Determination of cadmium and copper with ET-AAS after electrochemical deposition on a graphite electrode

The electrodeposition of cadmium and copper on a special graphite disk electrode has been performed at controlled potential. The electrode with the deposit has been inserted into the graphite atomizer HGA-400 by an adapted automatic sampler for the final determination by ET-ASS. The sensitivity of determination has been 0.371 (gl^-1)^-1 for cadmium and 0.025 (gl^-1)^-1 for copper for 2 min electrodeposition and increased linearly with the time of deposition. The limit of detection (3s_bl) has been 7.9 ngl^-1 Cd²⁺ and 0.11 gl^–1 Cu²⁺ for 2 min deposition and it has been improved with increased time of electrodeposition. The technique has been applied to the determination of both metals in seawater and to speciation in the presence of EDTA complexing agent.     

The composition of volatile and particulate hydrocarbons in urban air

Summary The hydrocarbon composition of the particle and gas phases in the urban atmosphere has been studied by filtration and parallel adsorption on active charcoal and polyurethane foam (PUF). Gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS) have been used for the analysis of the organic matter extracts obtained with each system. In the case of the particle and PUF samples these extracts were fractionated into aliphatic and aromatic compounds. This approach has allowed to identify up to 247 hydrocarbon molecules showing that C0–C5 alkylbenzenes are the major compounds in the charcoal extracts whereas C14–C23 n-alkanes, C0–C4 alkylnaphthalenes, C0–C4 alkylbiphenyls and C3–C5 alkylbenzenes are those predominantly found in the PUF materials. The particles essentially contain C17–C38 n-alkanes and parent polycyclic aromatic hydrocarbons (PAH). These qualitative differences are paralleled by a progressive concentration decrease from the more to the less volatile hydrocarbons. Thus, the total charcoal extracts average 80 g/m³, the PUF compounds represent 4 /m³ and the particle hydrocarbons 0.7 g/m³. These latter airborne materials are essentially composed of petrogenic residues 0.6 g/m³ (aliphatic fraction) whereas the pyrolytic PAH only involve 0.08 g/m³.     

Determination of fission product ruthenium by isotope dilution mass spectrometry

Isotope dilution mass spectrometry using enriched isotope⁹⁶Ru as a spike was applied to the determination of ruthenium as a fission product. Ruthenium in the solution was oxidized to RuO₄ by Ce/IV/ and separated from coexisting metal elements by distillation. Silica-gel technique was employed to enhance ion current of ruthenium in the mass spectrometric measurement. The lower detection limit was 0.005 g ml^–1 and the relative standard deviations /n=3/ for 1.2 and 0.05 g ml^–1 of ruthenium were 0.2 and 0.5%, respectively.     

Thermal Investigation of 1,2-propanediamine complexes of nickel(II) in the solid phase

Thermal studies have been carried out on [NiL₃]X₂·n H₂O, whereL=1,2-propanediamine;X=Cl^–, Br^–, SCN^–, 1/2SO ₄ ^2– and 1/2 SeO ₄ ^2– ; andn= 2, 1.5 and 0. [Ni₂L₅(NCS)₂](SCN)₂ and [NiL₂SO₄] have been synthesized pyrolytically in the solid-state from their mother diamine complexes. The deaquation behaviour of [NiL₃]SO₄·2 H₂O appears interesting, and its monohydrate undergoes a solid-state reaction (88–102°) without mass loss, showing an exothermic peak at 95 °C (H=– 5.1 kJ mole^–1).

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Zusammenfassung Thermische Untersuchungen wurden an [NiL₃]X₂,n H₂O ausgeführt, wobeiL-1,2-Propandiamin;X=Cl^–, Br^–, SCN^–, 1/2 SO ₄ ^2– und 1/2 SeO ₄ ^2– ;n=2, 1.5 und 0. [Ni₂Ls(NCS)₂](SCN)₂ und [NiL₂SO₄] wurden ausgehend von den entsprechenden Diaminkomplexen pyrolytisch im festen Zustand synthetisiert. Das Dehydratisierungsverhalten von [NiL₃]SO₄·2 H₂O scheint interessant zu sein, und beim entsprechenden Monohydrat wird eine ohne Massenverlust verlaufende Festkörperreaktion (88–102°) beobachtet, die sich durch einen exothermen Peak bei 95 °C (H=– 5.1 kJ mol^–1) zu erkennen gibt.

