Determination of heavy metals at the pg/g level in Antarctic snow with DPASV and IDMS

Summary Differential pulse anodic stripping voltammetry (DPASV) and isotope dilution mass spectrometry (IDMS) were used to analyse heavy metals in Antarctic snow samples. It was possible to determine Pb and Cd with DPASV at the German Antarctic station Georg-von-Neumayer whereas the analyses of Pb, Cd, Tl, Cr, Ni, Cu, Zn, and Fe with IDMS were carried out at the University of Regensburg. 80% of the elemental concentrations in surface snow samples analysed with IDMS lay in the following ranges: Pb=3–40 pg/g, Cd<0.2–3 pg/g, Tl<0.2 pg/g, Cr<0.8–15 pg/g, Ni<4.8–40 pg/g, Cu<11–30 pg/g, Zn=30–500 pg/g, and Fe=(0.5–1.5)×10³ pg/g. In most cases an acceptable agreement between the DPASV and IDMS results was obtained for Pb and Cd. More than 50% of all Pb analyses agreed within a deviation of 0–10 pg/g. The Cd results between both methods usually deviated by less than 1 pg/g. Slightly higher Pb concentrations were analysed in the average with IDMS compared with DPASV. This effect was not observed for the Cd data. A possible explanation for this fact are non-ionic Pb species in the melted snow samples, which cannot be analysed by DPASV. One particular investigation of Pb concentrations showed that the analysed data with DPASV decreased with the increasing length of sun-shine after a snowfall when samples of the same origin were determined. Blank control is the major requirement for accurate analysis results of heavy metals in this low concentration range. On the other hand, accuracy must always be tested by independent analytical methods. In this work it is shown that Pb and Cd can be analysed directly in the Antarctica with DPASV and that the result of this method is in acceptable agreement with the definitive method IDMS.

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Bestimmung von Schwermetallen im pg/g Bereich in antarktischen Schneeproben durch differentielle Pulsinversvoltammetrie und massenspektrometrische Isotopenverdünnungsanalyse

     

Determination of water-soluble and insoluble (dilute-HCl-extractable) fractions of Cd,Pb and Cu in Antarctic aerosol by square wave anodic stripping voltammetry: distribution and summer seasonal evolution at Terra Nova Bay (Victoria Land)

Eight PM10 aerosol samples were collected in the vicinity of the “Mario Zucchelli” Italian Antarctic Station (formerly Terra Nova Bay Station) during the 2000–2001 austral summer using a high-volume sampler and precleaned cellulose filters. The aerosol mass was determined by differential weighing of filters carried out in a clean chemistry laboratory under controlled temperature and humidity. A two-step sequential extraction procedure was used to separate the water-soluble and the insoluble (dilute-HCl-extractable) fractions. Cd, Pb and Cu were determined in the two fractions using an ultrasensitive square wave anodic stripping voltammetric (SWASV) procedure set up for and applied to aerosol samples for the first time. Total extractable metals showed maxima at midsummer for Cd and Pb and a less clear trend for Cu. In particular, particulate metal concentrations ranged as follows: Cd 0.84–9.2 μg g⁻¹ (average 4.7 μg g⁻¹), Pb 13.2–81 μg g⁻¹ (average 33 μg g⁻¹), Cu 126–628 μg g⁻¹ (average 378 μg g⁻¹). In terms of atmospheric concentration, the values were: Cd 0.55–6.3 pg m⁻³ (average 3.4 pg m⁻³), Pb 8.7–48 pg m⁻³ (average 24 pg m⁻³), Cu 75–365 pg m⁻³ (average 266 pg m⁻³). At the beginning of the season the three metals appear widely distributed in the insoluble (HCl-extractable) fraction (higher proportions for Cd and Pb, 90–100%, and lower for Cu, 70–90%) with maxima in the second half of December. The soluble fraction then increases, and at the end of the season Cd and Pb are approximately equidistributed between the two fractions, while for Cu the soluble fraction reaches its maximum level of 36%. Practically negligible contributions are estimated for crustal and sea-spray sources. Low but significant volcanic contributions are estimated for Cd and Pb (∼10% and ∼5%, respectively), while there is an evident although not quantified marine biogenic source, at least for Cd. The estimated natural contributions (possibly including the marine biogenic source) cannot account for the high fractions of the metal contents, particularly for Pb and Cu, and this suggests that pollution from long-range transport is the dominant source. Figure Aerosol sampling in Antarctica     

