption products on a natural Fe oxyhydroxide precipitate and Al/Si-bearing flocculent material showed sorption products and modes of surface attachment similar to those for the model substrates, indicating that the model substrates are useful surrogates for the natural sediments.     

The fate of mercury species injected into coelomic fluid of starfish Leptasterias polaris

Mature starfish Leptasterias polaris, collected in the St Lawrence Estuary (eastern Canada), were exposed to two mercury species (HgCI₂ and CH₃HgCI) via injections into the coelomic fluid. In vivo effects of some complexing agents (glutathione, mercaptoethanol and EDTA) on the distribution of ²⁰³Hg-labelled species in starfish organs and tissues and their possible role in mercury transport through membranes were studied over a 24 h period. The excretion of ammonia and mercury was also measured. When injected alone, inorganic mercury and methylmercury [CH₃Hg(II)] were distributed in all organs, with a preferential adsorption in gonads, pyloric caeca and stomach. Mercury excretion was very low under all conditions studied. Mercaptoethanol, a small thiol ligand, was very efficient in reducing both mercury species in the coelomic fluid and seems to have promoted translocation towards most organs of the starfish. Its action is attributed to the formation of small and neutral complexes, HgL₂ and CH₃HgL, which can diffuse through membranes preserving their integrity. Glutathione increased the translocation of CH₃Hg(II) towards surrounding organs, but had no apparent effect on inorganic mercury. EDTA promoted the transport of inorganic mercury only. These results highlight (1) the particular interest of starfish to workers studying in vivo chemical complexation of mercury species, and (2) the potential role of complexing molecules in the biotransport of mercury species through living membranes.     

Thorium removal from aqueous solutions of Mexican erionite and X zeolite

Thorium(IV) removal from aqueous solutions by erionite and X zeolite was investigated. The Th(IV) uptake at different thorium nitrate concentrations (from 0.25 to 25 mM) was evaluated. The thorium content in the aqueous solution was determined by neutron activation analysis. Th(IV) retained by zeolites was 1.7 and 3.7 meq/g for erionite and X zeolite. In order to explain the thorium sorption process in both zeolites, ion exchange mechanism was considered. It was found that thorium sorption behavior is strongly dependent of the type of zeolite, the separation factor for Mexican erionite was α^Th(IV) _Na(I)<1, this zeolite shows preference for Na(I) rather than for Th(IV), however, by X zeolite, α^Th(IV) _Na(I)~1, this value suggested an approximately ideal ion exchange behavior. The effect of pH on thorium sorption was also considered. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectrophotometric determination of mercury in soils with triphenyltetrazolium chloride

The formation of the acidocomplex of mercury(II) with triphenyl-tetrazolium chloride is studied spectrophotometrically in water-organic media. The composition of the complex is established as TTC:Hg:I = 1:1:1. The molar absorptivity (255) = (6.45 +/- 0.12) x 10(4) 1 mole(-1). cm(-1) is determined. The selectivity of the reaction is studied and the method for determination of mercury(II) 0.1-0.8 mug/ml is shown. Extraction investigations of the system discussed were carried out. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase was determined: extraction constant K(ex) = 3.16 x 10(4), distribution constant K(D) = 20.67, and association constant = 1.53 x 10(3). 5 A rapid and sensitive extractive-photometric method for determination of mercury(II) in soil was developed. The determination was carried out without preliminary elimination of mercury.     

UV irradiation controlled cold vapor generation using SnCl2 as reductant for mercury speciation.

A simple and ultrasensitive method, which was based on cold vapor generation (CVG) coupled to atomic fluorescence spectrometry (AFS), was proposed for speciation analysis of inorganic mercury (Hg2+) and methylmercury (MeHg) in water samples. In the presence of UV irradiation, all the mercury (MeHg+Hg2+) in a sample solution can be reduced to Hg0 by SnCl2; without UV irradiation, only Hg2+ species can be determined. So the concentration of MeHg can be obtained from the difference of the total mercury and Hg2+ concentration; thus, speciation analysis of Hg2+ and MeHg was simply achieved without chromatographic separation. Under the optimized experimental conditions, the limits of detection were 0.01 ng mL-1 for both Hg2+ and MeHg. The sensitivity and limit of detection were not dependent on the mercury species, and a simple Hg2+ aqueous standard series can be used for the determination of both Hg2+ and MeHg.