Two dimensional TLC determination of PAH in diluted automobile exhaust gases

A method is described for the determination of polycyclic aromatic hydrocarbons (PAH) in the diluted exhaust gas of diesel vehicles. Sampling is done by drawing off proportional streams from the dilution tunnel. The particulates deposited on filters are sublimed, and the sublimate is purified and prefractionated on silica gel. Further separation and quantitative determination of the PAH is performed by two dimensional TLC in conjunction with In situ fluorescence spectrometry. Results of theoretical considerations and experimental data on the distribution of the emitted PAH between particulate matter and the corresponding gas phase in diluted exhaust are presented. A modified Langmuir adsorption model is used to explain the effects of dilution ratio and sample temperature in the dilution tunnel. Comparison of the emission values for PAH obtained from diluted and undiluted exhaust shows good agreement. Furthermore, the PAH contents of the exhaust gas of several diesel-engined cars are also compared for various driving cycles.     

Über enolisierte Derivate der Chlorophyllreihe. 132-Desmethoxycarbonyl-173-desoxy-132,173-cyclochlorophyllid a-enol und eine Methode zur Einführung von Magnesium in porphinoide Ligandsysteme unter milden Bedingungen. (Vorläufige Mitteilung)

Enol derivatives in the chlorophyll series. 13²-Desmethoxycarbonyl-17³-desoxy-13²,17³-cyclochlorophyllide a-enol and a method for the introduction of magnesium into porphinoid ligands under mild conditions Magnesium transfer from the iodo-magnesium salt of 3,5-di-t-butyl-4-hydroxy-toluene (BHT) into methyl pheophorbide a is a fast process in methylenechloride/ether solution at ambient temperature. This procedure for the introduction of magnesium into labile chlorin ligands has made possible the preparation of a crystalline 13², 17³-cyclochlorophyllide a-enol. Concomitant use of the lithium salt of BHT facilitates the more critical insertion of magnesium into methyl bacteriopheophorbide a. The preparative success of these magnesium transfers depends crucially upon the solvent system used. Under conditions where the complexation of methyl pheophorbide a with iodo-magnesium-BHT is essentially complete within 2 minutes at 12° in methylenechloride/ether solution, strong inhibition of the magnesium transfer is observed by cosolvents such as pyridine, dimethylacetamide, dioxan or tetrahydrofuran.     

Strukturen caesiumhaltiger Fluoride. V. Die pseudohexagonale Wolframbronzestruktur der monoklinen Phase Cs0,4Zn0,4Fe1,6F6 und verwandter Cäsium-Übergangsmetallfluoride

Structures of Cesium-containing Fluorides. V. Pseudohexagonal Tungsten Bronze Structure of the Monoclinic Phase Cs_0.4Zn_0.4Fe_1.6F₆ and Related Cesium Transition Metal Fluorides The crystal structure of the pseudohexagonale phase Cs_0.4Zn_0.4Fe_1.6F₆ was refined in the monoclinic space group P2₁ (a = 747.4, b = 763.6, c = 746.1 pm, β = 120.0°, z = 3). Using 1067 single crystal reflections R = 6.3% was reached. Compared to the hexagonal tungsten bronze structure the corner-sharing of octahedra shows pronounced angles also along the unique axis (M? F? M = 159.0°). The average bridge angle in the framework of tilted octahedra is 149.6°. Structural relations are discussed.     

Zur Komplexbildung von N-(Thiocarbamoyl)benzamidinen

Complex Formation of N-(Thiocarbamoyl) benzamidines N-(Thiocarbamoyl)benzamidines 1 and N-(Thiocarbamoyl)-N′-phenyl-benzamidines 2 form in alcoholic solutions with Ni²⁺, Cu²⁺, Pd²⁺, Co³⁺, and Ag⁺ ions well crystallized chelates 1a ? h and 2a? h , respectively, with N/S coordination. The X-ray photoelectron spectra evidence the NH group as ligator in the case of chelates of 1 and the increased donor capacity compared with the isosteric oxygen ligator atom bound to nickel. This is confirmed by d-¹H-n.m.r. spectroscopy analyzing the value of ΔG_c^≠ for the rotational barrier for the Et₂N group of 1a     

Quality assurance in pesticide residue analysis

Summary During the last few years, the Working Group Pesticide Residues of the Food Chemistry and Forensic Chemistry Division of the Gesellschaft Deutscher Chemiker (German Chemical Society) has organised six laboratory performance tests on the analysis of pesticide residues in which numerous laboratories were involved. In these tests the choice of the analytical methods for the examination of fats or vegetable substrates was free. Organochlorine pesticides in concentrations of over 0.01 mg/kg were mostly readily identified, whereas in the analysis of organophosphorus residues often only the classic compounds (parathion, diazinon, etc.) were reported. Many a false positive result could have been avoided by using more adequate methods for confirmatory analysis. The quantitative results, however, were generally quite reliable and were mostly within the official acceptable dispersion range. It can be concluded that the performance of a residue laboratory is by no means constant, and that it is necessary to assess regularly the quality of the analytical results by participating in such interlaboratory tests.

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Qualitätssicherung bei Rückstandsanalysen von PflanzenschutzmittelnErfahrungen aus Ringversuchen

     

Large Scale Bioprocess for the Production of Optically Pure <Emphasis Type="Italic">L</Emphasis>-Carnitine

Summary. A competitive production method using the biotransformation of 4-butyrobetaine to enantiomerically pure L-carnitine was developed and scaled-up by Lonza. The process produces L-carnitine in 99.5% yield, and >99.9% enantiomeric excess (ee). Continuous and discontinuous processes were developed but the fed-batch process was found to be economically the most favourable process mode.