Determination of cadmium in slurries of marine sediment samples by electrothermal atomic absorption spectrometry using palladium and phosphate as chemical modifiers

A method for the determination of cadmium in slurries of marine sediment using palladium and phosphate as chemical modifier has been optimized. To stabilize the marine sediment slurry, Triton X-100 at 0.1% was used. To obtain a complete pyrolysis of the slurry sample two mineralization steps were used, the first at 480 °C and the second at 600 °C and 700 °C for phosphate and palladium, respectively. The precision and accuracy of the method have been studied by analyzing the Reference Material PACS-1 (marine sediment) of National Research Council Canada. The detection limits (LOD) were 11.9 g kg^–1 for phosphate and 42.0 g kg^–1 when palladium was used. These methods have been applied to the determination of cadmium in marine sediment samples from the Galicia coast and the results of both methods were compared; no significant differences were found between the two procedures.     

Flow injection analysis at μl/min flow rates

The characteristics of knitted open tube (KOT) figure eight reactors and coil reactors at l/min flow rates were compared using plate height (H) calculations and peak height measurements. Peak broadening independent of flow rate was seen for the figure eight KOT but not the coil at flow rates of 150–300 l/min. Below 150 /min, the plate height values of both reactors were inversely proportional to flow rate. It was concluded that a 0.5-m KOT figure eight reactor is the most effective way to introduce delay time for a 1 1 injection size and tubing of 0.3 mm I.D. Enhancement of peak height response was particularly pronounced at flow rates less than 100 l/min.     

Elements in car and truck tires and their volatilization upon incineration

The trace metal loading of used car and truck tires and the fractions of the metals volatilized upon incineration of the tire were determined. INAA was chosen due to its multielement analysis capability and its low detection limit for many elements. A high purity planar germanium detector was used. Among the elements measured were, Al (4–150 g/g), Ti (41–730 g/g), V (0.04–0.4g/g), Mg (>80–580 g/g), Zn (1–2.2%) as typical concentrations; also some amounts of antimony, bromine and arsenic have been found. Major differences in elemental concentrations have been observed between the tread and the wall of a tire, and also between different brands.     

A Sensor for the Determination of Electropositive Elements

An electrochemical sensor, namely, a graphite thick-film electrode modified with Au(III) was proposed for the determination of Hg, As, Se, and Cu. The detection limits for mercury and arsenic using the new sensor are 0.005 and 0.1 g/L, respectively.     

Production of certified reference material

Summary Carbon has been determined in 31 European reference steels in the range of 11–2561 g/g C, using an absolute calibration method.High-purity calcium carbonate was used as the calibration material and weighing was carried out by means of a balance with extremely small weighing error. Both synthetic calibration samples and test samples were processed alternatingly under identical conditions, and the analyses were completed in the shortest possible time.In 28 of the cases examined, results were lower than the certificate values, by an average of 27 g/g. The interval of uncertainty of the accuracy was 6 g/g (probability 99%).

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Herstellung zertifizierter ReferenzmaterialienGenaue Bestimmung von Kohlenstoff in Stählen im Bereich von 11–2561g/g

Zusammenfassung Die Kohlenstoffgehalte von 31 europäischen zertifizierten Referenzstählen im Arbeitsbereich von 11–2561 g/g Kohlenstoff wurden durch absolute Eichung überprüft.Die hinreichende Reinheit des Eichmittels Calciumcarbonat wurde sichergestellt und ein Wägesystem mit einem hinreichend kleinen Wägefehler benutzt.Das gleiche Verhalten von synthetischen Eichproben und Analysenproben im Analysenprozeß wurde hergestellt und beide Probearten wechselweise unter konstanten Systembedingungen innerhalb kürzester Zeitspanne untersucht. In 28 der untersuchten Fällen wurden im Mittel um 27 ppm tiefere Werte gefunden als in den Zertifikaten angegeben. Das Unsicherheitsintervall der Richtigkeit der gefundenen Werte lag mit einer Wahrscheinlichkeit von 99% im Mittel bei 6 g/g.

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Abbreviations CRM Certified reference material - ppm g/g The author thanks Mr. E. Weichert for his excellent direction of the practical work.     

