Polarographisches Verhalten der C2-Halogenkohlenwasserstoffe

Summary Investigations on the polarographic and voltammetric behaviour of organic halogen compounds were carried out in order to obtain information on the redox properties and how to develop determination and detection methods. In this second report the dp-polarographic behaviour of the halogen substituted C₂-compounds has been studied in different supporting electrolytes and in various solvents. The electrode processes are discussed and the possibilities for the polarographic determination of the C₂-halogen hydrocarbons. The detection limit is 0.25 g · ml^–1 and the linear current-concentration relationship is observed up to 25 g · ml^–1. A simple and rapid method is proposed for the dp-polarographic determination of 1,2-dibromoethane in gasoline; the relative standard deviation for 20 g · ml^–1 is ±1.8%.     

Determination of pentachlorophenol residues in wine and corks by solvent extraction methodology and specific gas chromatography detection

Summary A gas chromatographic methodology with selective detection is presented for the analysis in wines and corks of pentachlorophenol residues, which are suspected to be the most likely precursors of some off-flavours described in several wine samples. After derivatisation, pentachlorophenol acetate residues were monitored by electrolytic conductivity detection and/or mass spectrometric detection in the selective ion mode at m/z 264 and 266. Recoveries varied from 80 to 96% for wine samples fortified with 5 to 100 g l^–1 and from 83 to 91% for corks (fortified at 25 to 100 g kg^–1). The proposed methodology allowed for a determination limit of g l^–1 for wine and 10 g kg^–1 for corks.     

Extractive spectrophotometric determination of dioxouranium(VI) with the sodium salt of hexamethyleneiminecarbodithioate

The optimum conditions for the extractive spectrophotometric determination of dioxouranium(VI) with hexamethyleneiminecarbodithioate(HMICdt) have been established. Dioxouranium(VI) reacts with this ligand at pH 4.5 to form a yellowish-orange uncharged 12 metal-ligand complex which can be extracted by chloroform. The calibration graph was linear in the range of 1–20 g ml^–1 of dioxouranium(VI) at 335 nm. The molar absorptivity of the extracted species is 5.952×10³ l mol^–1 cm^–1 with Sandell's sensitivity of 0.04 g cm^–2. The average of 10 determinations of dioxouranium was 49.75 g for the samples containing 50 g of U(VI) and the variation from the mean at 95% confidence limit was 49.75±0.5955.     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.     

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.     

Extraction-spectrophotometric determination of uranium(VI) with PAR and N-octylacetamide

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·10⁴ 1·mol^–1·cm^–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml^–1. The system obeys Beer's law in the range of 0–5 g U·ml^–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.     

Synthesis of 5-arylidene derivatives of thiazane-2, 4-dithione

Thiazane-2,4-diones and their 3-aryl derivatives readily condense with aromatic aldehydes to give 5-arylidene derivatives. The compounds obtained are characterized by absorption maxima in the 290–310 m band, as well as by ill-defined bands at 260–270 and 420–440 m. The IR spectrum of 5-benzylidenethiazane-2, 4-dithione has bands at 7.02 (N-C-S), 7.52 (CH₂), 14.62 and 15.01 (C-S-C).     

Trace characterization of high-purity nickel by instrumental and radiochemical neutron activation analysis

Summary The high activity of the radionuclides ⁶⁵Ni (t_1/2=2.52 h) and ⁵⁸Co (t_1/2=70.8 d) imposes severe limitations on the performance of direct instrumental neutron activation analysis of nickel. The extent of the interference of the ⁵⁸Co depends on the ratio of the fluxes of the fast and thermal neutrons. A method of selective removal of cobalt, based on extraction with -nitroso--naphthol has been developed for the purpose of radiochemical NAA. Separation yields have been determined for 36 elements. The detection limits obtainable with both the instrumental and the radiochemical method are <10^–4 g/g for the elements Au, Eu, Ir, La, Sc and Sm, between 10^–4 and 10^–3 g/g for Cr, Cs, Hf, Hg, Lu, Re, Sb, Ta, Th, Tm and Yb, between 10^–3 and 10^–2 g/g for As, Ag, Br, Ce, Ga, Na, Ru, Se, W and Zn, and in the range 0.01–1 g/g for Ba, Cd, Co, Fe, In, K, Mo, Nd, Pd, Rb, Sn, U and Zr.     

