Sensitive HPLC-fluorometric and HPLC-MS determination of diarrhetic shellfish poisoning (SP)-toxins as 4-bromomethyl-7-methoxycoumarin esters

 Extracts containing the diarrhetic shellfish poisoning (DSP) toxins okadaic acid (OA), dinophysistoxin-2 (DTX₂), and dinophysistoxin-1 (DTX₁) were purified on a silica gel cartridge and derivatized with 4-bromomethyl-7 methoxycoumarin (BrMmc). After pre-column derivatization the BrMmc derivatives of the DSP toxins were directly injected into an HPLC system, isocratically eluted, and quantified by fluorescence detection. The signals of the esters showed good linearity in the fluorescence detector within the examined contamination range of 0.03 mg DSP/kg to 2.5 mg DSP/kg. The detection limits for the DSP toxins as 7-Mmc esters were 0.04 ng (corresponding to 0.05 mg DSP/kg). The chromatographic conditions allow to couple the HPLC device with mass spectrometry. The method was tested with various mussel tissue samples. Received: 14 December 1995/Revised: 26 January 1996/Accepted: 30 January 1996     

Topological study of intramolecular hydrogen bonding in beta-hydroxyethylperoxy radical and beta-hydroxyethoxy radical along its dissociation pathway

The presence of intramolecular hydrogen bond (IHB) in beta-hydroxyethylperoxy and beta-hydroxyethoxy radicals was investigated using the QTAIM topological study on UB3LYP/6-311++G(2d,2p) charge densities. Only one of the two conformers of beta-hydroxyethylperoxy radical which were previously considered to present IHB displays a bond critical point (BCP) associated to an IHB. Furthermore, the atomic energies and electron populations indicate no evidence of IHB in the second conformer. Nevertheless, very small differences in molecular energies were obtained using several one-step and multi-step methods (G3, G3B3) between both conformers. No BCP is found between the hydroxyl hydrogen and the oxygen in the most stable conformer or in the transition state for the dissociation path of beta-hydroxyethoxy radical. However, a BCP is formed in the last steps of this path, thereby yielding H-bonded products.     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

Inclusion-dependent mechanism of modification of cyclodextrins with heterocycles

Mono(6-deoxy-dimethylpyridinium)-β-cyclodextrins have been synthesized in reaction of mono (p-toluenesulfonyl) derivative of β cyclodextrin with the appropriate lutidine under microwave irradiation and conventional conditions. The results indicate that the mechanism consists of inclusion complex formation.     

Analysis of urban dust (PM<Subscript>2</Subscript>/PM<Subscript>10-2</Subscript>) in Daejeon city by instrumental neutron activation analysis

Summary As part of an air pollution monitoring study, airborne particulate matter (PM₂/PM_10-2) samples were collected from 2000 to 2003 at two sampling sites in an urban region, Daejeon, the middle of Korea. Mass concentrations of both fine and coarse fractions and that of the black carbon in the fine particles were measured using the Gent stacked filter unit sampler and the smoke stain reflectometer, respectively. In the collected samples the concentrations of 24 elements were analyzed using instrumental neutron activation analysis. Monitored data were investigated for their temporal trends under different environmental conditions and their seasonal correlation patterns. Crustal enrichment factors were also estimated to establish the contribution between anthropogenic and crustal origin. Patterns for airborne particle matter (APM) and elemental concentrations, seasonal variation of some marker elements were investigated. The results can be applied for the investigation of further air pollution sources and for the evaluation of air quality.     

Synthesis of indaphyrins: meso-tetraarylsecochlorin-based porphyrinoids containing direct o-phenyl-to-beta-linkages

The synthesis of indaphyrins, novel meso-tetraarylsecochlorin-derived chromophores incorporating o-phenyl-to-beta-linkages, is described. Oxidative diol cleavage of meso-tetraaryl-2,3-dihydroxy-2,3-chlorins results in the formation of a secochlorin bisaldehyde. Depending on the reaction conditions during the ring cleavage reaction, one or two of the aldehyde groups react with the adjacent o-phenyl positions, leading to an intramolecular electrophilic aromatic substitution of the o-phenyl proton, and the establishment of a direct o-phenyl-to-beta-linkage. The initially formed carbinol is spontaneously oxidized to the corresponding ketone. This modification forces the aryl groups into co-planarity with the macrocycle, allowing for interactions between the pi-electrons of the aryl groups, the ketone linkage, and those of the chromophore, resulting in a significant electronic modulation of the porphyrinic pi-system. The UV-vis spectroscopic properties of the free base, CuII, NiII, and ZnII indaphyrins are discussed.     

