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

     

Negative Thermionen-Massenspektrometrie von Selen

Summary Negative thermal ionization is used to determine the selenium isotope ratios in a double-filament ion source. A thin film of barium hydroxide on the rhenium ionization filament is applied to increase the Se^– thermal ion current. The produced Se^– ion beam is by a factor of about four higher when selenious acid instead of barium selenite or sodium selenate is used. A strong dependence of the ion current on the temperature of the ionization filament is found showing the maximum ion intensity at temperatures of 970–1000 C. The different selenium isotope ratios of samples with natural isotopic abundance can be determined with relative standard deviations of 0.3–0.6%. This reproducibility is a good basis to improve the accuracy of the selenium atomic weight in the future by a calibrated measurement. An enriched ⁸²Se spike is used to analyse selenium traces in aquatic systems with isotope dilution mass spectrometry down to the pg/g level. In the concentration range of 4–23 ng/g the selenium content is determined with relative standard deviations of 0.1–5%. The results agree well with those obtained with a hydride generation atomic absorption system. It is shown that the described method of isotope dilution mass spectrometry analyses the sum of the inorganic species selenate, selenite and selenide, but not volatile organic selenium compounds.

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Herrn Prof. Dr. W. Fresenius zum 75. Geburtstag gewidmet     

Chromspurenbestimmungen in anorganischen, organischen und w??rigen Proben mit der massenspektrometrischen Isotopenverdünnungsanalyse

It is shown that chromium traces in different inorganic, organic and aqueous samples can be determined over a wide concentration range with isotope dilution mass spectrometry. Electrolytic or chromatographic isolation steps are added to a system of sample preparation units for oligo-element determinations to analyse chromium besides other heavy metals. The isotope ratio⁵²Cr/⁵³Cr is measured in a thermal quadrupole mass spectrometer using a single-filament ion source with additions of silica gel and boric acid. In water samples, which contain humic substances, chromium concentrations of a few ng/g and less can be determined with relative standard deviations of about 1% and better. A differentiation is possible into the total chromium content and into chromium species which carry out isotope exchange reactions and those which are inert for an isotope exchange reaction. The chromium concentrations of four standard reference materials (two plants BCR 60 and 61, one tissue BCR 278, one sewage sludge BCR 144), which are not certified for chromium, are determined to be 29.4 g/g, 534 g/g, 0.78 g/g, and 466.1 g/g, respectively. In three different sediments total chromium concentrations between 100 g/g and 180 g/g are analysed with relative standard deviations of 0.6%–1.2%. Using aqua regia instead of nitric acid and hydrofluoric acid for the decomposition of sediments, only 60%–90% of the total chromium content is determined. However, the analysed chromium proportion dissolved in aqua regia is slightly higher when using isotope dilution mass spectrometry compared with other analytical methods. The detection limit is 0.3 pg chromium per g for water samples, 1.8 ng/g for organic substances, and 6 ng/g for materials with high inorganic proportions as for sediments, sewage sludges and soils.     

Negative thermal ionization mass spectrometry of selenium part 4. Selenium trace determination in sediments and related samples

Summary Selenium traces have been determined in different sediments (estuarine, river, lake), sandy soil and sewage sludge with isotope dilution mass spectrometry (IDMS). Negative selenium atomic ions are formed in a double-filament thermal ion source. The use of a silica gel technique for ionization improves the mass spectrometric sensitivity by a factor of 40 compared with the technique previously applied. An enriched⁸²Se spike is used for the isotope dilution process. The samples are decomposed with a mixture of conc. HNO₃ and conc. HE After decomposition selenium is separated by the formation of SeH₂ in a hydride generation system which is normally applied for atomic absorption spectrometry. The IDMS results for three standard reference sediments agree well with the certified values. In the case of three other standard reference materials, which are not certified for selenium up to now, the IDMS analyses were able to improve the selenium data given for information or as indicative values. The precision of the IDMS method in the concentration range of 0.2–3.5 g/g lies between 0.8 % and 4.1 %. The detection limit is 6 ng/g. A comparison with several other methods shows that IDMS is one of the very few analytical methods which produces accurate selenium results even at concentration levels of 0.2 g/g and less in sediments and related samples of environmental interest.

