Voltammetric determination of mercury(II) at a carbon paste electrode in aqueous solutions containing tetraphenylborate ion

The determination of mercury(II) ions can be achieved by monitoring the decrease in the oxidation peak of the tetraphenylborate ion in the presence of this metal ion at a carbon paste electrode. The reaction between mercury(II) and the tetraphenylborate ion results in the formation of diphenylmercury, thus providing the method with good selectivity over other metal ions. Using anodic stripping voltammetry in a neutral electrolyte, a linear dependence of the decrease of peak height was observed on increasing the mercury(II) concentration in the range 1 x 10(-6)-8 x 10(-9)M mercury(II). Zinc(II), cadmium(II), lead(II), nickel(II), cobalt(II), tin(II), potassium(I) and ammonium(I) ions did not interfere at a 1000-fold concentration excess. Iron(III) and chromium(III) did not interfere at a 250-fold and 50-fold concentration excess, respectively. Following masking procedures, copper(II), bismuth(III) and silver(I) did not interfere at a 100-fold concentration excess. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal.     

Mercury-assisted solvolyses of alkyl halides : Simple procedures for the preparation of nitrate esters,acetate esters,alcohols and ethers

The reactions of a wide variety of alkyl halides with mercury(I) and/or (II) nitrate in 1,2-dimethoxyethane, mercury(II) acetate in acetic acid, aqueous mercury(II) perchlorate, and mercury(II) perchlorate in alcohol solvents have been investigated; as a result, simple high yield procedures for the conversion of alkyl halides into the corresponding nitrate esters, acetate esters, alcohols and ethers have been developed.     

Enzymatic Methods for the Determination of Mercury(II)

Enzymatic methods for the determination of mercury(II) using native and immobilized enzymes from different classes and sources were considered. Enzymatic procedures were compared in sensitivity, selectivity, rapidity, and experimental techniques. The main approaches to controlling the performance characteristics of the enzymatic procedures were discussed. The application of these procedures to the determination of mercury(II) in particular samples (water and soils of different origin and biological fluids) was considered.     

Re‐evaluation of distillation and comparison with HNO3 leaching/solvent extraction for isolation of methylmercury compounds from sediment/soil samples

Distillation was re‐evaluated for the formation of artifacts arising from increasing naturally occurring mercury(II) concentrations, as opposed to previous identification of artifacts by spiking standard mercury(II) into samples. Naturally occurring mercury(II) concentrations lower than 2 µg g^?1 were found not to affect methylmercury (MeHg) results. However, when the natural concentrations of mercury(II) were greater than 2 µg g^?1, in contrast to standard mercury(II) spiked in samples, the MeHg concentrations measured were found to decrease (not increase) with increasing naturally occurring mercury(II) concentrations. This indicated that standard mercury(II) spiked in samples behaved differently from naturally occurring mercury(II) in the formation of MeHg artifacts during distillation. As a result, spiking standard mercury(II) into samples to identify the formation of MeHg artifacts is not adequate. It is difficult to explain why high naturally occurring mercury(II) suppresses MeHg measurements during distillation. In comparison with HNO₃ leaching/solvent extraction (and other existing techniques), distillation was found to generate results comparable for samples containing less than 2 µg g^?1 mercury(II). The HNO₃ leaching/solvent extraction showed significant advantages over other procedures, as this technique generated the highest recoveries with good precision for all samples analyzed, and the results were found to be independent of mercury(II) concentrations for both naturally occurring and spiked standard mercury(II). Thus, except for samples from high mercury‐contaminated fields, distillation is still a good choice. Both the positive bias (possibly caused by artifact formation of MeHg) and the negative bias (due to incomplete leaching, back‐adsorption, and/or decomposition of MeHg) were investigated. Geologically, physically, and chemically different samples were used for the investigation. Copyright © 2004 John Wiley & Sons, Ltd.     

Spectrophotometric determination of traces of metallic ions and their mixtures with 3-methyl-1,2-cyclopentanodione dithiosemicarbazone: I. Zinc,cadmium, and mercury

The properties of zinc, cadmium, and mercury complexes of 3-methyl-1,2-cyclopentanodione dithiosemicarbazone and the optimal conditions for their formation are described. The complexes were used with success in the photometric determination of traces of zinc, cadmium, and mercury. Seven procedures are proposed for the accurate analysis of Zn(II)-Cd(II), Zn(II)-Hg(II), Zn(II)-Bi(III), Cd(II)-Hg(II), Cd(II)-Bi(III), Hg(II)-Bi(III), and Zn(II)-Cd(II)-Hg(II) mixtures. Satisfactory results were obtained.     

