Spektralphotometrische Schnellmethode zur Bestimmung von Chlorid in Pflanzenmaterial

Zusammenfassung Eine spektralphotometrische Methode zur Bestimmung von Chlorid in Pflanzenmaterial wird vorgeschlagen. Die Probe wird nach Schöniger verbrannt und das Chlorid spektralphotometrisch bei 332 nm mit Quecksilberchloranilat als Reagens bestimmt. Störende Kationen werden durch Ionenaustausch entfernt. Die Methode wurde statistisch getestet und ihre Brauchbarkeit anhand von Pflanzenanalysen geprüft. Das Verfahren ist bei Einwaagen von 20 bis 100 mg für Chloridgehalte von 0,05 bis 5% geeignet.

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A rapid method for the spectrophotometric determination of chloride in plant material

Summary A spectrophotometric method for the determination of chloride in plant material is proposed. The sample is treated by Schoeniger combustion and the chloride is determined spectrophotometrically at 332 nm with mercury chloranilate as reagent. Interfering cations are eliminated by ion exchange. The method was tested statistically and its usefullness was demonstrated by analyses of plant materials. The method is suitable for chloride concentrations in the range of 0.05 to 5% in samples of 20 to 100 mg.

     

Operating principle of an electron monochromator in an axial magnetic field

Electron monochromators which are operated within an axial magnetic (guiding) field are especially suitable for the production of monochromatic electrons at low energies. Although in principle the technology of such devices has an appreciable historic background, we have discovered experimentally important new features, which cannot be understood using the previously published theories of operation. An in-depth study of the electron trajectories in a crossed electric and magnetic field using Simion1 showed a number of possible pitfalls, which have to be avoided in construction and operation. From our simulations we derived a novel design and operational method, which is currently under evaluation. We have already demonstrated that using this novel design an electron energy resolution of about 50 meV is realistic.     

Combined phase-sensitive acoustic microscopy and confocal laser scanning microscopy

Combined phase-sensitive acoustic microscopy (PSAM) at 1.2 GHz and confocal laser scanning microscopy (CLSM) in reflection and fluorescence has been implemented and applied to polymer blend films and fluorescently labeled fibroblasts and neuronal cells in order to explore the prospects and the various contrast mechanisms of this powerful technique. Topographic contrast is available for appropriate samples from CLSM in reflection and, with significantly higher precision, from the acoustic phase images. Material contrast can be gained from acoustic amplitude V(z) graphs. In the case of the biological cells investigated, the optical and acoustic images are very different and exhibit different features of the samples.     

Surface induced reactions of cluster ions

First results are presented from a new apparatus, consisting of a supersonic beam for generating neutral clusters, a variable energy electron gun for ionizing the clusters, and a tandem mass spectrometer set-up for studying surface induced reactions of mass and energy selected cluster ions. Rare gas cluster ions, fragment ions from SF₆, benzene ions and benzene cluster ions have been investigated so far. Cluster ion dissociation, intracluster ion molecule reactions and surface reactions with adsorbed hydrocarbons have been shown to be important reaction channels for these ion-surface collision at energies ranging from a few eV to 500 eV. The surface induced fragmentation spectrum is demonstrated to be a useful tool for probing binding energy and structure of cluster ions.     

Determination of trace amounts of Sb,Pb, Tl in water samples by inductively coupled plasma atomic emission spectrometry after a diantipyrylmethane-iodide third phase preconcentration

A preconcentration method based on third phase extraction has been developed and combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) for determination of Sb, Pb, Tl at trace levels in water samples. The reagents diantipyrylmethane and potassium iodide were applied for complexing Sb, Pb, Tl and producing a third phase extraction system. This third phase system produces relatively large enrichment factors and complete isolation of trace elements from high salt-containing matrices which influence strongly the plasma condition. Experimental parameters of the extraction, such as concentrations of complexing reagents, pH and extraction time have been optimized. Under the selected conditions, this third phase ICP-AES combination procedure gave multielemental detection limits for Sb, Pb, Tl which are superior by an order of magnitude or more to those obtained by ICP-AES alone without preconcentration. Precision of the technique is better than 10% at the 10 g/l level. The accuracy of this approach is demonstrated by its application to tapwater, artificial seawater and reference seawater samples.     

Capillary zone electrophoretic analysis of carbohydrates by direct and indirect UV detection

Summary The analysis of carbohydrates has been always hampered by their lack of UV absorbance above 200 nm, which is an especially challenging problem in capillary electrophoresis due to the very small (nl) sample volumes injected. The introduction of 2-aminopyridine as derivatizing agent allows sensitive direct UV detection of saccharides in the fmol range. However, due to the requirement of the presence of a free aldehyde group only aldoses and uronic acids can be determined. This limitation was recently overcome by means of precolumn derivatization withp-aminobenzoic acid or ethylp-aminobenzoate, which permits the analysis of fructose with a lower mass detection limit of 0.3 and 0.14 pmol, respectively. The detection limits for aldoses were even as low as 15 and 7 fmol. A more universal approach is the use of indirect UV detection, which permits the analysis of carbohydrates, including (1–2)-linked disaccharides and aldonic acids, at the lower pmol level without the need for derivatization.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Carrier-envelope phase measurement using a non phase stable laser

We demonstrate that the phase between the carrier and the pulse envelope of a few-cycle laser pulse can be retrieved from non phase stable laser systems, provided that such laser pulses are about 5 fs long and the repetition rate is in the order of 1 kHz. Our approach is based on online determination of the phase using f-2f interferometry. By a comparison of the self referencing interferometric signal with the photoelectron current emitted into a 7 degree solid angle parallel to the laser polarization, we obtain the absolute value of the carrier envelope phase. This is provided that a Coulomb correction for electron energies below 10 eV can be correctly taken into account. PACS 42.50.Hz; 42.65.Re; 32.80.Rm