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Negative Thermionen-Massenspektrometrie von Selen Teil 4. Selenspurenbestimmung in Sedimenten und vergleichbaren Proben

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Dedicated to Prof. Dr. G. Tblg on the occasion of his 60th birthday     

Determination of thyroxine and 3,5,3′-triiodothyronine by sub- and super-equivalence isotope dilution analysis

Trace amounts of thyroxine in model samples (160.0 ng.ml^–1 and 20.0 ng.ml^–1), and thyroxine and 3,5,3-triiodothyronine in blood plasma were determined by sub- superequivalence isotope dilution analysis and radio-immunoassay technique. Hormones were labelled by¹²⁵I. The separation of antibody-bound hormone from free hormone was performed by ultracentrifugation. The results show higher accuracy of the sub- super-equivalence isotope dilution method over that of radioimunoassay.     

Thallium determination in reference materials by Isotope Dilution Mass Spectrometry (IDMS) using thermal ionization

Summary Using Isotope Dilution Mass Spectrometry (IDMS) with thermal ionization, thallium concentrations were determined in reference materials from NIST and BCR, from other sources, and reference materials from the German Environmental Specimen Bank. ²⁰³Tl spike solution is applied for the isotope dilution technique. Thallium concentrations in the investigated materials range from 2.67 g Tl·kg^–1 to 963 g Tl·kg^–1 with a relative standard deviation from 0.14 to 10%. The detection limit was 0.1 ng thallium for this work.     

Negative thermal ionization mass spectrometry of selenium part 3.* Selenium trace determination in food samples

Summary Selenium traces are analysed in different animal tissue samples with isotope dilution mass spectrometry using the formation of negative Se^– thermal ions (NTI-IDMS) for isotope ratio measurements. An enriched⁸²Se spike is applied for the isotope dilution technique. After decomposition of the food samples with a HNO₃/HCIO₄ mixture selenium is separated by the formation of SeH₂ using a hydride generation system which is normally applied for atomic absorption spectrometry. Selenium hydride is absorbed in a cone. HNO₃ solution, from which sample mass spectrometric determinations are carried out. The recovery of selenium for the total sample treatment has been determined with a⁷⁵Se tracer to be about 62%. The precision of the IDMS method in the concentration range of 0.1–10 g/g lies between 1.8% and 4.1 %. The IDMS results agree well with the certified values of the analysed standard reference materials. A comparison of these results with those achieved by an isotope dilution method, using the formation of piazselenol and gas-chromatographic separation (GC-IDMS), and by hydride generation atomic absorption spectrometry (HGAAS) is given. Whereas the NTI-IDMS and GC-IDMS results are in very good agreement, HGAAS can be affected by interferences.

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Negative Thermionen-Massenspektrometrie von Selen Teil 3. Selenspurenbestimmung in Lebensmittelproben

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Part 2: see [131

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Isotopenverh?ltnismessung von Mo, V, Ti und Zr sowie deren Konzentrationsbestimmung in W?ssern mit einem Thermionen-Quadrupol-Massenspektrometer

Summary Negative MoO ₃ ^– and positive V⁺, Ti⁺, and Zr⁺ thermal ions are produced in a double-filament ion source to determine the isotope ratios of these elements in a quadrupole mass spectrometer. The average relative standard deviation for all isotope ratio measurements is 0.5%. The ratio Me⁺/MeO⁺ (Me=V, Ti, Zr) is followed dependent on the temperature of the ionization filament. A linear plot is obtained for log (Me⁺/MeO⁺) versus 1/T with increasing Me⁺/MeO⁺ ratios for higher temperatures using a single and a double-filament arrangement. An analytical procedure is developed, which allows the simultaneous measurement of Mo and V, and of Ti and Zr as well from one filament by a stepwise variation of the filament temperatures. Mo, V, Ti, and Zr traces in the ng/g and pg/g level of different water samples could be analysed with isotope dilution mass spectrometry using enriched isotopes of⁹⁷Mo,⁵⁰V,⁴⁷Ti, and⁹¹Zr. The precision lies usually in the range of 1 to 6% and the detection limits are 0.002 ng/g for Mo, 0.02 ng/g for V, 0.05 ng/g for Ti, and 0.01 ng/g for Zr using sample amounts of 250 g.     