Applications involving oxidation with potassium bromate : II. Potentiometric titration of chromium alone or in mixtures

A rapid and reliable determination of chromium was developed based on bromate oxidation of chromium(III) to chromium(VI). The reaction is complete under weakly acidic conditions and with cobalt(II) present as a catalyst. Unreacted bromate and chromium(VI) are then reduced with sulfite to bromide and chromium(III). The bromide is titrated potentiometrically with mercury(I) using a silver amalgam indicator electrode. Iron(III) if present is reduced by sulfite to iron(II) and does not interfere. Some binary and ternary metal mixtures containing chromium can be resolved by the determination of chromium, alone or with another metal, by the above procedure coupled with procedures for further sample portions involving the potentiometric titration of unreacted CyDTA or iodide, or both, with mercury(II).     

Determination of sulfur dioxide in solutions by pyridinium bromide perbromide and titrimetric and flow injection procedures

Sulfur dioxide can be determined by its reaction with pyridinium bromide perbromide using photometric titrations and flow injection procedures. Both methods are useful down to 30 ppm, and are unaffected by ammonia or nitrogen dioxide. Both mercury(II) and EDTA interfere under some circumstances.     

A study of the disproportionation of mercury(I) induced by gas sparging in acidic aqueous solutions for cold-vapor atomic absorption spectrometry

Instrumentation and procedures for the cold-vapor atomic absorption determination of mercury have been modified. Samples are analyzed by syringe injection under reducing and non-reducing conditions so as to allow mercury valence state differentiation. It is shown that chloride ion is effective in preventing mercury(I) disproportionation; in the absence of a strong mercury(II) complexing ligand, mercury(I) readily disproportionates when solutions are sparged with nitrogen. The data are consistent with the formation at the 10–500 ppb level of a Hg₂Cl₂ precipitate with a lower solubility product than the literature values.     

Back titration with mercuric nitrate in alkaline medium analysis of tertiary mixtures of mercury(II) with some other metals

Summary Tertiary mixtures each containing mercury(II) were analysed by simple procedures involving combination between the recent method of back titration with mercuric nitrate in alkaline medium, and the volumetric methods which make use of masking agents as cyanide. The content of mercury(II) in most mixtures is determined potentiometrically with potassium iodide using the silver amalgam as indicator electrode. End points are attended with fair accuracy within 0.02 ml titrant and with reasonable jumps from 60 to 90 mv per 0.1 ml of mercuric nitrate solution or from 170 to 200 mv per 0.1 ml of potassium iodide solution.     

Gas-chromatographic determination of organomercury(II) compounds

Gas chromatography has proved to be an invaluable technique not only for the identification and determination of organomercury(II) compounds but also for differentiating inorganically bound from organically bound mercury. It also offers a possible route for determining various inorganic species through their conversion into organomercury(II) compounds. These procedures and the chemical and instrumental problems associated with them are reviewed.     

A new procedure for the speciation of mercury in water based on the transformation of mercury (II) and methylmercury (II) into stable acetylides followed by HPLC analysis

Conversion of mercury(II) and methylmercury(II) species dissolved in water into di(phenylethynyl)mercury and methyl(phenylethynyl) mercury takes place in satisfactory yield under alkaline conditions by stirring the aqueous solution with phenylacetylene at room temperature. Mercury speciation is simply obtained by HPLC analysis of the two organometallic species. The presence of heavy metals such as copper(II), zinc(II), cadmium(II) and lead(II) in concentrations 10000 times higher than mercury is tolerated, while little interference is displayed by humic acids and cysteine. Seawater samples can also be analysed following a properly adapted procedure.     

Microdetermination of Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Hg, Pb, Bi and U in inorganic and organometallic compounds with morpholinium morpholine-N-dithiocarboxylate

The chelates of morpholinium morpholine-N-dithiocarboxylate with manganese(II), iron(II), iron(III), cobalt(II), nickel, copper(II), zinc, silver, cadmium, mercury(II), lead, bismuth and uranium(VI) have been prepared and their compositions elucidated. Simple, accurate and relatively rapid procedures for the gravimetric and titrimetric microdetermination of these metals in inorganic and organometallic compounds are presented.     

