Mercury speciation in environmental samples by cold vapour atomic absorption spectrometry with in situ preconcentration on a gold trap

A method has been developed for the determination of total and organic mercury in biological materials and sediments. A microwave assisted mineralization of the organic mercury, after its extraction from the matrix, is described. This procedure warrants complete transformation of Hg(II) and, consequently, the quantitative reduction to Hg(0). The conditions for mercury reduction were optimized by a central composite design. The preconcentration of the analyte has been achieved by amalgamation on a trap system, consisting in a pyrolytic graphite platform wound by a gold wire. Mercury was determined by cold vapour atomic absorption spectrometry. The method was validated by the analysis of two certified reference materials and applied to the determination of total and organic mercury species in mussel tissues and sediments. The method is simple and practical, and offers the advantage of not requiring special equipment to measure inorganic and organic mercury simultaneously.     

Organolead speciation in environmental samples: a review

The speciation of organolead in some environmental samples is reviewed. Sampling, storage and pretreatment methods for water, soil, sediment and air samples are discussed before an assessment of recent developments in analytical methods.     

Inorganic selenium speciation in environmental samples using selective electrodeposition coupled with electrothermal atomic absorption spectrometry

Speciation analyses are of increasing interest in the environmental, toxicological and analytical fields, because the toxicity and reactivity of trace elements depend strongly on the chemical forms in which they are present. A simple electrodeposition–electrothermal atomic absorption spectrometry method for speciation analysis of some organic and inorganic selenium species in typical environmental water and agricultural soil samples has been developed. The method is based on the selective reduction of water-soluble Se(IV) and selenocystine (Se–Cys) species by an uncontrolled applied potential (1.8 V) on a mercury-coated electrode. In acidic media (1.0 M HCl solution) the only inorganic selenium species electrodeposited was Se(IV), and, of the water-soluble organic selenium species Se–Cys and Se–Met only Se–Cys was electrodeposited onto the mercury electrode surface. The proposed methodology was successfully applied to the speciation and determination of selenium in a few environmental samples. The spiked recovery value varied between 91% and 99%. The suggested method has been shown to have a characteristic mass (m₀) of 25 pg, a limit of detection (LOD) of 1.0 μg L^− 1 and a relative standard deviation (RSD%) of 3.5% for 6 measurements at a concentration of 100 μg L^− 1 Se(VI).     

On-line microwave oven digestion flame atomic absorption analysis of solid samples

A manifold has been developed for on-line microwave oven digestion and flame atomic absorption spectrometric (FAAS) determination of metallic elements in solid samples. The use of a closed flow system permits sample treatment before analysis by FAAS, the direct injection of slurries avoids a filtration step and the interconnection of two conventional rotary injection valves allows the rapid introduction of samples and standards. The determination of lead in sewage sludge was employed as a test system for the proposed on-line sample digestion manifold. The procedure has a limit of detection of 0.2 μg Pb g^?1.     

Aluminium speciation in environmental samples: a review

Because of its toxic effects on living beings, Al may represent an environmental hazard, particularly under increased acidic conditions. Growing environmental concern over the presence of increased Al concentrations in soil solutions and fresh waters resulted in the development of numerous analytical techniques for the determination of Al species. Al has a very complex chemistry that is significantly influenced by pH. Different Al species are present in environmental solutions, and many of them are unstable. Contamination of samples and reagents by extraneous Al represents an additional problem in speciation of Al at trace concentrations. Due to these reasons quantitative determination of particular chemical forms of Al is still a very difficult task for analytical chemists. The most important analytical methodologies of the last decade and new trends for the speciation of Al in environmental samples are comprehensively reviewed here.     

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.     