Development of a definitive method for iodine speciation in aquatic systems

Summary A definitive method of isotope dilution mass spectrometry (IDMS) was developed to determine four different iodine species in aquatic systems (iodide, iodate and two organoiodine compounds: one of the organic species is chromatographically elutable from a column filled with an anion exchanger resin, the other one is not). The iodine species were analysed after the isotope dilution step with an enriched ¹²⁹I spike and after their chromatographic separation. The total iodine concentration was measured after decomposition of organic compounds in the aquatic system by UV irradiation. Different types of natural water samples (river water, water of a pond, moorland lake water) were analysed and important water parameters like pH-value, redox potential, oxygen content and dissolved organic carbon were measured for each of these samples. The total iodine concentration in the different samples differed only slightly in the range of 2–7 g/l. In most of the moorland lake water samples only the two organoiodine species could be detected. In these samples the concentration of iodide and iodate was less than the detection limit of 0.5 g/l and 0.1 g/l, respectively. On the other hand, all four iodine species could be determined in most of the river water samples. Positive correlations were found for the oxygen content of the water samples and the iodate concentration as well as for the redox potential and the anionic organoiodine compound.In memoriam of Dr. I. Linus Barnes who died in January, 1990. Dr. Barnes was senior scientist at the National Institute of Standard and Technology in Gaithersburg, USA. He made numerous outstanding contributions to the field of mass spectrometry and IDMS     

Application of isotope-dilution laser ablation ICP–MS for direct determination of Pu concentrations in soils at pg g<Superscript>−1</Superscript> levels

The methods available for determination of environmental contamination by plutonium at ultra-trace levels require labor-consuming sample preparation including matrix removal and plutonium extraction in both nuclear spectroscopy and mass spectrometry. In this work, laser-ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) was applied for direct analysis of Pu in soil and sediment samples. Application of a LINA-Spark-Atomizer system (a modified laser ablation system providing high ablation rates) coupled with a sector-field ICP–MS resulted in detection limits as low as 3×10^–13 g g^–1 for Pu isotopes in soil samples containing uranium at a concentration of a few g g^–1. The isotope dilution (ID) technique was used for quantification, which compensated for matrix effects in LA–ICP–MS. Interferences by UH⁺ and PbO₂⁺ ions and by the peak tail of ²³⁸U⁺ ions were reduced or separated by use of dry plasma conditions and a mass resolution of 4000, respectively. No other effects affecting measurement accuracy, except sample inhomogeneity, were revealed. Comparison of results obtained for three contaminated soil samples by use of -spectrometry, ICP–MS with sample decomposition, and LA–ICP–IDMS showed, in general, satisfactory agreement of the different methods. The specific activity of ^239+240Pu (9.8±3.0 mBq g^–1) calculated from LA–ICP–IDMS analysis of SRM NIST 4357 coincided well with the certified value of 10.4±0.2 mBq g^–1. However, the precision of LA–ICP–MS for determination of plutonium in inhomogeneous samples, i.e. if "hot" particles are present, is limited. As far as we are aware this paper reports the lowest detection limits and element concentrations yet measured in direct LA–ICP–MS analysis of environmental samples.Sergei F. Boulyga is on leave from The Radiation Physics and Chemistry Problems Institute, 220109 Sosny, Minsk, Belarus.     

