A new pyrrolidinedithiocarbamate screening method for the determination of methylmercury and inorganic mercury relation in hair samples by HPLC-UV-PCO-CVAAS

A new analytical screening technique for the determination of methylmercury and inorganic mercury in hair samples by HPLC-PCO-CVAAS has been developed. It is based on the extraction of mercury compounds by a buffered sodium pyrrolidinedithiocarbamate solution, separation by reversed-phase HPLC, post column oxidation by UV-irradiation, reduction with alkaline sodium borohydride, and determination by cold vapour atomic absorption detection. The standard deviation was 7% and recoveries were 90% for both compounds. The limit of detection (S/N = 3) for both compounds was calculated to be about 4 ppb.     

Determination of dimethyl-and diethylmercury with HPLC-CVAAS by on-line UV-irradiation

Summary A technique has been developed for the determination of dimethyl- and diethylmercury. It is based on the separation by reversed-phase HPLC, on-line decomposition of the dialkylmercury compounds by H₂O₂ and UV-irradiation, reduction with alkaline sodium borohydride, followed by gas liquid separation of mercury vapour and determination by cold vapour atomic absorption detection. The method permits the simultaneous determination of dimethyl- and diethylmercury by RP C18 HPLC-CVAAS. The limit of detection (S/N=3) for both compounds was calculated to be about 30 ppb.     

Determination of mercury species in natural waters at picogram level with on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS

A new technique has been developed for the determination of methyl-, ethyl-, methoxyethyl-, ethoxyethyl-, phenyl- and inorganic mercury in natural water samples. The mercury compounds have been complexed for the preconcentration on RP C18 columns by sodium pyrrolidinedithiocarbamate (SPDC), sodium diethyldithiocarbamate (SDDC) and hexamethyleneammonium (HMA) — hexamethylenedithiocarbamate (HMDC), separated by HPLC and determined by UV-PCO-CVAAS (ultra violet, post column oxidation, cold vapour atomic absorption spectrometry). The standard deviations are in the range of 6.9 to 11.8%. The recoveries amount to 86%, 78%, 88%, 83%, 79% and 84% for methyl-, ethyl-, methoxyethyl-, ethoxyethyl-, phenyl- and inorganic mercury for the enrichment from 300 ml water samples. The detection limit for methyl mercury is 0.5 ppt. This new on-line preconcentration procedure has been tested with rain, drinking, surface and process water samples.     

Speciation of mercury compounds in waste water by microcolumn liquid chromatography using a preconcentration column with cold-vapour atomic absorption spectrometric detection

A microcolumn liquid chromatographic method with cold-vapour atomic absorption spectrometric detection was developed for the speciation of mercury compounds in waste water. The sample solution containing mercury at the 4-ng level was injected onto a preconcentration column (27 mn × 0.51 mm i.d.) packed with Develosil-ODS (30 μm) and eluted with cysteine-acetic acid through a separation column (125 mm × 0.5 mm i.d.) packed with STR-ODS-H (5 μm). After oxidation, tin(II) chloride in sodium hydroxide solution was used to reduce mercury compounds to mercury. The generated mercury vapour was swept from a gas-liquid separator by argon into the detector cell and monitored at 253.7 nm. Mercury(II) chloride, methylmercury chloride and ethylmercury chloride, were well resolved and the determination was completed in less than 16 min. The method was successfully applied to the speciation of mercury compounds in waste water.     

Two methods for the speciation analysis of mercury in fish involving microwave-assisted digestion and gas chromatography-atomic emission spectrometry

In this paper a novel approach for the speciation analysis of mercury (methyl mercury and mercury II) in fish tissue using gas chromatography-microwave induced plasma atomic emission spectromertry is described. Focused microwave-assisted digestion which has been used previously in speciation analysis only for the determination of organotin and organoselenium compounds, was applied for sample preparation, a technique which enables mild, quick and complete dissolution of the sample. The important parameters for the digestion of fish tissues were optimised for the given analytical problem. Since no experience was available for the further treatment of the produced sample solution two different derivatisation/injection procedures were examined:

1. (1) ethylation with sodium tetraethylborate, extraction into hexane and injection with a cooled injection system and

2. (2) hydride generation with sodium tetrahydroborate together with purge-and-trap injection. The latter reaction has not been used previously for the determination of mercury species in fish samples.