On-line hyphenation of capillary electrophoresis with flame-heated furnace atomic absorption spectrometry for trace mercury speciation

Capillary electrophoresis (CE) was directly interfaced to flame-heated furnace atomic absorption spectrometry (FHF-AAS) via a laboratory-made thermospray interface for nanoliter trace element speciation. The CE-FHF-AAS interface integrated the superiorities of stable CE separation, complete sample introduction, and continuous vaporization for AAS detection without the need of extra external heat sources and any post-column derivation steps. To demonstrate the usefulness of the developed hybrid technique for speciation analysis, three environmentally significant and toxic forms of methylmercury (MeHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) were taken as model analytes. Baseline separation of the three mercury species was achieved by CE in a 60 cm long x 75 microm inner diameter fused-silica capillary at 20 kV and using a mixture of 100 mM boric acid and 10% v/v methanol (pH 8.30) as running electrolyte. The precision (relative standard deviation, RSD, n = 7) of migration time, peak area and peak height for the mercury species at 500 microg x L(-1) (as Hg) level were in the range of 0.9-1.2%, 1.5-1.9%, and 1.4-2.0%, respectively. The detection limit (S/N = 3) of three mercury species was 3.0 +/- 0.15 pg (as Hg), corresponding to 50.8 +/- 2.4 microg x L(-1) (as Hg) for 60 nL sample injection, which was almost independent on specific mercury species. The developed hybrid technique was successfully applied to the speciation analysis of mercury in a certified reference material (DORM-2, dogfish muscle).     

Combination of three analytical techniques for speciation of Al in environmental samples

An analytical scheme is proposed which combines three speciation techniques for determination of particular Al species in soil extracts and percolating waters. A cation-exchange fast protein liquid chromatography — inductively coupled plasma atomic emission spectrometry (FPLC-ICP-AES) procedure, a microcolumn chelating ion-exchange chromatography- atomic absorption spectrometry (MCC-ETAAS) technique and the 8-hydroxyquinoline spectrophotometric method (8HQ-spectrophotometry) were employed. The FPLC-ICP-AES procedure offers determination of Al³⁺ (retention time 4.5 min) and Al(OH)²⁺ species (retention time 4.0 min) which are separated from Al(OH)⁺ ₂ (retention time 1.5min). AlF²⁺ coelutes with Al(OH)²⁺ species, while Al(SO₄)⁺, AlF⁺ ₂ and negatively charged Al organic complexes coelute with Al(OH)⁺ ₂ species. The MCC-ETAAS technique enables determination of the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphate- and fluoro-Al complexes. Employing the 8HQ-spectrophotometry the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphato- and most of the labile organic Al species are determined. The sensitivities of these selected techniques were adequate for speciation of Al in the samples analyzed. On the basis of the specific selectivity of a particular technique various groups of Al species may be determined. Thus, the comparison of analytical data from complementary procedures provides more comprehensive information on Al species present in soil extracts and percolating waters.     

Application of a new resin functionalised with 6-mercaptopurine for mercury and silver determination in environmental samples by atomic absorption spectrometry

Polystyrene–divinylbenzene (8%) has been functionalised by coupling it through an ---N=N--- group with 6-mercaptopurine. The resulting chelating resin has been characterised by using elemental analysis, thermogravimetric analysis and infrared spectra. The resin is highly selective for Hg(II) and Ag(I) and has been used for preconcentrating Hg(II) and Ag(I) prior to their determination by atomic absorption spectrometry. The maximum sorption capacity for Hg(II) and Ag(I) was found to be 1.74 and 0.52 mmol g⁻¹, respectively, over the pH range 5.5–6.0. The calibration range for Hg(II) was linear up to 10 ng ml⁻¹ with a 3σ detection limit of 0.02 ng ml⁻¹; the calibration range for Ag(I) was linear up to 5 μg ml⁻¹ with a detection limit of 29 ng ml⁻¹. The recoveries of the metals were found to be 99.7±3.8 and 101.3±4.1% at the 95% confidence level for both Hg(II) and Ag(I). In column operation, it has been observed that Hg(II) and Ag(I) in trace quantities can be selectively separated from geological, medicinal and environmental samples.     