Simultaneous determination of picogram per gram concentrations of Ba,Pb and Pb isotopes in Greenland ice by thermal ionisation mass spectrometry

A technique has been developed to simultaneously measure picogram per gram concentrations of Ba and Pb by isotope dilution mass spectrometry, as well as Pb isotopic ratios in polar ice by thermal ionisation mass spectrometry. and Pb⁺ ions were employed for these determinations. A calibrated mixture of enriched ²⁰⁵Pb and ¹³⁷Ba was added to the samples providing an accuracy of better than approximately 2% for Pb/Ba element ratio determinations. Interference by molecular ions in the Pb mass spectrum occurred only at ²⁰⁴Pb and ²⁰⁵Pb, but these contributions were negligible in terms of precisions expected on picogram-sized Pb samples. The technique is illustrated with measurements on Greenland firn, using a drill-core section that includes the Laki volcanic eruption of 1783–1784. The data show deviations from the element concentrations indicating volatile metal enrichments, but the Pb isotopic signature of the Laki lava could not be identified.     

Isotope dilution gas chromatography/mass spectrometry for platinum determination in urine

The therapeutic importance of platinum (Pt) compounds, the growing accessibility of gas chromatography/mass spectrometry (GC/MS) systems in clinical laboratories, and the lack of a mass spectrometric method for the determination of Pt in biological samples motivated us to develop an isotope dilution GC/MS assay for Pt. The method is based on the use of lithium bis(trifluoroethyl) dithiocarbamate, Li(FDEDTC), as a chelating agent and enriched ¹⁹²Pt for isotope dilution. Conditions were optimized for the precise and accurate determination of isotope ratios of Pt by using a 10-m DB-l fused silica capillary column and a reverse-geometry double-focusing mass spectrometer with selected ion monitoring. An overall precision of 1% was obtained by combining within-run precision and between-run precision at the 10-ng level. No appreciable memory effect was observed when samples with different isotope ratios were analyzed sequentially. The method was validated by the quantitation of Pt in National Institute of Standards and Technology freeze-dried urine sample SRM 2670. A concentration value of 125 ± 6 /Lg/L (n = 6) was obtained by using four different sets of isotope ratios in the molecular ion and supports the National Institute of Standards and Technology recommended value of 120 ± ? μg/L. Limits-of-quantitation, estimated at 3 μg/L, are made possible by the high sensitivity of the method and the low blank value for Pt.     

Massenspektrometrische Iodspurenbestimmung in geochemischen Standard-Referenzmaterialien und in Meteoriten

Zusammenfassung Die massenspektrometrische Isotopenverdünnungsanalyse wird erstmalig zur Iodspurenbestimmung in Gesteinsproben, wie z. B. in geochemischen Standard-Referenzmaterialien und Meteoritenproben, eingesetzt. Für den Iodnachweis im Massenspektrometer werden negative I^–-Thermionen in einer Rhenium-Zweiband-Ionenquelle unter Verwendung eines Lanthansalzes als Ionisierungshilfe erzeugt. Als Indicatorisotop zur Isotopenverdünnung wird das langlebig-radioaktive ¹²⁹I verwendet. Der Aufschluß der Proben geschieht mit Flußsäure in einer Teflonbombe, wobei anschließend das Iod als AgI isoliert wird. Während ohne Zugabe einer Sulfitlösung nur ein geringer Anteil des Iods isoliert werden kann, erhöht sich die Isolierungsausbeute auf über 75% bei Vorhandensein dieses Reduktionsmittels. Mit dieser Methode werden einige geochemische Standards des Centre de Recherches Pétrographiques et Géochimiques in Nancy sowie verschiedene antarktische und nichtantarktische Steinmeteorite analysiert. Die dabei bestimmten Gehalte schwanken vom unteren ng/g- bis in den g/g-Bereich, wobei relative Standardabweichungen von 2–3% bei Gehalten > 100 ng/g erhalten werden. Die Nachweisgrenze liegt bei etwa 6 ng/g. Das beschriebene, massenspektrometrische Verfahren eröffnet als definitive Methode die Möglichkeit, erstmals auch Iodspuren in geochemischen Standards zertifizieren zu können. Bei der Anwendung auf antarktische Meteorite konnte damit auch ein Iodüberschuß in einigen dieser Proben gegenüber dem normalerweise bekannten Iodgehalt nicht-antarktischer Meteorite bestätigt werden. Für Iodgehalte ab dem oberen ng/g-Bereich wurde auch eine iodid-selektive Elektrode in Verbindung mit einem alkalischen Aufschluß und einer chromatographischen Abtrennung erfolgreich eingesetzt. Bei Verwendung von Sulfit als Reduktionsmittel lagen hier die Isolierungsausbeuten bei etwa 85%.

