Theoretical and Experimental Studies on a Metallorganic Complex of (Isopropylxanthato)(Phenyl)Mercury(I) [Hg(I)(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)(C<Subscript>4</Subscript>H<Subscript>7</Subscript>OS<Subscript>2</Subscript>)]

The title compound, (isopropylxanthato)(phenyl)mercury(I), was synthesized and characterized by elemental analysis, IR and thermogravimetric analysis. Density functional theory (DFT) method calculations were performed at B3LYP/CEP-121G and B3LYP/CEP-31G levels of theory, respectively. Vibrational frequencies were predicted, assigned, compared with the experimental values, and they are supported each other. The calculated results show that the strength of bond Hg—C is stronger than that of Hg—S, which is good agreement with the experimental data. The calculations of the second order optical nonlinearity and electronic absorption spectra are also performed.     

Analysis of organomercury compounds in sediments by capillary GC with atomic fluorescence detection

Analysis of methyl- and ethylmercury (MM and EM) halides in biological and environmental samples is generally performed by gas chromatography with electron capture detection. Tedious sample work-up protocols and poor chromatographic response (using packed columns) have, however, shown the need for the development of new methods in this field. This paper reports a sensitive method, free from these deficiencies, for the determination of methyl- and ethylmercury. The organomercury compounds (MM and EM) are first released from the sample matrix, by the combined action of acidic potassium bromide and cupric ions, and then extracted into dichloromethane. The initial extracts are subjected to thiosulfate clean-up and the organomercury species are isolated as their chloride derivatives by addition of cupric chloride, and subsequent extraction into a small volume of organic solvent. Capillary GC coupled with atomic fluorescence detection provided excellent separation efficiencies for methyl- and ethylmercury and proved to be a very selective and sensitive technique. The absolute detection limit for both MM and EM was found to be 0.2 pg.     

Simultaneous extraction of organotin, organolead and organomercury species from soils and litter

Extracting organotin compounds (OTC) from soils is difficult due to the high cation exchange and complexation capacity of soils, and little information about OTC in soils is available. In this study, a new extraction method, combining 1 M CaCl₂, 0.1% tropolone, and glacial acetic acid was developed. Recoveries of mono-substituted OTC from spiked plant litter, and soil samples were improved substantially to 40% compared to classical glacial acetic acid extraction commonly used in sedimentology, yielding <10% recovery in C-rich soil samples. Simultaneously, the recovery of other OTC, trimethyllead and monomethylmercury was satisfactory. The recoveries of most species from the spiked litter, upland and wetland soils exceeded 70%. The new method extracted much more organometallics from unspiked organic soils and litter than microwave- and ultrasound-assisted extraction and accelerated solvent extraction, most likely due to exchange of organometallics from the solid phase by Ca²⁺. The method is simple, highly efficient and with low contamination. Together with GC-ICP-mass spectrometry, the method allows the detection of these organometallics in the pg g⁻¹ range and it is particularly suitable for soil and plant materials with low organometallics contents.     

Improvement of quality control of speciation analysis using hyphenated techniques A decade of progress within the European Community

The awareness of a need for an improved control of environmental contamination levels has led to the development of new hyphenated techniques for the determination of a wide variety of chemical species (e.g., organotins, methyl-mercury, alkyl-lead compounds etc.). These techniques generally involve many analytical steps such as extraction, derivatisation, separation and detection which have to be carried out in such a way that the speciation is not changed during the abalytical process. The need for evaluating the method's performance has led the BCR programme of the European Commission (now Standards, Measurements and Testing programme) to conduct series of interlaboratory studies during the last decade. These projects followed a step-by-step approach for the evaluation of different steps of the analytical methods used, e.g., simple solutions to test the detection, cleaned extract to evaluate the separation, spiked samples to test the extraction and natural samples to evaluate the whole analytical procedures. These collaborative projects allowed most of the sources of errors related to either a technique or a laboratory to be detected and removed. This paper gives an account of discussions of possible errors occurring in speciation analysis and presents examples of technical scrutiny of hyphenated techniques using chromatography as applied to the determination of tributyltin, methyl-mercury and trimethyllead.     

