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.     

Sample treatment selection for routine mercury speciation in seafood by gas chromatography–atomic fluorescence spectroscopy

A general analytical strategy for mercury speciation in seafood samples has been proposed to increase sample throughput. This consists of the initial determination of total mercury content, and then mercury speciation using gas chromatography coupled to atomic fluorescence spectroscopy. The appropriate sample treatment for mercury speciation is selected between a method based on aqueous ethylation with sodium tetraethylborate (Approach A: a rapid methodology for samples with methylmercury concentrations between 150 and 2000 ng g^?1) and another one based on the determination of organomercury chlorides (Approach B: a much more time‐consuming methodology, applicable to samples with methylmercury at 1.2–200 ng g^?1). Both procedures have been used together for the analysis of bivalves and fish samples. Copyright © 2005 John Wiley & Sons, Ltd.     

The analysis of organic mercury compounds using liquid chromatography with on-line atomic fluorescence spectrometric detection

A new method for the analysis of organic mercury compounds is reported. The organomercurials are separated by high-performance liquid chromatography (HPLC). The compounds are converted to mercury(0) in a continuous-flow system by means of an oxidizing and a subsequent reducing solution. The elemental mercury generated is swept into the cell of an atomic fluorescence spectrometer (AFS) by a stream of argon. The compositions of the oxidizing solution, which contains peroxodisulphate and copper(II) in dilute sulphuric acid, and the reducing solution, which contains alkaline tin(II) chloride, were optimized, as were the gas–liquid separator (GLS), the condensing system and the geometry of the reaction coils. The method is applied to extracts of certified reference material (CRM) and to river sediments. High concentrations of methylmercury were found in the sediment samples. At one location, the presence of ethylmercury is derived from the sample chromatogram.     

GC-MIP-PED as an element-specific system for the determination of organomercury compounds

The application of the combination of gas chromatography and a self-developed plasma emission detector for organomercury speciation is presented. The system, basing on interference filter technology, is described briefly. The plasma and the optical system have to be optimized to reach highest sensitivity for mercury detection. Dimethyl-, methyl- and inorganic mercury as selected compounds have been separated on a GC column and calibrated to obtain the analytical performance data of the system used. Finally, the analysis of some real samples has been performed.     

Effect of the interface on separation in multicapillary gas chromatography-based hyphenated techniques for speciation analysis of organometallic compounds

This paper reports the effect of transfer line (TL) internal diameter (i.d.) on gas chromatographic separation characteristics such as efficiency and speed, when a multicapillary (MC) column is used for speciation analysis of mercury. Five different TL consisting of fused-silica capillaries with 0.15, 0.20, 0.25, 0.32, and 0.53 mm i.d. are compared. The separation efficiency and total chromatographic run time are critically affected by the i.d. of the TL. Narrow capillaries (i.d.0.20 mm) produce minimum peak dispersion whereas wide capillaries result in narrow peaks and shorter chromatographic analysis times. A thermodynamic approach is proposed to describe the motion of the analytes through the separation column and TL. The model provides good agreement with the experimental data for high pressures (35 psig) and wide TL (0.25 mm i.d.).Dedicated to the memory of Wilhelm Fresenius     

ICP-MS for elemental speciation studies

The use of inductively coupled plasma mass spectrometry (ICP-MS) coupled with separation techniques for the purpose of elemental speciation has recently gained a lot of attention. Much of this is due to ever improving separation capabilities of Chromatographic techniques, the high sensitivity of ICP-MS, and the continuing development of better interface techniques. Additionally, there is a growing awareness of the need to monitor various species of an analyte, rather than just total analyte concentrations, due to their often varying natures. For the sake of learning from different elemental speciation approaches, this review brings together some selected types of elemental speciation which have been recently seen in literature. These include separations using various forms of liquid chromatography, such as reversed phase, reversed phase ion pairing, micelle, ion exchange, and size exclusion. Elemental speciation employing gas Chromatographie separations and supercritical fluid separations are discussed as well as elemental speciation using capillary electrophoresis.     

Effects of sample preservation and storage on mercury speciation in natural stream water

Despite an increasing focus on low level methods for determination of mercury species in water over the last decades, few studies have paid attention to direct effects of different sample preparation methods (i.e. preservation techniques) on natural freshwater samples. In this study we show how different preservation techniques give significantly different concentrations of total and methylmercury in freshwaters (9 and 14% on average, respectively). Natural stream samples from a forested lake catchment were studied. Mean stream sample concentrations of total (3.6 ng/L) and methylmercury (0.06 ng/L) reflect levels typical for pristine humic boreal catchments. The main reason for the observed average differences in total and methylmercury concentrations is the use of one instead of two sample bottles and timing of sample acidification, respectively.     