The optimum parameters for both procedures were evaluated and the methods were validated by analysis of a standard reference material (CRM 464). The 3σ detection limits were (1) 3.0 pg g⁻¹ and (2) 12.5 pg g⁻¹.     

Simultaneous determination of inorganic mercury and methylmercury compounds in natural waters

The purpose of the present work was to develop a simple, rapid, sensitive and accurate method for the simultaneous determination of inorganic mercury (Hg(2+)) and monomethylmercury compounds (MeHg) in natural water samples at the pg L(-1) level. The method is based on the simultaneous extraction of MeHg and Hg(2+)dithizonates into an organic solvent (toluene) after acidification of about 300 mL of a water sample, followed by back extraction into an aqueous solution of Na(2)S, removal of H(2)S by purging with N(2), subsequent ethylation with sodium tetraethylborate, room temperature precollection on Tenax, isothermal gas chromatographic separation (GC), pyrolysis and cold vapour atomic fluorescence spectrometric detection (CV AFS) of mercury. The limit of detection calculated on the basis of three times the standard deviation of the blank was about 0.006 ng L(-1) for MeHg and 0.06 ng L(-1) for Hg(2+)when 300 mL of water was analysed. The repeatability of the results was about 5% for MeHg and 10% for Hg(2+). Recoveries were 90-110% for both species.     

Mercury speciation in sea food by flow injection cold vapor atomic absorption spectrometry using selective solid phase extraction

An on-line inorganic and organomercury species separation, preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS or CV-ETAAS) coupled to a flow injection (FI) method was studied. The inorganic mercury species was retained on a column (i.d., 3 mm; length 3 cm) packed to a height of 0.7 cm with a chelating resin aminopropyl-controlled pore glass (550 A) functionalized with [1,5-bis (2 pyridyl)-3-sulphophenyl methylene thiocarbonohydrazyde] placed in the injection valve of a simple flow manifold. Methylmercury is not directly determined. Previous oxidation of the organomercurial species permitted the determination of total mercury. The separation of mercury species was obtained by the selective retention of inorganic mercury on the chelating resin. The difference between total and inorganic mercury determined the organomercury content in the sample. The inorganic mercury was removed on-line from the microcolumn with 6% (m/v) thiourea. The mercury cold vapor generation was performed on-line with 0.2% (m/v) sodium tethrahydroborate and 0.05% (m/v) sodium hydroxide as reducing solution. The determination was performed using CV-AAS and CV-ETAAS, both approaches have been used and compared for the speciation of mercury in sea food. A detection limit of 10 and 6 ng l(-1) was achieved for CV-AAS and CV-ETAAS, respectively. The precision for 10 replicate determinations at the 1 microg l(-1) Hg level was 3.5% relative standard deviation (R.S.D.), calculated from the peak heights obtained. Both approaches were validated with the use of two certified reference materials and by spiking experiments. By analyzing the two biological certified materials, it was evident that the difference between the total mercury and inorganic mercury corresponds to methylmercury. The concentrations obtained by both techniques were in agreement with the certified values or with differences of the certified values for total Hg(2+) and CH(3)Hg(+), according to the t-test for a 95% confidence level. It is amazing how this very simple method is able to provide very important information on mercury speciation.     

