用间接法测定硫化物的研究

前人已经报道用汞的冷原子吸收法测定硫化物,利用Hg~(2+)和S~(2-)形成很稳定的化合物,使汞的吸光度值降低,根据其降低的程度来测定硫化物的含量。这种方法简便、灵敏,但对加入的Hg~(2+)量有较大的限制。S_2O_3~(2-)、CN~-、I~-等也有严重干扰,这些离子常与S~(2-)共存于水样中,所以,实际测定时,常需分离这些离子。     

Evaluation of high pressure oxygen microwave-assisted wet decomposition for the determination of mercury by CVAAS utilizing UV-induced reduction

The UV-induced cold vapor generation with formic acid coupled to AAS after high pressure oxygen microwave decomposition was developed for determination of total Hg in analytical samples. Certified reference materials were decomposed in 1.5 mol L^{− 1} HNO₃ and 0.6 mol L^{− 1} H₂O₂. Microwave decomposition with oxygen has allowed the use of diluted reagents. The oxygen at a pressure of ca. 15 bar was delivered during the mineralization to the closed vessel. Interference by unused residues of H₂O₂ and HNO₃ was observed. In order to overcome the negative effect of remaining oxidants pre-reduction with hydroxylammonium chloride at a concentration 0.75 mmol L^{− 1} was used. Recovery of mercury in four reference materials containing 0.20–1.99 µg g^{− 1} Hg were 99–104% of certificate values. The limits of detection and quantification in the sample solutions were determined as 0.12 and 0.38 µg L^{− 1}, which corresponds to absolute detection limits of 12 and 38 ng g^{− 1} for total mercury, respectively. The results were in good agreement with the t-test at a 95% confidence level of the certified values in the investigated reference materials. The relative standard deviation was better than 7% for most of the samples.     

Determination of mercury in biological materials by CV-AAS after wet digestion

The paper describes the determination of ultratrace concentrations of mercury in biological materials. Samples were digested in nitric acid under pressure in a polytetrafluoroethylene bomb. Mercury was determined in the digest solution by cold vapour atomic absorption spectrometry using stannous chloride reduction and two-stage gold amalgamation. The detection limit is 0.12 ng. Analysis of several certified reference materials yielded results in excellent agreement with the certified values. The results for blood serum of several subjects ranged from 0.2 to 0.8g 1^–1.Of the National Fund for Scientific Research (Belgium), to whom correspondence should be addressed     

Speciation analysis of mercury in water samples by cold vapor atomic absorption spectrometry after preconcentration with dithizone immobilized on microcrystalline naphthalene

Trace amounts of inorganic mercury (Hg²⁺) and methylmercury cations (MeHg²⁺) were adsorbed quantitatively from acidic aqueous solution onto a column packed with immobilized dithizone on microcrystalline naphthalene. The trapped mercury was eluted with 10 ml of 7 mol L^–1 hydrochloric acid solution. The Hg²⁺ was then directly reduced with tin (II) chloride, and volatilized mercury was determined by cold vapor atomic absorption spectrometry (CVAAS). Total mercury (Hgt) was determined after decomposition of MeHg⁺ into Hg²⁺. Hg²⁺ and MeHg⁺ cations were completely recovered from the water with a preconcentration factor of 200. The relative standard deviation obtained for eight replicate determinations at a concentration of 0.3 g L^–1 was 1.8%. The procedure was applied to analysis of water samples, and the accuracy was assessed via recovery experiment.     