Simultaneous determination of arsenic and selenium in biological samples by HG-AFS

A new method is proposed for simultaneous determination of traces of arsenic (As) and selenium (Se) in biological samples by hydride-generation double-channel non-dispersive atomic-fluorescence spectrometry (HG-AFS) from tartaric acid media. The effects of analytical conditions on fluorescence signal intensity were investigated and optimized. Interferences from coexisting ions were evaluated. Under optimum conditions linear response ranges above 20 g L^–1 for As and 32 g L^–1 for Se were obtained with detection limits of 0.13 and 0.12 g L^–1, respectively. The precision for elevenfold determination of As at the 4 g L^–1 level and of Se at the 8 g L^–1 level were 2.7 and 1.9% (RSD), respectively. Recoveries of 92.5–95.5% for As and 101.2–108.4% for Se were obtained for four biological samples and two certified biological reference materials. The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for simultaneous determination of As and Se in biological samples.     

Determination of nitrate in natural waters by flow-injection analysis

Summary Nitrate was determined in natural water samples by flow-injection spectrophotometry. It was reduced to nitrite with copperized cadmium and the nitrite thus produced reacted with p-aminoacetophenone and m-phenylenediamine. The limit of detection was about 1.5 g l^–1 for sample injections of 650 l. The sampling rate was about 40 samples h^–1 and the relative standard deviation was above 1% for 0.1–0.3 mg l^–1 nitratenitrogen. Nitrite present in the sample was determined separately and subtracted.

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Nitratbestimmung in natürlichen Wässern mit Hilfe der Fließinjektions-Analyse

Zusammenfassung Nitrat wird bei dieser Methode mit Hilfe einer Cu/Cd-Reduktionssäule zu Nitrit reduziert, das mit p-Aminoacetophenon und m-Phenylendiamin zur Reaktion gebracht wird. Die gebildete Verbindung wird spektral-photometrisch gemessen. Die Nachweisgrenze beträgt etwa 1,5 g/l bei injizierten Probevolumina von 650 l. Der Probendurchsatz beträgt 40/h. Die relative Standardabweichung liegt über 1% bei 0,1–0,3 mg/l Nitrat-Stickstoff. Vorhandenes Nitrit wird gesondert bestimmt und abgezogen.

     

Enrichment of sea-salt aerosols in short-lived222Rn daughter products-role of marine Fe/III/ hydroxide colloid

The interaction of short-lived Rn-daughter products /SLDP/, viz.²¹⁴Pb and²¹⁴Bi dissolved in sea-water with Fe/III/ hydroxide colloids followed by flotation of combined Fe-SLDP particles at the sea-air interface subsequently generating marine aerosols enriched in²¹⁴Bi and²¹⁴Pb have been studied under laboratory conditions. Rate constants for attachment of²¹⁴Bi and²¹⁴Pb to dispersed Fe/III/ colloids in the sea water are found to be 3.7×10^–4 min^–1 litre [g/Fe/]^–1 and 2.4×10^–4 min^–1 litre [g/Fe/]^–1, resp., /20°C/ over the concentration range of iron /III/ from 8 to 120 g liter^–1. The suggested mechanism of colloid flotation and aerosol generation might be responsible for some peculiarities of SLDP distribution in the lower marine atmosphere.     

Development and application of a simple routine method for the determination of selenium in serum by octopole reaction system ICPMS

The aim of the study was to develop an inductively coupled plasma mass spectrometry (ICPMS) method for robust and simple routine determination of selenium in serum. Polyatomic interferences on ⁷⁶Se, ⁷⁷Se, and ⁷⁸Se were removed by applying an octopole reaction system ICPMS with the reaction cell pressurized with H₂ gas. We developed a novel simple optimization routine for the H₂ gas flow based on a signal-to-noise ratio (SNR) calculation of the selenium signal measured in a single selenium standard. The optimum H₂ flow was 2.9 mL min^–1. The selenium content in serum was determined after a 50-fold dilution with 0.16 M HNO₃ and quantified by using addition calibration and gallium as an internal standard. The method detection limit was 0.10 g L^–1 for ⁷⁶Se and ⁷⁸Se and 0.13 g L^–1 for ⁷⁷Se. Human serum samples from a case-control study investigating if selenium was associated with risk of colorectal adenoma were analyzed. The average selenium concentration for the control group (n=768) was 137.1 g L^–1 and the range was 73.4–305.5 g L^–1. The within-batch repeatability (a batch is ten samples) estimated from 182 replicate analyses was 6.3% coefficient of variation (CV), whereas the between-batch repeatability was 7.4% CV estimated from 361 replicates between batches. The method accuracy was evaluated by analysis of a human serum certified reference material (Seronorm Serum level II, Sero A/S, Norway). There was a fairly good agreement between the measured average of 145±3 g L^–1 (n=36) and the certified value of 136±9 g L^–1. In addition the method was successfully applied for analysis of zinc serum concentrations without further optimization. For the Seronorm certified reference material a value of 911±75 g L^–1 (n=31) for zinc was obtained, which corresponds well to the certified zinc value of 920±60 g L^–1.     

