Anwendung der Streustrahl-Methode zur Bestimmung der Elemente in Mineral?lprodukten mit Hilfe der R?ntgenfluorescenz-Spektral-Analyse am Beispiel der Bleibestimmung in Ottokraftstoffen

Zusammenfassung In einem relativ einfach durchzuführenden Verbundverfahren wird Selen im Sauerstoff-strom innerhalb 15 min bei 1100–1150°C quantitativ aus den Metall- bzw. Metalloxidschmelzen verdampft und in einer mit flüssigem Stickstoff gekühlten Vorlage aufgefangen. Das aus der Vorlage mit einer definierten Menge verdünnter HNO₃ in Gegenwart von Ni-Nitrat gelöste Selen läßt sich direkt durch AAS mit dem Graphitofen (FAAS) äußerst nachweisstark und zuverlässig bestimmen. Die Nachweisgrenze (elektrodenlose Entladungslampe) liegt bei 3×10^–11 g Se. Der Verfahrensverbund erlaubt mit Probenmengen 10 g in Ag und Au Se-Gehalte 0,05 ppb,inCu 0,1 ppb,in Bi 0,2 ppb und in Pb 10 ppb zu erfassen. Für draht-, stab- und spanförmige Proben erhält man für Se-Gehalte von 2–0,002 ppm Variationskoeffizienten zwischen 3 und 6%. Die Vollständigkeit der Se-Verdampfung aus den Matrices Cu, Ag, Au und Bi wurde ebenso wie die Richtigkeit des Gesamtverfahrens durch systematische Untersuchungen belegt.

---

Determination of se by furnace atomic absorption spectrometry (FAAS) in the ppb-range in Cu, Cu alloys, Ag, Au, Pb and Bi after volatilization in an oxygen stream

Summary Selenium is evaporated in a multi-stage procedure within 15 min from metals or metal oxides fused at temperatures of 1100–1150°C under a stream of oxygen and is trapped in a receiver cooled with liquid nitrogen. The condensed SeO₂ is dissolved with a definite volume of diluted HNO₃ in the presence of Ni-nitrate and determined with high sensitivity and reliability by FAAS (electrodeless discharge lamp). The detection limit of the FAAS was found to be 3 · 10^–11 g of Se. The multi-stage procedure allows to detect Se levels 0.05 ppb in Ag and Au, 0.1 ppb in Cu, 0.2 ppb in Bi, and 10 ppb in Pb, respectively, with sample weights 10 g. For wire, rod, and chip samples the coefficients of variation are found to be between 3 and 6% for Se contents of 2 to 0.002 ppm. The quantitative evaporation of Se from Cu, Ag, Au, and Bi as well as the accuracy of the whole procedure have been checked systematically.

Die Arbeit wurde durch Mittel der DFG in dankenswerter Weise unterstützt.     

Novel metathesis catalysts based on ruthenium 1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidenes: synthesis, structure, immobilization, and catalytic activity

The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC)[=CH-2-(2-PrO)-5-NO(2)-C6H3]] (1) and [Ru(CF3COO)2(NHC)[=CH-2-(2-PrO)-5-NO2-C6H3]] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5 % of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9< or =PDI< or =2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24-2% of the supported catalysts, yields in RCM and ROCM were in the range of 76-100%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014% (0.14 ppm).     

Nucleophilic Addition of CH, NH, and OH Bonds to the Phosphadiazonium Cation and Interpretation of (31)P Chemical Shifts at Dicoordinate Phosphorus Centers

The phosphadiazonium cation [MesNP](+) reacts quantitatively with the fluorenylide anion, MesNH(2), and MesOH (Mes = 2,4,6-tri-tert-butylphenyl), resulting in formal insertion of the N-P moiety into the H-Y (Y = C, N, O) bonds. Specifically, reaction of MesNPCl with fluorenyllithium gives the aminofluorenylidenephosphine [crystal data: C(31)H(38)NP, monoclinic, P2(1)/c, a = 9.568(8) ?, b = 24.25(2) ?, c = 11.77(1) ?, beta = 101.38(8) degrees, Z = 4]. Similarly, reaction of [MesNP][GaCl(4)] with MesNH(2) gives the diaminophosphenium salt [MesN(H)PN(H)Mes][GaCl(4)] [crystal data: C(36)H(60)Cl(4)GaN(2)P, monoclinic, C2/c, a = 24.921(2) ?, b = 10.198(4) ?, c = 16.445(2) ?, beta = 93.32(1) degrees, Z = 4], and reaction with MesOH gives the first example of an aminooxyphosphenium salt [MesN(H)POMes][GaCl(4)]. It is proposed that the reactions involve nucleophilic attack at phosphorus followed by a 1,3-hydrogen migration from Y to N. Experimental evidence for the formation of sigma-complex intermediates is provided by the isolation of [MesNP-PPh(3)][SO(3)CF(3)] [crystal data: C(37)H(44)F(3)NO(3)P(2)S, triclinic, P&onemacr;, a = 10.663(1) ?, b = 19.439(1) ?, c = 10.502(1) ?, alpha = 103.100(7) degrees, beta = 113.311(7) degrees, gamma = 93.401(7) degrees, Z = 2]. As part of the unequivocal characterization of the aminooxyphosphenium salt, detailed solid-state (31)P NMR studies and GIAO calculations on the phosphenium cations have been performed. Contrary to popular belief, the phosphorus shielding in dicoordinate cations is not caused by the positive charge but results from efficient mixing between the phosphorus lone pair and pi orbitals.     