A new vapor generation system for mercury species based on the UV irradiation of mercaptoethanol used in the determination of total and methyl mercury in environmental and biological samples by atomic fluorescence spectrometry

A new vapor generation system for mercury (Hg) species based on the irradiation of mercaptoethanol (ME) with UV was developed to provide an effective sample introduction unit for atomic fluorescence spectrometry (AFS). Preliminary investigations of the mechanism of this novel vapor generation system were based on GC–MS and FT–IR studies. Under optimum conditions, the limits of determination for inorganic divalence mercury and methyl mercury were 60 and 50 pg mL⁻¹, respectively. Certified reference materials (BCR 463 tuna fish and BCR 580 estuarine sediment) were used to validate this new method, and the results agreed well with certified values. This new system provides an attractive alternative method of chemical vapor generation (CVG) of mercury species compared to other developed CVG systems (for example, the traditional KBH₄/NaOH–acid system). To our knowledge, this is the first systematic report on UV/ME-based Hg species vapor generation and the determination of total and methyl Hg in environmental and biological samples using UV/ME–AFS. Figure A new vapor generation system for mercury species using mercaptoethanol under UV irradiation was developed as an effective sample introduction unit for atomic fluorescence spectrometry     

Determination of total mercury in environmental and biological samples by flow injection cold vapour atomic absorption spectrometry

A simple and accurate method has been developed for the determination of total mercury in environmental and biological samples. The method utilises an off-line microwave digestion stage followed by analysis using a flow injection system with detection by cold vapour atomic absorption spectrometry.

The method has been validated using two certified reference materials (DORM-1 dogfish and MESS-2 estuarine sediment) and the results agreed well with the certified values. A detection limit of 0.2 ng g⁻¹ Hg was obtained and no significant interference was observed. The method was finally applied to the determination of mercury in river sediments and canned tuna fish, and gave results in the range 0.1–3.0 mg kg⁻¹.     

Thermodynamics,a suitable reporter in the design of mercury (II) ion selective electrodes

A fully functionalised calix[4]pyrrole derivative, namely, meso-tetramethyl-tetrakis[(diethylthiocarbamoyl)phenoxy] calix[4]-pyrrole, 1 has been synthesised and structurally characterised. Its complexing properties with metal cations in acetonitrile were investigated with particular emphasis on the thermodynamics of these systems. These data and those previously reported for a partially functionalised calix[4]arene based receptor, 5,11,17,23-tetra-tert-butyl[25,27 bis(diethylthiocarbamoyl)oxy]calix[4]arene, 2 were used to, i) further corroborate their use to predict the selectivity coefficients of carrier mediated mercury (II) ion selective electrodes (ISEs) and ii) to obtain approximate stability constant data from selectivity coefficients. The optimum working conditions of both electrodes were determined. It is shown that while the ISE based on 1 is characterised by a wider linear range and a lower mercury (II) detection than the one based on 2, the latter has the advantage of lower interference of other metal cations due to the much lower stability constants of bivalent cations relative to Hg(II). The response characteristics of these electrodes are compared with those found in the literature. SEM micrographs along with EDX spectra of the PVC membranes containing ionophore 1 or 2 unloaded and loaded with Hg(II) are reported.     

Determination of mercury in biological samples by cold vapor atomic absorption spectrometry following cloud point extraction with salt-induced phase separation

Method development for the pre-concentration of mercury in human hair, dogfish liver and dogfish muscle samples using cloud-point extraction and cold vapor atomic absorption spectrometry is demonstrated. Before the extraction, the samples were submitted to microwave-assisted digestion in a mixture of H₂O₂ and HNO₃. Cloud point extraction was carried out using 0.5% (m/v) ammonium O,O-diethyldithiophosphate (DDTP) as the chelating agent and 0.3% (m/v) Triton X-114 as the non-ionic surfactant. Phase separation was induced after the addition of Na₂SO₄ to a final concentration of 0.2 mol L⁻¹. Aliquots of the final extract were transferred to PTFE tubes and NaBH₄ and HCl were added. The mercury vapor was driven to a non-heated quartz tube for measuring the absorbance. The results obtained with salt-induced phase separation were in good agreement with the certified values at a 95% confidence level. An enrichment factor of 10 allowed a detection limit of 0.4 ng g⁻¹ to be obtained, which demonstrates the high sensitivity of the proposed procedure for the determination of mercury at trace levels.     

