Pressurised hot water extraction-microporous membrane liquid-liquid extraction coupled on-line with gas chromatography-mass spectrometry in the analysis of pesticides in grapes

Pressurised hot water extraction-microporous membrane liquid-liquid extraction was coupled on-line with gas chromatography-mass spectrometry (PHWE-MMLLE-GC-MS) for the analysis of pesticides in grapes. MMLLE serves as a trapping step after PHWE. Water from PHWE is directed to the donor side of the membrane unit and the analytes are extracted to the acceptor solution on the other side. The role of MMLLE is to clean and concentrate the extract before on-line transfer to the GC via a sample loop and an on-column interface using partially concurrent solvent evaporation. The extraction conditions were investigated, and then the quantitative features such as linearity, limit of quantification (LOQ), extraction yield and enrichment factors. LOQs in the range 0.3-1.8 microg kg(-1) were achieved. Procymidone and tetradifon were found in the skins of the grapes. The results were in good agreement with those obtained by liquid-solid and ultrasonic extractions.     

On the hypothetical protein F154 of the TTV1 virus/Thermoproteus Tenax. Part II: Synthesis of the trieicosapeptide,corresponding to the protein sequence 79–101

Summary For the identification of a protein predicted by DNA sequence analysis of the TTV1 virus from the archaebacteriumThermoproteus tenax, the trieicosapeptide H-Thr-Pro-Thr-Pro-Thr-Pro-Thr-Tyr-Asp-Ile-Thr-Tyr-Val-Val-Phe-Asp-Val-Thr-Pro-Ser-Pro-Thr-Pro-OH, corresponding to the protein fragment 79–101, was prepared by conventional methods of peptide synthesis. This sequence portion may possibly represent a suitable protein specific immunepitope.

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Zur Hypothese eines TTV1 Virus/Thermoproteus tenax F154-Proteins. Teil II: Synthese des Protein-fragments 79–101

Zusammenfassung Für den Nachweis der Expression des Proteins F154 — nach einer Sequenzanalyse des Genoms des TTV1 Virus im ArchaebakteriumThermoproteus tenax postuliert — wurde das Peptid H-Thr-Pro-Thr-Pro-Thr-Pro-Thr-Tyr-Asp-Ile-Thr-Tyr-Val-Val-Phe-Asp-Val-Thr-Pro-Ser-Pro-Thr-Pro-OH (Proteinfragment 79–101) mit Hilfe konventioneller Peptidsynthese hergestellt. Diese Peptidsequenz sollte ein geeignetes proteinspezifisches Immunepitop darstellen.

     

Preatomization behaviour of Se(-II), Se(IV), and Se(VI) in the graphite furnace without and with matrix modifiers

Summary Using ⁷⁵Se as a radiotracer, the preatomization behaviour of selenium in the graphite furnace was studied. The selenium forms investigated included Se(-II)-methionine, selenite, and selenate in a 0.2% HNO₃ solution, and in a 0.2% HNO₃ solution containing 1% NaCl. The effect of nickel nitrate and of the mixture of palladium/magnesium nitrates as matrix modifiers and of boron nitride coating of the graphite tube on the behaviour of selenium was investigated. The best stabilization effect for all oxidation states of selenium in the conventional graphite tube was achieved by using the mixture Pd/Mg. A considerable degree of modifier-free stabilization of selenuium could be achieved in boron nitride coated tubes. After the conversion of Se(IV) to a volatile piaselenol, a quantitative preatomization separation of Se(IV) from Se(VI) in the boron nitride coated tube was possible. However problems with these newtype tubes still to be solved include the need to increase the thermal stability of the coating.     

Intracellular localization of meso-tetraphenylporphine tetrasulphonate probed by time-resolved and microscopic fluorescence spectroscopy.

