Marine Sediment Reference Materials Research Articles

Rapid monitoring of 241Am in small amount of sediment samples by combining extraction chromatography for highly efficient separation of interfering and matrix elements and ICP-MS/MS measurement

The analysis of 241Am in environmental samples is of great importance in the fields of geological repositories and radiation protection. The triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) has a strong analytical and interference removal capability for long half-life radionuclides. In this study, the ability of ICP-MS/MS to determine ultra-trace level of 241Am in environmental samples was further explored. The instrumental sensitivity for Am detection was significantly improved (ca. 20 times) by employing an APEX-Ω high efficiency introduction system. The gases of O2 and He were introduced to the reaction cell for eliminating of interferences and Am was detected as AmO+ ions. High separation factors (>2000) of Am and Pu were obtained at proper gas flow rates by chemical resolution of the instrument. Meanwhile, the background signals caused by possible polyatomic interferences for 241Am and 243Am were sufficiently reduced. A simple and rapid chromatographic separation method for purposeful and efficient separation of 241Am from matrix and interfering elements was developed. The overall chemical recoveries were about 68% and the detection limit of 241Am for the established method was 0.18 fg g−1 (equivalent to 0.02 mBq g−1). Several marine sediment reference materials were analyzed for the validation of the method and the results showed that this method was suitable for the determination of 241Am in solid environmental samples. The method was finally applied to real marine sediment samples collected in the western North Pacific after the Fukushima nuclear accident.

Validation of Total Mercury in Marine Sediment and Biological Samples, Using Cold Vapour Atomic Absorption Spectrometry

A method for the measurement of total mercury (T-Hg) in environmental samples using cold vapour atomic absorption spectrometry (CV AAS) has been validated yielding a dynamic range (0.04–10.00 μg/kg) and high certified reference material (CRM) recovery (>90%). The validation was carried out according to International Union of Pure and Applied Chemistry (IUPAC) validation and Eurachem Guides. A freeze-dried and homogenised sample was weighed and then digested using Suprapur acids (HNO3, H2SO4, and HF) with potassium dichromate solution in a hot block digestion system. A calibration curve was constructed (R2 > 0.999). Two CRMs (Marine Sediment Reference Material (PACS-3) and Trace Elements in Muscle Tissue (Trace Elements and Methylmercury in Mussel Tissue (NIST2976)) were utilised for quality assurance and control. The limit of quantification (LOQ) calculated as 0.04 µg/kg, and uncertainty (U) calculated as 2%. The obtained results showed the suitability of this method for direct mercury measurement in environmental samples. Additionally, the proficiency of this method was recognised by accreditation under the standard of International Organization for Standardization (ISO/IEC 17025:2017) for competence of testing and calibration laboratories.

The determination of 52 elements in marine geological samples by an inductively coupled plasma optical emission spectrometry and an inductively coupled plasma mass spectrometry with a high-pressure closed digestion method

An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO3 acid system with a high-pressure closed digestion method (HPCD), is studied by an inductively coupled plasma optical emission spectrometry (ICP-OES) and an inductively coupled plasma mass spectrometry (ICP-MS). The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion, less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO3 system, the relative error (RE) for the analytical results are all less than 6.0%. The method detection limits are 2–40 μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials (GBW07309, GBW07311, GBW07313), rock reference materials (GBW07103, GBW07104, GBW07105), and cobalt-rich crust reference materials (GBW07337, GBW07338, GBW07339), the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation (RSD) and the relative error (RE) are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.

