A collaborative study of four methods of assay of benzylpenicillin

The assay of benzylpenicillin by iodimetric titration, spectrophotometry with a mercury(II) chloride—imidazole reagent, titration with mercury(II) nitrate in acetate buffer solution, and titration with mercury(II) perchlorate in aqueous pyridine solution, was examined in four laboratories. The first two methods were applied to two samples (the third one being the reference sample), the mercury(II) nitrate titration to three, and the mercury(II) perchlorate method to two samples. The four methods gave very similar results, but the purity obtained with the mercury(II) perchlorate method was slightly lower, and this procedure is less desirable because pyridine is used as solvent. There were no great differences in the relative standard deviations of the four methods. The titration with mercury(II) nitrate is preferred because it is an absolute method.     

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.     

On the reaction between iodide and mercury(II)

A survey on the iodide-mercury(II) reaction and its analytical uses is given. Titrations of iodide with mercury(II) in various acidities, using nitrate, acetate, and chloride as titrants and silver or platinum amalgam as the indicator electrode, showed that mercury(II) nitrate is the best titrant giving 0.46 V/0.1 ml potential break in comparison with 0.14 V/0.1 ml of mercury(II) chloride and 0.35V/0.1 ml of mercury(II) acetate, all titrants being 0.05 M in mercury(II).     

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.     

Simple Conjugated Polymers with On‐Chain Phosphorescent Iridium(III) Complexes: Toward Ratiometric Chemodosimeters for Detecting Trace Amounts of Mercury(II)

For the development of excellent optical probes for mercury(II), a series of simple conjugated polymers that contain phosphorescent iridium(III) complexes as receptors for mercury(II) were designed and synthesized. These conjugated polymers showed energy transfer from the polymer host to iridium(III) complex guest in both solution and the solid state. Unexpectedly, they can work as excellent polymer chemodosimeters for mercury(II) by utilizing the mercury(II)‐induced decomposition of iridium(III) complex. They exhibit a pronounced optical signal change with switchable phosphorescence and fluorescence, even when the concentration of a solution of mercury(II) in THF was as low as 0.5 ppb. With the addition of mercury(II), the phosphorescent emission intensity of iridium(III) complexes was quenched completely. As the emission from polymer backbones increased, the emission wavelength was redshifted simultaneously, thereby realizing ratiometric detection. Excellent selectivity toward mercury(II) over other potentially interfering cations was also realized. In addition, an obvious emission color change of polymer solution from red to yellow‐green was observed, thus realizing a “naked‐eye” detection of mercury(II). More importantly, the solid films of these polymer chemodosimeters also exhibited high sensitivity and rapid response to mercury(II), thereby demonstrating the possibility of the fabrication of sensing devices with fast and convenient detection of mercury(II). The sensing mechanism was also investigated in detail. This is the first report on chemodosimeters based on conjugated polymers with phosphorescent iridium(III) complexes.     

Mercury removal from aqueous and organo-aqueous solutions by natural Mexican erionite

The sorption of Hg(II) from aqueous and organo aqueous solutions was investigated by Mexican natural erionite. The mercury chemical species (anionic, cationic or neutral) were determined by high voltage electrophoresis, and the mercury chemical species present in the aqueous media were simulated by a program MEDUSA. The mercury sorption process was monitored during 48 hours. The mercury content was determined by neutron activation analysis. Mixtures of benzene/water[Hg(II)], toluene/water[Hg(II)] and ethanol/water[Hg(II)] were chosen as organo-aqueous media. It was found that both the mercury chemical species and the dielectric constant of solvents play an important role in the mercury sorption by erionite.     

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.     

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.     

Formation of ferrocyanides-IV Th(IV), Nd(III), UO(2)(II) and Hg(II)

The stoichiometry of the reaction between ferrocyanide and thorium, neodymium, uranyl ion and mercury(II) has been investigated. The first three give single products irrespective of the order of addition of the reagents, but the last does not. If mercury(II) is added to ferrocyanide Hg(2)Fe(CN)(6) is obtained, but if ferrocyanide is added to mercury(II) various cyanide complexes of mercury are formed. The K(sp) values for the precipitates are reported.     

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.     