Indicator Tubes and Indicator Powders for Determining Fluoride and Chloride Ions

Noncovalent immobilization of Arsenazo I, Alizarin Red, Xylenol Orange, and diphenylcarbazone by incorporation into silicic acid xerogels and modification of silica gels was studied, and procedures for determining fluoride and chloride ions by solid-phase spectrophotometry and test methods were developed. Reactions of immobilized reagents with aluminum(III), zirconium(IV), and mercury(II) were studied. The possibility of using immobilized reagent–metal ion–halide ion systems for the determination of halide ions was assessed. Indicator powders were proposed for determining 0.5–10 mg/L fluoride ions and 1–30 mg/L chloride ions, and indicator tubes were developed for determining 20–200 mg/L chloride ions. The determination of fluoride and chloride ions is based on exchange complexation reactions proceeding in the systems immobilized Xylenol Orange–zirconium(IV) and immobilized diphenylcarbazone–mercury(II), respectively. Performance characteristics of the developed procedures were estimated. The procedures were verified by determining halide ions in Narzan mineral water.     

Electrodeposition of mercury on glassy carbon electrode from very dilute mercury(II) solution

Flameless atomic absorption sepctrometry (AAS) has been applied to the investigation of the electroreduction of mercury at the glassy carbon (GC) electrode in dilute mercury(II) solution. The atomic mercury which is produced by electrolysis is found both in the electrolyte solution and on the electrode. The evaporation experiment combined with the flameless AAS clearly shows that mercury(0) deposits on the GC electrode as metallic mercury and adatoms depending strongly on the concentration of mercury(II) in the solution. The monolayer formation and underpotential deposition cannot be observed in the mercury(II)/GC electrode system.     

Behaviour of dilute solutions of mercury

It is shown that loss of radioactivity from labelled mercury(II) solutions is due to reduction of some mercury(II) by reductants adventitiously introduced, followed by disproportionation of mercury(I) and loss of metallic mercury in the gas phase. The loss can be prevented by addition of a small excess of an oxidant such as permanganate.     

Determination of Arsenic and Mercury in Various Environmental Matrices by Chemical Neutron Activation Analysis

Chemical neutron activation analysis was developed for determining trace amounts of arsenic and mercury in a variety of environmental matrices, including water, sediment, rock, plants, animal organs, etc: The adsorption procedure via magnesium oxide as the agent was applied to preconcentrate arsenic from the digested environmental matrices where arsenic in the form of As(V) ion could be highly efficiently adsorbed by hydrous magnesium oxide. On the other hand, the extraction procedure via lead diethyldithiocarbamate as the agent was applied to preconcentrate mercury from the digested environmental matrices where mercury in the form of Hg(II) ion could be highly efficiently extracted into the solution of lead diethyldithiocarbamte in dichloromethane. Both of the preconcentrated materials prepared ultimately in the solid states, i.e., arsenic in magnesium oxide and mercury in lead diethyldithiocarbamte were taken to be neutron irradiated. The γ spectra of the preconcentrated samples irradiated generally showed clear peaks of the product radionuclides from arsenic or from mercury by the different separation procedures. The possible interfering elements such as Na, Br, etc., were prominently minimized in respect of most of the preconcentrated samples. The reliability and accuracy of the proposed analytical methods for detecting arsenic and mercury can be confirmed by the assay of commercial standard reference materials including sediment, rock, plants, and animal organs.     

Ammonium 2-(2'-lepidylazo)-1-naphthol-4-sulphonate as indicator in mercurimetric determination of halides

The use of ammonium 2-(2'-lepidylazo)-1-naphthol-4-sulphonate as indicator in titrimetric estimation of chloride, bromide and iodide with mercury(II) has been examined. The precision, accuracy and applicability of the procedures have been evaluated.     

Titrimetric estimation of cysteine alone and in the presence of other amino-acids

Cysteine has been determined alone and in the presence of other amino-acids by titration with mercury(II) at pH 6.2 or 9.2, and with lead at pH 9.2. In all three procedures, a 1:1 complex is formed.     

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.     

Chloro Complexes of Mercury(II) in Aqueous Perchlorate Media: Equilibrium and Electronic Absorption Spectra

The literature data on the equilibrium constants of formation of HgCl^– _{3 solv} and HgCl^2– _{4 solv} from HgCl_{2 solv} and Cl^– _solv in aqueous perchlorate–chloride solutions were generalized. The individual electronic absorption spectrum of the trichloro complex of mercury(II) was obtained for the first time, and the effect of the ionic strength on the spectra of di-, tri-, and tetrachloro complexes of mercury(II) was considered. The previously developed procedures for the resolution of absorption spectra into individual bands were found to be suitable for interpretation of spectral changes experimentally observed for solutions as the result of stepwise complexation. The parameters of the absorption bands in the spectra of chloro complexes of mercury(II) were determined.