Electrochemical generation of antimony volatile species, stibine, using gold and silver mercury amalgamated cathodes and determination of Sb by flame atomic absorption spectrometry

The electrochemical generation of antimony volatile species (stibine) using Au and Ag mercury amalgamated cathodes is described. Compared with some other cathode materials commonly used for electrochemical hydride generation, performance of the amalgamated cathodes is substantially better in the following aspects: higher interference tolerance, higher erosion resistance and longer useful working time. Using the amalgamated cathodes, it could be shown that interferences from major constituents at high concentrations, especially from transition metals, affecting stibine generation are not as significant as they are using other cathode types in regards to sensitivity and useful working time. Results obtained using the Ag/Hg amalgamated cathode showed a slightly higher sensitivity than the corresponding results obtained using the Au/Hg cathode. The Au/Hg cathode, which to our knowledge has not previously been used to generate stibine, showed considerably longer useful working time than the Ag/Hg one. The optimum catholytes for electrolytic generation of stibine (SbH3) from Sb(III) and Sb(V) using the Au/Hg electrode were aqueous solutions containing 0.5molL−1 H2SO4 and 0.5molL−1HCl, respectively. Under optimized conditions, using the Au/Hg cathode and comparing to aqueous standards calibration curves, detection limits (3σ) of 0.027µgL−1 for Sb(III) and 0.056µgL−1 for Sb(V), were obtained. To check accuracy a marine sediment reference material (PACS-2, NRC) was analyzed using a method purportedly developed for this task. Good agreement, 95% confidence, was found between the certified and the experimental values for Sb. The proposed method was also applied to the determination of Sb in aqueous solutions of marine sediments samples from Comuna de Bajo Alto Provincia de El Oro—Ecuador. Recoveries of five replicate determinations of these samples were in the range of 98–103% thus showing acceptable accuracy in the analysis of real samples.

A Method of Measurement of 239Pu, 240Pu, 241Pu in High U Content Marine Sediments by Sector Field ICP–MS and Its Application to Fukushima Sediment Samples

An accurate and precise analytical method is highly needed for the determination of Pu isotopes in marine sediments for the long-term marine environment monitoring that is being done since the Fukushima Dai-ichi Nuclear Power Plant accident. The elimination of uranium from the sediment samples needs to be carefully checked. We established an analytical method based on anion-exchange chromatography and SF-ICP-MS in this work. A uranium decontamination factor of 2 × 10(6) was achieved, and the U concentrations in the final sample solutions were typically below 4 pg mL(-1), thus no extra correction of (238)U interferences from the Pu spectra was needed. The method was suitable for the analysis of (241)Pu in marine sediments using large sample amounts (>10 g). We validated the method by measuring marine sediment reference materials and our results agreed well with the certified and the literature values. Surface sediments and one sediment core sample collected after the nuclear accident were analyzed. The characterization of (241)Pu/(239)Pu atom ratios in the surface sediments and the vertical distribution of Pu isotopes showed that there was no detectable Pu contamination from the nuclear accident in the marine sediments collected 30 km off the plant site.

Reevaluation of Th and U concentrations in marine sediment reference materials using isotope dilution MC-ICP-MS: towards the analytical improvements in dose rate estimation for luminescence dating

The thorium and uranium concentrations of four marine sediment reference materials (CRMs NIST 1646a, NRCC HISS-1, MESS-3 and PACS-2) were determined using isotope dilution-multiple collector-inductively coupled plasmas-mass spectrometry (ID-MC-ICP-MS), aiming at helping the assessment of reliability in dose rate estimation for luminescence dating. Quintuplicate analyses of the CRMs revealed their intrinsic heterogeneity in the concentration of both elements (up to 23% and 8% for thorium and uranium, respectively, in 2σ standard error level) for individual sub-samples of about 100 mg. The thorium and uranium concentrations of all CRMs determined in this study were significantly lower (up to 45%) than the provided or reported informative values, requiring reevaluation of their reference concentrations. The use of informative thorium and uranium concentrations in these CRMs as standard values for elemental analysis of unknown samples will result in overestimated dose rates, and thus age underestimation when applied to luminescence dating techniques.