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[N³L₃]₂· n₂O, L=1,2-,=l^–, Br^–, SCN^–, 1/2 SO ₄ ^2- , 1/2SeO ₄ ^2- , an=2, 1.5 0. [Ni₂L₅(NCS)₂](SCN)₂ [NiL₂SO₄] . [N³L₃]S₄·2 ₂ , 88–102° , 95 ° =– 5.1 ·^–1.

     

The oxidative addition of hydrogen sulfide to the electron-rich triple bond: The isolation and characterization of compounds that contain the Re2(μ-H)(μ-SH) cluster unit

The reactions of Re₂X₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) with H₂S in THF afford the dirhenium (III) complexes Re₂(-H)(-SH)X₄(-dppm)₂, the first examples of the oxidative addition of an S-H unit across an electron-rich metal-metal triple bond. The bromide complex Re₂(-H)(-SH)Br₄(-dppm)₂ (C₂H₅)₂O crystallizes in the space group P2₁/n witha=16.631(2) Å,b=15.967(3) Å,c=19.904(2) Å, =92.698(7)°,V=5279(2) ų, andZ=4. The structure which was refined toR=0.053 (R _w=0.070) for 4903 data withI>3.0(I), shows the presence of an edge-shared bioctahedral geometry with a very short Re-Re distance of 2.4566(7) Å. While the hydrogen atoms of the -H and -SH ligands were not located in the X-ray structure determination, their presence is confirmed by IR and¹H NMR spectroscopy.     

Diacetylenic Derivatives of Fe2(CO)6(μ-EE′): Spectroscopic Investigations of Fe2(CO)6{μ-EC(H) = C(C≡ CMe)E′} (E = E′, E ≠ E′; E, E′ = S, Se, Te)

The diacetylenic adducts, Fe₂(CO)₆{-EC(H) = C(C CMe)E} (E = E, E E; E, E = S, Se, Te) (1–8) have been obtained from the room temperature stirring of Fe₂(CO)₆(-EE) with HC CC CMe in methanol solvent containing sodium acetate. Compounds 1–8 have been characterized by IR and multinuclear NMR (¹H, ¹³C, ⁷⁷Se, and ^l25Te) spectroscopy. Trends in the chemical shifts of ⁷⁷Se and ¹²⁵Te NMR spectra of Fe₂(CO)₆{-EC(H) = C(C CMe)E} with a variation of EE are discussed.     

Preconcentration of copper, cadmium, and lead with a thiacalix[4]arenetetrasulfonate-loaded Sephadex A-25 anion-exchanger for graphite-furnace atomic-absorption spectrometry

A rapid column-adsorption method has been developed for concentrating traces of copper, cadmium, and lead in water prior to their determinations by graphite-furnace atomic-absorption spectrometry. The adsorbent used was prepared by loading a strongly basic anion-exchanger QAE-Sephadex A-25 (50 mg) with thiacalix[4]arenetetrasulfonate (20 mol). Two-hundredfold preconcentration of the analyte elements was achieved by passing 100 mL of sample solution (pH 8.0) through a column packed with the adsorbent (6 mm i.d.×7 mm high) at a flow rate of 10 mL min^–1 and by the subsequent elution with 500 L of aqueous nitric acid solution (1 mol L^–1). The practical applicability of the proposed method was evaluated by analyzing certified reference seawater samples.     

Reactivity of coordinated O2? towards. One-electron oxidants

Ion-radical complexes Ti(IV) (O ₂ ^– ) are unreactive towards most oxidants except Ce(IV) and Cr₂O ₇ ^2– . The one-electron redox potential for the O_{2 coord.}/O _{2 coord.} ^– couple lies between 1 and 1.6 V.

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- O ₂ ^– Ti(IV) , Ce(IV) Cr₂ O ₇ ^2– . - O_{2 .}/O ₂ ^– . 1 1,6 .

