An investigation of 3μm reverse-phase octadecylsilane packing materials for high-performance liquid chromatography

Summary The efficiency of high-performance liquid chromatography columns packed with 5 m and 3 m reverse-phase octadecylsilane packing materials has been evaluated using four test mixtures. Both stopped flow and valve injection have been used and typical efficiencies are given.     

A new detection method of99Tc by nuclear excitation

A new nuclear excitation process,⁹⁹Tc (, )^99mTc reaction, was applied for the first time to radioactivation analysis of technetium. Bremsstrahlung irradiation of⁹⁹Tc samples gave the reaction product^99mTc which emits -ray measurable with ease by a semiconductor detector. The production rate of^99mTc per g⁹⁹Tc was linearly correlated with the flux of bremsstrahlung. The detection limit of⁹⁹Tc was estimated to be nanogram order (0.63 Bq⁹⁹Tc) under the optimum irradiation condition. Possible interference by¹⁰⁰Ru(, p)^99mTc reaction was also studied, which could be discriminated from the (, ) reaction by simultaneously occurring⁹⁸Ru (, p)⁹⁷Ru reaction.     

Study of solid-phase reaction of RbNO3 with V2O5

Using DTA, TG and DTG methods, the reaction between RbNO₃ and V₂O₅ in the molar ratio 65 in air atmosphere was studied. The reaction proceeds stepwise. In individual steps of the reaction the formation of RbV₃O₈, RbVO₃ and Rb₃V₅O₁₄ was observed. Rubidium pentavanadate is thermally unstable. At 1000°, RbVO₃ and Rb₂V₄O₁₁ were identified as products of its thermal decomposition. Rubidium tetravanadate was also prepared by the isothermal reaction of RbNO₃ with V₂O₅ in the molar ratio 11.

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Zusammenfassung Unter Anwendung der DTA-, TG- und DTG-Methoden wurde die Reaktion RbNO₃-V₂O₆ bei dem Molverhältnis von 65 in Luft untersucht. Die Reaktion verläuft stufenweise. Bei den einzelnen Stufen der Reaktion wurde die Bildung von RbV₃O₈, RbVO₃ und Rb₃V₅O₁₄ beobachtet. Rubidiumpentavanadat ist thermisch instabil. Bei 1000° wurden RbVO₃ und Rb₂V₄O₁₁ als Produkte seiner thermischen Zersetzung beobachtet. Rubidiumtetravanadat wurde auch durch die isotherme Reaktion von RbNO₃-V₂O₅ bei dem Molverhältnis von 11 hergestellt.

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Résumé On a étudié par ATD, TG et TGD dans l'air, la réaction RbNO₃-V₂O₅ (rapport molaire 65). La réaction s'effectue par étapes, avec formation de RbV₃O₈, RbVO₃ et Rb₃V₅O₁₄. Le pentavanadate de rubidium est thermiquement instable. A 1000°, RbVO₃ et Rb₂V₄O₁₁ ont été identifiés comme produits de la décomposition thermique. Le tétravanadate de rubidium a également été préparé par voie isotherme en faisant réagir RbNO₃-V₂O₅ (rapport molaire 11).

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, , RbNO₃-V₂O₅ 6 5. . RbV₃O₈, RbVO₃ Rb₃V₅O₁₄. 1000° RbVO₃ Rb₂V₄O₁₁, . RbVO₃-V₂O₅ 11.

     

Polyhydroxysteroids from the Far-Eastern starfishCtenodiscus crispatus

Four new polyhydroxysteroids, 5-cholesta-3,5,6,15,16,25,26-heptaol, 24-ethyl-5-cholesta-3,5,6,15,28,29-heptaol-29-sulfate, (22E)-24-methyl-5-cholest-22-ene-3,5,6,15,25,26-hexaol-26-sulfate, 24-propyl-5-cholesta-3,5,6,8,15,28,29-heptaol, and the known 5-cholesta-3,5,6,15,16,26-hexaol, have been isolated from the starfishCtenodiscus crispatus.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1821–1825, October, 1994.     