Solvent impregnated hollow fibre for a selective preconcentration of Pb(II) in an on-line determination by flame atomic absorption spectrometry

A solvent impregnated hollow fibre (SIHF) module has been developed for the preconcentration of lead by using bis(2-ethylhexyl) phosphoric acid (DEHPA) dissolved in kerosene as extractant. The module has been designed for an on-line determination of trace amounts of lead(II) at mg l⁻¹ (ppm) level by flame atomic absorption spectrometry (FAAS).

The SIHF system is based on the metal liquid–liquid distribution between aqueous solutions of different acidity and the mentioned organic solution. The highest enrichment factor of Pb(II) was determined at pH=4.0 using a formic acid/formiate buffer solution.

Preconcentration experiments were carried out at low lead(II) concentration (mg l⁻¹ level) by using the SIHF module. This study includes the influence of hydrodynamic and chemical conditions on the loading and elution of Pb(II) on the SIHF, i.e., flow rate through the fibres, acidity of the eluent (as nitric acid concentration) and the chemical nature of the acid used in the elution. Breakthrough curves were determined for different sampling flow rates, 0.54 ml min⁻¹ was selected to minimise the loading volume of Pb(II) sample. 0.1 M nitric acid was chosen as eluent solution, and perchloric acid also shows appropriate elution characteristics. The degree of concentration obtained for Pb(II) are of 10 fold the original concentration. The quantification limit for Pb(II) achieved with this preconcentration system is 0.17 mg l⁻¹.

The results obtained indicate that the SIHF system can be applied for on-line determination of trace amounts of lead(II) by FAAS.     

Determination of very low levels of dissolved mercury(II) and methylmercury in river waters by continuous flow with on-line UV decomposition and cold-vapor atomic fluorescence spectrometry after pre-concentration on a silica gel-2-mercaptobenzimidazol sorbent

A new, simple and sensitive method for the simultaneous determination of mercury(II) and methylmercury chloride at sub-ng l⁻¹ levels in river waters is described. Inorganic and organic mercury were preconcentrated from fresh water samples simultaneously on a laboratory-made column containing 2-mercaptobenzimidazol loaded on silica gel and then quantitatively eluted with 0.05 M KCN solution and 2.0 M HCl to desorp inorganic and methylmercury species, respectively. After irradiation with an intensive UV source, MeHg⁺ was decomposed and mercury vapours were generated from inorganic and organic mercury using an acidic SnCl₂ solution in a continuous flow system and were subsequently determined with a cold vapour atomic fluorescence (CV-AFS) spectrometer. Detection limits (3σ) were 0.07 and 0.05 ng l⁻¹ (as Hg) for mercury(II) chloride and methylmercury chloride, respectively. Relative standard deviations of method (%R.S.D.) were 8.8 and 10 for inorganic and organomercuric species in the river water, respectively. The analysis of real samples, taken from different rivers, showed that inorganic mercury levels ranged from 4.0±0.6 to 12±1 ng l⁻¹ (as Hg and 95% confidence limit) and methylmercury levels at 0.2±0.02 ng l⁻¹(as Hg).     

Synthesis and characterization of bis(organothiolato)mercury(ii) complexes by disproportionation of Hg2Cl2 in the presence of thiols

Mercury(I) chloride disproportionates to mercury metal and bis(organothiolato)mercury(II) in the presence of some thiols in good yields. The products were analyzed by means of ¹H?NMR and gas chromatographic–mass spectrometry (GC/MS), which indicated that the complexes are monomers in the gas phase and decomposed at elevated temperature to mercury(0) and corresponding disulfides.     