Chemical Characterization of Cobalt Crust from Afanasy-Nikitin Seamount in the Eastern Indian Ocean by Inductively Coupled Plasma Time-of-Flight Mass Spectrometry

Analytical methodology was developed for the chemical characterization of cobalt crust samples collected from the Afanasy-Nikitin seamount in Eastern Equatorial Indian Ocean by inductively coupled plasma time-of-flight mass spectrometry (ICP-TOF-MS). Concentrations of geochemically significant groups of different trace elements such as large-ion-lithophile elements (e.g., Rb, Cs), high field strength elements (e.g., Ta, Nb, Hf and Zr), rare earth elements in addition to a few major and minor elements were determined in these samples. Samples (~50 mg) were digested in closed digestion vessels for 48 h before the expulsion of Si and the residues were taken in 5 % nitric acid. 103Rh was used as an internal standard. Matrix matching external calibrations were utilized in order to compensate for the spectroscopic and non-spectroscopic interferences. The detection limits obtained for various elements were in the range 1–0.01 ng/ml for majority of the elements analyzed. Accuracy for the determination of different elements is assessed by measuring them in a few cobalt crust samples, ferromanganese nodules and similar marine sediment reference materials. Also, there is a very good agreement between the data sets obtained by ICP-TOF-MS as well as the well established ICP-quadrupole MS on cobalt crust samples. The precisions obtained in this study are <5 % RSD for majority of the elements with comparable accuracy. The results are in agreement with certified and reference values wherever available for comparison. The geochemical characteristics of these rare marine sediments have been described.

Multi-elemental analysis of marine sediment reference material MESS-3: one-step microwave digestion and determination by high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS)

AbstractSingle-step microwave digestion methods using four different acidic dissolving reagents were investigated with the main objective to obtain a simple, rapid method for multi-elemental analysis of marine sediment samples by high resolution inductively coupled plasma-mass spectrometry (HRICP-MS), especially for environmental studies. Closed-vessels microwave digestion procedures were carried out using the reagents as follows: HNO3, mixture of HNO3-HCl (φ r = 9: 1), aqua regia, and mixture of HNO3-HCl-HF (φ r = 8: 1: 1). The elements analyzed were: Al, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Mo, Na, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, and Zn. Good recoveries were established for many of the metals analyzed even when only nitric acid was employed. However, for a good recovery of Sb and Tl, aqua regia should be employed.

Comprehensive analysis for major, minor and trace element contents and Sr-Nd-Pb-Hf isotope ratios in sediment reference materials, JSd-1 and MAG-1

In view of the requirement of a well-characterized and easily available aquatic sediment reference material, a comprehensive analysis comprising of fifty major, minor and trace elements as well as Sr‐Nd‐Pb‐Hf isotopes were carried out in the stream sediment reference material, JSd-1, issued by the Geological Survey of Japan. The data for marine sediment reference material, MAG-1, issued by U.S. Geological Survey is also obtained for comparison. The elements were divided into two groups: Group I and Group II. Elements in Group I form stable soluble ions in HNO3; and those in Group II form soluble oxo- and fluoro-complexes in HF, such as Zr, Nb, Hf, Ta, etc. For Group I, the sample was decomposed with HF in a tetra fluoro ethylene (TFE) bomb at 245°C for 96 hrs with Mg addition. The elemental concentration was measured by quadrupole type inductively coupled plasma source mass spectrometry (ICP-QMS) and sector field type ICP-MS (ICPSFMS) using isotope dilution-internal standardization (ID-IS) methods. The aliquot of the sample solution was passed through 3-step column chemistry for isotope ratio determination of Pb by multiple collector (MC) ICP-MS and thermal ionization mass spectrometry (TIMS), and Sr and Nd by TIMS. For Group II elements, the sample was decomposed with HF in a TFE bomb with the same time and temperature settings. Zr, Mo, Sn, Sb and Hf were determined by ID, and Nb and Ta by ID-IS using ICP-QMS. The original JSd-1 powder showed heterogeneity for Group II elements, indicating insufficient pulverization and distribution. Thus, we further pulverized the powder and measured the concentration, which showed improved homogeneity. The aliquot for the re-pulverized powder was passed through 2-step column chemistry, and the Hf isotope ratio was determined by MC-ICP-MS. Thus a new data on the trace elements as well as Sr‐Nd‐Pb‐Hf isotope ratios is provided for JSd-1 and MAG-1 in this paper.