Selective determination of antimony(III) and antimony(V) in liver tissue by microwave-assisted mineralization and hydride generation atomic absorption spectrometry

Antimony(III) and antimony(V) species have been selectively determined in liver tissues by optimizing the acidic conditions for the evolution of stibine using the reduction with sodium borohydride. The results show that a response for Sb(III) of 0.5 to 20 g l^–1 was selectively obtained from samples in a 1 mol l_–1 acetic acid medium. The best response for total antimony from 1 to 20 g l^–1 is obtained after sample treatment with a 0.5 mol l^–1 sulfuric acid and 10% w/v potassium iodide. Microwave digestion has been necessary to release quantitatively antimony species from sample slurries. The amount of Sb(V) was calculated from the difference between the value for total antimony and Sb(III) concentrations. A relative standard deviation from 2.9 to 3.1% and a detection limit of 0.15 and 0.10 g l^–1 for Sb(III) and total Sb has been obtained. The average accuracy exceeded 95% in all cases comparing the results obtained from recovery studies, electrothermal atomic absorption spectrometry and the analysis of certified reference materials.Dedicated to Professor Dr. Peter Brätter on the occasion of his 60th birthday     

Vergleichende Untersuchungen der Konzentrationen von Dimethylarsons?ure, As(III) und As(V) in Boden- und Luftstaubproben

Zusammenfassung Es wird ein Analysenverfahren vorgestellt, das die Abtrennung und Bestimmung von Dimethylarsonsäure (DMAS) und As(III) aus Festproben erlaubt.DMAS wird aus der Festsubstanz verflüchtigt und mit einem mikrowelleninduzierten Plasma und optischer Emissionsspektrometrie nachgewiesen. As(III) wird mittels eines Extraktionsverfahrens aus der Festsubstanz abgetrennt und atomabsorptionsspektrometrisch (AAS) nachgewiesen. Die Bestimmung von Gesamtarsen erfolgt nach Druckaufschluß des Probenmaterials ebenfalls atomabsorptionsspektrometrisch. Die Analysenverfahren werden auf die Untersuchung von Boden- und Luftstaubproben angewendet. Die Gehalte der einzelnen As-Spezies, die in verschiedenen Bodenproben bestimmt werden, zeigen eine starke Abhängigkeit von der Bodentiefe. Die Gehalte der einzelnen Spezies in den Luftstaubproben sind stark abhängig vom Standort und von den Witterungsbedingungen. Die Gesamtarsengehalte in den Bodenproben schwankten zwischen 1 und 22 g As/g Boden; in Luftstaub lagen die Werte zwischen 12 und 61,4 g As/g Luftstaub. Die maximale Konzentration an DMAS in Bodenproben lag bei 11,2 ng DMAS/g Boden. Die Gehalte an As(III) schwankten zwischen 0,3 und 10,5 g As(III)/g Boden und 3 und 30,3 g As(III)/g Luftstaub.

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Comparative investigations of the concentrations of dimethylarsonic acid, As(III) and As(V) in soil and airborne dust samples

Summary An analytical method is described for the separation and determination of dimethylarsonic acid (DMAA) and As(III) in solid samples. DMAA is volatilized from the solid material and detected with a microwave induced plasma and optical emission spectroscopy. As(III) is extracted from the solid material and detected by atomic absorption spectroscopy. After decomposition under pressure, the total arsenic content is also detected by atomic absorption spectroscopy. These analytical methods are used for the investigation of soil and airborne aerosol samples. It has been found that the contents of the different arsenic species, analyzed in different soil samples depends strongly on the depth of the soil whereas in airborne aerosol samples, the contents of the different As-species is strongly dependent on the sampling site and on the meteorological conditions. The total arsenic concentrations varied from 1 to 22 g As/g soil in soil samples and from 12 to 61.4 g As/g aerosol in airborne aerosol samples. The maximum concentration of DMAA found in soil samples was 11.2 ng DMAA/g soil. The concentrations of As (III) varied from 0.3 to 10.5 g As(III)/g soil in soil samples and from 3 to 30.3 g As(III)/g aerosol in airborne aerosol samples.

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

Radioimmunoassay of somatotropin using second antibody polyethylene glycol combination separation system

We describe a radioimmunoassay procedure for human somatotropin using second antibody — polyethylene glycol (PEG) combination for the separation of antibody bound and free antigen. The assay is done by a single incubation of 18 hours or with one hour pre-incubation and 3 hours post-incubation at room temperature (25 °C) and uses 0.1 m of serum sample. The assay covers a range of 0–40 g/ and has a sensitivity of 0.6 g/ of somatotropin. The assay is validated by inter-assay and intra-assay variations, recovery and parallelism tests.     