Speciation analysis for mercury in gas condensates by capillary gas chromatography with inductively coupled plasma mass spectrometric detection

A method allowing species-selective determination of atomic mercury, non-polar dialkylated mercury compounds,polar monoalkylated species and inorganic mercury complexes in natural gas condensates was developed. Inductively coupled plasma mass spectrometry was employed as a detection method for capillary gas chromatography and compared with microwave induced plasma atomic emission detection for the analysis of hydrocarbon-rich matrices. The method was based on two consecutive injections allowing comprehensive speciation analysis. First a sample aliquot was diluted with toluene and analysed for Hg0 and individual dialkylmercury compounds. Then, another aliquot was butylated with a Grignard reagent for the species specific determination of Hg(II) and monoalkylated mercury species. The detection limits were down to 0.08 pg level.     

The determination of mercury in organic compounds

The micro oxygen-flask combustion technique in combination with the sodium diethyldithiocarbamate titration is a rapid and useful method for determination of mercury in organic compounds. Chlorine and bromine do not interfere; iodine does. When the organic compound contains both mercury and chlorine, the chloride ions can be titrated argentometrically in the same absorption solution after the titration of mercury.     

Determination of methylmercury and inorganic mercury in water samples by slurry sampling cold vapor atomic absorption spectrometry in a flow injection system after preconcentration on silica C18 modified

A novel method for preconcentration of methylmercury and inorganic mercury from water samples was developed involving the determination of ng l⁻¹ levels of analytes retained on the silica C₁₈ solid sorbent, previous complexation with ammonium pyrrolidine dithiocarbamate (APDC), by slurry sampling cold vapor atomic absorption spectrometry (SS-CVAAS) in a flow injection (FI) system. Several variables were optimized affecting either the retention of both mercury species, such as APDC concentration, silica C₁₈ amount, agitation times, or their determination, including hydrochloric acid concentration in the suspension medium, peristaltic pump speed and argon flow-rate. A Plackett-Burman saturated factorial design permitted to differentiate the influential parameters on the preconcentration efficiency, which were after optimized by the sequential simplex method. The contact time between mercury containing solution and APDC, required to reach an efficient sorption, was decreased from 26 to 3 min by the use of sonication stirring instead of magnetic stirring. The use of 1 mol dm⁻³ hydrochloric acid suspension medium and 0.75% (m/v) sodium borohydride reducing agent permitted the selective determination of methylmercury. The combination of 5 mol dm⁻³ hydrochloric acid and 10⁻⁴% (m/v) sodium borohydride was used for the selective determination of inorganic mercury. The detection limits achieved for methylmercury and inorganic mercury determination under optimum conditions were 0.96 and 0.25 ng l⁻¹, respectively. The reliability of the proposed method for the determination of both mercury species in waters was checked by the analysis of samples spiked with known concentrations of methylmercury and inorganic mercury; quantitative recoveries were obtained.     

硼氢化钠还原-无色散原子荧光法测定茶叶中汞

建立了汞的硼氢化钠还原－无色散原子荧光测定方法,在最佳条件下,荧光强度与汞浓度在0－25μg/L范围内呈线性关系,相关系数0．9991,检出限0．02μg/L。用拟定的方法测定了茶叶中的汞,回收率为91．6％－98．3％,变异系数不超过5．2％。     

Voltammetric quantification and speciation of mercury compounds

The use of a carbon paste electrode modified with a thiolic resin for the determination of inorganic mercury and organomercury compounds, present simultaneously in a sample, is described. The compounds are first preconcentrated at the electrode surface by means of a purely chemical reaction with the modifier on the electrode surface. The high affinity of the modifier for the mercury compounds ensures low limits of detection and determination. Differentiation between several mercury species is possible by control of the reduction potential applied to the working electrode. This selective reduction results in the formation of atomic mercury at the electrode surface which can be determined with a very high sensitivity by means of its re-oxidation wave in cyclic voltammetry. Optimization of the instrumental parameters and evidence for the reduction processes are discussed. Analysis of inorganic mercury in the presence of methylmercury, with a detection limit of 4 μg Hg 1⁻¹, and of methylmercury in the presence of inorganic mercury, with a detection limit of 2 μg Hg 1⁻¹, is described in detail. In both cases the preconcentration time is 6 min. Other organomercury species can also be quantified. Application of the method to environmental aquatic samples is discussed.     