     

Thermal decomposition of γ-irradiated cadmium bromate

The thermal decomposition of -irradiated cadmium bromate was studied by dynamic thermogravimetry. The reaction order, activation energy, frequency factor and entropy of activation were computed using the Coats-Redfern method and were compared with those of the unirradiated salt. Irradiation enhances the decomposition and the effect increases with irradiation dose. The activation energy decreases on irradiation. The mechanism for the decomposition of unirradiated and irradiated cadmium bromate follows the Avrami model equation, 1-/1-/^1/3=kt, and the ratecontrolling process is a phase-boundary reaction assuming spherical symmetry.     

Thermal analysis of complexes of cadmium chloride picoline

The thermal decomposition of the, and- picoline complexes of cadmium were studied by means of TG-DTG-DTA. In connection with the preparation of the complex compounds, it was established that the ligand number was influenced by the reaction medium. The thermal decomposition took place stepwise, and intermediates were formed which could be isolated with a derivatograph by the freezing-in method. The structures and properties of these previously unknown compounds were investigated by far-IR spectroscopy and X-ray powder diffraction.

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Zusammenfassung Der thermische Zersetzungsprozess der Komplexverbindungen von Cadmiumchlorid mit-, - oder-Picolin wurde durch simultane TG-DTG-DTA im Derivatograph untersucht. Die Ligandenzahl der Komplexverbindungen wird durch das Reaktionsmedium bei der Präparation beeinflusst. Die thermische Zersetzung erfolgt stufenweise, Zwischenprodukte konnten mittels Derivatograph durch die Einfriermethode isoliert werden. Struktur und Eigenschaften dieser bisher unbekannten Verbindungen wurden durch Fern-IR-Spektroskopie und Röntgenpulverbeugung untersucht.

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- -, -. , . , « ». .

     

Catalytic oxidation of cycloalkane heteroanalogs as a way to polyfunctional compounds

Liquid phase oxidation of cycloalkane diheteroanalogs catalyzed by compounds of Cu²⁺, Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺ has been studied. It has been established that these catalysts can be applied to intensify, oxidize and increase the selectivity of this process.

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: Cu², Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺. .

     

Ligand-Promoted Transformation of the μ3-η2-Vinylidene Ligand in the Reaction between RuCo2(CO)9(μ3-η2-C=CHPh) and 4,5-Bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). X-Ray Structure of RuCo2(CO)7(bpcd)(μ3-η2-C=CHPh)

The reaction of the heterometallic vinylidene cluster RuCo₂(CO)₉(₃-²-C=CHPh) with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) proceeds readily in the presence of Me₃NO to furnish the new cluster RuCo₂(CO)₇(bpcd)(₃-²-C=CHPh) as the sole product. This cluster has been isolated by preparative chromatography and characterized in solution by IR spectroscopy. The molecular structure was determined by X-ray diffraction analysis, which has confirmed the chelation of the bpcd ligand to the ruthenium center and the change in the coordination mode exhibited by the vinylidene ligand. RuCo₂(CO)₇(bpcd)(₃-²-C=CHPh) crystallizes in the triclinic space group P , a = 10.5788(9), b = 11.909(1), c = 19.526(2) Å, = 84.491(9)°, = 78.068(8)°, = 63.760(7)°, V = 2158.7(4) ų, Z = 2, and d _calc = 1.581.     

Isocratic high-performance liquid chromatographic determination of plasma adenosine

Summary Due to manifold physiological and cardioprotective actions of adenosine, the demand for a simple but accurate method to determine its concentration in plasma is increasing. The aim of this study was firstly to develop a simple isocratic method instead of the gradient elution or peak-shifting techniques used earlier and secondly to check conflicting data on the composition of stop-solution, added to the sample in order to prevent changes in adenosine concentration. Isocratic elution improved signal to noise ratio and concentrations of 100 mol L^–1 dipyridamole and 2.5 mol L^–1 erythro-9(2-hydroxy-3-nonyl)adenine in the blood sample effectively prevented both adenosine formation and degradation, even without the use of a 5-ecto-nucleotidase inhibitor. Lowering the concentration of dipyridamole to 25 mol L^–1 caused more than a tenfold increase of adenosine concentration in two out of five cases and even 100 mol L^–1 dipyridamole alone is not sufficient to inhibit adenosine deaminase in blood samples.     