Adsorption of mercury(II) on macroreticular styrene-divinylbenzene copolymer beads

The adsorption characteristics of mercury(II) on several kinds of styrene-divinylbenzene copolymer beads having different surface properties were studied. It was found that the polymer beads selectively adsorbed mercury(II) from solutions over a wide range of pH with high efficiency. The amount of mercury(II) adsorbed increased with increase in specific surface area of the polymer beads and the adsorption behaviour was found to be of the Langmuir type. The presence of chloride strongly reduced the adsorption, but this interference was not observed with nitrate, sulphate, perchlorate, cadmium(II), cobalt(II), copper(II), nickel(II), silver(I) and zinc(II). More than 95% of the mercury(II) adsorbed on a column of polymer beads could be recovered with dilute hydrochloric acid.     

Fluorescence Determination of Merucury(II) Using a Thymine Aptamer

A label-free thymine-rich sequence and a molecular beacon were synthesized to construct a highly sensitive and selective fluorescence probe for the determination of mercury(II). The aptamer of the thymine-rich sequence selectively bonded with mercury(II) with an accompanying change in the fluorescence intensity of the molecular beacon due to the higher affinity of the aptamer with mercury(II). The limit of detection was 12.7 nanomolar, and a linear relationship was obtained between the fluorescence and mercury(II) concentrations up to 1 micromolar. The assay was highly selective for the mercury(II) and not significantly affected by other metal ions.     

Oxidation of Phenols and Hydroquinones by Mercury(II) Trifluoroacetate and Mercury(II) Oxide

Treatment of phenols with mercury(II) salts normally results in rapid electrophilic aromatic mercuration and formation of arylmercurial derivatives in good yield. The use of mercury(II) salts as oxidants for phenols and hydroquinones has not, however, been investigated in any detail. In 1935, Montignie reported that hydroquinone reduced mercury(II) iodide to mercury(O), but the organic reaction product was not identified.¹ A similar observation was made by Koton,² who found that reaction of hydroquinone, 4-hydroxy-aniline and pyrogallol with mercury(II) acetate did not result in mercuration but led to formation of mercury(0), while Ohno has described the “strong reducing action” of catechol and nitrohydroquinones to mercury(II) salts.³ Mercury(II) acetate has been shown to oxidise hydroquinone and 1,4-bis[β-(2,5-dihydroxyphenyl)-α-methylethylamino] anthraquinone to the corresponding quinones,^4,5 and treatment of 2,6-di-t-butyl-4-methylphenol—with mercury(II) oxide has been found to give the expected products of phenolic oxidative coupling via quinone methide formation.⁶     

Enhancement effect of iron addition for the decomposition of organic mercury as studied by continuous flow analysis with cold vapor atomic absorption spectrometric detection

Summary A continuous flow analysis is described for the determination of total mercury by cold vapor atomic absorption spectrometry. Organic mercury compounds such as methylmercury(II) chloride, ethylmercury(II) chloride and phenylmercury(II) chloride were decomposed by potassium peroxodisulphate with addition of ferric chloride as catalytic reagent. The reducing reagent used was tin(II) chloride in sodium hydroxide solution. With 1,000 mg Fe/l added in the decomposition process, we found that methylmercury(II) chloride and ethylmercury(II) chloride gave response signals similar to those of mercury(II) chloride. The proposed method was applied to the analysis of total mercury in waste water. Permanent address: Department of Chemistry, Faculty of Mathematics and Natural Sciences, Andalas University, Padang, West Sumatra, Indonesia     

Preparation and properties of a new chelating resin containing imidazolyl azo groups

 A new chelating resin incorporating imidazolyl azo groups into a matrix of polystyrene divinylbenzene has been prepared. The exchange capacity of the resin for the ions mercury(II), silver(I) and lead(II) as a function of pH has been determined. The resin exhibits no affinity to alkali, or alkaline earth metals. It is highly selective for only mercury(II) and silver(I). In column operation it has been observed that mercury(II) in trace quantities is very effectively removed from river water spiked with mercury(II) at the usual pH of natural waters. Received: 2 January 1996/Revised: 11 April 1996/Accepted: 16 April 1996     

Model reactions for abiotic mercury(II) methylation: Kinetics of methylation of mercury(II) by mono-, di-, and tri-methyltin in seawater