Determination of Cd,Pb, and Cu in the Atmospheric Aerosol of Central East Antarctica at Dome C (Concordia Station)

Trace heavy metals Cd, Pb, and Cu were determined (by square wave anodic stripping voltammetry) in aerosol samples collected at Dome C (the Italo-French Station Concordia), a remote site of the Central East Antarctic plateau, for which no data are available until now. During the Austral Summer 2005–2006, three PM10 high-volume impactors were installed in two locations nearby of Concordia station: the first one very close and downwind of the station (about 50 m north), the other two (very close to each other) in a ‘distant’ site, upwind of the station and close to the astrophysics tent (not used in that expedition) at ~800 m south of Station Concordia. For each sample, the availability of the mass of the aerosol collected (obtained by differential weighing carried out on site), in addition to the volume of the filtered air, allowed us to express results both in terms of metal mass fractions in the aerosol and in the usual way of metal atmospheric concentrations. Metal contents increased in the order Cd < Pb < Cu with the following ranges of values: Cd 1.0–8.4 µg g⁻¹ (0.09–3.1 pg m⁻³), Pb 96–470 µg g⁻¹ (12–62 pg m⁻³), and Cu 0.17–20 mg g⁻¹ (0.027–2.4 ng m⁻³). From the metal temporal profiles obtained we estimated the following background values for the area of Dome C, expressed both in mass fractions and in atmospheric concentrations: Cd 1.2 ± 0.2 µg g⁻¹ (0.24 ± 0.13 pg m⁻³), Pb (here fixed as upper limit) 113 ± 13 µg g⁻¹ (21 ± 8 pg m⁻³), and Cu 0.91 ± 0.48 mg g⁻¹ (0.12 ± 0.07 ng m⁻³). The highest values were observed in the first part of the season, and particularly for the site close to the station, possibly related to sample contamination linked to intense activity at the Concordia station connected with the beginning of the expedition, including aircraft arrivals/departures. Increments of up to 10 times (and even 20 times for Cu) were recorded with respect to the background values. The metal excesses of the contaminated over background samples were found approximately, except for Cu, in the same proportion of the metal contents of the special Antarctic blend (SAB) diesel fuel, which is used almost exclusively at Concordia Station. The effect of the wind direction was also observed. Thus in the intermediate period of the campaign, when the wind direction reversed for several days with respect to the prevailing one, Cd and Pb metal contents decreased at the sampling point installed close to the station, now upwind of Concordia station, and increased at the ‘clean’ site astrophysics tent, turned downwind at the main station. No simple and easily interpretable effect of the wind direction was observed for Cu, which suggests that some other extemporaneous and not clearly identified factor may have intervened in this case. These results suggest that the human impact at Dome C influences mainly the zone very close to the station, but also the area in the neighborhood, including the supposed clean site of the astrophysics tent (about 800 m far from the station), when the wind direction reverses with respect to the prevailing one, leaving the site downwind of the station Concordia. Since no other data are reported for the Dome C area, our results are compared with literature data referred to the South Pole Station (the only other plateau site for which data are available) and several other coastal Antarctic sites, observing that our results (excluding Cu) are the lowest ever observed for Antarctic aerosol.     

First Systematic Voltammetric Measurements of Cd,Pb, and Cu in Hydrofluoric Acid-Dissolved Siliceous Spicules of Marine Sponges: Application to Antarctic Specimens