Spanning [Pt2(μ-S)2(PPh3)4] metalloligands with 1,4-dimercurated durene

Reaction of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] with 0.5 mol equivalents of durene-1,4-bis(mercuric acetate) [AcOHgC₆Me₄HgOAc] in methanol gives the polynuclear complex [{Pt₂(μ-S)₂(PPh₃)₄}₂(μ-1,4-C₆Me₄Hg₂)]²⁺, isolated as its and salts. Positive-ion ESI mass spectra indicate that [{Pt₂(μ-S)₂(PPh₃)₄}₂(μ-1,4-C₆Me₄Hg₂)]²⁺ undergoes fragmentation by successive loss of PPh₃ ligands, while the ESI mass spectrum of the salt showed additional ions [Pt₂(μ-S)₂(PPh₃)₄(HgC₆Me₄HgPh)]⁺ and [Pt₂(μ-S)₂(PPh₃)₄HgPh]⁺ as a result of phenyl transfer from to Hg. A single-crystal X-ray structure determination on [{Pt₂(μ-S)₂(PPh₃)₄}₂(μ-1,4-C₆Me₄Hg₂)](BPh₄)₂ shows that the cation crystallises on a centre of symmetry, with structural features that are comparable to those of the previously characterised complex [Pt₂(μ-S)₂(PPh₃)₄HgPh]BPh₄.     

Organomercury Compounds in Organic Synthesis

Organomercurials have been known since 1850 and many synthetic routes to these compounds presently exist. The ability of these compounds to accommodate a wide variety of functional groups and to tolerate quite diverse reaction conditions makes them attractive as synthetic intermediates. While the solvomercuration-demercuration and divalent carbon transfer reactions remain the most widely used of the organomercurial reactions, a number of new synthetic procedures employing organomercurials have been developed in recent years. Many of these involve transmetallation reactions with palladium salts.     

Crystal structures of organomercury(II) derivatives of cyclohexanone and benzaldehyde thiosemicarbazones

The crystal and molecular structures of the organomercury(II) complexes [Hg(C₆H₅)(chtsc)], 1, and [Hg(C₆H₅C₅H₄N)(btsc)], 2, obtained from the reaction of phenylmercury(II) acetate with cyclohexanone thiosemicarbazone (Hchtsc) and that of [2-(pyridin-2′-yl)]phenyl]mercury(II) acetate with benzaldehyde thiosemicarbazone (Hbtsc), respectively, are described. Both 1 and 2 are monoclinic, space group C2/c. Complex 1 has a distorted T-shaped geometry {C-Hg-S, 161.91(10)°} and 2 can be considered to have a distorted seesaw geometry {C-Hg-S, 171.2(10)°}. In both complexes the ligands act as bidentate chelating anions bonding through azomethine N¹ and thiolato S atoms.     

Separation of Organomercury Species Using Nonaqueous Capillary Electrophoresis Coupled with Sample Stacking and Electrokinetic Injection Techniques

A nonaqueous capillary electrophoresis (NACE) method, 30 mM ammonium acetate in methanol as background electrolyte (BGE), was developed for separation of the organomercury species without complexing reagents. The effects of different solutes and solvents in BGE were studied. Three species of organomercury, methylmercury, ethylmercury and phenylmercury, were separated well and all the number of theoretical plates were over 10⁶. The present NACE method was also coupled with sample stacking and electrokinetic injection techniques to enhance the detection sensitivity. Under the optimum conditions, the limit of detection (S/N = 3) is 18 ng mL⁻¹ and the linear relation range from 40 to 750 ng mL⁻¹ were obtained for methylmercury.     

Improvements in the methylmercury extraction from human hair by headspace solid-phase microextraction followed by gas-chromatography cold-vapour atomic fluorescence spectrometry

Improvements in the methylmercury extraction from human hair by solid-phase microextraction followed by gas chromatography coupled to cold-vapour atomic fluorescence spectrometry (GC-CVAFS) have been carried out. They consisted in the optimisation of the digestion step prior to the aqueous-phase ethylation and in the GC-CVAFS interface set-up. The main digestion parameters such as acid type, concentration, temperature and time have been optimised for hair sample analysis, thereby avoiding methylmercury degradation. Moreover, the stability of the digested samples was evaluated to improve the sample throughput.     

Simultaneous determination of organotin,organolead, and organomercury compounds in environmental samples using capillary gas chromatography with atomic emission detection

As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples was investigated. Pentylmagnesium bromide was used to pentylate ionic organotin, organolead, and organomercury compounds; the pentyl derivatives were then separated by GC and determined by AED. Several important GC-AED parameters, including the type of injector inlet, carrier gas flow rate, and helium make-up gas flow rate, were optimized for the simultaneous determination of these organometallic compounds. Their minimum detectable concentrations were approximately 1.0 to 2.5 ng/mL using a 0.5-μL on-column injection. The calibration curves exhibited good linearity between 2.5 and 2500 ng/mL for organotin and organolead compounds, and between 2.5 and 10000 ng/mL for organomercury compounds.