Quantitative goldbestimmung in filmmaterialien mittels flammenloser atomabsorption

A graphite rod electrothermal atomizer has been used for the AAS determination of traces of gold in hydrochloric and in hydrobromic acid solutions, and also after extraction into HBr-saturated methyl isobutyl ketone. Photographic film samples were decomposed first by enzyme action then by nitric acid/peroxide oxidation, and the gold was extracted into MIBK. For 10-μl aliquots of solution the 3s limits of detection were 3 × 10^?10g for aqueous solutions, 7 × 10^?10g for MIBK, and 7 × 10^?9 g/cm² for film.     

Preconcentration and determination of Sn- and Pb-organic species in environmental samples by SPME and GC-AED

A new sample preparation and preconcentration technique - solid phase microextraction (SPME) - is reported for the application of several tinorganic compounds and tetrabutyllead in aqueous samples. The solvent-free procedure is rapid in comparison with liquid-liquid extraction or SFE but also sensitive. Analytical variables of the extraction such as adsorption and desorption time, stirring rate and temperature has been investigated. The determination has been performed by GC coupled with atomic emission detection (AED). After optimization of the conditions of SPME a calibration was realized on the basis of a multicomponent standard solution, prepared by ethylation of organotin salts directly in the sample using sodium tetraethylborate (NaBEt(4)) without prior separation of the analytes from the matrix. The method permits preconcentration. Values of about 10 can be reached. A detection limit of 0.09 pg Sn and 0.08 pg Pb can be achieved under optimized conditions. The proposed procedure has been successfully applied to the analysis of organotin compounds in various slurry samples.     

Métallation et alkylation des thioimidoesters: application en synthèse

Alkylation of delocalized anions resulting from metallation of N-phenyl thioimidoesters (precursors of dithioesters and thiolesters) takes place on nitrogen with “saturated” thioimidoesters (alkane thiomidates). On the contrary, unsaturated thiomidoesters (α or β-ethylenic, α-arylated) are regioselectively alkylated on the α carbon atom by alkyl or allylic halides. The possibilities for synthesis offered by successive uses of the reactivities of thioimidoester and dithioester functions (allowing in particular two electrophilic additions on two vicinal carbons) are illustrated by the syntheses of terpenic compounds lavandulal (and lavandulol) and ar-curcumene.     

Straightforward Synthesis of 2‐Aryl‐1‐alkynylphosphonates and Arylpropiolates

A protocol for the direct cross coupling of trialkylsilyl‐alkynes bearing electron‐withdrawing groups and aryl halides using a Pd/Ag catalytic system is described. The procedure allows the straightforward synthesis of a variety of alkynylphosphonates and aryl propiolates derivatives in good yields.     

Photoleitfähigkeit additiv verfärbtet SrF2-Kristalle

Additively coloured SrF₂ crystals proved to be photoconducting in the region of the coloration bands from 700 to 200 nm, the photocurrents showing some characteristics of photoelectric primary currents. Without applying an external voltage the same photoresponse is measured in the polarizing field of the crystals. Photoelectric excitation (analogous to theF′-centres in crystals of the NaCl-type) could not positively be established. The assignment of the relative spectral photosensitivity to the absorption spectra of the coloured crystals has not yet been possible. In interpreting the photoconduction effects it cannot completely ruled out whether chemical impurities play some part in the photoconduction process.     

Concerning Papaver bracteatum Lindl. On the structure of the Alkaloids E

From Papaver bracteatum LINDL . «Halle III» a new alkaloid representing the rhoeadine type has been isolated, the structure of which was elucidated by means of high resolution mass spectrometry and NMR. spectroscopy mainly.     

AAS-Untersuchungen über Verdampfungs- und plasmaprozesse in der Graphitrohrküvette Zur Optimierung der Bestimmungen von Cd-, Zn- und Mn-Spuren in AIIIBV-Halbleiter-Matrices

As a basis for optimizing the analysis conditions for the determination of traces of Cd, Zn and Mn in A^III B^V semiconductor samples by graphite furnace atomic absorption spectrometry (AAS), the authors made a systematic investigation of the matrix effects. The evaporation behaviour of the matrices was studied to assess the possibility of thermal separation of trace element and matrix. Absorption spectra of Ga³⁺ and In³⁺ matrices in 1 N HCl and 1 N HNO₃ between 190 and 330 nm were measured to explain unspecific absorption effects. Intense absorption bands were identified as originating from the diatomic molecules GACl, InCl, GaO and InO. Absorbance vs time curves were determined to study the effects of the matrices on the AA signals. It was established that the formation of diatomic molecules in the gaseous state is a major cause of signal depressions. This effect occurs when the analytes and the matrices or their anionic components evaporate concomitantly. Strong signals depressions were found when the matrices were present in hydrochloric acid (formation of CdCl, ZnCl and MnCl), but not when nitric acid was used. The eventually adopted analytical conditions were chosen so as to make an optimum use of the thermal hydrolysis of the matrices. A detailed discussion of the results is presented and it is shown that direct trace determinations with nitric acid solutions are feasible below the ppm (μg/g) level with a sample size of 0.01 to 0.2 mg.     

Detection of arsenic-containing hydrocarbons in canned cod liver tissue

Arsenic is a metalloid well known to be potentially toxic depending of its species. Lipid-soluble arsenicals (arsenolipids) are present in a wide range of biological samples in which they could play a role in the biosynthesis of organoarsenic compounds from inorganic arsenic compounds. Arsenolipids have recently attracted considerable interest. In order to gain deeper insights into the impact of arsenolipids new analytical approaches for reliable determination of this class of arsenic-containing hydrocarbons in various matrices are needed.High concentrations of arsenolipids were found in seafood which served as sample material in this study. We report the investigation of three arsenolipids found in canned cod liver from which they were extracted and purified by solid phase extraction (SPE) using a silica gel column and ethyl acetate/methanol as eluent. Analytical studies were conducted by means of gas chromatography coupled with ICP-MS, MIP-AES and EI-qMS and by TOF-MS. The results obtained by GC-ICP-MS and GC-MIP-AES showed the existence of numerous arsenic compounds in the SPE fractions collected. Three major peaks were found within a retention time window between 10 and 25 min. The presence of arsenic compounds in the fish tissue could be confirmed using GC-EI-qMS analysis. Corresponding information of the molecular weights of the major arsenic species were provided by TOF-MS which allows highly accurate mass determinations. The results showed the presence of the arsenic-containing hydrocarbons with the following molecular formulas: C₁₇H₃₇AsO (calculated for [M+H]⁺ 333.2133; found 333.2136; Δm = 0.90 ppm); C₁₉H₄₁AsO (calculated for [M+H]⁺ 361.2446; found 361.2446; Δm = 0.00 ppm); C₂₃H₃₇AsO (calculated for [M+H]⁺ 405.2133; found 405.2145; Δm = 2.96 ppm). Suggestions for the corresponding structures are discussed.