Simultaneous determination of zinc and mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by differential rate kinetics and flow injection analysis

A rapid and sensitive differential rate kinetic method for the simultaneous and sequential determination of zinc and mercury with 5,10,15,20-tetrakis-(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS₄) has been based on flow injection spectrophotometry. By proper stopped-flow of the merging zone, the metalloporphyrin complexes of zinc and mercury were simultaneously determined at the maximum absorbance wavelength of 425.7 nm with the proportional equation. The relative standard deviations for 1.0 g/ml zinc and 5.0 g/ml mercury with 100 l sampling volume were 0.43% and 0.62%, respectively, for 8 parallel determinations. The calibration graphs were linear over the concentration range 0–3.0 g Zn/ml and 0–12.0 g Hg/ml. The method has been applied to the analysis of synthetic water samples with satisfactory recovery.     

Study of the absorption spectra of the 4f electron transition of the Nd and Er complexes with 2-isobutylformyl-1,3-dione-indane in the presence of TX-100 and its analytical application

The absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 2-isobutylformyl-1,3-dione-indane and TX-100 have been studied by normal and derivative spectrophotometry. Their molar absorptivities at the maximum absorption bands are about 7.2 (at 571 nm) times greater for neodymium and 13.1 (at 519 nm) times greater for erbium than those in the absence of the complexing agents. Use of second derivative spectra both eliminates the interference from other rare earths and increases the sensitivity from neodymium and erbium. Beers law is obeyed from 020 g/ml for neodymium and 025 g/ml for erbium. The relative standard deviations are 1.2% and 1.6% for 5.0 g/ml of neodymium and 8.0 g/ml of erbium, respectively. The detection limits (signal-to-noise ratio=2) are 0.14 g/ml and 0.20 g/ml. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.     

Flame atomic absorption spectrometric determination of cadmium and copper in biological reference materials using on-line sorbent extraction preconcentration

Summary Cadmium and copper at the g/g to ng/g level in plant and animal tissue reference materials, and at the g/l level in urine were determined by flame atomic absorption spectrometry using on-line sorbent extraction preconcentration based on flow injection techniques. Bonded silica reversed phase sorbent with octadecyl functional groups (RP-C 18), packed in a 100 l column, was used to collect the diethylammonium-N,N-diethyldithiocarbamate (DDTC) complex formed on-line in the sample digests at low pH. Methanol was used to elute the analyte chelates directly into the nebulizer-burner system of the spectrometer. Small air segments introduced before and after elution prevented the eluent from mixing with the sample solution and increased the sensitivity. A sampling frequency of 85/h could be obtained with a sample loading time of 30 s at a flow rate of 4.0 ml/min. The enrichment factor for both elements was 20 and the enhancement factors, including the effect of the organic solvent and with the flow spoiler removed, were 126 and 114 for cadmium and copper, respectively. The detection limits (3) were 0.15 g/l for cadmium and 0.2 g/l for copper. The precision was 2.3% and 1.4% r.s.d. for 10 g/l Cd and 45 g/l Cu, respectively (n=11). Results for the determination of cadmium and copper in various biological reference materials were typically in good agreement with certified values. Low recoveries were observed, however, for cadmium in samples containing high levels of copper and/or iron, such as bovine liver.On leave from Flow Injection Analysis Research Center, Institute of Applied Ecology, Academia Sinica, Shenyang, China     

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.     

Accurate determination of lead in wines by inductively coupled plasma mass spectrometry

Summary The capability of inductively coupled plasma mass spectrometry (ICP-MS) for Pb determinations in wine samples is studied. An evaluation is made of the signal behaviour in aqueous ethanolic medium. The effect of preliminary sample preparation on signal suppression or enhancement is investigated in conjunction with the ability of internal standardization to correct for it. As a result, an accurate and precise method of analysis is described in which the sample preparation is limited to a 10-fold dilution and external calibration is applied for quantitation. A detection limit of 0.2 g 1^–1 Pb in wine is achieved. The Pb content of ten different wines was found to range around 40 g 1^–1 with extreme values of 1.63 and 58.8 g 1^–1.     