Determination of plutonium isotopes in freshwater lake sediments by sector-field ICP-MS after separation using ion-exchange chromatography

The determination of Pu isotopes in lake sediments is important for many studies, such as Pu pollution source identification, sediment mixing estimation, erosion evaluation and establishment of deposition chronology in lakes. In this paper, a simple analytical method using sector field inductively coupled plasma mass spectrometry (ICP-MS) combined with two-stage chromatographic separation and purification of Pu was developed based on the optimization and adaptation of the previously published method for marine samples with an emphasis on the study of the elimination of interferences for the analysis of freshwater lake sediments. A strong base anion-exchange resin (AG MP-1M) was used to purify Pu isotopes with concentrated HBr as the final eluent for Pu elution. The chemical yields were ca. 64% and the decontamination factor for U was ca. 10 5. The developed method was validated using a freshwater lake sediment reference material (SRM-4354) and a marine sediment reference material (IAEA-368), and applied to the determination of Pu isotopes in sediment samples of Lake Poyang, East China. For the analysis of certified reference materials, both 239+240Pu activity of 31.6 mBq g −1 and 240Pu/ 239Pu atom ratio of 0.033 for IAEA-368 were comparable to the certified value and/or literature values. As for SRM-4354, 239+240Pu activity of 3.90 mBq g −1 agreed well with the certified value. However, the mean 240Pu/ 239Pu atom ratio of 0.144 was lower than those reported by other laboratories. This difference suggested that this material may be isotopically inhomogeneous. 240Pu/ 239Pu atom ratios of Poyang Lake sediment samples ranged from 0.185 to 0.192 with a mean value of 0.187±0.004, indicating that plutonium pollution originated from global fallout.

METAL FRACTIONATION IN SEDIMENTS: A COMPARATIVE ASSESSMENT OF FOUR SEQUENTIAL EXTRACTION SCHEMES

Four sequential chemical extraction schemes for metal analysis (a 4-step modified protocol originally proposed by the Standards, Measurements and Testing Programme (SM&T - formerly BCR) of the European Union, Tessier and Hall 5-step procedures and 6-step Grimalt's scheme) were compared. Each procedure was applied to four sediment samples collected from two rivers, Nakagawa (NR) and Tamagawa (TR), Tokyo, Japan. Additionally, a certified marine sediment reference material (JMS-1) was also extracted for the comparison. To evaluate the partitioning of metals among different geochemical forms, the concentration of chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) were measured by Zeeman-corrected atomic absorption spectrometry. Other major elements and mineralogy of sediments were also determined on bulk prior to extracting by X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis, respectively, which allowed qualitative correlation between the fractionation results obtained and the presence of defined geochemical phases. The total concentrations of metals were determined after strong acid attack and the analytical precision was verified by using JMS-1. Significant proportions of elements were found in non-residual fractions among the schemes (average 83, 91, 76, 93 and 59% for Cr, Cu, Pb, Zn and Ni, respectively) in the more anthropogenically impacted NR sediments. The highest mobility was observed for Pb and Zn among the four schemes while the lowest was for Cr and Ni. Results of the comparison among the total metal levels for the four schemes based upon the sum of sequential extraction steps for each element showed significant differences for Cr, Ni and Zn. On the other hand, the sum of non-residual phases of the four schemes showed no significant differences for Cr, Cu and Zn but the SM&T and Hall schemes showed significant differences from others for Pb and Ni, respectively. Generally, good recoveries were achieved with the Hall scheme (range 92-109%) and the Fe-Mn oxides occlued phase of this scheme was the most effective owing to the high tendency to extract metals. In addition, Grimalt scheme produced the lowest recovery of Cr and the concentrations of residual fraction of other elements were also lower.