Characterization of As (V), As (III) by selective reduction/adsorption on palladium nanoparticles in environmental water samples

Hydrazine (HZ) and sodium borohydride (BH) are commonly used reagents for the production of palladium nanoparticles (PdNP) in aqueous solution and also for the reduction of arsenic from higher oxidation state to lower oxidation state. A methodology based on the quantitative adsorption of reduced arsenic species on PdNP generated in situ by BH and HZ is described to characterize As (V) and As (III) in environmental water samples. It was observed that PdNP obtained by BH gave quantitative recovery of As (V) and (III) and the PdNP obtained by HZ could account for As (III). The reduced palladium particles are collected and dissolved in minimum amount of nitric acid. The quantification of arsenic was carried out using GFAAS. Optimization of the experimental conditions and instrumental parameters were investigated in detail. The proposed procedure was validated by applying it for the determination of the content of total As in Certified Reference Material BND 301-02 (NPL, India). The detection limit of arsenic in environmental water samples was 0.029 μg L⁻¹ with an enrichment factor of 50. The relative standard deviation (R.S.D.) for 10 replicate measurements of 5 μg mL⁻¹ was 4.2%. The proposed method was successfully applied for the determination of sub ppm to ppm levels of arsenic (V), (III) in environmental water samples.     

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate as a solvent for extraction and preconcentration of mercury with determination by cold vapor atomic absorption spectrometry

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate abbreviated as [C₄tmsim][PF₆] was synthesized and developed as a novel medium for liquid/liquid extraction of inorganic mercury in this work. Under optimal condition, o-carboxyphenyldiazoamino-p-azobenzene abbreviated as CDAA reacted with inorganic mercury to form a neutral Hg-CDAA complex, the complex was rapidly extracted into ionic liquid phase. After back-extracting into aqueous phase with sulfide sodium solution, the mercury concentration was detected by cold vapor atomic absorption spectrometry. The extraction and back-extraction efficiencies were 99.9 and 100.1% for 5.0 μg L⁻¹ standard mercury in 1000 mL of water solution, respectively. The detection limit, calculated using three times the standard error of estimate of the calibration graph, is 0.01 ng of mercury per milliliter water sample. The proposed method has been used to the determination of trace inorganic mercury in natural water with satisfactory results. Moreover, Zeta potential and surface tension of [C₄tmsim][PF₆] solution were measured and applied to explain the extraction mechanism of [C₄tmsim][PF₆] system.     

Comparative structural study of the complexation behaviour of silver(I), cadmium(II), mercury(II), and palladium(II) with a 17-membered N3O2-donor macrocycle

A comparative investigation of the coordination behaviour of the 17-membered, N₃O₂-donor macrocycle, 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane, L, with the soft metal ions Ag(I), Cd(II), Hg(II), and Pd(II) is reported. The X-ray structures of 12 complexes have been determined and a range of structural types, including both mononuclear and dinuclear species, shown to occur. In particular cases the effect of anion variation on the resulting structures has been investigated; L reacts with AgX (X = NO₃, ClO₄, PF₆, OTf and CN) to yield related 2:2 (metal:ligand) complexes of types [Ag₂L₂(NO₃)₂] (1), [Ag₂L₂](ClO₄)₂ · 2DMF (2), [Ag₂L₂](PF₆)₂ · 2DMF (3), [Ag₂L₂](OTf)₂ (4) and [Ag₂L₂(μ-CN)][Ag(CN)₂] · H₂O (5). In all five complexes the ether oxygens of each ring are unbound. In 1–4 the macrocycles are present in sandwich-like arrangements that shield the dinuclear silver centres, with each silver bonded to two nitrogen donors from one L and one nitrogen from a second L. A Ag···Ag contact is present between each metal centre such that both centres can be described as showing distorted tetrahedral geometries. In the case of 5 a rare single μ₂-κC:κC symmetrically bridging two-electron-donating cyano bridge links silver ions [Ag···Ag distance, 2.7437(10) Å]; the macrocyclic ligands are orientated away from the dinuclear metal centres. In contrast to the behaviour of silver, reaction of cadmium(II) perchlorate with L resulted in a mononuclear sandwich-like complex of type [CdL₂](ClO₄)₂ · CH₃CN (6). Again, the ether oxygens do not coordinate, with each L binding to the cadmium centre only via its three nitrogen donors in a facial arrangement such that a distorted octahedral coordination geometry is attained. Reaction of L with HgX₂ (X = ClO₄, SCN and I) yielded the monomeric species [HgL(ClO₄)₂] (7), [HgL(SCN)₂]·CH₃CN (8) and [Hg₂L₂](HgI₄)₂ · 2L (9), in which all five donors of L are bound to the respective mercury centres. However, reaction of L with Hg(NO₃)₂ in dichloromethane/methanol gave a mononuclear sandwich-like complex [HgL₂](NO₃)₂ · 2CH₃OH (10) without anion coordination. Reaction of K₂PdCl₄ and Pd(NO₃)₂ with L yielded the 1:1 complexes [PdLCl]Cl · H₂O (11) and [PdL(NO₃)]NO₃ · CH₃OH (12), respectively, in which the metal is bound to three nitrogen donors from L along with the corresponding chloride or nitrate anion. Each palladium adopts a distorted square-planar coordination geometry; once again the ether oxygens are not coordinated.     