GC FPD method for the simultaneous speciation of butyltin and phenyltin compounds in waters

A method is described for the simultaneous determination of nanogram amounts of mono-, di- and tri-butyltin compounds in water. The procedure is based on the conversion of tin compounds to volatile species by Grignard pentylation and analysis using GC with flame photometric detection (GC FPD). The ionic compounds are extracted from diluted acidified (HBr) aqueous solutions by using a pentane-tropolone solution. The extracted organotin compounds are pentylated by a Grignard reagent and purified on a Fluorisil column before analysis by GC FPD. The detection limits are 20 ng dm^?3 for butyltin compounds and 50 ng dm^?3 for phenyltin compounds. Recoveries from spiking experiments in tap-water and natural seawater matrices, in which no organotin compounds were detected, were greater than 90% for most of the alkyltin compounds.     

Inter‐laboratory validation of EPA method 3200 for mercury speciation analysis using prepared soil reference materials

Determinations of the concentration of individual mercury species from environmental samples have increased significantly over the past decade. The techniques used for the determination of mercury species in soils or sediments generally involve a series of analytical steps (extraction, separation, detection) that may all be prone to systematic errors. An inter‐laboratory validation study of the EPA draft method 3200 was conducted under the auspices of the United States Environmental Protection Agency on two specifically prepared soil matrices. The study was performed successfully by a limited number of participating laboratories. Evaluation of the data demonstrates that the method is more highly efficient for extracting the highly toxic methylmercury than inorganic mercury. The proposed method does not induce transformation of methylmercury to inorganic mercury. Copyright © 2004 John Wiley & Sons, Ltd.     

A multinjection strategy for mercury speciation

A multiinjection strategy has been developed to increase the sampling throughput of the high-performance liquid chromatography determination of inorganic-mercury, methylmercury, ethylmercury and phenylmercury. The method involves the injection of samples each 3.5 min, in spite of the fact that phenylmercury retention time corresponds to 9.04 min. In the selected conditions, the sampling frequency was 11 h⁻¹ in front of that of 6 h⁻¹, obtained by conventional injection of each sample after the complete elution of Hg species. Additionally, the analytical reagents consumption was reduced drastically in almost 50%. The main characteristics of the chromatographic separation were maintained and only the resolution of phenylmercury was reduced from 10.3 to 1.7 and that of ethylmercury from 4.6 to 3.1.     

Acid extraction treatment of sediment samples for organotin speciation; occurrence of butyltin and phenyltin compounds on the cadiz coast,south-west spain

A method is described for leaching of nanogram amounts of mono-, di and tri-butyltin compounds and mono-, di- and tri-phenyltin compounds from sediments. The procedure is based on soaking the sediments in a water–hydrogen bromide mixture (2:3) with magnetic stirring for 1 h followed by extraction with 0.02% (w/v) tropolone solution in pentane for 2 h. Organotins are determined by GF FPD after clean-up through a Florisil column and derivatization by Grignard pentylation. The method has been applied to the study of water and sediments in different areas of south-west Spain. Predominant species are butyltins, especially tributyltin (TBT), which has high values in waters and sediments of Puerto de Santa Maria and Cadiz Bay, as well as in sediments of the Sancti Petri Channel, which suggests a harmful action on biota. A direct relation has been found beween organotin levels and distance of potential focus determined by boating activities. In addition, the relative occurrence of dibutyltin (DBT) and monobutyltin (MBT) together with TBT has been noted, possibly as a result of a degractation process, and the influence of grain size of sediment and presence of organic matter on organotin accumulation has been studied.     

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.     

Evaluation of a purge-and-trap injection system for capillary gas chromatography-microwave induced plasma-atomic emission spectrometry for the determination of volatile selenium compounds in water

A method is presented for the selective determination of the volatile selenium species dimethylselenide and dimethyldiselenide, using a commercially available purge-and-trap injection system coupled to capillary gas chromatography-microwave induced plasma-atomic emission spectrometry. The efficiency of the purging step was evaluated and the parameters affecting the purge and trap processes were optimized. The method was applied to the determination of volatile selenium compounds in lake water. Relative detection limits of 2ng/l for dimethylselenide and dimethyldiselenide, corresponding to an absolute detection limit of 10 pg, were achieved.     

Organotin speciation in environmental samples by capillary gas chromatography and pulsed flame photometric detection (PFPD)

Pulsed flame photometric detection (PFPD) for gas chromatography was applied to organotin compounds as standards and in environmental samples. Ethylated organotin species (n-propyl-, n-butyl- and phenyl-) were extracted from spiked artificial seawater and from an environmental sample. Selectivity towards tin is shown in the analysis of highly polluted seawater samples from a commercial port where no significant interferences are found. The self-cleaning capability and long-term stability of PFPD is shown in this work during 140 days of continuous operation. The absolute limit of detection for this capillary GC–PFPD technique ranged from 0.2 to 0.4 pg (Sn) for tetraethyl- to tetraphenyl-tin, allowing determination of sub-nanogram/litre concentrations of organotin compounds. © 1997 John Wiley & Sons, Ltd.     