Development of a method for speciation of inorganic arsenic in waters using solid phase extraction and electrothermal atomic absorption spectrometry

A solid phase extraction (SPE) procedure based on Amberlite IRA 900 resin was developed for speciation and separation of inorganic arsenic species (III, V) and total As in water samples. The As species and total As in eluent solutions were determined by electrothermal atomic absorption spectrometry (ETAAS) using Ni chemical modifier with 1200°C pyrolysis temperature. Experimental parameters such as pH value, sample volume, flow rate, volume and concentration of eluent solution for As(V) were optimised and 98.0 ± 1.9% recovery was found at pH 4.0. Experimental adsorption capacity of the resin for As(V) was investigated and 229.9 mg g^–1 was found. Under optimised experimental conditions, instrumental parameters such as limit of detection (LOD) and limit of quantification (LOQ) found were 0.126 and 0.420 µg L^–1, respectively. Interference effects of coexisting ions in the sample matrix on the recovery of As(V) were investigated. Concentration of As(III) was obtained by subtracting As(V) concentration found at pH 4.0 from total As(III + V) found at pH 8.0. The accuracy of the method proposed by using the resin was tested for analysing As species in a waste water standard reference material (SRM, CWW-TM-D) and spiked real water samples with recovery above 95%. The method proposed was also applied to the determinations of As species and total As in underground hot waters and tap water with relative error below 3%.     

Improvement in arsenic speciation,using hydride generation and atomic absorption spectrophotometry

Improvements in arsenic speciation in sea-water using hydride generation, cold trapping and AAS are reported. Progressive addition of sodium tetrahydroborate and pH optimization are essential to obtain reliable results. The response factor for As^III, As^v, methylarsonic acid and dimethylarsinic acid is nearly the same when sulphuric acid is used for the hydride generation step.     

A new specific polymeric material for mercury speciation: Application to environmental and food samples

A new polymeric material (Patent: P201400535) highly specific for mercury is presented. Its great capability to pre-concentrate and selectively elute inorganic mercury and methylmercury are the main figures of merit. The polymer can be reused several times. To our knowledge, this is the only polymer proposed in the literature for direct inorganic mercury and methylmercury speciation without need of chromatography or quantification by difference. The polymer formation is based on the reaction of a vinyl derivative of 8-hydroxiquinoline as monomer, and 2-(Methacryloylamino) ethyl 2-Methyl Acrylate (NOBE) as co-monomer. Random radical polymerization by the precipitation method was carried out using Azobisisobutyronitrile (AIBN) as initiator. The polymer was characterized by SEM and FTIR. Adsorption binding isotherms were evaluated using Langmuir and Freundlich models, showing high adsorption capacity for both inorganic and organic mercury species. The polymer was employed to sequentially determine inorganic mercury and methylmercury, using a solid phase extraction (SPE) scheme. Cross reactivity of several ions, as well as matrix effects from a high saline matrix like seawater was irrelevant as the retained fractions mostly eluted during the washing step. The procedure was first validated by analyzing a certified reference material (BCR 464) and finally applied to commercial fish samples. The speciation proposed procedure is cheap, fast, and easy to use and minimizes reagents waste.     

Screening of antimony in PVC by solid sampling-graphite furnace atomic absorption spectrometry

The development of two-stage control systems is of great interest when a large number of samples are analysed in order to check that they fulfil certain requirements. If the first stage is carried out using an inexpensive method with a high throughput which makes it possible to filter out the majority of the samples that fulfil the requirements, the procedure is not only less time-consuming but also more economical. Direct determination of metals in solid samples by graphite furnace atomic absorption spectrometry (GFAAS) appears, in principle, to be a suitable analytical technique for screening purposes since it provides sufficiently reliable results in a reasonably short time. In this paper it is applied with satisfactory results to antimony content control in a PVC sample.     