Critical evaluation of various extraction procedures for the speciation of butyltin compounds in sediments

The efficiency of different extraction procedures for the simultaneous determination of butyltin compounds in marine sediments by gas chromatography–mass spectrometry (GC--MS) was critically evaluated in the present work. Three different polar solvents (acetic acid, a mixture of acetic acid with methanol, and a mixture of acetic acid, methanol, and water) and three different extraction approaches (mechanical shaking, ultrasonic, and microwave-assisted extraction) were used for the extraction of butyltin compounds from PACS-2 certified marine sediment reference material. Before determination by GC--MS, extracted butyltin species were derivatized with sodium tetraethyl borate and extracted into iso-octane. The results indicated that 30-min ultrasonic extraction with 100% acetic acid provided satisfactory recoveries for all certified butyltins. The developed analytical method was successfully applied for determination of butyltin compounds in coastal sediments of the Northern Adriatic Sea. The results demonstrated that butyltins were present in all sediments analysed.

Rare Earth and Other Trace Element Content of NRCC HISS‐1 Sandy Marine Sediment Reference Material

The National Research Council (NRC), Ottawa, Canada sandy marine sediment reference material HISS‐1 was characterised for thirty‐seven trace elements by neutron activation optimised irradiation, cooling and counting protocols using the low power Miniature Neutron Source Reactor (MNSR) as a neutron source. This INAA methodology quantified twenty additional elements including ten rare earth (Ce, Dy, Eu, Ho, La, Lu, Nd, Sm, Tb and Yb) and ten other elements (Ba, Br, Cs, Ga, Hf, Rb, Sc, Ta, Th and Zr) missing in the final NRCC certification. A large number of values produced by different irradiation schemes together with the use of certified reference materials in the quantification step that showed good precision, provided confidence in the results. The reliability of the REE data was checked by plotting chondrite‐normalised graphs.

Dithiocarbamate functionalized or surface sorbed Merrifield resin beads as column materials for on line flow injection–flame atomic absorption spectrometry determination of lead

This article describes the preparation of dithiocarbamate immobilized/functionalized and diethylammonium dithiocarbamate (DDTC) sorbed Merrifield Chloromethylated Resin (MCR) beads and comparison of these materials for on-line flow injection (FI)–flame atomic absorption spectrometry (FAAS) determination of lead. The above two materials enrich lead quantitatively over an identical optimal pH range (8.0–9.0), a preconcentration/loading time (up to 4 min) and elution with acidified methanol (a minimum of 0.01 mol L −1 HNO 3 in methanol). However, the detection limit for lead using dithiocarbamate functionalized MCR beads is 1.3 μg L −1 compared to 3 μg L −1 for DDTC sorbed MCR beads. Again, the sensitivity enhancement over direct FAAS signal is 48- and 27-fold, respectively. In addition, dithiocarbamate functionalized MCR beads offers better precision compared to DDTC sorbed MCR beads as the corresponding relative standard deviation (R.S.D.) values for five successive determinations of 0.20 μg mL −1 are 1.44 and 4.36%, respectively. The accuracy of the developed on-line FI–FAAS procedure employing dithiocarbamate functionalized MCR beads as column material was tested by analyzing Certified Reference Material (CRM) of soil (IAEA soil-7) and marine sediment reference material (MESS-3) supplied by International Atomic Energy Agency (IAEA), Vienna and National Research Council (NRC), Canada, respectively. Furthermore, the developed procedure has been successfully tested for the analysis of surface, pond, ground and effluent water and soil samples collected from the vicinity of lead acid battery industry in India.