Speciation and GC retention indices of some organotin compounds in water

Analytical methods have been developed for the quantitative determination of Bu₄Sn, Bu₃Sn⁺, Bu₂Sn²⁺, BuSn³⁺, Me₃BuSn, Me₂Bu₂Sn, MeBu₃Sn, MeBuSn²⁺, Me₂BuSn⁺ and MeBu₂Sn⁺ in water. Organotin compounds are extracted from water with tropolone at 0.1 % in n-pentane, derivatized with n-pentylmagnesium bromide and determined by gas chromatography with flame photometric detection or flame ionization detection. Absolute detection limits are 0.05-0.12 ng and 1.2-13 ng as tin, respectively. The method was applied to the analysis of spiked tap-water containing 0.3-1000 ng cm^?3 of each of the organotin compounds.     

Elemental speciation for chromium in chromium picolinate products

Chromium picolinate products have been examined for different forms of chromium, using chromatographic separation and inductively coupled plasma mass spectrometric detection. The brands we evaluated contained no detectable amount of elemental chromium(VI), the toxic form. Since chromium picolinate might have other chromium forms as impurities, different products may contain different forms of chromium species. Compared with ion-exchange, reversed-phase chromatography showed excellent chromium recovery based on the amount stated on the product label.     

Mercury species immobilized on sulphydryl cotton: A new candidate reference material for mercury speciation

A batch of sulphydryl cotton microcolumns was prepared and charged with a mixed Hg standard solution (methyl-, ethyl- and inorganic Hg, 10 g l^–1 as Hg, 3 ml) and stored at 4 °C in a light-tight box. At regular time intervals over a 4 month period microcolumns were removed and Hg species were quantified by gas chromatography microwave-induced plasma atomic emission spectrometry (after elution, extraction and derivatization steps). It was found that analyte recoveries for methyl- and inorganic Hg were quantitative over the 4 month period while ethyl-Hg species appeared to be stable for up to 2 months.     

Extraction tool and matrix effects on arsenic speciation analysis in cell lines

Arsenic glutathione (As–GSH) complexes have been suggested as possible metabolites in arsenic (As) metabolism. Extensive research has been performed on the toxicological and apoptotic effects of As, while few reports exist on its metabolism at the cellular level due to the analytical challenges. In this study, an efficient extraction method for arsenicals from cell lines was developed. Evaluation of extraction tools; vortex, ultrasonic bath and ultrasonic probe and solvents; water, chemicals (methanol and trifluoroacetic acid), and enzymes (pepsin, trypsin and protease) was performed. GSH effect on the stability of As–GSH complexes was studied. Arsenic metabolites in dimethylarsino glutathione (DMA(GS)) incubated multiple myeloma cell lines were identified following extraction. Intracellular GSH concentrations of myeloma cell lines were imitated in the extraction media and its corresponding effect on the stability and distribution of As metabolites was studied. An enhancement in both extraction recoveries and time efficiency with the use of the ultrasonic probe was observed. Higher stabilities for the As species in water, pepsin and trypsin were obtained. The presence of 0.5 mM GSH in the extraction media (PBS, pH 7.4) could not stabilize the As–GSH complexes compared to the 5 mM GSH, where high stabilization of the complexes was observed over a 5 day storage study. Finally, the speciation analysis of the DMA(GS) culture incubated cell lines in the presence or absence of GSH revealed the important role GSH plays in the preservation of DMA(GS) identity. Hence, caution is required during the extraction of arsenicals especially the As–GSH complexes, since their identification is highly dependent on GSH concentration.     

Occurrence and chemical speciation analysis of organotin compounds in the environment: A review

Environmental concerns regarding organotin compounds have increased remarkably in the past 20 years, due in large part to the use of these compounds as active components in antifouling paints [mainly tributyltin (TBT)] and pesticide formulations [mainly triphenyltin (TPhT)]. Their direct introduction into the environment, their bio-accumulation and the high toxicity of these compounds towards “non-target” organisms (for example: oysters and mussels) causes environmental and economic damage around the world. As a consequence, the presence and absence of organotin compounds is currently monitored in a range of environmental matrices (e.g., water, sediment and shellfish) to examine the utility of controls meant to regulate the level of contamination as required in some EC Directives and the Water Framework Directive 2000/60/EC. To evaluate the environmental distribution and fate of these compounds and to determine the effectives of legal provisions adopted by a number of countries, a variety of analytical methods have been developed for organotin determination in the environment. Most of these methods include different steps such as extraction, derivatisation and clean up. The aim of the present review is to evaluate the environmental distribution, fate and chemical speciation of organotin compounds in the environment.     

Biological and environmental reference materials from the National Institute for Environmental Studies (Japan)

Biological reference materials for elemental speciation were prepared at the National Institute for Environmental Studies. A new human hair reference material, prepared by cryogenic grinding using a ceramic disc mill, is in the process of certification for methyl-Hg and trace elements. Hijiki seaweed reference material was prepared for As speciation studies, primarily for use in the analysis of As(V). Scallop tissue reference material will be certified for arsenobetaine.