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Mass spectrometric iodine trace determinations in geochemical standard reference materials and in meteorites

Summary Isotope dilution mass spectrometry is being used for the first time to analyse iodine traces in rocks, e. g. in geochemical standard reference materials and in meteorites. Iodine is measured in the mass spectrometer by producing negative I^– thermal ions using a rhenium double-filament ion source and a lanthanum salt as an auxiliary chemical for ionization. The long-lived radioactive ¹²⁹I is applied as a spike for the isotope dilution technique. The decomposition of the sample is carried out with hydrofluoric acid in a teflon bomb and iodine is isolated as AgI. By adding some drops of a sulfite solution, the isolation yield for this procedure is above 75% whereas a much less portion of the total iodide can only be isolated without this reducing agent. With this method different geochemical standards from the Centre de Recherches Pétrographiques et Géochimiques in Nancy as well as various Antarctic and non-Antarctic meteorites have been analysed. The iodine contents of these samples are in the range between some ng/g and some g/g. Relative standard deviations of 2–3% are obtained for contents above 100 ng/g. The detection limit is about 6 ng/g. The mass spectrometric analysis is a definitive method and opens the possibility to certify iodine traces in geochemical standards for the first time. Applying this method for the analysis of Antarctic meteorites, an iodine excess in some of these samples compared to the normal iodine concentration in non-Antarctic meteorites could be confirmed. Iodine contents in the higher ng/g level could also be analysed by an iodide-selective electrode in combination with an alkali fusion and a chromatographic separation of iodide. By using sulfite for reduction, isolation yields of about 85% could be obtained.

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Herrn Prof. Dr. K. H. Lieser zum 65. Geburtstag gewidmet

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Herrn Prof. Dr. L. Schultz, MPI Mainz danken wir für die Überlassung der Meteoritenproben, Herrn Dr. K. Govindaraju, Nancy für diejenige der geochemischen Standards. Im Zusammenhang mit der Untersuchung antarktischer Meteorite möchten wir die gute Zusammenarbeit mit Frau Dr. G. Dreibus, Herrn Prof. L. Schultz und Herrn Prof. H. Wänke vom MPI in Mainz hervorheben. Der Deutschen Forschungsgemeinschaft, die im Rahmen des Schwerpunktprogramms Antarktisforschung die Untersuchungen über Meteorite unterstützt hat, und dem Fonds der Chemischen Industrie danken wir für die finanzielle Hilfe.     

Isotope dilution mass spectrometry of microelectronically relevant heavy metal traces in high-purity cobalt

Summary Because cobalt and its silicides are increasingly used in microelectronic devices, an isotope dilution mass spectrometric (IDMS) method has been developed for trace analysis of relevant heavy metals (U, Th, Fe, Zn, Tl, and Cd) in high-purity cobalt. The measurements of the isotope ratios were carried out with a small thermal ionization quadrupole mass spectrometer by producing positive thermal ions in a single- or double-filament ion source. For the trace/matrix separation and the isolation of the different heavy metals, anion-exchange chromatography and an extraction method for iron were applied. The detection limits obtained were (in ng/g): U=0.007, Th=0.017, Tl=0.06, Cd=1, Zn=8, and Fe=11, which demonstrates that the particularly critical radioactive impurities uranium and thorium could be analysed down to the low pg/g range. Three cobalt samples of different purity were analysed with concentrations ranging from about 0.1 ng/g for U and Th in an ultra high-purity material produced for microelectronic purposes, up to about 70 g/g for Cd in a cobalt sample with declared purity of 99.8%. Because IDMS usually results in accurate analytical results, it can be used in the future for calibration of other methods like glow discharge mass spectrometry, as could be shown by analysing one cobalt sample by both methods. IDMS can also be applied for the production of urgently needed certified standard reference materials in this important field of high technology.Presented at the ANAKON '93 conference     

