μ+ relaxation correlated with susceptibility in the van‐Vleck paramagnet PrIn3

A previously unobserved increase of the magnetic susceptibility in PrIn₃ at low temperatures is reported. The increase is shown to correlate nicely with a large increase in the transverse μSR depolarization rate. Evidence supports the conclusion that both phenomena are related to some degree of atomic disorder in the structure, and an associated strong Pr CEF level changes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Polarographische Bestimmung von Dimethylnitrosamin in Fischprodukten

Zusammenfassung Es wird ein Verfahren zur polarographischen Bestimmung von Dimethylnitrosamin in Fischprodukten beschrieben. Die Abtrennung aus dem Probenmaterial erfolgt zur Vermeidung von Verlusten durch Destillation im Vakuum unterhalb von 40° C. Störende Stoffe werden aus dem Destillat durch Durchleiten von Stickstoff entfernt.

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Summary A procedure for the polarographic determination of dimethylnitrosoamine in fish products is proposed. The separation from the sample material is achieved by distillation in vacuum below 40° C in order to prevent losses. Interfering substances are removed from the distillate by deaerating with nitrogen.

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Vorliegende Arbeit wurde auf Anregung von Fiskeridirektoratets Kjemisk-Tekniske Forskningsinstitutt und von Sildolje- og Sildemelindustriens Forskningsinstitutt begonnen und ihre Weiterführung durch Mittel des Norges Teknisk-Naturvitenskapelige Forskningsråd ermöglicht, wofür an dieser Stelle bestens gedankt wird.     

Dye-sensitized SnO2 electrodes with iodide and pseudohalide redox mediators

Dye-sensitized mesoporous nanocrystalline SnO2 electrodes and the pseudohalogen redox mediator (SeCN)2/SeCN- or (SCN)2/SCN- or the halogen redox mediator I3-/I- were implemented for regenerative solar cell studies. Adsorption isotherms of the sensitizers Ru(deeb)(bpy)2(PF6)2, Ru(deeb)2(dpp)(PF6)2, and Ru(deeb2(bpz)(PF6)2, where deeb is 4,4'-diethylester-2,2'-bipyridine, dpp is 2,3-dipyridyl pyrazine, and bpz is bipyrazine, binding to the SnO2 surface were well described by the Langmuir model from which the saturation coverage, Gamma0 = 1.7 x 10(-8) mol/cm2, and surface-adduct formation constant, Kad = 2 x 10(5) M(-1), were obtained. Following excited-state interfacial electron transfer, the oxidized sensitizers were reduced by donors present in the acetonitrile electrolyte as shown by transient absorption spectroscopy. With iodide as the donor, a rate constant k > 10(8) s(-1) was measured for sensitizer regeneration. In regenerative solar cells, it was found that the incident photon-to-current conversion efficiencies and open circuit voltages (Voc) were comparable for (SeCN)2/SeCN- and I3-/I- for all three sensitizers. The Voc varied linearly with the logarithm of the short circuit photocurrent densities (Jsc), with typical correlations of approximately 50-60 mV/decade. Capacitance measurements of the SnO2 electrode in the presence of I3-/I-, (SeCN)2/SeCN- or (SCN)2/SCN- are reported.     

Quantification of volatile solvents in blood by static headspace analysis

A static headspace method for determination of volatile solvents in blood was developed. The solvents determined were 1,1,1-trichloroethane, toluene, xylene (o-, m- and p-), ethylbenzene, styrene, alpha-methylstyrene and 4-methylstyrene at concentrations ranging from 0.01 to 1 mug/ml. Internal standard calibration was used. Parameters affecting sensitivity and precision were determined and optimized.     