Verhalten von ng- und μg-Mengen biochemisch interessierender Amine bei Trennverfahren,wie Ionenaustausch-Chromatographie,Mitfällung und Extraktion

The behaviour of ng- and μg-amounts of amines of biochemical interest is compared. ng-amounts are co-precipitated from aqueous solutions with the tetraphenyloborates of potassium, ammonium and creatinine. A separation from potassium chloride, ammonium chloride and creatinine is achieved by extraction of the amines with methanol. The elution volumes of about 50 amines during ion-exchange chromatography using a weakly acidic resin are compared. A procedure has been elaborated by which the amines can be collected from urine.     

Zur Darstellung von Oxiden cyclischer,sekundärer Arsine

Hydrolysis of 1-chloro-arsolane, C₄H₈AsCl, and 1-chloro-arsenane, C₅H₁₀AsCl, leads to oxides C₈H₁₀As₂O and C₁₀H₂₀As₂O, respectively. On direct alkylation of arsenic trioxide with 1.4-butane- and 1.5-pentane-bis-magnesium bromide these oxides are formed only in trifling amounts. Better results are gained by alkylation of N,N-dimethylaminodichloroarsane into amino-arsolane and amino-arsenane, which are also transformed into these oxides by hydrolysis. By hydrolysis of 1.4-dichloro-diarsenane only a small amount of 1.4-epoxo-arsenane is formed, whereas mainly a dimer of this oxide results. Solvolysis of 2.6-dichloro-diarsa-[3.3.0]-bicyclooctane with water, hydrogen sulphide or methylamine leads to 7-oxa-, 7-thia- and 7-methylaza-2.5-diarsa-noradamantane, respectively.     

Quelques precisions sur les effets catalytiques des micelles cationiques hydroxylees

The alkaline hydrolysis of p-nitrophenyl acetate and of CH₃CO₂(CH₂)₂N⁺(CH₃)₂C₁₆H₃₃, Br^? was studied in the presence of micelles C₁₆H₃₃N⁺(CH₃)₂CH₂CH₂OH, Br^? and CTAB, C₁₆H₃₃N⁺(CH₃)₃,Br^?. A pathway involving an intermediate is suggested for the hydrolysis of the ester. Hydrolysis rate of the intermediate in the presence of micelles is the same as hydrolysis rate for the ester in the absence of micelles. Consequently, hydrolysis of p-nitrophenyl acetate is not catalysed by one type of micelle, while it is enhanced by another type of micelle.     

Quantitative goldbestimmung in filmmaterialien mittels flammenloser atomabsorption

A graphite rod electrothermal atomizer has been used for the AAS determination of traces of gold in hydrochloric and in hydrobromic acid solutions, and also after extraction into HBr-saturated methyl isobutyl ketone. Photographic film samples were decomposed first by enzyme action then by nitric acid/peroxide oxidation, and the gold was extracted into MIBK. For 10-μl aliquots of solution the 3s limits of detection were 3 × 10^?10g for aqueous solutions, 7 × 10^?10g for MIBK, and 7 × 10^?9 g/cm² for film.     

Die Analytik wasserl?slicher Cellulose?ther

Zusammenfassung Es werden allgemeine und qualitative Merkmale von Natrium-Carboxymethylcellulose, Methylcellulose und Hydroxyäthylcellulose sowie gravimetrische und titrimetrische Bestimmungsmöglichkeiten der wasserlöslichen Celluloseäther insbesondere im Zusammenhang mit dem Substitutionsgrad beschrieben.Verfahren zur Ermittlung der Viscosität von Lösungen, des Polymerisationsgrades und des Gelteilchengehaltes werden besprochen. Abschließend werden charakteristische Beispiele für das analytische Vorgehen bei Substanzgemischen gegeben, die nur einen geringen Anteil Celluloseäther enthalten.

---

Analysis of water-soluble cellulose ethers

General and qualitative characteristics of sodium carboxymethylcellulose, methylcellulose and hydroxyethylcellulose are presented and gravimetric and titrimetric methods for the determination of water-soluble cellulose ethers are described, especially with regard to the degree of substitution. Procedures for the measurement of the viscosity of solutions, of the degree of polymerisation and of the content of gel particles are discussed. Characteristic examples are presented for the treatment of mixtures containing only a small percentage of cellulose ethers.

---

---

Erweiterte und umgearbeitete Fassung eines Vortrages, gehalten am 28. 6. 1971 in Baden-Baden.

---

Frau Dr. G. Bartelmus, Analyt. Laboratorium der Fa. Kalle AG, sprechen wir an dieser Stelle unseren herzlichen Dank für wertvolle Beratung aus.     

Comments on the electronic properties of cyclopropane,cyclobutane, and cyclohexane

Spectral quantities of cyclopropane, cyclobutane, cyclohexane, and of several derivatives, have been calculated by a semiempirical all-valence electron SCF-CI MO method. In cyclopropane, HOMO is practically localized in the carbon-frame, and LVMO is purely so. In cyclobutane, these two MO's are based on C-H bonds, while cyclohexane holds an intermediate position. Despite the overall similarity-experimental and computed-of the spectra of these molecules, assignments are non-parallel. Like cyclopropane, cyclobutane can extend conjugation, but to a diminished degree; cyclohexane behaves in this respect like an acyclic alkane. An interpretation of this gradation, in terms of the nature of high-lying MO's, is proposed.