Preconcentration of inorganic antimony(III) in environmental samples by PSTH-Dowex microcolumn and determination by FI-ETAAS

A flow injection on-line sorption preconcentration system has been synchronously coupled to an electrothermal atomic absorption spectrometry (ETAAS) system for the selective determination of trace amounts of Sb(III) in water, soil and plant. The determination was achieved by selective complexation and sorption of Sb(III) with [1,5-bis(2-pyridyl)-3-sulphophenyl methylene thiocarbonohydarzide (PSTH) immobilized on an anion-exchange resin (Dowex 1× 8-200)] at a wide range of pH, quantitative elution with 50 μl of 2 M HNO₃ and subsequent ETAAS detection. ETAAS determination of the analyte was performed in parallel with the preconcentration of the next sample. Using a preconcentration time of 60 s and a sample loading flow rate of 2.8 ml min⁻¹, an enhancement factor of 12 was obtained in comparison with direct injection of 50 μl aqueous solution, resulting in a sampling frequency of 31 samples h⁻¹. The detection limit (3 s) was 2 μg l⁻¹ and the precision was 3.1% (R.S.D.) for 11 replicate determinations at 10 μg l⁻¹. The accuracy of the proposed method was demonstrated by analyzing one certified sample and different spiked samples.     

The behaviour of different organometallic compounds in the presence of inorganic mercury(II): transalkylation of mercury species and their analysis by the GC–MIP–PED system

It is shown that four different mercury species are formed by the abiotic reaction of inorganic mercury with different, ecologically relevant, organolead and organoarsenic compounds. Therefore solutions of tetraethyl-lead, trimethyl-lead chloride and dimethylarsonic acid were prepared and mixed with stock solutions of inorganic mercury at different concentrations. The final solutions were analyzed for their content of newly synthesized mercury species. The analysis was carried out by using a system of solid-phase micro-extraction (SPME): capillary gas chromatography (GC), microwave-induced plasma (MIP) and a plasma-emission detector (PED). We found that transfer of one or two alkyl groups to the inorganic mercury is possible under the conditions mentioned below. The transalkylation rate depends on the kind of organometallic compound and on the pH. The results were confirmed by the reaction with inorganic mercury and analysis of a soil sample, containing tetraethyl-lead and trimethyl-lead, in which not only the monoalkyl compound, but also the dialkylated compound of the relevant inorganic metal, were found. © 1997 John Wiley & Sons, Ltd.     

Determination of Hg(II) in Environmental Water Samples by Dispersive Liquid Phase Microextraction Combined with Flame Atomic Absorption Spectrometry

In this study, a method of dispersive liquid phase microextraction combined with the flame atomic absorption spectrometry was proposed for the determination of trace Hg using diphenylthiocarbazone as chelating reagent. Several factors which have effect on the microextraction efficiency of Hg, such as pH, extraction and dispersive solvent type and their volume, concentration of the chelating agent, extraction time were investigated, and the optimized experimental conditions were established. After extraction, the enrichment factor was 68. The detection limit of the method was 45 ng mL^?1, and the relative standard deviation for eight determinations of 2 μg mL^?1 Hg was 1.7%. The results for the determination of Hg in environmental water samples (tap water, well water, mineral water and Caspian sea water) have demonstrated the applicability of the proposed method.     