Isotope dilution ICP-MS with laser-assisted sample introduction for direct determination of sulfur in petroleum products

Inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with direct laser-assisted introduction of isotope-diluted samples into the plasma, using a laser ablation system with high ablation rates, was developed for accurate sulfur determinations in different petroleum products such as sulfur-free premium gasoline, diesel fuel, and heating oil. Two certified gas oil reference materials were analyzed for method validation. Two different ³⁴S-enriched spike compounds, namely, elementary sulfur dissolved in xylene and dibenzothiophene in hexane, were synthesized and tested for their usefulness in this isotope dilution technique. The isotope-diluted sample was adsorbed on a filter-paper-like material, which was fixed in a special holder for irradiation by the laser beam. Under these conditions no time-dependent spike/analyte fractionation was only observed for the dibenzothiophene spike during the laser ablation process, which means that the measured ³⁴S/³²S isotope ratio of the isotope-diluted sample remained constant—a necessary precondition for accurate results with the isotope dilution technique. A comparison of LA-ICP-IDMS results with the certified values of the gas oil reference materials and with results obtained from ICP-IDMS analyses with wet sample digestion demonstrated the accuracy of the new LA-ICP-IDMS method in the concentration range of 9.2 g g^–1 (sulfur-free premium gasoline) to 10.4 mg g^–1 (gas oil reference material BCR 107). The detection limit for sulfur by LA-ICP-IDMS is 0.04 g g^–1 and the analysis time is only about 10 min, which therefore also qualifies this method for accurate determinations of low sulfur contents in petroleum products on a routine level.This article is dedicated to Wilhelm Fresenius who has continuously supported the academic career of Klaus G. Heumann and the analytical work of his group.     

Development of an ICP-IDMS method for accurate routine analyses of toxic heavy metals in polyolefins and comparison with results by TI-IDMS

An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method was developed as a suitable method - with respect to its sensitivity, precision, accuracy, and time-consumption - for the analysis of toxic heavy metal traces (Pb, Cd, Cr, and Hg) in polyolefins. Results for Pb, Cd, and Cr were compared with those obtained by thermal ionization isotope dilution mass spectrometry (TI-IDMS), which was used as a reference method. Because of its high first ionization potential and its high volatility mercury could not be determined by TI-IDMS. A multi-element spike solution, containing isotopically enriched 206Pb, 116Cd, 53Cr, and 201Hg, was used for the isotope dilution step. Decomposition of the polyolefin samples was carried out with concentrated HNO3 at temperatures of about 300 degrees C in a high pressure asher (HPA). This procedure decomposes polyolefins completely and allows isotopic equilibration between sample and spike isotopes. Detection limits of 16 ng/g, 5 ng/g, 164 ng/g, and 9 ng/g were obtained for Pb, Cd, Cr, and Hg by ICP-IDMS using only sample weights of 0.25 g. In different commercially available polyethylene samples heavy metal concentrations in the range of < 5 ng/g to 4 x 10(3) ng/g were analyzed. Both mass spectrometric methods were applied within the EU project "Polymeric Elemental Reference Material (PERM)" for the certification of two polyethylene reference materials. The ICP-IDMS results agreed very well with those of TI-IDMS which demonstrates the accuracy of the ICP-IDMS method also suitable for routine analyses.     