The usual presence of mercury(II) with monodi-, and tri-methyltin in water, sediments, and plants in estuarine environments suggests possible abiotic formation of methylmercury via methyl transfer from methyltin compounds. Kinetics studies of reactions between mercury(II) and methyltin compounds under pseudo-first-order conditions in seawater show that relative rate of methylmercury formation under the same conditions are: monomethyltin <trimethyltin> dimethyltin. This order is explainable mainly by the speciation and charge of methyltin compounds in seawater and by the existence of mercury(II) as a tetrachloro anion. A factorial experiment with the variables pH and salinity (seawater diluted with deionized water) showed that pH, but not salinity, is significant at the 95% confidence level; and that reaction rates increase as pH increases. These results suggest the possibility of abiotic methylation of mercury(II) in seawater. Additional experiments in seawater demonstrated an absence of methylation of mercury(II) (14 days) and mercury(0) (35 days) by methyl iodide.     

Plasticized open-cell polyurethane foam as a universal matrix for organic reagents in trace element preconcentration : Part II. Collection of mercury traces on dithizone and diethyldithiocarbamate foams

The analytical suitability of zinc dithizonate foam for the collection and preconcentration of traces of mercury(II) has been examined. The effect of pH, plasticizer and chelating agent concentration on the collection rate of mercury has been critically investigated. The capacity for mercury(II) of a TBP-plasticized zinc dithizonate foam at pH 6 is 23.4 μeq g^?1. The effect of plasticizer on the rate of recovery of mercury with sodium thiosulphate solution is also discussed. The preparation of zinc diethyldithiocarbonate foam is described. Traces of mercury(II) can also be collected rapidly and quantitavely by this foam.     

Preparation and comprehensive characterization of [Hg6(alanine)4(NO3)4].H2O

A new mercury-alanine complex has been isolated from reaction mixtures of mercurous nitrate dihydrate and alanine (L and D enantiomers). The solid-state structure contains mercury(I) and mercury(II) associated by alanine ligands in a polymeric array. The disproportionation of mercury(I) to mercury(II) and mercury(0) was facilitated by alanine and is evidenced by the appearance of mercury(0) in reactions of mercury(I) with the 20 common amino acids. This complex is the first mercury(I)-amino acid complex characterized in the solid state. The compounds have been comprehensively characterized using X-ray crystallography, solid-state and solution-state nuclear magnetic resonance spectroscopy, vibrational spectroscopies, and electrospray ionization mass spectrometry.     

High frequency titrations: The mercury(ii)-thiocyanate reaction

Soluble complex-formation of mercury(II) thiocyanate has been studied oscillometrically. The titration of mercury(II) nitrate with thiocyanate gives one inflection corresponding to the formation of Hg(SCN)₂, while in the reverse titration the formation of Hg(SCN)⁺ is also indecated. The method is useful for a rapid determination of very small quantities of mercury or thiocyanate in highly dilute solutions. The titrations can be effected in presence of nitric acid provided its total acidity in the system does not exceed about $\text{1}\text{300}$N. Further Work on the mercury(II) -halide and mercury(II)-cyanide reactions is in progress.     

Surface-enhanced Raman scattering in nanoliter droplets: towards high-sensitivity detection of mercury (II) ions

We report a new method for the trace analysis of mercury (II) ions in water. The approach involves the use of droplet-based microfluidics combined with surface-enhanced Raman scattering (SERS) detection. This novel combination provides both fast and sensitive detection of mercury (II) ions in water. Specifically, mercury (II) ion detection is performed by using the strong affinity between gold nanoparticles and mercury (II) ions. This interaction causes a change in the SERS signal of the reporter molecule rhodamine B that is a function of mercury (II) ion concentration. To allow both reproducible and quantitative analysis, aqueous samples are encapsulated within nanoliter-sized droplets. Manipulation of such droplets through winding microchannels affords rapid and efficient mixing of the contents. Additionally, memory effects, caused by the precipitation of nanoparticle aggregates on channel walls, are removed since the aqueous droplets are completely isolated by a continuous oil phase. Quantitative analysis of mercury (II) ions was performed by calculating spectral peak area of rhodamine B at 1,647 cm⁻¹. Using this approach, the calculated concentration limit of detection was estimated to be between 100 and 500 ppt. Compared with fluorescence-based methods for the trace analysis of mercury (II) ions, the detection sensitivities were enhanced by approximately one order of magnitude. The proposed analytical method offers a rapid and reproducible trace detection capability for mercury (II) ions in water.