Study of CO oxidation on the (111) face of nickel during Ni?NiO phase transition

CO oxidation on the (111) face of Ni has been studied over a wide temperature range and reactant ratio in CO+O₂ reaction mixtures. A significant nonstationary increase in the reaction rate due to the formation of a two-dimensional surface oxide has been found. Subsequent formation of threedimensional NiO(111) phase sharply decreases the CO oxidation rate.

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CO (111) Ni (CO+O₂). , . , NiO(111) CO.

     

Colloid chemical studies of polystyrene latices polymerized without any surface-active agents

Summary The influence of secondary minimum for the stability of spherical colloid has been studied using a series of soap-free polystyrene latices from 350 m to 1400 m in diameter.The critical flocculation concentration (c. f. c.) and the zeta-potential at the c. f. c. for each latex were determined with several salts of different ionic valencies. The values of c. f. c. varied with the particle size, reaching a maximum value at 750 m and then decreasing gradually with the diameter.Another phenomenon detected in the experiment was the complete reversibility of coagulation which was observed only in the cases of large size latices, i. e., the coagulates of large size particles were fully redispersed in the solution by stirring. The time-dependence of their sedimentation curves was reproducible.These experimental results could not be explained by the simple theoretical consideration for stability of suspension. The satisfactory explanation is given only using the term of secondary minimum of interaction potential, i. e., the origin of coagulation was shifted from the ordinary primary minimum to the shallow secondary minimum at about 750 m of the particle diameter.

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Zusammenfassung Der Einfluß des Sekundär-Minimum auf die Stabilität von Kolloiden wurde an seifenfreien Polystyrol-Latex-Suspensionen mit einem Durchmesser von 350 m bis 1400 m untersucht. Die kritische Flockungskonzentration (c. f. c.) und das Zeta-Potential bei c. f. c. wurde mit verschiedenen Salzen bestimmt.Der Wert von c. f. c. ändert sich mit der Teilchengröße.Ein weiterer wichtiger experimenteller Befund ist die vollständige Reversibilität der Flockung bei größeren Latices.Derartige Versuchsergebnisse können durch das Sekundär-Minimum befriedigend erklärt werden.

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With 7 figures in 10 details and 2 tables     

Simultaneous determination of cobalt,nickel and iron by multi-wavelength spectrophotometry

A method for the simultaneous spectrophotometric determination of cobalt, nickel and iron based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide is proposed. The absorption curves of these complexes overlap severely in the scanning range 390–510 nm. The analyte concentrations are calculated by a least squares fit of the pure spectra to the mixture spectra, which therefore makes the simultaneous determination of these metallic ions possible without tedious pretreatment. The detection limits afforded by the proposed method range from 0.05 g/ml for Fe and Ni to 0.1 g/ml for Co. Root-mean-squared errors of prediction of 0.085 g/ml for Co, 0.048 g/ml for Ni and 0.1172 g/ml for Fe were obtained using the wavelength range 400–510 nm and 0.147 g/ml for Co, 0.107 g/ml for Ni and 0.127 g/ml for Fe using the wavelength range 420–434 nm. The effect of interferences is studied and the proposed method is applied to analysis for the above elements in synthetic samples and real samples, such as biological materials and alloys.     

Untersuchungen zur Bestimmung von Spurenelementen in Blutserum mit Hilfe der Totalreflexions-R?ntgenfluoreszenzanalyse

Summary The quantitative determination of trace elements in human blood serum by Total Reflection X-Ray Fluorescence Analysis (TXRF) is influenced by absorption- and reflection-effects caused by the organic (proteins) and inorganic (P, S, Na, K, Ca, Cl) matrices. To minimize these effects we have developed a sample preparation technique based on the decomposition of the organic matrix and followed by the separation of the trace elements from the organic matrix by ion-exchange. The described method enables the simultaneous determination of K (1584 g), Ca (666 g), Fe (22 g), Cu (9.6 g), Zn (8.8 g), Se (0.97 g), Sn (1.3 g), Pb (0.12 g) and Rb (1.6 g) (obtained values in parentheses).