The effects of solvent pH on spectral properties and fluorescence decay kinetics were investigated in order to characterize the microenvironment of meso-tetraphenylporphine tetrasulphonate (TPPS4) taken up by cells. Steady-state absorption and fluorescence spectra of TPPS4 in buffer solutions of different pH were used to identify a ring protonated species at pH less than or equal to 4. This dictation could also be distinguished from the unprotonated form by its altered fluorescence decay time (3.5 vs. 11.4 ns). In addition, time-resolved spectroscopy gave some evidence of a monocationic species existing at pH 6-9. This was concluded from the occurrence of another component with a decay time of 5 ns. Measurements of the spectral and kinetic properties of the fluorescence emission of single epithelial cells (RR1022) incubated with TPPS4 indicated that the sensitizer was mainly localized in a microenvironment with a pH of 5, a value which occurs intracellularly only within lysosomes. Cells kept in the dark exhibited the characteristic spectra of both the dication and the neutral form. The fluorescence decay showed two components with decay times of 2.6 ns and 10.6 ns. Irradiation of the cells changed the decay times to 4.6 ns and 13.4 ns and the dication fluorescence emission peak vanished, which is in accordance with the results obtained from buffer solutions at pH greater than or equal to 6. Therefore, we deduce that the photodynamic action leads to a rupture of the lysosomes and that the sensitizer is released into the surrounding cytoplasm.     

Untersuchungen über die Adsorption von Gasgemischen

Zusammenfassung Es werden Mischadsorptionsmessungen am SystemAceton-Chloroform mit einem Dampfdrukminimum an homogenen Oberflächen an Mikroglaskügelchen (2 bis 12 ) in einem rel. Druckbereich zwischen 0,1 und 0,9 ausgeführt. Dabei ist der Sättigungsdruck jeweils der Dampfdruck der mit der Gasphase im Adsorptionsgleichgewicht korrespondierenden flüssigen Phase imp _o , -Diagramm. Zugleich wurde die Zusammensetzung der adsorbierten Mischphase bestimmt und daraus die partielle Adsorption der Komponenten als Funktion des rel. Druckes bei verschiedener Zusammensetzungen der Gasphase.Für partielle Adsorption wurde auf der Grundlage eines vonHill entwickelten Ansatzes in Verbindung mit einer Gl. vonTheimer eine Formel aufgestellt, die die experimentellen Ergebnisse gut wiedergibt.Es werden Adsorptionswärmen für die verschiedenen Belegungsdichten in Abhängigkeit von der Zusammensetzung der Gasphase bestimmt.Mit 18 AbbildungenHerrn Prof.L. Ebert zum 60. Geburtstag gewidmet.     

Combining the lattice-sum and reaction-field approaches for evaluating long-range electrostatic interactions in molecular simulations

A new scheme, the lattice-sum-emulated reaction-field (LSERF) method, is presented that combines the lattice-sum (LS) and reaction-field (RF) approaches for evaluating electrostatic interactions in molecular simulations. More precisely, the LSERF scheme emulates a RF calculation (based on an atomic cutoff) via the LS machinery. This is achieved by changing the form of the electrostatic interactions in a standard LS calculation (Coulombic) to the form corresponding to RF electrostatics (Coulombic plus quadratic reaction-field correction term, truncated at the cutoff distance). It is shown (both analytically and numerically) that in the limit of infinite reciprocal-space accuracy, (i) the LSERF scheme with a finite reaction-field cutoff and a given reaction-field permittivity is identical to the RF scheme with the same parameters (and an atomic cutoff), and (ii) the LSERF scheme is identical to the LS scheme in the limit of an infinite reaction-field cutoff, irrespective of the reaction-field permittivity. This new scheme offers two key advantages: (i) from a conceptual point of view, it shows that there is a continuity between the RF and LS schemes and unifies them into a common framework; (ii) from a practical point of view, it allows us to perform RF calculations with arbitrarily large reaction-field cutoff distances for the same computational costs as a corresponding LS calculation. The optimal choice for the cutoff will be the one that achieves the best compromise between artifacts arising from the dielectric heterogeneity of the system (short cutoff) and its artificial periodicity (long cutoff). The implementation of the LSERF method is extremely easy, requiring only very limited modifications of any standard LS code. For practical applications to biomolecular systems, the use of the LSERF scheme with large reaction-field cutoff distances is expected to represent a significant improvement over the current RF simulations involving comparatively much shorter cutoffs.     