Ultrasensitive Square Wave Anodic Stripping Voltammetry is used for the first time for the systematic determination of Cd, Pb, and Cu in siliceous spicules of marine sponges; the procedure is performed directly in hydrofluoric acid solution, according to a procedure previously established in our laboratory, with the aim of demonstrating the feasibility of such measurements and to improve knowledge of heavy metal distribution in Porifera. The following Demospongiae species are considered: Sphaerotylus antarcticus, Haliclona sp., Kirkpatrickia coulmani, and Inflatella belli from the Ross Sea, Antarctica, and Petrosia ficiformis from the Mediterranean Sea, Italy. The method shows a good accuracy; the analytical variability is approximately ±10% for all the metals studied and for all the measurements performed, showing a good repeatability of the method in consideration of low metal concentrations (order of tenths of µg g^?1 dry weight, i.e., of hundreds of ng L^?1 in the HF solution). In particular, the concentrations of heavy metals in the body of the sponge vary in the range 0.038–0.93 µg g^?1 dry weight (d.w.) for Cd, 0.024–0.52 µg g^?1 d.w. for Pb, and 0.32–1.3 µg g^?1 d.w. for Cu. Similar ranges of concentration were recorded in the oscula of S. antarcticus and I. belli. Heavy metal concentration in the spicules can vary within and between specimens and, in particular, siliceous spicules of Antarctic sponges show higher concentrations of Cd and Pb and lower concentrations of Cu than those from the Mediterranean.     

Preconcentration of lead,cadmium, copper and zinc in water at the pg g−1 level by non-boiling evaporation

An evaluation of the non-boiling evaporation technique for the preconcentration of Pb, Cd, Cu, Zn at the pg g^?1 level in water samples is presented. Various improvements were made to allow efficient control of contamination problems at these extremely low concentrations. They include the choice of FEP Teflon for the evaporation containers and the use of sophisticated cleaning, ageing and pre-conditionning procedures. Detailed calibration graphs were obtained down to the sub-pg g^?1 level by processing ultra-low concentration standards. This technique was then applied to the determination of these four metals in snow samples collected in Greenland and Antarctica.     

Simultaneous Determination of Cadmium,Lead, Copper,and Thallium in Highly Saline Samples by Anodic Stripping Voltammetry (ASV) Using Mercury‐Film and Bismuth‐Film Electrodes

This paper describes a comparative study of the simultaneous determination of Cd(II), Pb(II), Tl(I), and Cu(II) in highly saline samples (seawater, hydrothermal fluids, and dialysis concentrates) by ASV using the mercury‐film electrode (MFE) and the bismuth‐film electrode (BiFE) as working electrodes. The features of MFE and BiFE as working electrodes for the single‐run ASV determinations are shown and their performances are compared with that of HMDE under similar conditions. It was observed that the stripping peak of Tl(I) was well separated from Cd(II) and Pb(II) peaks in all the studied saline samples when MFE was used. Because of the severe overlapping of Bi(III) and Cu(II) stripping peaks in the ASV using BiFE, as well as the overlapping of Pb(II) and Tl(I) stripping peaks in the ASV using HMDE, the simultaneous determination of these metals was not possible in highly saline medium using these both working electrodes. The detection limits calculated for the metals using MFE and BiFE (deposition time of 60 s) were between 0.043 and 0.070 μg L^?1 for Cd(II), between 0.060 and 0.10 μg L^?1 for Pb(II) and between 0.70 and 8.12 μg L^?1 for Tl(I) in the saline samples studied. The detection limits calculated for Cu(II) using the MFE were 0.15 and 0.50 μg L^?1 in seawater/hydrothermal fluid and dialysis concentrate samples, respectively. The methods were applied to the simultaneous determination of Cd(II), Pb(II), Tl(I), and Cu(II) in samples of seawater, hydrothermal fluids and dialysis concentrates.     

Certification of the contents of some heavy metals (Cd, Cu, Hg, Ni, Pb and Zn) in three types of soils

Summary The element contents of Cd, Cu, Hg, Ni, Pb and Zn of three types of soil were certified. The preparation, homogeneity and stability are reported. The certified contents as well as values for Co, Cr, Mn and Se and for the aqua regia soluble contents Cd, Cr, Cu, Mn, Ni, Pb and Zn are given.

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Zertifizierung von Schwermetallspuren (Cd, Cu, Hg, Ni, Pb und Zn) in drei Bodenproben

Zusammenfassung In drei verschiedenen Bodenproben wurden die Elementgehalte an Cd, Cu, Hg, Ni, Pb und Zn zertifiziert. Es wird berichtet über die Bereitung, Homogenität und Stabilität. Die zertifizierten Gehalte sowie der Gehalt an Cr, Co, Mn und Se und der Gehalt an königswasserlöslichem Cd, Cr, Cu, Mn, Ni, Pb und Zn werden angegeben.