Determination of fifteen priority phenolic compounds in environmental samples from Andalusia (Spain) by liquid chromatography–mass spectrometry

This work describes the optimisation of a method to determinate fifteen phenolic compounds in waters, sediments and biota (green marine algae) by liquid chromatography coupled to mass spectrometry (LC-MS) with atmospheric pressure chemical ionisation (APCI) in the negative mode. The LC separations of the studied compounds and their MS parameters were optimised in order to improve selectivity and sensitivity. Separation was carried out with a C₁₈ column using methanol and 0.005% acid acetic as mobile phase in gradient mode. The molecular ion was selected for the quantitation in selective ion monitoring (SIM) mode. A solid-phase extraction (SPE) method was applied in order to preconcentrate the target analytes from water samples. However, extraction of the compounds from sediment and biota samples was carried out by liquid–solid extraction with methanol/water after studying the influence of other organic solvents. In addition, a clean-up step by SPE with HLB Oasis cartridges was necessary for sediments and biota. The proposed analytical methodology was validated in the target environmental matrices by the analysis of spiked blank matrix samples. Detection limits were 10–50 ng L^–1 for water, 1–5 g kg^–1 for sediments and 2.5–5 g kg^–1 for biota samples. Good recoveries and precision values were obtained for all matrices. This methodology has been successfully applied to the analysis of incurred water, sediment and biota samples from Andalusia (Spain).     

Determination of sulfur and selected trace elements in metallothionein-like proteins using capillary electrophoresis hyphenated to inductively coupled plasma mass spectrometry with an octopole reaction cell

The determination of sulfur in biologically relevant samples such as metalloproteins is described. The analytical methodology used is based on robust on-line coupling between capillary electrophoresis (CE) and octopole reaction cell inductively-coupled plasma mass spectrometry (ORC–ICP–MS). Polyatomic ions that form in the plasma and interfere with the determination of S at mass 32 are minimised by addition of xenon to the collision cell. The method has been applied to the separation and simultaneous element-specific detection of sulfur, cadmium, copper, and zinc in commercially available metallothionein preparations (MT) and metallothionein-like proteins (MLP) extracted from liver samples of bream (Abramis brama L.) caught in the river Elbe, Germany. Instrumental detection limits have been calculated according to the German standard procedure DIN 32645 for the determination of sulfur and some simultaneously measured trace elements in aqueous solution. For sulfur detection limits down to 1.3 g L^–1 (³⁴S) and 3.2 g L^–1 (³²S) were derived. For the other trace elements determined simultaneously detection limits ranging from 300 ng L^–1 (⁵⁸Ni) to 500 ng L^–1 (⁶⁶Zn, ⁵⁵Mn) were achieved. For quantification of sulfur and cadmium in a commercially available MT preparation under hyphenated conditions the use of external calibration is suggested. Finally, the need for proper sample-preparation technique will be discussed.     

Total arsenic content of nine species of Antarctic macro algae as determined by electrothermal atomic absorption spectrometry

Total arsenic in nine species Antarctic macro algae has been measured, by electrothermal atomic absorption spectrometry using a Pd/Mg(NO₃)₂ matrix modifier, to determine their capacity to accumulate the element. Macro algae were collected in February during the 2000 austral summer season at Jubany Station (Argentinean scientific station) around Potter Cove, King George Island. An optimized two-step microwave (MW) program was used to digest the samples. Dried samples were treated with HNO₃, H₂O₂, and HF, left overnight, then subjected to the first MW cycle. After cooling HNO₃ and HClO₄ were added and samples were subjected to the second MW cycle of digestion treatment. The effect of power and time on As recovery was examined. The analytical features of the method were: detection limit, 0.24 g g^–1 (dry mass); precision (RSD), 4.2–5.7%; recovery 91–105%. A wide range of As-retention capacity (41.0–447 g g^–1 dry mass) was observed among the different species. The highest levels of As were found in Phaeurus antarcticus (447 g g^–1 dry mass). This organism satisfies several prerequisites to be considered for consideration as a biomonitor in future studies.