Determination of picogram amounts of lipoxin A4 and lipoxin B4 by high-performance liquid chromatography with electrochemical detection

A new method for the determination of lipoxins with electrochemical detection after high-performance liquid chromatography is described. The half-wave potentials of lipoxin A4 and lipoxin B4 at a glassy carbon electrode and a mobile phase of methanol-water (65:35 v/v) and 1 mM trifluoroacetic acid was found to be +1.14 V versus an Ag/AgCl reference electrode. The use of trifluoroacetic acid instead of sulphuric acid and lithium perchlorate led to a background current of 6-8 nA at +1.20 V. The detection limits for both lipoxins, based on a signal-to-noise ratio of 3:1 were found to be 5-10 pg (15-30 fmol). The new method was applied to an extract of human polymorphonuclear granulocytes, preincubated with 15-hydroxyeicosatetraenoic acid and stimulated with Ca2+ ionophore A23187.     

Neuere Entwicklungen der flammenphotometrischen Analysenverfahren

Zusammenfassung Es wird gezeigt, daß man durch Einsatz von reduzierenden Flammen, durch Einsatz von Chemiluminescenzvorgängen in Flammen, durch Atomabsorptionsverfahren, durch Modulations- und Differentiations-operationen eine Reihe von weiteren Elementen mit den schnellen und spezifischen Flammenmethoden analytisch gut erfassen kann. Hierbei wird insbesondere auf die Bestimmung von Spurenelementen in Mikroproben mit möglichst einfachen Mitteln eingegangen.

---

Summary It is demonstrated that one can grasp analytically well a series of further elements with the quick and specific flame methods by use of chemiluminescence processes in flames, by atomic absorption methods, by operations of modulation and differentiation. Hereby the determination of trace elements is specifically treated in microprobes with the most possible simple means.

---

---

Unterstützt mit Mitteln der Deutschen Forschungsgemeinschaft.

---

Herrn Prof. Dr. Bohnstedt zum 65. Geburtstag gewidmet.

---

Meinen Mitarbeitern, insbesondere Herrn Dipl. Phys. W. Lang und Frau B. Gutsche, die an den zuletzt besprochenen Ergebnissen einen maßgeblichen Anteil hatten, als auch der Deutschen Forschungsgemeinschaft sei an dieser Stelle herzlichst gedankt.     

Identification of iodoorganic compounds in kerosene from nuclear fuel reprocessing

In kerosene samples from nuclear fuel reprocessing, iodoalkanes with chain-lengths from C₄ to C₁₃ have been identified. The kerosene samples were purified by means of solid-phase extraction. By this method other fission products like¹²⁵Sb and¹⁰⁶Ru were quantitatively removed from the solution. The only remaining radioactive nuclide was thus¹²⁹I. The iodoorganic compounds in the kerosene from the solvent were enriched from 6000 Bq/L to 100 000 Bq/L¹²⁹I by vacuum distillation. Chromatographic separation by HPLC, fractionation, and -measurement of the fractions showed that at least one polar and one nonpolar iodoorganic compound were present. Derivatisation of the iodoorganic compounds with, 1,4-diazabicyclo-2,2,2-octane to quatermary ammonium salts and²⁵²Cf plasma desorption mass spectrometry of the products revealed that the main iodoorganic constituents in the kerosene were iodobutane as polar and iodododecane as nonpolar compound in approximately equal concentrations.     