     

Certification of the contents of some heavy metals (Cd, Co, Cu, Mn, Hg, Ni, Pb and Zn) in three types of sewage sludge

Summary The element contents of Cd, Co, Cu, Mn, Hg, Ni, Pb and Zn of three different types of sewage sludge were certified. The preparation, the homogeneity and the stability are reported. The certified contents as well as values for Cr and Se and for the aqua regia soluble contents of Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn are given.

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Zertifizierung von Schwermetallspuren (Cd, Co, Cu, Mn, Hg, Ni, Pb und Zn) in drei Klärschlammproben

Zusammenfassung In drei verschiedenen Klärschlammproben wurden die Elementgehalte an Cd, Co, Cu, Mn, Hg, Ni, Pb und Zn zertifiziert. Es wird berichtet über die Herstellung, Homogenität und Stabilität. Die zertifizierten Gehalte sowie der Gehalt von Cr, Se und der Gehalt an königswasserlöslichem Cd, Cr, Co, Cu, Mn, Ni, Pb und Zn werden angegeben.

     

Assessing spatial distribution,sources, and potential ecological risk of heavy metals in surface sediments of the Nansi Lake,Eastern China

The study is conducted to investigate the spatial distribution, sources and ecological risk of seven heavy metals in surface sediments of Nansi Lake, Eastern China. A total of 29 samples were collected in surface sediments of Nansi Lake, and were analyzed for three nutrients (TN, TOC and TP), two major metals (Al and Fe), as well as seven trace metals (As, Cd, Cr, Cu, Hg, Pb and Zn). The mean concentrations of As, Cd, Cr, Cu, Hg, Pb, Zn, Fe and Al were 14.41, 0.22, 71.10, 30.1, 0.048, 29.14, 90.2, 30,816 and 70,653 mg kg^?1, respectively, and the mean contents of these metals were higher than the background values with the exception of Cu and Fe. The spatial distribution indicated that the contents of all seven heavy metals were characterized by relatively higher contents in the upper lake than the lower lake. The hotspots with high values of As, Cd and Hg were associated with the river mouths, and the hotspots of Pb were mainly located around the dam in the central part, while no significant associations were displayed between spatial distribution of Cr, Cu, Zn and the river mouths. The mean enrichment factor (EF) values of As, Cd, Hg and Pb were 2.03, 2.93, 3.21 and 2.18, respectively, showing their moderate enrichment, while Cr, Cu and Zn with mean EF values of 1.19, 0.89 and 1.01 were deficiency to minimal enrichment. Multivariate and geostatistical analyses suggested that PC1 controlled by Cr, Cu and Zn was a lithogenic component, and come from parent rocks leaching. PC2 including Cd and partially Hg represented the factor from industrial wastewater discharge. PC3 showed elevated loadings of As and partially Cd, and could be attributed to the agricultural practices. While PC4 including Pb and partially Hg, was dominated by coal combustion. The results of potential ecological risk suggested that sediment environment of Nansi Lake suffered from high ecological risk.     

The determination of trace metals in mineral waters : Part I. Atomic Absorption Spectrometric Determination of Cd,Co, Cr,Cu, Ni and Pb by Electrothermal Atomization After Concentration by Co-precipitation

Procedures based on flameless atomic absorption spectrometry are described for the determination of Cd, Co, Cr, Cu, Ni and Pb in mineral waters. Because of matrix effects and the inadequate detection limits for direct determinations, the metals are separated from the macrocomponents by precipitation of their tetramethylenedithiocarbamates with iron(III) as collector, or by co-precipitation on Fe(OH)₃. The detection limits are 0.005, 0.3, 0.08. 0.10, 2 and 0.10 μg l^- for Cd, Co, Cr, Cu, Ni and Pb, respectively, and are satisfactory for the determination of these elements in mineral waters. The precision is 2–7%.     