Halbquantitative Isotopenverdünnungsanalyse im Mikro- und Submikrogrammbereich mit Hilfe der Ringofenmethode

Zusammenfassung Ein halbquantitatives Analysenverfahren wird beschrieben, das im wesentlichen eine Kombination der Isotopenverdünnungsanalyse mit der Ringofentechnik ist: Zu der Probelösung eines Ions (xg) wird eine stets gleiche Menge (a g) des gleichen Ions in radioaktiv markierter Form zugesetzt. Mit einem geeigneten Fällungsreagens wird ein Anteil (b g) vonx +a ausgefällt und auf einem Rundfilter mit Hilfe der Ringofenmethode abgetrennt. Die den Anteilenb undx + a – b entsprechenden Zählraten werden bestimmt. Die Auswertung der Meßergebnisse erfolgt graphisch mit Hilfe einer Eichkurve.Am Beispiel der Bestimmung von Ca²⁺, PO₄ ^3– und Fe³⁺ wird die Methode erläutert. Mengen von einigen Zehntel bis zu einigen Mikrogramm der genannten Ionen können ausreichend genau bestimmt werden.

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Summary A semiquantitative analytical procedure is described that essentially is a combination of the isotope dilution analysis with the ring oven technique. To the test solution of an ion (x g) there is added an always constant amount (a g) of the. same ion in radioactive labelled form. A portion (b g) ofx +a is precipitated with a suitable precipitant and collected on a circular filter with the aid of the ring oven method. The counter rates corresponding to the portionsb andx + a – b are determined. The evaluation of the data is made by a graphic method with the aid of a standard curve.The method is discussed using as example the determination of Ca²⁺, PO₄ ^3–, and Fe³⁺. Amounts ranging from several tenths to several micrograms of these ions can be determined with adequate accuracy.

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Résumé On décrit un procédé d'analyse semiquantitative combinant principalement l'analyse par dilution isotopique avec la technique du four annulaire. On ajoute à la solution contenant l'ion à analyser (x g) une quantité toujours égale (a g) du même ion sous forme marquée radioactive. A l'aide d'un réactif précipitant approprié, on précipite une partie (b g) dex +a et l'on effectue la séparation sur un filtre rond par la méthode du four annulaire. On détermine les valeurs correspondant aux partiesb etx +a – b. En utilisant une courbe d'étalonnage, on effectue graphiquement le calcul des résultats des mesures.On explique la méthode en prenant l'exemple du dosage de Ca²⁺, PO₄ ^3– et Fe³⁺. On a pu doser avec suffisamment de précision des quantités allant de quelques dixièmes de microgrammes d'ions connus à quelques microgrammes.

     

Redox Properties of Rhodium(III) Oxo-Bridged Carboxylate Complexes

Chemical and electrochemical oxidation of rhodium (III) oxo-bridged carboxylate complexes was studied. The chemical [with O₃ and Ce(IV) salts] or electrochemical (at potentials of 1.00-1.20 V) oxidations of the binuclear complexes [Rh₂(-O)(-O₂CCH₃)₂(H₂O)₆]^{2 +} and [Rh₂(-O)(-O₂CCF₃)₂(H₂O)₆]^{2 +} leads to the superoxo complexes [Rh₂(-O)(O₂-)(-O₂CCH₃)₂(H₂O)₅]⁺ and [Rh₂(-O)(O₂ ^-)(-O₂CCF₃)₂(H₂O)₅]⁺ with terminal coordination of O₂-. The trinuclear acetate [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺, unlike its trifluoroacetate analog [Rh3(₃-O)(-O₂CCF₃)₆(H₂O)₃]⁺, is oxidized only electrochemically at a potential of 1.38 V. The oxidation of [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺ is reversible and involves formation of an unstable superoxo group O₂ ^- between two Rh₃III(₃-O) cores.     

A FIA-system for As(III)/As(V)-determination with electrochemical hydride generation and AAS-detection

A flow-injection system with electrochemical hydride generation and atomic absorption detection for As(III)/As(V) determination is described. A simple electrolytic flow-through cell has been developed and optimized. Several cathode materials like Pt, Ag, Cu, C and Pb have been tested. The influence of the electrolysis current, concentration of sulfuric acid, carrier stream, flow rate, sample volume and interferences by other metals on the arsenichydride generation have been studied. For the determination of total inorganic arsenic, As(V) is reduced to As(III) on-line by postassium iodide or L-cysteine at 95° C. The influence of the temperature and the reduction medium on this pre-reduction step has been tested. The calibration curve is linear in the range of 5 to 50 g/L for As(III) and total inorganic arsenic and shows a higher sensitivity than in case of reduction with sodium tetrahydroborate. The detection limit is 0.4 g/L for As(III) and 0.5 g/L for total inorganic arsenic at a sample volume of 1 mL.     