Fallout analysis of atmospheric water precipitations

Summary A rapid ion-exchange method for the determination of ¹⁴⁴Ce, ¹³⁷Cs, ⁸⁹Sr, ⁹⁰Sr and ¹⁴⁰Ba in 2–30 liter samples of atmospheric water precipitations is described. The samples, containing up to 300 mg of calcium, are sorbed on a specially shaped column filled with Dowex 50, X-8 or Dowex 50W, X-8. Radio-cerium and radio-caesium are stripped from the column with 0.6 M ammonium glycolate/ 0.2 M NaCl, pH 5, radio-strontium and radio-barium with 0.15 M ammonium citrate, pH 7.5. The isolated radio-nuclides are counted on a low-background beta-counter: ¹⁴⁴Ce as CeO₂, ¹³⁷Cs as Cs-dipicrylaminate, ⁸⁹Sr/⁹⁰Sr as SrCO₃, ⁹⁰Y as Y₂O₃, and ¹⁴⁰Ba as BaCO₃. The mean chemical yields amount to 95% for cerium, 85% for caesium, 95% for strontium, 95% for yttrium and 65% for barium. With parallel determinations at levels of a few picocuries, the deviations of the results from the respective mean values generally do not exceed ± 5%. With a 30 l sample the limit of detection amounts to 0.005 Ci/l for ¹⁴⁴Ce, 0.006 Ci/l for ¹³⁷Cs, 0.005 Ci/l for ⁹⁰Sr, and 0.006 Ci/l for ¹⁴⁰Ba.

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Zusammenfassung Es wird eine schnelle Ionenaustauschmethode für die Bestimmung von ¹⁴⁴Ce, ¹³⁷Cs, ⁸⁹Sr, ⁹⁰Sr und ¹⁴⁰Ba in 2–30 l Proben von atmosphärischen Wasser-Niederschlägen beschrieben. Die Proben, mit einem Calciumgehalt bis zu 300 mg, werden in eine besonders gestaltete, mit Dowex 50, X-8 oder Dowex 50 W, X-8 gefüllte Säule eingewaschen. Radio-Cer und Radio-Caesium werden mit 0,6 M Ammoniumglykolat/0,2 M NaCl, pH 5, Radio-Strontium und Radio-Barium mit 0,15 M Ammoniumcitrat pH 7,5 eluiert. Die isolierten Radio-Nuklide werden in einem Beta-Antikoinzidenzzähler gemessen: ¹⁴⁴Ce als CeO₂, ¹³⁷Cs als Cs-dipikrylaminat, ⁸⁹Sr/⁹⁰Sr als SrCO₃, ⁹⁰Y als Y₂O₃ und ¹⁴⁰Ba als BaCO₃. Die mittlere Rückgewinnung der zugesetzten Träger beträgt für Cer 95%, 85% für Caesium, 95% für Strontium, 95% für Yttrium und 65% für Barium. In Parallelbestimmungen mit Gehalten von einigen Ci/l, überschreiten die Abweichungen der Ergebnisse von den entsprechenden Mittelwerten im allgemein nicht 5%. Bei einer 30 l-Probe beträgt die untere Nachweisgrenze 0,005 Ci/l für ¹⁴⁴Ce, 0,006 Ci/l für ¹³⁷Cs, 0,005 Ci/l für ⁹⁰Sr und 0,006 Ci/l für ¹⁴⁰Ba.

     

Differential pulse voltammetric methods for the simultaneous estimation of uranium-iron and uranium-cadmium mixtures in solution

Differential pulse voltammetric methods have been developed for the simultaneous estimation of the constituents of uranium-iron and uranium-cadmium mixtures in solution. A mixture of 1M H₃PO₄–1M KH₂PO₄ (with a pH1.5), was found to be the most ideal supporting electrolyte for both methods, among many that were evaluated for their suitability. In uranium-iron mixtures the calibration for iron was found to be linear up to 150 g ml^–1 (r²=0.9986), while that of uranium up to 500 g ml^–1 (r²=0.999). Iron at 6.7 g ml^–1 level could be determined in the presence of 800 fold uranium (wt/wt) without significant interference. Uranium at 21 g ml^–1 level could be analyzed with 5-fold iron (wt/wt). This upper limit of iron was due to the precipitation of iron as phosphate. In the case of uranium — cadmium mixtures, cadmium calibration for cadmium was found to be linear up to 1300 g ml^–1 (r²=0.9993). Concentration levels of 4.6 g ml^–1 Cd could be determined at a 500-fold excess (wt/wt) of uranium. Uranium calibration was linear up to 500 g ml^–1 (r²=0.999) and 21 g ml^–1 uranium could tolerate up to a 1000-fold excess of cadmium (wt/wt). Both procedures could tolerate 10 g ml^–1 levels of metal ions, such as chromium, copper, manganese, molybdenum and vanadium.     

