Eine Bemerkung zu quadratischen Divisionsalgebren

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The Use of Proton Nuclear Magnetic Resonance Spectroscopy for the Determin- ation of pK a Values in Aqueous/Organic Solutions for Basic Analytes Employed in Column Characterisation Protocols

Proton nuclear magnetic spectroscopy has been used to measure pK _a values of two basic analytes in a range of aqueous/organic eluents. The results support the hypothesis that the poor correlation in terms of ion exchange capacity with values greater than pH 7 may be attributed to the difference in the ionisation of the silica surface and not differences in ionisation of the basic analytes under the differing chromatographic conditions (i.e. temperature, type and amount of modifier) employed in two commonly used HPLC stationary phase characterisation procedures (Tanaka and Snyder).     

Enzymatic determination of urea in undiluted whole blood by flow injection analysis using an ammonium ion-selective electrode

A flow-injection system is described for the assay of urea in undiluted whole blood. Urea is quantified by means of an ammonium ion-selective electrode covered with a membrane with covalently immobilized urease. The enzymatically generated ammonium ion is directly related to the urea concentration. Interference from potassium is reduced by adjusting the potassium ion concentration in the carrier stream and in the aqueous calibration solutions to 4.0 mM; it can be eliminated by measuring the potassium ion concentration in the sample separately and applying a mathematical correction for the K⁺ contribution to the signal. The linear measuring range is 1–40 mM urea, with an injection frequency of 40 h^?1 and a standard deviation of 1% for whole blood samples. The result of the measurement is obtained within 25 s from the time of injection. Vatiations in the hematocrit level of the sample have no effect on the measurement. The results obtained by the flow-injection method are in excellent agreement with those found routinely at a local hospital. The sensor is stable for more than 25 days.     

Amperometric assay of glucose and lactic acid by flow injection analysis

A computer-controlled flow-injection system is described for the assay of D-glucose and L-lactic acid in undiluted plasma. Glucose or lactate is quantified by coupling an immobilized glucose oxidase or lactate oxidase membrane with an amperometric sensor; the hydrogen peroxide generated is directly related to the concentration of glucose or lactate. The linear range is 0–40 mM and 0–10 mM for glucose and lactic acid, respectively. The sample frequency is 60 h^?1 with a standard deviation of less than 1.5%. Correlation with the results for blood plasma obtained by routine clinical analyzers was good for both glucose and lactic acid.     

Determination of enantiomeric purity of (S)-carboranylalanine using capillary column supercritical fluid chromatography

Carboranylalanine, the o-carborane analogue of phenylalanine, is a potential candidate for boron neutron capture therapy of cancer. In this paper a method is described for the determination of enantiomeric purity of (S)-carboranylalanine as the (N- trifluoroacetyl)propylester using open tubular column supercritical fluid chromatography with a chiral stationary phase consisting of permethyl-β-cyclodextrin methyloctylsiloxane.     

Mass spectrometry of hydroxy dicarboxylic acids as trimethylsilyl derivatives. Rearrangement fragmentations

Gas chromatography—mass spectrometry offers a convenient method for the separation and identification of hydroxy dicarboxylic acids as open-chain trimethylsilyl (TMS) derivatives. Mass spectra were studied of aldaric (tartronic, tartaric, pentaric and hexaric) acids and deoxyaldaric (malic, 2-deoxypentaric, 2-deoxyhexaric, 3-deoxypentaric and 3-deoxyhexaric) acids. The different structural types can be readily identified from their characteristic spectra. The most prominent fragmentations involving the rupture of one bond are the loss of a siliconlinked methyl group and the formation of α-cleavage ions by carbon chain cleavage. The further decay is characterized by a number of significant rearrangements specific of TMS derivatives. Several of these can be classified as involving migration of a TMS group to an oxygen atom or migration of an ester OTMS group to a silicon atom. Concomitant loss of a stable molecule often provides a driving force. Prominent odd-electron ions are formed by a McLafferty-type rearrangement of a TMS group. The decomposition of several even-electron ions can be regarded as analogous to that rearrangement.     

Study of the23Na EFG tensor as determined from first order NMR satellite lines near the ferroelectric phase transition of AgNa(NO2)2

The²³Na NMR first order quadrupolar satellite lines are detected and studied in AgNa(NO₂)₂ single crystals near the paraelectric-ferroelectric phase transition. Although the intensities of the satellites are small the components of the electric field gradient tensor (EFG) at the²³Na sites could be deduced from the angular dependence of the first order quadrupolar line splitting with respect to rotations around the three crystallographic axes by applying the Volkoff method. In the paraelectric phase the principal axes system of the EFG coincides with the crystallographic axes system whereas in the ferroelectric phase there is a strongly temperature dependent small non diagonal element _xz (T). The EFG principal components _xx and _yy are strongly influenced whereas the EFG principal component _zz is nearly not affected by the ferroelectric phase transition. The observed temperature dependences of the EFG components are related to the temperature variation of the normalized spontaneous polarizationS(T) by assuming a coupling term which is quadratic inS(T). Finally the problem of the intensities of the satellite lines is discussed.     

Konstruktion der sämtlichen Lösungen einer Riemannschen Funktionalgleichung durch Dirichlet-Reihen mit Eulerscher Produktentwicklung. II

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Über die arithmetischen Eigenschaften eines Systems multiplikativer Modulfunktionen von Primzahlstufe

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