Comparative study of copper(II) and cadmium(II) salts as catalytic reagents in the determination of mercury by continuous-microflow cold vapour atomic absorption spectrometry

A continuous-microflow method with cold vapour atomic absorption spectrometric detection was used for the determination of mercury. A comparison of copper(II) and cadmium(II) salts as catalytic reagents is described in detail It was found that in the presence of at least 80 mg 1^?1 of copper(II) salt a similar signal was obtained for both inorganic mercury [mercury(II) chloride]and organic mercury [methylmercury(II) chloride]. With a cadmium(II) salt at least 100 mg 1^?1 were required.     

Sequential determination of Se(IV) and Se(VI) by flow injection-hydride generation-atomic absorption spectrometry with HCl/HBr microwave aided pre-reduction of Se(VI) to Se(IV)

In this study a flow injection (FI) system used in conjunction with hydride generation (HG), atomic absorption spectrometry (AAS) and microwave (MW) aided pre-reduction of selenite (Se(IV)) to selenate (Se(IV)) with HCl:HBr has been developed in order to differentiate both inorganic selenium species. As full control of the MW reduction step is possible, the experimental approach allows the use of milder acidic conditions (10% v/v of HCl and HBr) than those conventionally accomplished with hydrochloric acid alone (≥50% v/v). Experimental parameters were optimized by the univariate optimization method. In either case, the linear range was from 1.0 to 30 μg l⁻¹. The detection limits based on 3σ of the blank signal were 0.25 μg l⁻¹ for Se(IV) and 0.30 μg l⁻¹ for Se(VI). The reproducibility, about 3% RSD and recoveries of different amounts of Se(VI) and Se(IV) added to water and orange juice samples (97–103%) were good. The main advantage of the proposed method is that the sequential determination of Se(IV) and Se(VI) is performed at a high sampling frequency (ca. 50 samples per h) in a closed system without Se losses, and with a minimum sample waste, operator attention, and sample manipulation.     

Highly selective determination of total mercury(II) sub microgram per liter by β-cyclodextrin polymer solid-phase spectrophotometry using 1,3-di-(4-nitrodiazoamino)-benzene

A highly selective β-cyclodextrin polymer solid-phase spectrophotometric (β-CDPSPS) method is described for the determination of total mercury(II) sub microgram per liter. The methods are based on the chromogenic reaction of mercury(II) with 1,3-di-(4-nitrodiazoamino)-benzene (DNAAB) loaded on β-cyclodextrin polymer (β-CDP). In pH 10.0 borax buffer, Hg(II)-DNAAB complex on β-CDP gives a positive peak at 445 nm and a negative one at 545 nm. The absorbance was measured at two peaks and the net absorbance (A_s) was calculated between the difference of positive and negative peaks. The apparent molar absorptivity is 1.1 × 10⁷ l mol⁻¹ cm⁻¹ (82-fold of it in solution) for 100 ml sample and the linear range of the determination is 0.062-250 μg l⁻¹. The selectivity for coexistent ions was greatly improved, only silver(I) interfered with the mercury determination and the amount of the others was reduced 25-1000 times compared to previous solution method. The interference caused by silver(I) can be eliminated using tri-n-octylmethylammonium bromide as masking agent. The detection limit and the quantification limit were found to be 0.024 and 0.062 μg l⁻¹, respectively. The relative standard deviation of ten replicate determinations of 5.0 μg mercury(II) in 100 ml sample was of 2.4%. The method was validated by analyzing the water and soil reference materials and successfully applied to the determination of mercury(II) in locally collected water and dust samples.