Organometallic Aspects of the Fischer-Tropsch Synthesis

The Fischer-Tropsch Synthesis counts among the industrial-scale processes having a versatile and broad product range, and has for decades offered the most attractive possibility for the use of coal as a source of heating oil and fuels. This conceivably simple reaction, the catalytic hydrogenation of carbon monoxide, generally leads to simple hydrocarbons as well (i.e. short chain olefins) that have been sought as chemical feedstocks since the oil crisis of the seventies, but fails to provide the large-scale, economic process required, due in large part to the minimal selectivity of traditional Fischer-Tropsch processes. In an effort to solve this problem current research in this sector is concerned not only with the optimization of old and the development of new catalytic systems, but also increasingly with the elucidation of numerous relevant reaction mechanisms. This article will discuss, from the viewpoint of an organometallic chemist, the significance of typical model reactions, both with regard to some fundamental aspects of synthesis gas chemistry, and in comparison with previous views concerning the mechanism of the Fischer-Tropsch Synthesis. The importance of various unique classes of complexes that have been studied in the context of Fischer-Tropsch chemistry is also evaluated with regard to their importance in the synthesis of hydrocarbons from carbon monoxide and hydrogen. It emerges that the primary steps of the reductive oligomerization of carbon monoxide are best described by the carbide/methylene mechanism, as originally proposed by Hans Fischer and Franz Tropsch.     

Classification of bicovariant differential calculi on quantum groups of type A,B, C and D

Under the assumptions thatq is not a root of unity and that the differentialsdu _j ⁱ of the matrix entries span the left module of first order forms, we classify bicovariant differential calculi on quantum groupsA _n–1 ,B _n ,C _n andD _n . We prove that apart one dimensional differential calculi and from finitely many values ofq, there are precisely2n such calculi on the quantum groupA _n–1 =SL _q (n) forn3. All these calculi have the dimensionn ². For the quantum groupsB _n ,C _n andD _n we show that except for finitely manyq there exist precisely twoN ²-dimensional bicovariant calculi forN3, whereN=2n+1 forB _n andN=2n forC _n ,D _n . The structure of these calculi is explicitly described and the corresponding ad-invariant right ideals of ker are determined. In the limitq1 two of the 2n calculi forA _n–1 and one of the two calculi forB _n ,C _n andD _n contain the ordinary classical differential calculus on the corresponding Lie group as a quotient.     

Flammenspektrophotometrischer Insecticidnachweis mit einem Filterflammenphotometer

Zusammenfassung Die in einer vorangegangenen Arbeit beschriebene Methode zur Bestimmung von chlorhaltigen Insecticiden in Extrakten aus tierischen und menschlichen Nahrungsmitteln wird durch folgende Maßnahmen wesentlich vereinfacht: a) Statt eines Spektralphotometers für den flammenspektrophotometrischen Nachweis wird ein einfaches Filterflammenphotometer verwandt. b) Das vorangegangene Extraktionsverfahren wird durch Weglassen eines Extraktionsschrittes wesentlich vereinfacht. Die Nachweisgrenzen der Methode und die Wiederauffindungsraten werden durch dieses Vorgehen sogar verbessert.

---

Flame -spectrophotometric determination of pesticides with a filter-photometer

In a preceding paper a flamespectrophotometric method for the analysis of chlorinated pecticides in extracts of animal and human food-stuffs was described. Now this method was simplified by using a flame photometer with filters instead of a photometer with monochromators and by omission of one extraction step. In spite of these simplifications the detection limits are improved and a better recovery is obtained.

---

---

Die Arbeit wurde mit Mitteln der Deutschen Forschungsgemeinschaft unterstützt.     

Synthesis and structural characterization of novel bridged platinum(II) biscarbene complexes

Novel bridged platinum(II) biscarbene complexes are reported: 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) (3) and 1,1′-dimethyl-3,3′-ethylene-4-diimidazolin-2,2′-diylidene platinum(II) complexes 4 are directly accessible in high yields starting from platinum halides. The one-pot synthesis obviates the need for multi-step reactions via metal precursors or free carbenes. An X-ray crystal structure of 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) dibromide (3b) confirmed the structural similarity to the known corresponding palladium complexes. Since free 1,1′-di-R-3,3′-methylene-4-diimidazolin-2,2′-diylidenes are only available in low yields this synthetic route provides an easy access to the corresponding carbene complexes.     

About the ratio of the size of a maximum antichain to the size of a maximum level in finite partially ordered sets

LetP be a finite partially ordered set. The lengthl(x) of an elementx ofP is defined by the maximal number of elements, which lie in a chain withx at the top, reduced by one. Letw(P) (d(P)) be the maximal number of elements ofP which have the same length (which form an antichain). Further let . The numbers and as well as all partially ordered sets for which these maxima are attained are determined.