A toxic reagent-free method for normal-phase matrix solid-phase dispersion extraction and reversed-phase liquid chromatographic determination of aldrin,dieldrin, and DDTs in animal fats

A method for the determination of aldrin, dieldrin, DDT, DDE, and DDD contamination in animal fats (beef tallow, lard, and chicken fat) without using toxic reagents is developed, that uses high-performance liquid chromatography after the sample has been prepared by matrix solid-phase dispersion (MSPD) with acidic alumina oxide. A reversed-phase C₁-silica column with a mobile phase of 50% (v/v) ethanol solution (in water) and a photo-diode array detector were used for the determination. Average recoveries of the target compounds (0.2–5.0 g g^–1) ranged from 84–98%, with coefficients of variation of <5%. The limits of quantitation were 0.16 g g^–1 for AD, 0.10 g g^–1 for DD, 0.06 g g^–1 for DDT, 0.07 g g^–1 for DDE, and 0.05 g g^–1 for DDD. No toxic reagents were used at all.     

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.     

Crystal and Molecular Structure of (BzlMe3N) 2 + [Fe2OCl6]2-

The crystal and molecular structure of (BzlMe₃N) ₂ ⁺ [Fe₂OCl₆]^2- has been determined. The asymmetric unit contains two benzyltrimethylammonium cations and two half -oxo-bis(trichloro-iron(III)) anions. The bridging -oxygen atoms of these anions are located over crystallographic symmetry elements. Therefore, the two anions resulting from the symmetry operations correspond to two different conformers presenting angular and linear dispositions of the Fe-O-Fe bond angle. Mössbauer spectrum consists of two asymmetric lines that are adequately simulated by two equally populated quadrupole doublets associated with the two iron sites.     

Extraction and Spectrophotometric Determination of Osmium by Tetramethylthiuram Disulphide in Toluene

Summary Tetramethylthiuram disulphide (TMTD) is used for the extraction and spectrophotometric determination ofg quantities of osmium. 15 ml of 1.052×10^–3 M TMTD in toluene quantitatively extracts osmium from7 M HCl. The complex attains maximum colour intensity in 2 hours. It is red in colour and exhibits two max. One at 445 nm and the other at 504 nm. The maximum at 504 nm is more significant. Beer's law was found to hold good over the concentration range of 1.7 to 26.7g of osmium per ml. The Ringbom plot shows the optimum range of 9.42 to 23.65g of osmium per ml. The optimum period of equilibration is 30 seconds and the complex is stable up to 5 hours. The extracted species shows the composition to be 1 1 (Os TMTD). It is possible to extract and determine osmium in the presence of other platinum metals with composition corresponding to the ore osmiridium.

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Zusammenfassung Tetramethylthiuramdisulfid (TMTD) wurde zur Extraktion und spektrophotometrischen Bestimmung von Mikrogrammengen Osmium verwendet. 15 ml einer 1,052.10^–3-molaren Lösung von TMTD in Toluol dienen zur Extraktion von Os aus 7-m Salzsäure. Der entstandene rote Komplex erreicht innerhalb 2 Stunden maximale Farbintensität und zeigt zwei Absorptionsmaxima bei 445 nm und 504 nm. Letzteres ist signifikanter. Zwischen 1,7 und 26,7g Os/ml gilt das Beersche Gesetz. Nach der Ringbom-Gleichung liegt die geeignetste Konzentration zwischen 9,42 und 23,65g Os/ml. Nach 30 sec stellt sich das Gleichgewicht ein und bleibt bis zu 5 Stunden konstant. Die extrahierte Substanz entspricht der Zusammensetzung 1 1 (Os TMTD). Os läßt sich auch in Gegenwart anderer Platinmetalle so extrahieren und bestimmen.