Separation of twenty underivatized essential amino acids by capillary zone electrophoresis with contactless conductivity detection

Twenty underivatized essential amino acids were separated using capillary zone electrophoresis and consequently detected with contactless conductivity detection (CCD). A simple acidic background electrolyte (BGE) containing 2.3 M acetic acid and 0.1% w/w hydroxyethylcellulose (HEC) allowed the electrophoretic separation and sensitive detection of all 20 essential amino acids in their underivatized cationic form. The addition of HEC to the BGE suppressed both, electroosmotic flow and analyte adsorption on the capillary surface resulting in an excellent migration time reproducibility and a very good analyte peak symmetry. Additionally, the HEC addition significantly reduced the noise and long-term fluctuations of the CCD baseline. The optimized electrophoretic separation method together with the CCD was proved to be a powerful technique for determination of amino acid profiles in various natural samples, like beer, yeast, urine, saliva, and herb extracts.     

Extension of the application range of UV-absorbing organic solvents in capillary electrophoresis by the use of a contactless conductivity detector

A contactless conductivity detection (CCD) system is used for capillary zone electrophoresis (CZE) with non-aqueous solvents of the buffering background electrolyte, which exhibit strong UV absorbance below 230 nm. It is found that the CCD characteristics with such solvents (propylene carbonate, N,N-dimethylformamide and N.N-dimethylacetamide as examples) is the same as with aqueous solutions: the same signal and noise is obtained for a given electric conductance of the background electrolyte, independent of the kind of the solvent. Therefore CCD enables the extension of the application range to solvents with restricted use for common UV detection in CZE due to their unfavourable or even unfitting optical properties. The applicability of CCD is demonstrated by CZE of aliphatic ammonium compounds in these solvents.     

Microstructure and sensing properties of nanocrystalline indium oxide prepared using hydrothermal treatment

Nanocrystalline indium(III) oxide samples were prepared using soft chemistry. The microstructure (particle size and shape, specific surface area, pore-size distribution) and sensing properties of In₂O₃ were studied as functions of synthesis parameters. Indium oxide synthesis including hydrothermal treatment produces materials having high sensing sensitivity in NO₂ detection.     

Beitrag zur Chemie der Ceritmetalle III

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Reversed phase UHPLC/ESI-MS determination of oxylipins in human plasma: a case study of female breast cancer

The ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC/MS) method was optimized and validated for the determination of oxylipins in human plasma using the targeted approach with selected reaction monitoring (SRM) in the negative-ion electrospray ionization (ESI) mode. Reversed phase UHPLC separation on an octadecylsilica column enabled the analysis of 63 oxylipins including numerous isomeric species within 12-min run time. The method was validated (calibration curve, linearity, limit of detection, limit of quantification, carry-over, precision, accuracy, recovery rate, and matrix effect) and applied to 40 human female plasma samples from breast cancer patients and age-matched healthy volunteers (control). Thirty-six oxylipins were detected in human plasma with concentrations above the limit of detection, and 21 of them were quantified with concentrations above the limit of quantitation. The concentrations determined in healthy controls are in a good agreement with previously reported data on human plasma. Quantitative data were statistically evaluated by multivariate data analysis (MDA) methods including principal component analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA). S-plot and box plots showed that 13-HODE, 9-HODE, 13-HOTrE, 9-HOTrE, and 12-HHTrE were the most upregulated oxylipin species in plasma of breast cancer patients.

     

Kraftstoffe

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Beitrag zur Chemie der Ceritmetalle

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Zur maassanalytischen Bestimmung des Tellurs

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