Hyphenation of column liquid chromatography and Raman spectroscopy via a liquid-core waveguide: chemometrical elimination of spectral eluent background

In column liquid chromatography (LC) coupled to conventional Raman spectroscopy (RS) removal of the spectral background of the eluent is often demanding, because of the strong signals of the organic modifier. A new chemometrical method is proposed, called the eluent background subtraction (EBS) method, which can correct for small shape and intensity differences of the eluent spectra. The variations in the eluent spectra are modelled using principal component analysis (PCA). The PCA loading vectors are subsequently used for eluent background correction of the elution spectra of the analyte. The loading vectors are fitted under these spectra by an asymmetric least-squares method. This method was successfully applied under various experimental conditions and performed much better than conventional background correction methods. Analyte detectability was improved by (weighted) averaging of all elution spectra and smoothing via a p-spline function.     

Vollautomatische rechnergesteuerte Titrationssysteme

Zusammenfassung Durch Titrationen auf konstante Potentialschritte anstelle konstanter Volumenschritte lassen sich höhere Genauigkeiten durch Anwendung besserer Auswerteverfahren bei potentiometrisch indizierter Titration erreichen. Über eine einfache Formel wird eine günstige Steuerung der Volumenschritte erreicht. Die Ergebnisse lassen sich durch eine Kontrolle der Potentiale während der Dosierung wesentlich verbessern.

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Fully automatic computer-controlled titration systems2. Dynamic control of reagent dosage

Summary Titrations in respect to constant potential steps have advantages to titrations with constant steps in reagent volume, for there are more sufficient evaluation methods. A simple algorithm is described to calculate the next step of reagent addition. More precise results in the potential steps are obtained if the potential is controlled by computer during dosage.

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Teil 1: Fresenius Z Anal Chem 308, 437 (1981)     

Substrates for the at-line coupling of capillary electrophoresis and surface-enhanced Raman spectroscopy

In this preliminary study, we evaluated four different types of substrate for the at-line coupling of capillary electrophoresis and surface-enhanced (resonance) Raman spectroscopy, CE-SER(R)S, with emphasis on spectral repeatability. We tested Sub1: etched silver foil, Sub2: a vapour-deposited silver film, Sub3: a silver oxalate-precoated silica TLC plate and Sub4: a silica TLC plate on which colloid and poly(l-lysine) were manually added to the analyte spots, used earlier in at-line CE-SE(R)RS. All substrates were first tested by manual spotting using trans-1,2-bis(4-pyridyl)ethylene (BPE) as a model compound for SERS and crystal violet (CV) as a model compound for SE(R)RS. The spectral features of the SE(R)RS spectra of BPE and CV showed a most satisfactory repeatability on all substrates. As expected, the signal intensities varied considerably between runs; this implies that quantification in at-line CE-SE(R)RS should rather be done by means of an on-line absorbance detector. In addition, the suitability of Sub1, Sub2 and Sub4 as deposition substrates after CE was explored using two cationic dyes: CV and basic fuchsin (BF). Good-quality SERRS spectra could be recorded on all three substrates. Although Sub1 and Sub2 have a poor water-sorptivity, they were found to be good substrates for at-line CE-SERRS. They do not require any post-deposition addition of silver colloid and could therefore become attractive alternatives for Sub4.     

Torsion and Abelianization in Equivariant Cohomology

Let X be a topological space upon which a compact connected Lie group G acts. It is well known that the equivariant cohomology H ^* _G (X; Q) is isomorphic to the subalgebra of Weyl group invariants of the equivariant cohomology H ^* _T (X; Q), where T is a maximal torus of G. This relationship breaks down for coefficient rings k other than Q. Instead, we prove that under a mild condition on k the algebra H ^* _G (X; k) is isomorphic to the subalgebra of H ^* _T (X; k) annihilated by the divided difference operators.     

Telomerization: Advances and Applications of a Versatile Reaction

A chameleonic reaction : The transition‐metal‐catalyzed telomerization of 1,3‐dienes with different nucleophiles leads to the synthesis of numerous products which can be applied in the cosmetic and pharmaceutical industry as well as in polymers and flavors. This Review shows the versatility of the telomerization based on recent research and industrial applications.

     

Rechnergesteuerte Kalibrierung ionensensitiver Elektroden

Analytical and Bioanalytical Chemistry - Der üblichen Kalibrierung ionensensitiver Elektroden mit Hilfe von Standardlösungen wird ein rechnergesteuertes Verfahren gegenübergestellt....     

A highly efficient method for the hydroaminomethylation of long-chain alkenes under aqueous, biphasic conditions

The use of salts of secondary and primary amines with different inorganic and organic acids in hydroaminomethylation enables the quantitative conversion of 1-octene with high selectivity for saturated amines. We propose that a cationic rhodium species is formed under the acidic conditions which catalyses the hydrogenation of the enamine or imine formed subsequently. Thus the use of acids and amine salts enables the hydroaminomethylation of long-chain alkenes under aqueous, biphasic conditions with quantitative conversions and short reaction times.