Chemiluminescence Determination of Glucose, Fructose and their Mixture by the Stopped-Flow Mixing Technique

 The chemiluminescence reaction of lucigenin with glucose and fructose in the presence of Brij-35 and in alkaline solution was used to develop kinetic methods for the determination of both hexoses individually and mixed together. A stopped-flow mixing module coupled to a photomultiplier tube allowed kinetic and equilibrium measurements, which were used for the individual determination of glucose and fructose. The same measurements were used to analyse the mixture of both sugars using a two equation system, which was resolved by multiple linear regression. The ranges of the calibration graphs obtained by using kinetic and equilibrium measurements were 25–1000 μg ml⁻¹ and 75–1100 μg ml⁻¹, respectively, for glucose and 1–350 μg ml⁻¹ and 5–250 μg ml⁻¹, respectively, for fructose. Mixtures of glucose and fructose in ratios between 1:0.4 and 40:1 were satisfactorily resolved. Received February 27, 2002; accepted August 6, 2002     

Synthesis and characterization of a new iron (II)— dinitrogen compound with PDTA as ligand

A new dinitrogen complex of formula Na₂[Fe(PDTA) (N₂] (H₂O)₂ has been synthesized in aqueous solution from [Fe(H-PDTA) (H₂O)], 3/2H₂O and NaN₃. The complex has been characterized by chemical analysis, IR and electronic spectra, and magnetic measurements. The thermal decomposition process has been studied by using DTA and TG techniques. The evolution of gases was followed by Gas Chromatography.     

Microwave spectra of deuterated furans. Revised molecular structure of furan

The microwave spectra of furan, [2-D], [3-D] and [2,5-D₂] furans have been reinvestigated. Also the spectrum of [D₄]furan was assigned and measured. Determination of atomic coordinates by mono- and disubstitution is discussed. The complete substitution structure has been redetermined confirming results of earlier work.     

über das ?therische ?l des kretischen Diptams Origanum dictamnus L.

The essential oil from the leaves of the greek plant dictamnos, Origanum dictamnus L., Amaracus dictamnus L., Amaracus tomentosus Moench, was subject to gaschromatographic and mass spectrometric analysis. 9 substances could be identified, the main component being carvacrol. No pulegone was found.     

Dense Linear Manifolds of Monsters

In this paper the new concept of totally omnipresent operators is introduced. These operators act on the space of holomorphic functions of a domain in the complex plane. The concept is more restrictive than that of strongly omnipresent operators, also introduced by the authors in an earlier work, and both of them are related to the existence of functions whose images under such operators exhibit an extremely wild behaviour near the boundary. Sufficient conditions for an operator to be totally omnipresent as well as several outstanding examples are provided. After extending a statement of the first author about the existence of large linear manifolds of hypercyclic vectors for a sequence of suitable continuous linear mappings, it is shown that there is a dense linear manifold of holomorphic monsters in the sense of Luh, so completing earlier nice results due to Luh and Grosse-Erdmann.     

Simultaneous determination of p-hydroxybenzoic acid and parabens by capillary electrophoresis with improved sensitivity in nonaqueous media

New methods based on nonaqueous capillary electrophoresis (NACE) were developed as promising alternatives for the simultaneous separation and determination of p-hydroxybenzoic acid (PHBA) and a group of parabens (methyl, ethyl, propyl, butyl and benzyl p-hydroxybenzoates), with good resolution and excellent sensitivity. As an effective on-line preconcentration technique, large-volume sample stacking (LVSS) was successfully combined with NACE allowing significant sensitivity enhancement. Identification and quantification of the analytes were performed by diode array detection (DAD). The influence of different parameters, such as buffer apparent pH, concentration of electrolyte, temperature, applied voltage and sample volume, on the efficiency, resolution and sensitivity of the electrophoretic separation was studied. The analytical performance was evaluated, and both NACE-DAD and LVSS-NACE-DAD methods showed good linearity, precision and instrumental LODs at low ng/mL levels. These LODs were compared with those described in the literature, and it was found that NACE-DAD method was comparable to GC-MS, while LVSS-NACE-DAD procedure achieved sensitivity similar to LC-MS, LC-MS/MS and GC-MS/MS, even using conventional ultraviolet-visible absorption detection. To test their suitability, proposed methods were evaluated for the analysis of PHBA and parabens at low and sub-ng/mL levels in environmental water samples.     

Ground state isomerism in betacarboline hydrogen bond complexes: The charge transfer nature of its large Stokes shifted emission

The hydrogen bonding and excited state proton transfer reactions between betacarboline, 9H-pyrido[3,4-b]indole, BC, and 1,1,1,3,3,3-hexafluoropropan-2-ol, HFIP, have been studied in the aprotic solvents cyclohexane and toluene by absorption, steady state and time resolved fluorescence measurements. On the basis of these results and those of previous works (Refs. [A. Sánchez-Coronilla, C. Carmona, M.A. Muñoz, M. Balón, Chem. Phys., 327 (2006) 70] and [A. Sánchez-Coronilla, M. Balón, M.A. Muñoz, C. Carmona, Chem. Phys. 344 (2008) 72]) two main fundamental conclusions can be drawn on the photophysical behaviour of BC. Thus, it is shown, for the first time, that the non-cyclic double hydrogen bond complexes formed through both nitrogen atoms of BC, DHB, can suffer, in their ground state, an isomerisation process. These adducts acquire a quinoid structure in cyclohexane, but maintain a dipolar zwitterionic structure in toluene. Moreover, it is concluded that the observed large Stokes shifted emission, around 520 nm, is not due, as it has been so far generally accepted, to the emission of a BC zwitterionic phototautomer, but to the intramolecular charge transfer, ICT, excited state emissions of the DHB hydrogen bond adducts.