Analysis of organic compounds in environmental samples by headspace solid phase microextraction

The analysis of samples contaminated by organic compounds is an important aspect of environmental monitoring. Because of the complex nature of these samples, isolating target organic compounds from their matrices is a major challenge. A new isolation technique, solid phase microextraction, or SPME, has recently been developed in our laboratory. This technique combines the extraction and concentration processes into one step; a fused silica fiber coated with a polymer is used to extract analytes and transfer them into a GC injector for thermal desorption and analysis. It is simple, rapid, inexpensive, completely solvent-free, and easily automated. To minimize matrix interferences in environmental samples, SPME can be used to extract analytes from the headspace above the sample. The combination of headspace sampling with SPME separates volatile and semi-volatile analytes from non-volatile compounds, thus greatly reducing the interferences from non-target compounds. This paper reports the use of headspace SPME to isolate volatile organic compounds from various matrices such as water, sand, clay, and sludge. By use of the technique, benzene, toluene, ethyl-benzene, and xylene isomers (commonly known as BTEX), and volatile chlorinated compounds can be efficiently isolated from various matrices with good precision and low limits of detection. This study has found that the sensitivity of the method can be greatly improved by the addition of salt to water samples, water to soil samples, or by heating. Headspace SPME can also be used to sample semi-volatile compounds, such as PAHs, from complex matrices.     

Comparison of extraction procedures for arsenic speciation in environmental solid reference materials by high‐performance liquid chromatography–hydride generation‐atomic fluorescence spectroscopy

Water and ‘soft’ extractions (hydroxylammonium hydrochloride, ammonium oxalate and orthophosphoric acid) have been studied and applied to the determination of arsenic species (arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) in three environmental solid reference materials (river sediment, agricultural soil, sewage sludge) certified for their total arsenic content. The analytical method used was ion exchange liquid chromatography coupled on‐line to atomic fluorescence spectroscopy through hydride generation. Very low detection limits for arsenic were obtained, ranging from 0.02 to 0.04 mg kg^?1 for all species in all matrices studied. Orthophosphoric acid is the best extractant for sediment (mixed origin) and sludge samples (recent origin) but not for the old formation soil sample, from which arsenic is extracted well only by oxalate. Both inorganic forms (As(III) and As(V)) are significant in all samples, As(V) species being predominant. Moreover, organic forms are found in water extracts of all samples and are more important in the sludge sample. These organic forms are also present in the ‘soft’ extracts of sludge. Microwave‐assisted extraction appears to minimize the risk of a redox interconversion of inorganic arsenic forms. This study points out the necessity of combining direct and sequential extraction procedures to allow for initial arsenic speciation and to elucidate the different mineralogical phases–species associations. Copyright © 2002 John Wiley & Sons, Ltd.     

Evaluation of ion imprinted polymers for the solid phase extraction and electrothermal atomic absorption spectrometric determination of palladium in environmental samples

The complexes of Pd(II) with ammonium pyrrolidinedithiocarbamate (APDC), N,N′-diethylthiourea (DET) and dimethylglyoxime (DMG) were prepared and imprinted into a polymeric network. The ion-imprinted polymers (IIPs) were synthesized by copolymerization of 4-vinylpyridine (VP) and styrene as functional monomers and divinylbenzene as a cross-linking agent in the presence of 2,2-azo-bis-isobutyronitrile as an initiator. The influence of sample volume, pH and flow rate on the extraction efficiency of Pd was studied under dynamic conditions. Pd(II) could be quantitatively retained on each of the studied sorbents at the pH range of 0.5 to 1.0, and eluted with an acidic solution of thiourea. The polymer with the imprinted Pd-DET-VP complex offered the highest selectivity for Pd(II) over certain matrix components, such as Pt(IV), Ni(II) and Cu(II). The low sample pH is an important advantage of the separation procedure, as it allows an effective separation of Pd(II) from complex environmental matrices. The developed separation method was successfully applied to the electrothermal atomic absorption spectrometric (ETAAS) determination of trace amounts of Pd in tap and river water, grass, and certified platinum ore (CRM SARM 7 and SARM 76) samples with reproducibility below 6.5%. The detection limit for Pd(II) obtained by ETAAS after the pre-concentration on Pd-DET-VP polymer was 0.012?ng?mL^?1 for 75?mL sample volume.     