Tetradentate bis(o-iminobenzosemiquinonate(1-)) pi radical ligands and their o-aminophenolate(1-) derivatives in complexes of nickel(II), palladium(II), and copper(II)

The coordination chemistries of the potential tetradentate ligands N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)ethylenediamine, H4[L1], the unsaturated analogue glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil), H2[L2], and N,N'-bis(2-hydroxy-3,5-di-tert-butylphenyl)-2,2-dimethylpropylenediamine, H4[L3], have been investigated with nickel(II), palladium(II), and copper(II). The complexes prepared and characterized are [Ni(II)(H3L1)2] (1), [Ni(II)(HL2)2].5/8CH2Cl2 (2), [Ni(II)(L3**)] (3), [Pd(II)(L3**)][Pd(II)(H2L3) (4), and [Cu(II)(H2O)(L4)] (5), where (L4)2- is the oxidized diimine form of (L3)4- and (L3**)2- is the bis(o-iminosemiquinonate) diradical form of (L3)4-. The structures of compounds 1-5 have been determined by single crystal X-ray crystallography. In complexes 1 and 2, the ligands (H3L1)- and (HL2)- are tridentate and the nickel ions are in an octahedral ligand environment. The oxidation level of the ligands is that of an aromatic o-aminophenol. 1 and 2 are paramagnetic (mu(eff) approximately 3.2 mu(B) at 300 K), indicating an S = 1 ground state. The diamagnetic, square planar, four-coordinate complexes 3 and [Pd(II)(L3**)] in 4 each contain two antiferromagnetically coupled o-iminobenzosemiquinonate(1-) pi radicals. Diamagnetic [Pd(II)(H2L3)] in 4 forms an eclipsed dimer via four N-H.O hydrogen bonding contacts which yields a nonbonding Pd.Pd contact of 3.0846(4) A. Complex 5 contains a five-coordinate Cu(II) ion and two o-aminophenolate(1-) halves in (L4)2-. The electrochemistries of complexes 3 and 4a ([Pd(II)(L3**)] of 4) have been investigated, and the EPR spectra of the monocations and -anions are reported.     

Hochtemperatur-kalorimeter zur genauen bestimmung von mischungsenthalpien

A high-temperature calorimeter is described which permits the measurement of mixing enthalpies of liquid alloys and of solution enthalpies of solid alloys at temperatures ranging up to 1000°C. The suitability of the apparatus is shown by its application to the measurement of the mixing enthalpies of the liquid alloys in the indium-antimony system.     

Stereochemical studies, 47, saturated heterocycles, 25 a simple stereospecific synthesis of oxazasteroids

8-Aza-12-oxasteroids have been synthesized in a simple three-step process. As a consequence of two stareocontrolled reactions, the product is a stereospecifically homogeneous isomer with all-$\text{trans}$ ring junctions; its structure has been determined by ¹H and ¹³C NMR spectroscopy and X-ray diffraction.     

Trace and major element compositions of Black Sea aerosol

Instrumental neutron activation analysis (INAA), flame atomic absorption spectrometry (FAAS), flame atomic emission spectrometry (FAES), graphite furnace atomic absorption spectrometry (GF-AAS), ion chromatography (IC) and visible spectrometry (VIS) were used to determine the composition of atmospheric aerosols, collected at a rural site in the Western Black Sea Coast of Turkey. A total of 354 daily aerosol samples were analyzed for 46 trace and major elements and ions. Sample preparation, quality control procedures, instrumental operating conditions for INAA and source apportionment work is presented.