Capillary electrophoretic determination of mercury compounds in different matrixes

Summary Capillary electrophoresis has been used to separate inorganic (Hg²⁺) and organic (methyl-, ethyl-, and phenylmercury) mercury compounds as their cysteine complexes. The optimized electrophoretic separation was performed in fused-silica capillary tubing at 25 kV with 25mm sodium borate buffer (pH 9.3). Identification and quantification of the mercury species at mg L⁻¹ levels was achieved by use of UV detection at 200 nm. The relative standard deviation (n=10) ranged from 0.38 to 0.51% for migration times and from 0.43 to 2.94% for corrected peak areas. Good recovery (>90%) was obtained for all four mercury species in surface waters, and for inorganic mercury and methylmercury in five- to tenfold diluted biofluids (urine, saliva, and cerebrospinal fluid). TheLOQ values obtained were too high to be useful for determination of mercury species in real samples. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Electrochemical studies of homocysteine and homocystine at mercury electrodes

The behaviour of homocysteine and cysteine at mercury electrodes is compared. The one-electron oxidation associated with thiols is shown to be the same for both compounds in acidic phosphate buffer, giving rise to an adsorbed thiol—mercury complex, (RS)₂Hg, at the electrode surface. Formation of this complex is utilized in the cathodic stripping voltammetric determination of homocysteine; the detection limit is 10^?9 M after a deposition time of 90 s at a hanging mercury drop electrode. The similar E_{$\text{1}\text{2}$} values for homocysteine and cysteine mean that prior separation is needed for their individual determination. Amperometric detection with a mercury-coated goal electrode after separation by cation-exchange liquid chromatography provides a method for the simultaneous determination of both compounds. Reduction of homocystine at the mercury electrode is also compared to that of cystine. The more negative reduction potential, and the maximum observed for homocystine on d.c. polarograms, which is not seen for cystine, is attributable to different reaction kinetics at the mercury electrode; the products of both the 2-electron reductions are the corresponding thiol-containing amino acids.     

Dithizone derivatives as sensitive water soluble chromogenic reagents for the ion chromatographic determination of inorganic and organo-mercury in aqueous matrices

Water-soluble sulfonate and the novel carboxylate analogues of dithizone, combined with ion interaction chromatography on a Dionex Acclaim 120 C18 silica column (250 x 4.6 mm id) with an eluent consisting of 10 mM tetrabutylammonium bromide and 60:40 methanol:water, have been developed as highly sensitive chromogenic ligands for the quantitative isocratic determination of inorganic and organo-mercury compounds in aqueous matrices in under 12 min. Using an optimised post column reagent system containing 0.65 mM dye, 0.5% Triton X-100 and 50 mM sodium hydroxide, good linearity (0-7.5 mg L(-1) R2 > 0.999), reproducibility using peak area measurements (RSD 0.69-1.38%, n = 8), and limits of detection (4-12 microg L(-1)) were achieved for methyl mercury, inorganic mercury and phenyl mercury.     

Determination of total and methyl mercury in human permanent healthy teeth by electrothermal atomic absorption spectrometry after extraction in organic phase

A simple and sensitive method has been developed for determination of inorganic and methyl mercury in biological samples by ETAAS. For determination of methyl mercury; it was transferred to toluene phase by acid leaching extraction method. For total mercury after digestion of samples; it was extracted to toluene phase by means of the chelating agent diethyldithiocarbamate. Formation of complex between MeHg and diethyldithiocarbamate enhance the MeHg signal and increases the reproducibility. Furthermore, Pd-DDC was used as modifier for both mercury and methyl mercury determinations. The optimization performance was independently carried out by modifying the parameters such as temperature of mineralization, atomization and gas flow rate for methylmercury and inorganic mercury in ETAAS. The limits of detection were 0.15 and 0.12 μg g⁻¹ for methyl mercury and total mercury, respectively. The repeatability of the measurements of whole procedure were 15.8% for methyl mercury and 16.9% for total mercury determination. The accuracy of the method has been investigated by means of spiking different amounts of methylmercury and inorganic mercury to the samples. The recoveries were found within the range of 88-95% for methyl mercury and 85-92% for total mercury. For determination of total mercury, the method was validated by CVAAS. The obtained results by the present procedure were in good agreement with those of the CVAAS. The proposed method was applied for 30 human permanent healthy teeth (without filling) which significant positive correlations were found among number of amalgam filling and total mercury and MeHg.     

