1,2-Epoxycarotinoide. 3. Mitteilung. Isolierun von 1,2-Epoxy-1,2-dihydrolycopin aus Tomaten

1,2-Epoxycarotenoids: Isolation of 1,2-Epoxy-1,2-dihydrolycopene from Tomatoes The optically active, 1,2-epoxy-1,2-dihydrolycopene was isolated from tomatoes. Its constitution was established by comparison with the racemic synthetic compound.     

Determination of phthalates in crude extracts of sewage sludges by high-resolution capillary gas chromatography with mass spectrometric detection

A simple solvent extraction by ethyl acetate without subsequent cleanup was used to determine 16 phthalic acid esters (PAEs), including bis(2-ethylhexyl) phthalate (DEHP), in sewage sludge samples from different catchment areas. The compounds were separated on a gas chromatographic capillary column with a nonpolar HT-8 stationary phase. For most of the PAEs, internal standard quantification with deuterated dibutyl phthalate (DBP) and deuterated DEHP was best achieved by using electron ionization mass spectrometry in the selected-ion monitoring mode. Because of its high concentrations in the sludges, DEHP was quantified in the full-scan acquisition mode. Molecular weight and ester-type information for the PAEs was obtained in the positive chemical ionization mode with methane as the reagent gas. Finally, selected sewage sludges containing different amounts of industrial wastewater were analyzed by the proposed method. DEHP was the most abundant compound found at 21-114 mg/kg x dm, followed by the lower-molecular weight PAEs diethyl phthalate, diisobutyl phthalate, and DBP and the higher-molecular weight compounds butylbenzyl phthalate, dicyclohexyl phthalate, di-n-octyl phthalate, and dinonyl phthalate, which were present mostly at <1 mg/kg x dm.     

High-resolution study of x-ray resonant Raman scattering at the K edge of silicon

We report on the first high-resolution measurements of the K x-ray resonant Raman scattering (RRS) in Si. The measured x-ray RRS spectra, interpreted using the Kramers-Heisenberg approach, revealed spectral features corresponding to electronic excitations to the conduction and valence bands in silicon. The total cross sections for the x-ray RRS at the 1s absorption edge and the 1s-3p excitation were derived. The Kramers-Heisenberg formalism was found to reproduce quite well the x-ray RRS spectra, which is of prime importance for applications of the total-reflection x-ray fluorescence technique.     

Quantitative determination of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and organochlorine pesticides in sewage sludges using supercritical fluid extraction and mass spectrometric detection.

Supercritical CO2 extraction (SFE) proved to be a valuable, fast, quantitative and partly selective extraction technique for determining polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and chlorinated pesticides (OCPs) in sewage sludges of different catchment areas based on a comparison study with certified reference materials (CRMs) and on recovery data. Most PCB extracts could be measured directly after SFE whereas for PAHs a short clean-up improved the final separation by high-resolution capillary gas chromatography. Due to the amount of coextracted compounds and the low levels of OCPs, extracts obtained by SFE had to be submitted to a multistep clean-up for final measurement. Average concentrations of 6.9 mg/kg dry mass (dm) for the sum of the 16 Environmental Protection Agency PAHs, 0.1 mg/kg dm for the sum of the seven PCB congeners and 0.002-0.072 mg/kg dm for the OCPs were found in the sewage sludges. Compared to studies performed earlier in our laboratory PAHs are still present in similar concentrations whereas PCB levels have decreased significantly. OCPs could be detected in only low amounts. A correlation between sludge type and degree of contamination could only be found for PAHs.     

Operator algebras and a theorem of Dieudonne

LetA be aC*-algebra with second dualA″. Let (φ _n)(n=1,...) be a sequence in the dual ofA such that limφ _n(a) exists for eacha εA. In general, this does not imply that limφ _n(x) exists for eachx εA″. But if limφ _n(p) exists whenever p is the range projection of a positive self-adjoint element of the unit ball ofA, then it is shown that limφ _n(x) does exist for eachx inA″. This is a non-commutative generalisation of a celebrated theorem of Dieudonné. A new proof of Dieudonné’s theorem, for positive measures, is given here. The proof of the main result makes use of Dieudonné’s original theorem.     

Optimization of the isocratic non-aqueous reverse phase (NARP) HPLC separation of trans/cis-α-and β-carotenes

Non-aqueous reverse phase chromatography was used to optimize the separation of all-trans-α- and β-carotenes and their cis isomers extracted from dried carrots. The technique can easily be applied to routine assays. Optimization was carried out by modifying the concentrations of methylene chloride and acetonitrile, and by studying the influence of temperature on the capacity factors and selectivity. The effect of the type of C 18 stationary phase bonding (mono- and polyfunctional) on separation was also examined. The need for polymeric bonding on the stationary phase is stressed for the realization of the trans/cis isomer separation.     

Calculation of the molar absorptivity of polyphenols by using liquid chromatography with diode array detection: the case of carnosic acid

Antioxidant activity of vegetable extracts is related to the nature and the amount of active components, mainly polyphenols; therefore, a correct quantification of these molecules should be required to define their concentration in such kind of vegetable extracts. A fast and accurate method to calculate molar absorption coefficients (epsilon), by using HPLC, has been tested on standard polyphenols and caffeine, and should be widely adapted for standardless quantitative analysis. Molar absorptivity (epsilon) of carnosic acid (CA) was determined from 200 to 300 nm, by the proposed method and those values were compared to tert-butyl-hydroxytoluene (BHT) ones for further comparative quantification.