Zur coulometrischen Chloridbestimmung in konzentrierten S?uren mit potentiometrischer Indizierung und Polarisationsspannungsindikation

Zusammenfassung Die coulometrische Bestimmung geringer Chloridmengen im Gemisch von Methanol und 35%iger Schwefelsäure, 53%iger Phosphorsäure oder 37%iger Perchlorsäure kann ohne den Zusatz eines Leitelektrolyten sowohl mit potentiometrischer Indizierung als auch mit Polarisationsspannungsindikation vorgenommen werden. Das Verfahren mit potentiometrischer Indizierung, bei dem sich das Gesamttitrationsvolumen aus 10 ml Säure und 40 ml Methanol zusammensetzt, erlaubt die Bestimmung von 2,0 g/ml mit einer relativen Standardabweichung von 0,5%. Die kleinste noch bestimmbare Konzentration liegt bei 1,0 g/ml. Eine Erweiterung des erfaßbaren Konzentrationsbereiches ermöglicht die Anwendung der Polarisationsspannungsindikation. Im Gemisch von 1 ml Säure und 8 ml Methanol können noch 0,4 g/ml mit guter Genauigkeit titriert werden. Bei 2,0 g/ml Chlorid beträgt die relative Standardabweichung 2%. Für die Konzentration an der Nachweisgrenze errechnet sich 0,08 g/ml.

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Summary The coulometric estimation of small contents of chloride in a mixture of methyl alcohol and 35% sulphuric, 53% phosphoric or 37% perchloric acids can be performed without adding any supporting electrolyte. Both the two coulometric methods, with potentiometric indication as well as by indicating the end point with two identical electrodes polarized by practically constant current can be used. The potentiometric indication method, whereby the total titration volume consists of 10 ml of acid und 40 ml of methyl alcohol, permits the determination of 2.0 g/ml chloride with a relative standard deviation of 0.5%. The smallest concentration which is just possible to be determined is 1 g/ml. By application of the second coulometric method the estimation limit can be minimized. In a mixture of 1 ml of acid and 8 ml of methyl alcohol, it is possible to titrate 0,4 g/ml. The relative standard deviation for the concentration of 2,0 g/ml has been found to be 2%. The limit of detection is 0.08 g/ml.

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Herrn Prof. Dr. M. von Stackelberg zum 70. Geburtstag gewidmet.

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Wir danken Herrn Chem.-Ing. K. Zinke für seine Mitarbeit.     

Rapid determination of halogens in milk by instrumental neutron activation analysis

The absolute concentrations of iodine, bromine and chlorine in milk, have been determined by epithermal neutron activation followed by high resolution gamma-ray spectrometry. Two kinds of milk commonly consumed in Israel have been investigated. The concentration of iodine, bromine and chlorine were found to be 0.18–0.30 g/ml, 2.02–2.85 g/ml and 0.65 mg/ml, respectively. The method is fast, selective, accurate and highly sensitive.     

Landolt-Reaktionen auf „Chlorgrundlage“ und ihre Anwendung zum Nachweis und zur Bestimmung katalytisch wirkender Spurenelemente. I

Zusammenfassung Gemische aus Ascorbinsäure, Hydrazin oder Zinn(II)-chlorid mit sauren, Chlorat und Chlorid enthaltenden Lösungen reagieren nach Art der bekannten Landolt-Reaktion unter Chlorausscheidung, die sich mit o-Tolidin indizieren läßt. Die Reaktion wird von Vanadin(V), Eisen(III) oder Osmium(VIII) katalysiert. Auf dieser Grundlage lassen sich diese Elemente sowohl chronometrisch wie auch mit Hilfe der Simultan-komparationsmethode bestimmen. Die Nachweisgrenzen liegen bei 0,1g V, 0,3g Fe bzw. 0,1g Os. Die Arbeitsvorschrift für die Analyse im Konzentrationsbereich 1 bis 10g/5 ml wird angegeben. Der relative Fehler bei der Simultankomparationsmethode liegt innerhalb 2%. Der Einfluß fremder Ionen wurde untersucht.