Sensitive determination of gaseous mercury in air by cold vapour atomic fluorescence spectrometry after amalgamation

A method was developed for the determination of mercury in air, using preconcentration by amalgamation on gold absorbers followed by measurement by atomic fluorescence spectrometry (AFS). The system has a detection limit of ca. 2.0 pg and the precision is in the range 5–10% (relative standard deviation). The accuracy was confirmed by comparison with cold vapour atomic absorption spectrometry. The method was applied to the determination of gaseous mercury in both indoor and outdoor air. As a result of the sensitivity small sample volumes can be analysed and only short sampling times are required. The method is thus suitable for continuous monitoring of mercury and for the fast and reliable determination of gaseous mercury in the atmosphere, even at background levels.     

Sequential quantification of methyl mercury in biological materials by selective reduction in the presence of mercury(II), using two gas–liquid separators

The present procedure is based on the sequential selective reduction of mercury(II) and methyl mercury using two gas–liquid separators in series. Cold vapor atomic absorption spectrometry was used for detection. Mercury(II) is reduced by a 0.01% m/v sodium tetrahydroborate solution and driven to the absorption cell in the first separator. The methyl mercury species is reduced by the same reductant but at a 0.3% m/v concentration, and in the presence of iron(III) chloride. Parameters such as argon flow rate, and the NaBH₄ and dithiophosphoric acid diacyl ester concentrations were optimized. At the optimized conditions, and using aqueous standards for calibration, the corresponding limits of detection (3σ_b, n=10) were 400 and 600 ng l⁻¹ for mercury(II) and methyl mercury, respectively. The sample throughput was 12 h⁻¹. The procedure was used for the determination of methyl mercury in dogfish liver and dogfish muscle certified reference materials, and good concordance between found and certified values was observed.     

On-line high-performance liquid-chromatographic separation and cold vapor atomic absorption spectrometric determination of methylmercury and inorganic mercury

A reversed-phase high-performance liquid chromatography (HPLC) method with cold vapor atomic absorption spectrometry (CV-AAS) detection is developed for mercury speciation. In this paper, the efficiency of tetrabutylammonium bromide reagent and sodium chloride in a methanol-water mixture as mobile phase is evaluated for HPLC separation of methylmercury and inorganic mercury coupled with on-line CV-AAS determination. Both mercury species are separated on a reversed-phase C(18) column. Several parameters (e.g. composition and flow-rate of mobile phase) are investigated for the optimization of HPLC separations. CV-AAS technique parameters are also studied for their effect on sensitivity (sodium borohydride and sodium hydroxide concentrations in the reducing agent, reducing agent flow-rate, length of the reduction coil and nitrogen flow-rate). Quantitative recoveries for both inorganic mercury and methylmercury are obtained from a spiked natural water sample.     

硝酸、硫化钠溶液浸取冷原子荧光法选择性测定土壤及河流沉积物中硫化汞

本文研究了饱和硫化钠溶液对土壤样品中硫化汞的浸取效率(其加标回收率达100%),以及用硝酸和硫化钠溶液对样品中汞的选择性浸取并研究了土壤中硫化汞垂直分布。提出了利用硝酸、饱和硫化钠溶液浸取,由冷原子荧光法选择性测定土壤及河流沉积物中硫化汞的新方法。用该方法对同一样品进行8次测定,其相对标准偏差为7.1%。