Semi-automatic catalytic titration of some aminopoly-carboxylic acids,copper(II), and cobalt(II)

Summary A semi-automatic potentiometric method is described for the catalytic titrimetric determination ofg amounts of some aminopolycarboxylic acids. The method is based on their inhibitory effect on the copper(II)-catalyzed periodate-thiosulfate reaction. Amounts of EDTA in the 0.7–600g range (10^–6–8×10^–5 M), of DCTA in the 7–7000g range (10^–6–10^–3 M), of EGTA in the 0.8–800g range (10^–7–10^–4 M), and of DTPA in the 4–800g range (5×10^–7–10^–4 M) were determined with average relative errors and coefficient of variation of about 0.4–1%. The method has also been used for the indirect catalytic titrimetric determination ofg amounts of Cu²⁺ and Co²⁺ ions with about the before mentioned accuracy and precision.

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Halbautomatische katalytische Titration einiger Aminopolycarbonsäuren sowie von Cu(II) und Co(II)

Zusammenfassung Eine halbautomatische potentiometrische Methode zur katalytischen Maßanalyse von Mikrogrammengen einiger Aminopolycarbonsäuren wurde angegeben. Sie beruht auf dem Hinderungseffekt gegenüber der Cu(II)katalysierten Perjodat-Thiosulfatreaktion. EDTA in Mengen von 0,7–600g, DCTA in Mengen von 7–7000g, EGTA in Mengen von 0,8–800g und DTPA in Mengen von 4–800g wurden mit einem mittleren relativen Fehler von etwa 0,4–1% bestimmt. Das Verfahren wurde auch zur Bestimmung von Cu(II) und Co(II) mit der angeführten Genauigkeit verwendet.

     

Simultaneous determination of neodymium and erbium in rare earth mixture with 5,7-dibromo-8-hydroxyquinoline and TX-100 by third-derivative spectrophotometry

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 5,7-dibromo-8-hydroxyquinoline in the presence of octylphenol poly(ethyleneglycol)ether have been studied by normal and third-derivative spectrophotometry. The proposed method is free of interference of other rare earths. The calibration graphs were linear up to 18 g/ml of neodymium and 21 g/ml of erbium (in the final solution). The derivative molar absorptivities are 395 l.mol^–1.cm^–1 for neodymium and 3421.mol^–1.cm^–1 for erbium. The corresponding values of Sandell's sensitivity were 0.36 and 0.49 g.cm^–1, respectively. The relative standard deviations evaluated from ten independent determinations of 2.5 g/ml of neodymium and erbium are 1.5 and 3.8% for neodymium and 1.8 and 4.1% for erbium in absence and presence of 70 g of lanthanum, respectively. The detection limits (signal to noise ratio=2) are 0.23 g/ml for neodymium and 0.30 g/ml for erbium. The method has been used for the determination of neodymium and erbium in mixed rare earths with satisfactory results.     

Flow-Injection Methods for Determining Europium in Mixtures of Lanthanides(III)

Possible approaches to the flow-injection determination of europium(III) in the presence of other lanthanides are studied. One of the approaches is based on the direct amperometric detection of europium(III) in a flow-injection system with a glassy-carbon electrode at a potential of –0.85 V (against a saturated calomel electrode). The linear calibration range is 5.0 × 10^–5–5.0 × 10^–4M of europium, and the limit of detection is 1.8 × 10^–5M (2.8 g/mL). The throughput capacity is 90 h^–1for a sample volume of 600 L. Another approach involves the online reduction of europium(III) to europium(II) in a flow Jones mini-reductor filled with amalgamated zinc, followed by the spectrophotometric detection of europium(II) using redox reactions between europium(II) and iron(III) in the presence of 1,10-phenanthroline, molybdophosphoric acid, or Methylene Blue. In the latter case, the calibration curve is linear in the range 0–5.0 × 10^–6M europium(III), the limit of detection is 9.0 × 10^–8M (0.014 g/mL). The throughput capacity is 180 h^–1for a sample volume of 200 L. The performance parameters of the proposed flow-injection methods are estimated using the analysis of artificial mixtures and dissolved samples of samarium(III) oxide and lanthanum(III) fluoride containing europium impurities as an example.     