Isothiocyanate controlled architecture,spectroscopic, and magnetic behavior of copper(II) l–arginine complexes

Abstract

We synthesized an l–arginine complex with the formula [Cu(l–Arg)₂(NCS)]·(NCS)·H₂O (1) (l–Arg = l–arginine). Two cis-chelated l–arginine zwitterions form the basal plane, while the weakly N-bonded isothiocyanate is located at the apex of the distorted square pyramidal structure (τ?=?0.143). The non-coordinated NCS^? anions held layers together in a 3-D supramolecular network. The crystal structure, spectroscopic (FT–IR, Raman, NIR–Vis–UV, EPR) and magnetic properties of 1 have been compared with [Cu(l–Arg)(NCS)₂] (2). For 1, two absorptions are observed for ν(C?=?N) stretching vibrations, corresponding to NCS^? ions N-bonded to the central Cu(II) (2077?cm^?1) and in the lattice (2057?cm^?1). In 2 a single band is observed at 2102?cm^?1, indicating equivalent NCS^? ions in the structure. The EPR spectra of complexes show anisotropic signal with g_⊥ and g_|| 2.062, 2.235 (1), and 2.08, 2.225 (2) characteristic for cis-N₂O₂ and N₃O donor sets in the xy plane, respectively. The unpaired electron mainly occupies the d_x2–y2 orbital, also confirmed by the single envelope of d–d bands at ca. 16,000?cm^?1 for 1 and 16,500?cm^?1 for 2. The magnetic properties ofcompounds are characteristic of a very weak antiferromagnetic interaction with J?=??0.055?cm^?1 and J?=??0.096?cm^?1 for 1 and 2, respectively.     

Determination of alpha-tocopherol in infant foods by liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometry

A novel, sensitive and specific method for the quantification of alpha-tocopherol in two infant foods (milk and cereals) using liquid chromatography on-line with positive atmospheric pressure chemical ionisation mass spectrometry detection (LC/APCI-MS) has been developed. The samples were first saponified in order to eliminate fats and to transform tocopherol esters into free tocopherol, followed up by a liquid-liquid extraction of the analyte in petroleum benzine/diisopropyl ether (75:25, v/v) prior to injection onto the LC system. For the quantification, deuterium-labelled tocopherol was used as internal standard and the samples were monitored in selected ion monitoring (SIM) mode. Calibration curves between 1-40 microg/mL of alpha-tocopherol showed a good linear correlation (r(2) = 0.99994), and the detection limit was determined to be 2.5 ng/mL. The within-day and between-day precision were determined for several dietetic infant formulae and certified reference samples, and found to be below 3.5%. The accuracy determined on a Nestlé reference sample (milk powder) was calculated to be 115.2 +/- 1.2%, which confirms the robustness of the proposed method. This study shows that single quadrupole LC/MS can be applied for the quantification of vitamins in food and the method offers better sensitivity and selectivity than traditional method such as LC-UV. This would simplify the preparation of the food samples and consequently enhance the vitamin analysis throughput in the food area.     

Superspreading driven by Marangoni flow

The spontaneous spreading (called superspreading) of aqueous trisiloxane ethoxylate surfactant solutions on hydrophobic solid surfaces is a fascinating phenomenon with several practical applications. For example, the ability of trisiloxane ethoxylate surfactants to enhance the spreading of spray solutions on waxy weed leaf surfaces, such as velvetleaf (Abutilion theophrasti), makes them excellent wetting agents for herbicide applications. The superspreading ability of silicone surfactants has been known for decades, but its mechanism is still not well understood. In this paper, we suggest that the spreading of trisiloxane ethoxylates is controlled by a surface tension gradient, which forms when a drop of surfactant solution is placed on a solid surface. The proposed model suggests that, as the spreading front stretches, the surface tension increases (the surfactant concentration becomes lower) at the front relative to the top of the droplet, thereby establishing a dynamic surface tension gradient. The driving force for spreading is due to the Marangoni effect, and our experiments showed that the higher the gradient, the faster the spreading. A simple model describing the phenomenon of superspreading is presented. We also suggest that the superspreading behavior of trisiloxane ethoxylates is a consequence of the molecular configuration at the air/water surface (i.e. small and compact hydrophobic part), as shown by molecular dynamics modeling. We also found that the aggregates and vesicles formed in trisiloxane solutions do not initiate the spreading process and therefore these structures are not a requirement for the superspreading process.     