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Summary Mixtures of ascorbic acid, hydrazine or tin(II) chloride react with solutions containing acids, chlorate and chloride in accord with the familiar Landolt reaction, with liberation of chlorine. The latter can be detected witho-tolidine. The reaction is catalyzed by vanadium(V), iron(III) or osmium(VIII). On the basis of this behavior, it is possible to determine these elements chronometrically and also with the aid of the simultaneous comparation method. The detection limits are 0.1g V, 0.3g Fe, or 0.1g Os. The working directions are given for the analysis in the concentration range from 1 to 10g/5 ml. The relative error in the simultaneous comparation method is within 2%. The influence of foreign ions was studied.

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Résumé Les mélanges d'acide ascorbique, d'hydrazine ou de chlorure d'étain-II avec des solutions acides contenant chlorate et chlorure réagissent suivant la réaction bien connue de Landolt avec libération de chlore mis en évidence par l'o-tolidine. La réaction est catalysée par le vanadium-V, le fer-III ou l'osmium-VIII. Sur ce principe, on peut doser ces éléments aussi bien par chronométrie que par la méthode de comparaison simultanée. Les limites de dilution se situent à 0,1g V, 0,3g Fe ou 0,1g Os. On indique le mode opératoire de l'analyse dans le domaine de concentration de 1 à 10g/5 ml. L'erreur relative pour la méthode de comparaison simultanée est inférieure à 2%. On a étudié l'influence des ions étrangers.

     

Determination of boron in food and biological reference materials by neutron capture prompt-γ activation

Summary Boron concentrations were determined by in-beam neutron capture prompt- activation analysis for 31 food and biological reference materials prepared by the National Institute of Standards and Technology, Agriculture Canada, the National Institute for Environmental Studies of Japan, and the International Atomic Energy Agency. Sensitivity and background enhancements that are consequences of neutron scattering in hydrogenous matrices such as biological reference materials are discussed, as are correction methods for nuclide interferences, with emphasis on sodium. The limit of quantitation for these materials is 1.0–2.5 g/g and the limit of detection is 0.3–0.8 g/g, depending on the irradiation time. For materials with boron levels 30 g/g (e.g., most botanicals), the total analytical uncertainty is 2%.Temporary summer employment at the United States Food and Drug Administration, 200 C St., SW, Washington, DC 20204, USA     

Estimation and Comparison of Pore Charge on Titania and Zirconia Membranes Prepared by Sol-Gel Route Using Zeta Potential Measurement

An attempt has been made to synthesize ceramic titania and zirconia membranes by sol-gel process by filtering respective viscous colloidal sol through microporous alumina support and gelling followed by sintering at 400°C and 470°C respectively. The static charge on the pores of the so formed membranes and the pore size distribution determine the applicability in filtering colloidal solution. The mean pore size from SEM were found to be 0.65 m and 0.54 m for titania and zirconia membranes respectively with 1.47 × 10⁷/cm² as pore density for both. The filtration characteristics during membrane layer formation showed that the membrane layer formation started after 35 minutes in the case of titania membrane and 40 minutes in the case of zirconia membrane. From the gravimetric estimation of water content of the membranes the thickness of the membrane was found out to be 3 m and the porosity was found out to be 0.30 for both the cases. The particle charge density was estimated from the zeta potential and the particle size. The pore charge density was estimated from the particle charge density, pore density, pore diameter and the thickness of the membrane layer. The membrane pore charge density was found to vary between 3 to –1 Coulombs/cm² in the case of titania membrane and 7 to –0.5 Coulombs/cm² in the case of zirconia membrane in the pH range 1–12.     

Determination of trace arsenic in hydrofluoric acid by hydride generation and atomic absorption spectrometry

Practical procedures are given for determination of arsenic(III) and (V) in hydrofluoric acid by means of hydride generation and atomic absorption spectrometry. Arsenic(III) can be determined by direct generation of arsine with sodium borohydride in hydrochloric/hydrofluoric acid medium, arsenic(V) being only slightly reduced under the conditions used. For its determination, arsenic(V) has to be prereduced with potassium iodide, and even then its reduction to arsenic(III) and then arsine is far from complete. It is possible to determine it in presence of arsenic(III) by a difference method, but this is recommended only if the As(V)/As(III) ratio is greater than 1. Total arsenic can be determined after oxidation of As(III) and evaporation of most of the hydrofluoric acid. The limit of determination is 5 g/l for arsenic(III) and 0.25 g/l for total arsenic; the relative standard deviation is about 10%.