Trace metal characterisation of marine sediment reference materials MESS-3 and PACS-2 in dilute HCl extracts

A number of extraction methods are currently used to characterise metals in marine sediments. These include total digestion involving HF, extraction with concentrated acid, partial extraction with weak acid, or a more complicated multiple stage sequential extraction scheme (e.g. BCR) (Mudroch et al., 1999). Partial extraction methods are attractive because they are simple, fast, relatively safe, and they target labile phases and reservoirs containing metals

Preconcentration of uranium(VI) by solid phase extraction onto dicyclohexano-18-crown-6 embedded benzophenone

The preparation of a solid phase extractant (SPE), dicyclohexano-18-crown-6 embedded benzophenone, for preconcentration of uranium(VI) is described. The uranium(VI) can be quantitatively retained from 0.5 l solution on 1% dicyclohexano-18-crown-6 embedded benzophenone in the pH range 6.0-7.0, and then eluted with 5.0 ml of 1M HCl. Uranium(VI) content of the eluent was determined spectrophotometrically by Arsenazo III. Calibration graphs are rectilinear over the uranium(VI) concentration in the range of 0.004-0.4mg.ml-1. Five replicate determinations of 40mg of uranium(VI) present in 0.5 l sample gave a mean absorbance of 0.185 with a relative standard deviation of 2.45%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2.0mg.l-1. The accuracy of the developed preconcentration procedure was tested by analyzing standard marine sediment reference material. The uranyl ion content of soils and sediments was estimated spectrophotometrically after the preconcentration procedure and compared to the results gained by standard inductively coupled plasma mass spectrometry (ICP-MS).

Synthesis of xanthate functionalized silica gel and its application for the preconcentration and separation of uranium(VI) from inorganic components

A new chelating solid extractant prepared by the chemical immobilization of xanthate on silica gel was characterized by Fourier transform infra red spectrometry (FTIR), thermogravimetric analysis (TGA) and microanalysis and used for the preconcentration and separation of uranyl ion prior to its determination by Arsenazo-III. The effect of pH, weight of the solid extractant, volume of the aqueous phase and the interference of neutral electrolytes, cations and anions on the determination of uranium, have been studied in detail to optimize the conditions for trace determination of uranium(VI). The accuracy of the developed procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA-SOIL-7) reference materials. The results obtained on analysis of soil and sediment samples are comparable to standard ICP-MS values.

Determination of cadmium, chromium and lead in marine sediment slurry samples by electrothermal atomic absorption spectrometry using permanent modifiers

A procedure for the determination of cadmium, chromium, and lead in marine sediment slurries by electrothermal atomic absorption spectrometry is proposed. Slurry was prepared by mixing 10 mg of ground sample with particle size smaller than 50 μm completed to the weight of 1.0 g with a 3% nitric acid and 10% hydrogen peroxide solution. The slurry was maintained homogeneous with an aquarium air pump. For cadmium, the best results were obtained using iridium permanent with optimum pyrolysis and atomization temperatures of 400 and 1300 °C, respectively, a characteristic mass, m o (1% absorption), of 2.3 pg (recommended 1 pg). Without modifier use, zirconium, ruthenium, and rhodium m o were 3.4, 4.1, 4.6, and 4.8 pg, respectively. For chromium, the most sensitive condition was obtained with zirconium permanent with optimum pyrolysis and atomization temperatures of 1500 and 2500 °C, m o of 6.6 pg (recommended 5.5 pg); and without modifier use, rhodium, iridium, and ruthenium m o were 5.3, 8.8, 8.8, and 8.9 pg, respectively. For lead, the best modifier was also zirconium, m o of 8.3 pg for the optimum pyrolysis and atomization temperatures of 600 and 1400 °C, respectively, (recommended m o of 9.0 pg). For iridium, ruthenium, without modifier, and rhodium, m o were 14.7, 15.5, 16.5, and 16.5 pg, respectively. For all the modifiers selected in each case, the peaks were symmetrical with r 2 higher than 0.99. Being analyzed ( n = 10), two marine sediment reference materials (PACS-2 and MESS-2 from NRCC), the determined values, μg l −1, and certified values in brackets, were 2.17 ± 0.05 (2.11 ± 0.15) and 0.25 ± 0.03 (0.24 ± 0.01) for cadmium in PACS-2 and MESS-2, respectively. For chromium in PACS-2 and MESS-2 the values were 94.7 ± 5.6 (90.7 ± 4.6) and 102.3 ± 10.7 (106 ± 8), respectively. Finally, for lead in PACS-2 and MESS-2, the results obtained were 184 ± 7 (183 ± 8) and of 25.2 ± 0.40 (21.9 ± 1.2), respectively. For cadmium and lead in both samples and chromium in PACS-2, calibration was accomplished with aqueous calibration curves. For chromium in MESS-2, only with the standard addition technique results were in agreement with the certified ones. The limits of detection ( k = 3, n = 10) obtained with the diluents were 0.1, 3.4, and 3.6 μg l −1 for cadmium, chromium, and lead, respectively.