Synthesis of some 1,3,8-trisubstituted pyrimido[4,5-c][2,7]-naphthyridin-6-ones as potential antitumor agents

Condensation of three 2,4-disubstituted 6-aminopyrimidines with methyl 1-benzyl-4-oxo-3-piperidinecarboxylate afforded, in each case, new tricyclic, angular 1,3,8-trisubstituted pyrimido[4,5-c][2,7]naphthyridin-6-ones. 2,4,6-Triaminopyrimidine gave the 7,8,9,10-tetrahydrocyclo condensed product 5 as anticipated. However, the use of 2-amino-4-oxo- or 2,4-dioxo-6-aminopyrimidine afforded the dehydrogenated, 9,10-dihydrotricyclic products 11 and 12 . The growth of leukemia L1210 cells in culture were inhibited 50% by the 1,3-diamino analog 5 at 2 × 10⁻⁶M and by the 1,3-dioxo analog 12 at 10⁻⁵M.     

Targeted borate complex formation as followed with electrospray ionization Fourier transform ion cyclotron mass spectrometry: monomolecular model system and polyborate formation

Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) was applied to identify boric acid(B degrees)/borate(B-) complexes in a monomolecular model system, composed of aqueous caffeic acid and boric acid/borate solutions in various concentration ratios at pH 9.2. Using negative mode electrospray ionization as a 'soft' ionization technique, clusters of polyborate were detected beside the well-known BL degrees , BL- and BL2- complexes. An algorithm for the detection of boron complexes, based on their accurate mass and isotope patterns, is proposed which enabled the assignment of elemental compositions/structural formulae of boron/ligand complexes. We present experimental evidence of self-oligomerization of up to six borate units with caffeic acid, resulting in stable covalently bound polyborate-polyol complexes.     

Halide coordination to zinc porphyrin sensitizers anchored to nanocrystalline TiO2

The coordination of halide ions to 5-(3,5-dicarboxyphenyl)-10,15,20-tri- p-tolylporphinatozinc(II) anchored to mesoporous nanocrystalline (anatase) TiO 2 thin films (TiO 2/ZnP) immersed in propylene carbonate was quantified. The addition of tetrabutylammonium halide salts to the external propylene carbonate electrolyte resulted in a red shift in the absorption spectrum with the maintenance of five isosbestic points. The absorption spectra were within experimental error the same for ZnP and ZnP-X (-) compared to TiO 2/ZnP and TiO 2/ZnP-X (-): A SoretZnP = 427 nm (epsilon = 574 000 M (-1) cm (-1)), A SoretZnP-Cl (-) = 435 nm (epsilon = 905 000 +/- 12 000 M (-1) cm (-1)), A SoretZnP-Br (-) = 436 nm (epsilon = 776 000 +/- 30 000 M (-1) cm (-1)), and A SoretZnP-I (-) = 437 nm (epsilon = 620 000 +/- 56 000 M (-1) cm (-1)). Titration studies with the halides revealed sharp isosbestic points consistent with formation of a 1:1 halide/porphyrin adduct. Equilibrium constants for ZnP were found to be 1670 M (-1) for Cl (-), 96 M (-1) for Br (-), and 5.5 M (-1) for I (-), and the corresponding values for TiO 2/ZnP were significantly smaller, 780 M (-1), 70 M (-1) and 3.4 M (-1). A quasi-reversible wave was observed by cyclic voltammetry of TiO 2/ZnP, E 1/2(ZnP (+/0)) = +790 mV vs Ag/AgCl, that was shifted 160 mV after addition of excess chloride, E 1/2(ZnP-Cl (0/-)) = +630 mV. In regenerative solar cells with quinone/hydroquinone redox mediators, TiO 2/ZnP and TiO 2/ZnP-X (-), where X is Cl, Br, or I, were found to convert light into electrical power. The photocurrent action spectrum demonstrated that energy conversion was initiated by light absorption of ZnP and/or the halide adduct.