The development of a method for the determination of trace elements in fuel alcohol by ETV-ICP-MS using isotope dilution calibration

A method for the determination of Ag, Cd, Cu, Pb and Tl in fuel alcohol by isotope dilution electrothermal vaporization inductively coupled plasma mass spectrometry (ID ETV-ICP-MS) is proposed. The analytes were separated in two groups: Ag and Cu were determined without modifier and Cd, Pb and Tl with the use of Pd as chemical modifier. The employed ETV operational conditions were pyrolysis temperature of 800 °C for Cd, Pb and Tl and of 900 °C for Ag and Cu and vaporization temperature of 2400 °C for both groups. Seven common, one with additive and one anhydrous fuel ethanol samples were analyzed. The spiked and reference isotopes were, respectively, ¹⁰⁹Ag and ¹⁰⁷Ag, ¹¹²Cd and ¹¹¹Cd, ⁶³Cu and ⁶⁵Cu, ²⁰⁶Pb and ²⁰⁸Pb and ²⁰³Tl and ²⁰⁵Tl. The added amounts of the enriched isotope material were the same for all samples: 4.6 ng of ¹⁰⁹Ag, 5 ng of ¹¹²Cd, 21.1 ng of ⁶³Cu, 9 ng of ²⁰⁶Pb and 0.21 ng of ²⁰³Tl. The blank was bi-distilled ethanol, acidified with 0.3% (v/v) nitric acid, as the samples. The limits of detection (LODs) were calculated as three times the standard deviation of the concentrations in the blank (n = 10) and were, in μg L⁻¹, for Ag: 0.02, for Cd: 0.08, for Cu: 0.1, for Pb: 0.05 and for Tl: 0.001. The obtained concentrations in the samples were in agreement with those obtained by external calibration (EC), according to the paired t-test. The isotope dilution (ID) showed to be a robust, fast and simple calibration technique for the analysis of fuel ethanol.     

A study of the direct determination of Cd, Cr, Cu, Pb and Zn in certified reference materials of soils by solid sampling electrothermal atomic absorption spectrometry

A simple and rapid method for the direct determination of Cd, Cr, Cu, Pb and Zn in soil was developed. The method was developed using three certified reference materials of soil: Eutric Cambisol, Orthic Luvisols and Rendzina, which differed in their matrix composition. Chemical modifiers were essential to achieve reproducible and interference-free signals for the analytes studied. The best results were obtained with a Pd/Mg(NO₃)₂ admixture for the determination of Cd, Pb and Zn and NH₄F for Cu. The combination of W (as a permanent modifier) and Mg(NO₃)₂ provided well-defined signal profiles for Cr. The following spectral lines were used: Cd 228.8 nm, Cr 520.6 nm, Cu 218.2 nm, Pb 205.3 nm and Zn 307.6 nm. The limit of detection was 4.2 ng g^− 1 for Cd, 1.1 μg g^− 1 for Cr, 0.5 μg g^− 1 for Cu, 1.3 μg g^− 1 for Pb and 8.6 μg g^− 1 for Zn for the maximum sample mass used. Under optimized conditions, the analyte and matrix were separated effectively in situ, and aqueous standards could be used for calibration.     

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

Kinetic Studies of Metal Speciation Using Inductively-Coupled Plasma Mass Spectrometry

Abstract

Kinetic studies of uptake of metal ions by the Chelex batch technique were made to determine Cd, Cu and Pb speciation in model solutions, a snow sample and a river surface water sample. Inductively-coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS) were used for direct determination of these metals. ICP-MS with the solution nebulization technique minimized contamination and adsorption problems involved in the discrete sampling technique of GFAAS, and hence, gave more precise and accurate results. Also, ICP-MS allowed collection of many more data points than GFAAS and was able to resolve components with similar rates of dissociation, which could not always be resolved by GFAAS with its discrete sampling technique. ICP-MS was therefore preferable to GFAAS for kinetic studies of metal speciation. The kinetic data were analyzed by the iterative deconvolution method. The applicability of the Chelex batch technique to metal speciation was validated by analysis of model solutions containing these metal ions with or without EDTA, NTA and fulvic acid. Use of the Chelex batch technique for Cd, Cu and Pb speciation in snow and river surface water samples revealed a number of kinetically distinguishable components of these metals (as complexes) ranging from one to three, probably present as aquo ions or inorganic complexes in the snow sample, and bound to macromolecules/and or colloidal materials in the river surface water sample.     