Spektrophotometrische Titanbestimmung mit Chromotrops?ure

Zusammenfassung Die Chromotropsäure ist ein analytisch wertvolles Reagens auf Eisen (III)₂₃, Chrom (VI)⁹, Kupfer, Niob²⁴ und besonders auf Titan (IV). Die Reaktion mit Chromotropsäure ist die empfindlichste (pD 5,9) und in Gegenwart von Ascorbinsäure weitgehend selektive Titanreaktion.In den Titan(IV)-lösungen bilden sich mit Chromotropsäure abhängig von der Zusammensetzung und dem p_H-Wert der Lösung sowie von der Konzentration der Reaktionspartner stufenweise mehrere Chelate. In den Lösungen mit Reagensüberschuß liegen folgende Chelatgleichgewichte vor: TiO²⁺ + 2 H₂R² TiO(RH)₂ ^4– + 2 H⁺ (Absorptionsmaximum470 m), P_H 0–2; TiO²⁺ + 2 H₂R^2– TiOR₂ ^6– + 4 H⁺ (470 m), p_H1–3,5; TiOR₂ ^6– + H₂R² TiOR₃ ^10– + 2 H⁺ (420 m), p_H 3,2–7,0; TiOR₂ ⁶ + 2H₂R^2– TiR₄ ^12– + 2 H + H₂O (470 m), p_H 1,7–2,4.Die beiden stabilen Chelate TiOR₂ ^6– und TiOR₃ ^10– können bei begrenzten Reaktionsbedingungen zur spektrophotoinetrischen Titanbestimmung ausgenutzt werden. Die Bestimmung bei p_H 2,9–3,2 und 467m in Gegenwart von Ascorbinsäure ermöglicht die Titanbestimmung neben einer Zahl von fremden Ionen. Sie ist die für die Praxis geeignetste Methode.Herrn Prof. Dr. A. Oká zum 55. Geburtstag gewidmet.Den Firmen E. Merck, Darmstadt und Reagencia, Kralupy, bin ich für das freundliche Überlassen der Präparate der Chromotropsäure mit herzlichem Dank verpflichtet.     

Quantitative chemical analysis on paper. I

Summary A method has been proposed for the determination of small quantities of Cl^–, SCN^– and I^– in mixtures. The method is based on the use of filter paper evenly impregnated with Ag₂CrO₄. The method permits the determination of 5 to 50g of Cl^–; 15 to 100g of I^– and 10 to 150g of SCN^– with an accuracy of 1.5%.The method may also be used for determination of SCN^– alone.

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Zusammenfassung Ein Verfahren für die Bestimmung kleiner Mengen Chlorid, Rhodanid und Jodid in deren Gemischen wird vorgeschlagen. Es beruht auf der Verwendung eines mit Silberchromat gleichmäßig imprägnierten Filtrierpapierstreifens und ermöglicht die Bestimmung von 5 bis 50g Chlorid,15 bis 100g Jodid und 10 bis 150g Rhodanid mit einer Genauigkeit von 1,5%. Das Verfahren kann auch für die Bestimmung von Rhodanid allein verwendet werden.

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Résumé On a proposé une méthode pour le dosage de petites quantités de Cl^–, SCN^–, et I^– en mélanges. La méthode est fondée sur l'emploi d'un papierfiltre uniformément imprégné d'Ag₂CrO₄. Elle permet le dosage de 5 à 50g de Cl^–, 15 à 100g d'I^– et de 10 à 150g de SON^–, à la précision de 1,5%. On peut aussi utiliser la méthode pour le dosage de SCN^– seul.

     

Di-μ-hydroxo bridge-cleavage reactions between [Co(nta)(μ-OH)]2 2− and different monodentate ligands

The cleavage of the di--hydroxo bridges of [Co(nta)(-OH)]₂ ^2– by dimethylaminopyridine (dmap) and pyridine (py) has been investigated. [Co(nta)(-OH)]₂ ^2– equilibrates rapidly in aqueous basic solutions with a mono--hydroxo bridged Co^III species [pK _OH = 3.26(2)] and both these species react with the incoming ligand to form different ion associated species which react in the subsequent rate-determining steps (k ₁ and k ₂) to form presumably a ligand-substituted, mono-bridged species, [(nta)(OH)Co--OH-Co(nta)(L)]^2–. Values for k ₂, the preferred mono--hydroxo bridged substitution pathway for these reactions, vary between 6.8(2) × 10^–4 s^–1 (py) and 8.5(4) × 10^–2 s^–1 (dmap).     

Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Liquid Chromatography

A rapid and accurate HPLC method has been developed for simultaneous determination of pioglitazone and glimepiride. Chromatographic separation of the two pharmaceuticals was performed on a Cosmosil C₁₈ column (150 mm × 4.6 mm, 5 m) with a 45:35:20 (v/v) mixture of 0.01 m triammonium citrate (pH adjusted to 6.95 with orthophosphoric acid), acetonitrile, and methanol as mobile phase, at a flow rate of 1.0 mL min^–1, and detection at 228 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation, and robustness [1, 2]. Linearity, accuracy, and precision were found to be acceptable over the ranges 2.50–30.00 g mL^–1 for pioglitazone and 0.10–10.00 g mL^–1 for glimepiride.