Improved determination of arsenic in environmental and geological specimens using HG-AFS

A sensitive and robust analytical procedure for the determination of arsenic in plant, coal, and sediment samples using hydride generation-atomic fluorescence spectrometry (HG-AFS) has been developed. The optimised concentrations of NaBH4 and HCl required for arsine generation were 1% (m/v) and 4.5 M, respectively. Seven certified plant reference materials (CTA-OTL-1 Oriental Tobacco Leaves, CTA-VTL-2 Virginia Tobacco Leaves, GBW 07602 Bush Branches and Leaves, NIST 1547 Peach Leaves, NIST 1573a Tomato Leaves, NIST 1575 Pine Needles and NIST 1515 Apple Leaves), two certified coal reference materials (NIST 1632c Bituminous Coal and NIST 1635 Subbituminous Coal), and one marine sediment reference material (GBW 07316 Marine Sediment) were analysed for quality control purposes. Sample digestion was carried out on 200 mg sample aliquots with 3 ml HNO3 and 0.1 ml HBF4, heated in a microwave autoclave up to a temperature of 240 °C. After digestion, no evaporation of HNO3 to remove acid from the digests is needed before arsine generation can be carried out. External standard solutions were matched for the HNO3 concentration in the analyte solutions (0.042 M HNO3). Potassium iodide was found to be the ideal reagent for the quantitative reduction of As(V) to As(III), in contrast to L-cysteine. The detection limit (3σ) for As(III) was 6 ng l−1, which is 1–2 orders of magnitude lower than that reported recently by other authors using HG-AFS. This sensitive, robust and low-cost analytical procedure will be applied to the determination of As in sediment samples to help understand the mechanisms of both natural and anthropogenic As accumulation in wetlands.

Speciation analysis of mercury by solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma–time-of-flight-mass spectrometry

This paper reports the development of an analytical approach for speciation analysis of mercury at ultra-trace levels on the basis of solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma–time-of-flight mass spectrometry. Headspace solid-phase microextraction with a carboxen/polydimethylsyloxane fiber is used for extraction/preconcentration of mercury species after derivatization with sodium tetraethylborate and subsequent volatilization. Isothermal separation of methylmercury (MeHg), inorganic mercury (Hg 2+) and propylmercury (PrHg) used as internal standard is achieved within a chromatographic run below 45 s without the introduction of spectral skew. Method detection limits (3 × standard deviation criteria) calculated for 10 successive injections of the analytical reagent blank are 0.027 pg g −1 (as metal) for MeHg and 0.27 pg g −1 for Hg 2+. The repeatability (R.S.D., %) is 3.3% for MeHg and 3.8% for Hg 2+ for 10 successive injections of a standard mixture of 10 pg. The method accuracy for MeHg and total mercury is validated through the analysis of marine and estuarine sediment reference materials. A comparison of the sediment data with those obtained by a purge-and-trap injection (PTI) method is also addressed. The analytical procedure is illustrated with some results for the ultra-trace level analysis of ice from Antarctica for which the accuracy is assessed by spike recovery experiments.