Preconcentration and Fractionation of Cd, Co, Cu, Ni, Pb and Zn in Natural Water Samples Prior to Analysis by Inductively Coupled Plasma Atomic Emission Spectrometry

The strong cation exchanger Dowex 50W-x4 was used for the enrichment of traces of Cd, Co, Cu, Fe, Ni, Pb and Zn in mineral and mine waters as an alternative to the commonly applied procedures based on the application of chelating resins. The resin used was found suitable for complete retention of these metals both from the solutions of very low pH as well as those close to neutral, thus eliminating the need to buffer the samples. An analytical scheme based on filtration and solid phase extraction with Dowex 50W-x4 was proposed for partitioning Cd, Co, Cu, Fe, Ni and Pb in the examined waters. The fraction of metals associated with the suspended particles was determined after filtration through a 0.45 µm pore size filter and decomposition of the deposited matter. For the evaluation of fractions of the labile metal species and the total dissolved metals, the untreated filtrates and the solutions resulting from their digestion, respectively, were passed through Dowex 50W-x4 cation exchange columns. The retrieval of the metals was completed using a 4.0 mol L⁻¹ solution of HCl. The described metal preconcentration and fractionation protocol offered the enrichment factor of 25 with detection limits equal to 22, 30, 92, 41, 70, 36 and 340 ng L⁻¹, respectively for Cd, Co, Cu, Fe, Ni and Pb. Reasonably good precision and accuracy were attained.     

Determination of components of the Cd(II)-Pb(II)-Cu(II) system in aqueous solutions of (polyethylene imine)methylthiourea by stripping voltammetry

Conditions were studied for the stripping voltammetric determination of components of the Cd(II)-Pb(II)-Cu(II) system in aqueous solutions of (polyethylene imine)methylthiourea (PMT), the most efficient polymer complexant for the membrane preconcentration of heavy metal ions. It was shown that PMT significantly enhances the selectivity of determining Pb(II) and Cd(II) in solutions of Cu(II) by stripping voltammetry. Pb(II) and Cd(II) can be determined in the presence of up to 200- and 50-fold amounts of Cu(II), respectively. The limits of detection for Pb(II) and Cd(II) after a 40-s accumulation were 6.9 x 10^-8 and 6.8 x 10^-7 M, respectively.     

Simultaneous Determination of Pb and Cd Traces in Water Samples by Anodic Stripping Voltammetry Using a Modified GC Electrode

The determination of Pb and Cd with a Nafion‐modified glassy carbon electrode and Cu‐DPABA complex (Cu‐DPABA–NA/GCE; DPABA is methyl 3,5‐bis{bis‐[(pyridin‐2‐yl)methyl]amino}methyl‐benzoate) as an alternative electrode for anodic stripping voltammetry was described. Pb and Cd were accumulated in acetate buffer pH 4 at a potential of ?1.4 V (vs. Ag/AgCl electrode) for 120 s followed by a DPASV scan from ?1.2 to ?0.2 V. Under optimum conditions the calibration curves were linear in the range of 4.8×10^?9–5.0×10^?5 and 5.0×10^?9–5×10^?5 mol L^?1 for Pb and Cd, respectively. Detection limits were 1.8×10^?9 and 1.2×10^?9 mol L^?1 for Pb and Cd, respectively. Different parameters and conditions, such as membrane ingredients, accumulation time, potential and pH value were optimized. A study of interfering substances was also performed. A significant increase in current was achieved at the modified electrode in comparison with the bare glassy carbon electrode. The validation of the proposed method was made by Pb and Cd determination in the certified reference material Groundwater CRM 610 (BCR, Community Bureau of Reference, Brussels, Belgium). The electrode was successfully applied for determination of Pb and Cd in river water with a high content of organic contaminants without any pretreatment.     

A new strategy for preparation of hair slurries using cryogenic grinding and water-soluble tertiary-amines medium

