Glow discharge mass spectrometry

Over the past twenty years or so, glow discharge mass spectrometry (GDMS) has become the industry standard for the analysis of trace elements in metals and semiconductors. A review of its history is followed by a picture of the present situation and a look to where the future may lie. Applications are summarised, including the ability of GDMS to offer depth-resolved data and non-conductor analysis, and the well-documented quantitative nature of the results is reviewed. The effects resulting from the physical properties of the analyte material are discussed at length. Finally, recent work such as fast flow sources and pulsed glow discharges is reviewed.     

Syntheses and structures of structurally diverse potassium beta-diketiminates derived from the ligand [(N(SiMe3)C(Ph))2CH

The compounds [K((mu-N(SiMe3)C(Ph))2CH)(thf)2]infinity 1, [K(mu-N(SiMe3)C(Ph)C(H)C(Ph)NH)L]2 [L = (thf)2 2, tmen 3], [K(mu-NSi(Me)2C(Ph)C(H)C(Ph)N)(thf)3]2 4 and [K(N(H)C(Ph))2CH](thf)0.5 5 have been prepared from K[(N(SiMe3)C(Ph))2CH] and the X-ray structures of 1-4 are reported.     

Second-order Green's function calculations of the ionization potential of a (H2)7 chain embedded in a homogeneous electric field

Summary The vertical ionization potential and the related pole strength of a model alternant chain of 14 hydrogen atoms subject to a homogeneous electric field, parallel to the chain and of increasing intensity are calculated, in the framework of a 6–31G** basis set, at the second-order level of the many-body Green's function theory. Trends observed with orbital relaxation, pair removal and pair relaxation effects are interpreted in terms of deformations of the electron density.     

Dinitrogen reduction by TmII,DyII, and NdII with simple amide and aryloxide ligands

Dinitrogen can be reduced to the planar M2(mu-eta2:eta2-N2) structure without employing cyclopentadienyl or complicated polydentate ligands using the recently discovered divalent oxidation states of Tm(II), Dy(II), and Nd(II). Complexes of these ions with common monodentate amide and aryloxide ligands can effect N2 reduction. THF solutions of LnI2 (Ln = Tm, Dy) in the presence of 2 equiv of NaN(SiMe3)2 reduce dinitrogen to form {[(Me3Si)2N]2(THF)Ln}2(mu-eta2:eta2-N2) complexes that have planar Ln2N2 units and 1.264(7) and 1.305(6) A NN bonds consistent with (N2)2- moieties. With the stronger reductant Nd(II), aryloxides are sufficient ancillary ligands: the NdI2/2KOC6H3tBu2-2,6 (KOAr) system forms [(ArO)2(THF)2Nd]2(mu-eta2:eta2-N2), which has a 1.242(7) A NN bond.     

The Role of Carnitine Acyltransferases in the Maintenance of Cell Function

Summary. Carnitine acyltransferases catalyse equilibria between acyl-CoA esters and the respective acylcarnitines. Therefore, they act not only as pathway enzymes, but also as modulators of acyl-CoA concentrations within individual sub-cellular compartments. Because acyl-CoA esters are potent biologically active metabolites, carnitine acyltransferase activities are potentially able to affect a diverse range of physiological processes, ranging from insulin secretion, to appetite control, and insulin sensitivity of tissues. The distinctive subcellular distributions of the different types of carnitine acyltransferases also enables them to participate in the transfer of acyl moieties across intracellular membranes, and of particular acylcarnitine esters across the plasma membrane and into the plasma. Pharmacological strategies that make use of these properties to improve cell function are discussed.     

Optimale Bedingungen der Atomabsorption, erl?utert am periodischen System der Elemente

Zusammenfassung Die 42 wichtigsten, durch Atomabsorption erfaßbaren Elemente wurden nach einem einheitlichen Verfahren hinsichtlich der günstigsten Betriebsbedingungen untersucht. Die Elemente der 1. und 2. Neben gruppe und der 2. Hauptgruppe werden mit möglichst geringem Strom der Hohlkathodenlampe am empfind lichsten nachgewiesen. Alle übrigen Elemente liefern bei maximalem Lampenstrom günstigste Ergebnisse. In den einzelnen Gruppen kann man eine Abnahme der notwendigen Flammentemperatur zur Probenverdampfung mit Zunahme der Periode feststellen. Bei den Elementen der 4. Nebengruppe (Ti, Zr, Hf) kann Mußsäure und in geringem Maße Salzsäure die Verdampfungsblockierung durch Bildung von Oxiden vermindern.

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Optimum conditions of atomic absorption, illustrated by means of the periodic system

The 42 most important elements which can be determined by atomic absorption were examined according to a common method in order to establish the most favourable working conditions. The elements of groups IB and IIA and IIB were determined with the highest sensitivity at the lowest possible current of the hollow cathode lamp. All other elements yielded optimum results at maximum lamp current. In the individual groups the flame temperature required for sample evaporation decreased as the period increased. With the elements of group IVA (Ti, Zr, Hf) the evaporation blocking by formation of oxides could be reduced by hydrofluoric acid and, to a lesser extent, hydrochloric acid.