Some Comments on the Matter Wave-light Wave Hypothesis

From the de Broglie matter wave hypothesis and Planck’s energy quantization law, and assuming conservation of energy in the absorption of a photon and its consequent conversion to kinetic energy of motion by a material particle initially at rest, one can deduce a simple mathematical relationship between the wavelength λ (or frequency ν), of the photon absorbed by the particle at rest, and the resulting de Broglie matter wave length, λ_D, of the particle with kinetic energy of motion of mv²/2. The relationship so deduced, λ_D∝√λ, suggests that visible wavelengths of light, from about 4000 ?, in the violet, to beyond about 7000 ?, in the red, on absorption by an electron at rest, lead to material electron wavelengths, λ_D, of the order of the size of the electron transfer proteins seen in the photosynthetic reaction centers of photosynthesizing organisms, at about a size of 50–100 ?. In addition to understanding the mechanism of photosynthesis as a material wave mediated phenomenon, further areas of importance of the relations pointed out in this paper are in the design of experiments to gain a deeper understanding of the basic tenets of wave mechanics, and in the use of tunable lasers to probe various properties of material waves, and to precisely control their properties for applications including lithography.     

THE USE OF LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY TO MONITOR THE ALLOMERIZATION REACTIONS OF CHLOROPHYLL a and PHEOPHYTIN a:m IDENTIFICATION OF THE ALLOMERS OF PHEOPHYTIN a

Abstract— This paper reports a new method for monitoring the allomerization reactions of chlorophyll a and pheo-phytin a. Complex mixtures are generated from illuminating pure compounds and monitored using both diode array high-performance liquid chromatography (DAD-HPLC) and liquid chromatography-mass spectrometry (LC-MS). LC-MS allows molecular weight and fragment ion analysis of significant HPLC peaks. Five products of the degradation of chlorophyll a can be simultaneously detected in a mixture, namely the monohydroxy allomer, the methoxylactone allomer, pheophytin a and the two corresponding allomers of the pheophytin. It is demonstrated that more than one pathway must be involved in the in vitro photodegradation of chlorophyll a as shown by the simultaneous existence of several intermediates.     

Thermal and mechanical properties of PE/organoclay nanocomposites

Polyethylene/montmorillonite clay nanocomposites were obtained via direct melt intercalation. The clay was organically modified with four different types of quaternary ammonium salts. The objective of this work is to study the use of montmorillonite clay in the production of nanocomposites by means on rheological, mechanical and crystallization properties of nanocomposites and to compare to the properties of the matrix and PE/unmodified clay nanocomposites. In general, the tensile test showed that the yield strength and modulus of the nanocomposites are close to the pure PE. Apparently, the mixture with Dodigen salt seems to be more stable than the pure PE and PE/unmodified clay.     

Density Functional Theory and Low-Temperature Matrix Investigations of CO-Loss Photochemistry from [(C<Subscript>5</Subscript>R<Subscript>5</Subscript>)Ru(CO)<Subscript>2</Subscript>]<Subscript>2</Subscript> (R = H,Me) Complexes

The photochemical CO-loss products of the diruthenium complexes [CpRu(CO) ₂]₂ (5; Cp = ⁵-C₅H₅), [Cp*Ru(CO)₂]₂ (5*; Cp* = ⁵-C₅(CH₃)₅) and CpCp*[Ru(CO)₂]₂ (5) have been studied experimentally in low-temperature (96 K) matrices in 3-methylpentane by using IR spectroscopy. It is proposed that all three complexes undergo single-CO-loss chemistry but that the products have different structures. The single-CO-loss product from 5 is proposed to have one bridging and two terminal carbonyl ligands, whereas 5* and 5 generate triply bridged CO-loss products similar to that observed from [CpFe(CO)₂]₂ and [Cp*Fe(CO)₂]₂. Double-CO-loss from 5* and 5* 9 is also apparently observed. Relativistic DFT calculations have been carried out on various isomers of the starting materials and on potential CO-loss products from 5. The calculations suggest that the triply bridged product Cp₂Ru₂(-CO)₃ (6) might have a singlet ground state in contrast to the corresponding diiron complex Cp₂Fe₂(-CO)₃ (3), which has a triplet ground state.