The investigation of trace metal contents in hair can be used as an index of exposure to potentially toxic elements. Direct determination of Cd, Cu and Pb in slurries of hair samples was investigated using an atomic absorption spectrometer with Zeeman-effect background correction. The samples were pulverized in a freezer/mill for 13 min, and hair slurries with 1.0 g l⁻¹ for the determination of Cu and Pb, and 5.0 g l⁻¹ for the determination of Cd, respectively, were prepared in three different media: 0.1% v/v Triton X-100, 0.14 mol l⁻¹ HNO₃, and 0.1% v/v of CFA-C, a mixture of tertiary amines. The easiest way to manipulate the hair samples was in CFA-C medium. The optimum pyrolysis and atomization temperatures were established with hair sample slurries spiked with 10 μg l⁻¹ Cd²⁺, 30 μg l⁻¹ Pb²⁺, and 10 μg l⁻¹ Cu²⁺. For Cd and Pb, Pd was used as a chemical modifier, and for Cu no modifier was needed. The analyte addition technique was used for quantification of Cd, Cu, and Pb in hair sample slurries. A reference material (GBW076901) was analyzed, and a paired t-test showed that the results for all elements obtained with the proposed slurry sampling procedure were in agreement at a 95% confidence level with the certified values. The cryogenic grinding was an effective strategy to efficiently pulverize hair samples.     

新型薄膜扩散梯度装置定量测量水环境中重金属形态

采用以纤维素透析膜为扩散相, 0.05 mol/L羧甲基纤维素钠(CMC)溶液为结合相的薄膜扩散梯度(DGT)装置(CMC-DGT)定量累积和测量水溶液中Cu²⁺, Cd²⁺和Pb²⁺的有效态; 考察了pH值和离子强度对CMC-DGT累积Cu²⁺, Cd²⁺和Pb²⁺的影响以及不同配体(乙二胺四乙酸二钠、 单宁酸和黄腐酸)对重金属有效态的影响; 测量了外加标的天然水和工业废水中重金属的有效态浓度; 并比较了不同结合相DGT装置对同一水体中重金属的有效态浓度. 实验结果表明, 0.05 mol/L CMC溶液对Cu²⁺, Cd²⁺和Pb²⁺累积容量分别为0.24, 0.11和0.45 mg/mL; 定量累积的最佳pH值范围分别为3.7～8.0, 4.7～9.0和4.7～8.0; 随着离子强度的增大, CMC-DGT对Cu²⁺, Cd²⁺和Pb²⁺的累积容量下降; CMC-DGT能够定量地累积配制水中的游离Cu²⁺, Cd²⁺和Pb²⁺, 回收率分别为92.1%, 100.6%和96.4%; 当有配体存在时, 随着配体浓度的增大, CMC-DGT测量的Cu²⁺, Cd²⁺和Pb²⁺有效态的浓度随之下降; 在过滤工业废水、 河水和湖水中, 不同结合相DGT装置对重金属有效态的测量值不同. 结果表明, CMC可作为DGT技术新的液态结合相.     

Ultrasensitive determination of heavy metals at the sub-picogram per gram level in ultraclean Antarctic snow samples by inductively coupled plasma sector field mass spectrometry

Assessing changes in heavy metals concentrations in Antarctic snow dated from the last century is of high interest to determine to which extent the most remote regions of our planet are contaminated for these metals, and to have a better understanding into their long-range transport from the different natural and anthropogenic source areas to the Antarctic continent. Such investigations are unfortunately very difficult because the concentrations to be measured are exceedingly low, down to the sub-picogram per gram level. They require a strict control of contamination problems from field sampling to laboratory analysis, and the use of ultrasensitive analytical techniques.

We present here important advances in the analytical protocols for obtaining reliable data on the occurrence of heavy metals in Antarctic snow. Utmost precautions were taken to obtain a series of large size ultraclean snow blocks from the wall of a 8.3 m clean hand-dug pit at a remote site in Coats Land, Antarctica. These blocks were then sub-sampled inside a laminar flow clean bench in a cold room, using ultraclean protocols, to provide high-resolution heavy metal times series. V, Cr, Mn, Cu, Ag, Ba, Pb, Bi and U were then determined directly, without any pre-concentration step, by the ultrasensitive inductively coupled plasma sector field mass spectrometry (ICP-SFMS) technique in clean room conditions. Calibration of the instrument was performed using ultralow concentrations standards, and extreme precautions were taken to ensure the cleanliness of the instrument and its introduction system. The results show that it is possible to accurately measure a variety of heavy metals in Antarctic snow, down to the sub-picogram per gram level, using this approach. Examples of the data obtained for the Coats Land site are finally presented. For U, the observed concentrations range from 0.004 to 0.21 pg/g; they are the first data ever obtained for this metal for Antarctic snow and ice.