Liquid chromatography-hydride generation-atomic fluorescence spectrometry hybridation for antimony speciation in environmental samples

Atomic fluorescence spectrometry was used as an element-specific detector in hybridation with liquid chromatography (LC) and hydride generation for the speciation of Sb(III), Sb(V) and trimethylantimony dichloride (TMSbCl₂). The three species were poorly resolved in a single chromatogram but good results were obtained by anion-exchange chromatography, using a mobile phase with 20 mM EDTA and 8 mM hydrogenphthalate to separate Sb(III) and Sb(V) and 1 mM carbonate at pH 10 to separate Sb(V) and TMSbCl₂. Calibration graphs were linear between 2 and 100 μg l⁻¹. Detection limits were 0.9, 0.5 and 0.7 μg l⁻¹ for Sb(III), Sb(V) and TMSbCl₂, respectively. The method was applied to the speciation of antimony in environmental samples.     

Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry

A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing.     

Selenium speciation by high-performance liquid chromatography with on-line detection by atomic absorption spectrometry

Several approaches to the determination of selenomethionine, selenocystine, selenite and selenate by high-performance liquid chromatography with online detection by atomic absorption spectrometry are described. The N?2,4-dinitrophenyl derivatives of selenomethionine, selenoethionine, selenocystine and phenylmercury(II) cystineselenoate were recovered from aqueous solution, separated on a Nucleosil 5-NO₂ reversed-phase HPLC column with a methanolic mobile phase containing acetic acid and triethylamine, and detected with a quartz thermochemical hydride-generating interface–atomic absorption spectrometry (AA) system. The restriction of having to perform chromatography with an organic mobile phase (to support the combusion process) was overcome with a new interface design capable of operation with either organic or aqueous HPLC mobile phases. Using aqueous acetic acid (0.015% v/v) containing 0.1% (w/v) ammonium acetate delivered at 0.5cm³ min^?1, selenate, selenite, selenomethionine, selenocystine and selenoethionine were separated virtually to baseline on a cyanopropyl-bonded phase HPLC column. Other selenium compounds which were investigated included methane seleninic and methane selenonic acids as well as the crude oxidation product mixtures resulting from the treatment of selenomethionine and selenocystine with hydrogen peroxide. A procedure for extracting selenate, selenite, selenomethionine, selenocystine and selenoethionine from spiked water or ground feed supplement into liquefied phenol resulted in acceptable recoveries for the latter four analytes but was unacceptably low for selenate.     

Chromium speciation using activated alumina microcolumns and sequential injection analysis-flame atomic absorption spectrometry

A new procedure has been developed for chromium speciation in water by sequential injection analysis and flame atomic absorption spectrometry. The method involves the online retention of Cr(VI) anionic species and Cr(III) cationic species on alumina microcolumns, prepared by packing activated alumina in polytetrafluoroethylene tubes, followed by selective elution of Cr(VI) with 2 mol l⁻¹ NH₄OH and of Cr(III) with 0.2 mol l⁻¹ HNO₃. Studies were carried out on the effect of retention and elution conditions for both Cr species. The limit of detection values, established as the concentration corresponding to three times the standard deviation of blank measurements divided by the slope of the calibration line, achieved were 42 μg l⁻¹ for Cr(VI) and 81 μg l⁻¹ for Cr(III). The relative standard deviation of three independent determination of natural spiked samples were lower than 10% for concentration levels between 0.5 and 2 mg l⁻¹ of Cr. The developed procedure was applied to the analysis of two effluent sewage waters, and results obtained compared well with those obtained by a batch procedure. Recovery studies on natural spiked samples provided results between 93 and 103% for Cr(VI) and from 100 to 106% for Cr(III) for samples spiked with single species. For samples spiked with both Cr(VI) and Cr(III), the average recoveries varied from 86 to 101% for Cr(VI) and from 91 to 117% for Cr(III).