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet     

Selective determination of neodymium and erbium in mixtures with other lanthanides by second-derivative spectrophotometry of complexes with benzoyl-indan-1,3-dione and cetylpyridinium chloride

The absorption spectra of 4f electron transitions of the neodymium and erbium complexes with benzoyl-indan-1,3-dione and cetylpyridinium chloride have been studied by conventional and derivative spectrophotometry. The second-derivative spectrum has been used to eliminate the interference of the other lanthanides, and to increase the sensitivity by a further factor of 4–6. Beer's Law is obeyed for 6–29 g/ml Nd and 7–33 g/ml Er. The relative standard deviations evaluated from 10 independent determinations of 5.0 g/ml Nd and Er were 1.1% (Nd) and 1.6% (Er). The detection limits obtained from the sensitivity of the calibration graphs and 3s _b, (standard deviation of the blank,n = 11) were 0.63 g/ml Nd and 0.61 g/ml Er. The quantification limits (10s _b) were 2.1 g/ml Nd and 2.0 g/ml Er. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.     

A double-bonded niobium(III) compound with a formamidinate core: Nb2(μ-SMe)2(μ-DTolF)2 (η2-DTolF)2.2 toluene,DToIF= di-p-tolylformamidinate

The reaction of NaEt₃BH with Nb₂(-SMe₂)₃Cl₆ results in the transfer of a hydride ion to dimethylthioether with concomitant production of methane. Further reaction with potassium di-p-tolylformamidinate, KDTolF, yields Nb₂(-SMe)₂(-DTolF)₂²-DTolF:)₂.2 toluene, 1. In the latter, two thiomethoxide ions and two DTolF groups bridge the trivalent niobium atoms. Each of the other two DTolF groups chelate a metal atom to give the molecule an edge-sharing bioctahedral structure, The niobium-niobium distance of 2.655(2) A is consistent with the presence of a double bond between the metal atoms.     

On the use of azo dyes for the spectrophotometric determination of uranium and thorium in mixed solvents

Summary Solochrome Black 6 BN in an acetate buffered medium containing methanol reacts with U(IV) to give a blue complex which permits photometric determination with 5g U/ml to 100g U/ml.In the presence of zinc acetate, uranyl ion also may be spectrophotometrically determined by means of the same dye. From 2g U/ml to 40g U/ml may be determined with a relative error of less than ± 0.05.

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Zusammenfassung Es werden zwei Methoden zur spektrophotometrischen Bestimmung von Uran mittels Solochromschwarz 6 BN beschrieben. Dieser Farbstoff bildet mit U(IV) in acetatgepuffertem, methanolhältigem Medium einen blaugefärbten Komplex, der die Bestimmung von 5 bis 100g U/ml erlaubt.Mit demselben Farbstoff lassen sich auch 2 bis 40g U/ml in Lösungen von Uranylchlorid bestimmen.

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Résumé Le noir solochrome 6 BN en milieu tampon acétique contenant du méthanol réagit avec U-IV en donnant un complexe bleu qui permet le dosage photométrique de 5 g U/ml à 100 g U/ml.En présence d'acétate de zinc, on peut aussi doser l'ion uranyle par spectrophotométrie avec le même colorant. On peut doser de 2 g U/ml à 40 g U/ml avec une erreur relative inférieure à ± 0,05.

     

Effect of molybdenum catalysis on the perborate-bromide reaction. Kinetics and mechanism and some theoretical considerations

In the presence of molybdenum, both the uncatalyzed and the catalyzed reactions proceed simultaneously. An equation for k_cat was derived and the effect of temperature was described through a temperature function F(T) by the use of the Arrhenius-Eyring equation. A plausible mechanism is postulated and the theoretical background given for the analytical application of molybdenum.

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. k_cat, -. .