     

Kinetics of formation and dissociation of lanthanide(III) complexes with the 13-membered macrocyclic ligand TRITA4-

The tetraazamacrocyclic ligand TRITA(4-) is intermediate in size between the widely studied and medically used 12-membered DOTA(4-) and the 14-membered TETA(4-). The kinetic inertness of GdTRITA(-) was characterized by the rates of exchange reactions with Zn(2+) and Eu(3+). In the Zn(2+) exchange, a second order [H(+)] dependence was found for the pseudo-first-order rate constant (k(0)=(4.2 +/- 0.5) x 10(-7) s(-1); k'=(3.5 +/- 0.3) x 10(-1) M(-1)s(-1), k" =(1.4 +/- 0.4) x 10(3) M(-2)s(-1)). In the Eu(3+) exchange, at pH <5 the rate decreases with increasing concentration of the exchanging ion, which can be accounted for by the transitional formation of dinuclear GdTRITAEu(2+) species. At physiological pH, the kinetic inertness of GdTRITA(-) is considerably lower than that of GdDOTA(-)(t(1/2)= 444 h (25 degrees C) vs. 3.8 x 10(5) h (37 degrees C), respectively). However, GdTRITA(-) is still kinetically more inert than GdDTPA(2-), the most commonly used MRI contrast agent (t(1/2)= 127 h). The formation reactions of LnTRITA(-) complexes (Ln = Ce, Gd and Yb) proceed via the rapid formation of a diprotonated intermediate and its subsequent deprotonation and rearrangement in a slow, OH(-) catalyzed process. The stability of the LnH(2)TRITA* intermediates (log K(LnH2L*)= 3.1-3.9) is lower than that of the DOTA-analogues. The rate constants of the OH(-) catalyzed step increase with decreasing lanthanide ion size, and are about twice as high as for DOTA-complexes.     

Determination of uranium by XRF analysis following its preconcentration with some organic precipitants

The determination of uranium in natural waters by XRF analysis after its preconcentration with some organic precipitants is described.¹⁰⁹Cd source is used for the excitation of L-series X-rays of uranium. Separation yield, kinetics of coprecipitation and the possibility of preparing thin-layer samples for XRF analysis were studied in detail for uranium concentration with α-nitroso-β-naphtol, methylene blue with ammonium thiocyanate, tannin with urotropine and other precipitants. A procedure using coprecipitation of uranium with α-nitroso-β-naphtol from 500 ml samples of surface or waste, waters is proposed.     

Polarographische Simultanbestimmung von Niob und Zinn in der bin?ren Legierung

Zusammenfassung Die Möglichkeit der gleichzeitigen Bestimmung von Niob und Zinn mit Hilfe der Polarographie wird untersucht. Es wird gefunden, daß die Bestimmung zwar nicht gleichspannungspolarographisch, wohl aber square-wave-polarographisch durchführbar ist. Zur Analyse der binären Nb-Sn-Legierungen (etwa Nb₃Sn) ist 8,0±0,1 m HCl+10 Vol-% Äthylenglykol als Grundelektrolyt geeignet. In diesem Elektrolyten erscheinen die erste Reduktionswelle des Niobs, Nb^VIV, und die zweite Reduktionswelle des Zinns, Sn^IISn, gut getrennt und vermeßbar. Die Differenz der Spitzenpotentiale (E _pNb^V/IV= -0.26V, E _pSn^II/O= -0.46V gegen Quecksilber-Bodenelektrode) beträgt 200 mV.Die beschriebene Methode hat im Vergleich zu den bekannten nichtpolarographischen Analysenvorschriften den Vorzug, eine bis zu 100 mal kleinere Einwaage (bei vergleichbarer Reproduzierbarkeit) und einen verringerten Zeitaufwand zu erfordern.Bei Einwaagen von 2–14 mg beträgt die Genauigkeit der Niobbestimmung 1% rel., die der Zinnbestimmung 2% rel. Eine einzelne Niob-Zinn-Simultanbestimmung dauert 4 Std.

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Summary The possibility of a simultaneous polarographic determination of niob and tin is investigated.It has been found that the determination cannot be carried out by direct current polarography, but square-wave polarography yields good results.8.0±0.1 M HCl+10 vol-% ethylene glycol is suitable as supporting electrolyte for the analysis of the binary Nb-Sn-alloys (Nb₃Sn).In this supporting electrolyte the first reduction-wave of niobium Nb^VNb^IV, and the second reduction wave of tin, Sn^IISn⁰, are well developed and separated. The difference of the peak potential (E _pNb^V/IV= -0.26V, E _pSn^II/O= -0.46V vs. mercury-pool electrode) is 200 mV. Compared with conventional methods the method described has the advantage of requiring smaller amounts of sample (up to 100 times smaller by weight at comparable reproducibility) with a saving of time.With sample amounts of 2 to 14 mg the accuracy of the niobium determination is 1% rel., that of the tin determination is 2% rel. One single simultaneous determination of niobium and tin takes about four hours.

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

Pseudohalogenometallverbindungen: LVIII. Reaktionen von diphenylphosphorylazid und perfluor-n-hexylsulfonylazid mit triphenylphosphan-komplexen von platin(0), rhodium(I), iridium(I), ruthenium(0), kobalt(II) und kupfer(I)

Diphenylphosphorylazide N₃P(O)(OPh)₂ reacts with Pt(PPh₃)₃, Pt(PPh₃)₂(C₂H₄), trans-RhCl(CO)(PPh₃)₂, Ru(CO)₃(PPh₃)₂, CoCl₂(PPh₃)₂ and CuCl(PPh₃)₂ to give the azido complexes Pt(PPh₃)₂(N₃)R, Pt(PPh₃)₂(N₃)₂R₂, the urylene complex RhCl(PPh₃)₂(RNCONR) and the phosphine imine complexes Ru(CO)₃(RPPh₃)₂, CoCl₂(RNPPh₃)₂, CuCl(RNPPh₃)₂, respectively, (RP(O)(OPh)₂). The oxidative addition of n-C₆F₁₃SO₂N₃ to Pt(PPh₃)₄ and Pt(PPh₃)₂(C₂H₄) affords the complexes Pt(PPh₃)₂(N₃)R and Pt(PPh₃)₂(N₃)₂R₂, respectively, (RSO₂C₆F₁₃. The compounds are characterized by elemental analysis and by their IR spectra.