Partial structure elucidation of the most abundant octa and nonachlorotoxaphene congeners in marine mammals by using conventional electron ionization mass spectrometry and mass spectrometry/mass spectrometry

Summary Conventional electron ionization (EI) mass spectrometry (MS) and MS/MS techniques were applied to the analysis of two abundant octa and nonachlorobornanes isolated from seals of the Baltic sea and originating from technical toxaphene. The exact sterical structures of the two compounds were previously determined using nuclear magnetic resonance (NMR) spectroscopy by two independent research groups. The MS and MS/MS data generated in this study allowed partial structure elucidation of these polychlorobornanes, in particular revealing the distribution of the Cl substituents between the six-membered carbon ring, the bridge and the bridgehead in the parent bornane structure. Fragmentation of the six-membered carbon ring and the bridge by retro-Diels-Alder (RDA) and related mechanisms was discovered by studying specific parent/daughter ion transitions. The detailed fragmentation pathways formulated may be applicable to the structure elucidation of other toxaphene congeners and the monitoring of strategic transitions is highly selective for the detection of these compounds in technical toxaphene and in environmental samples.     

HPLC isolation and NMR structure elucidation of the most prominent octabromo isomer in technical octabromo diphenyl ether

The major octabromo isomer of technical octabromo diphenyl ether mixture (technical octaBDE) DE-79 was isolated by RP-HPLC. Three serially coupled columns (each 250 mm long) enabled a good separation of the target compound from other congeners using 100% ACN as eluent. Approximately 100 microg of the target compound was isolated with a purity of >90% and investigated by MS for confirmation of the degree of bromination. 1H-NMR and 2-D 1H-13C correlation NMR spectra unequivocally clarified that the octaBDE in question is 2,2',3,3',4,4',6,6'-octabromodiphenyl ether (BDE 197). Based on annual production rates of technical BDE products (1999/2001), approximately 380 tons of BDE 197 were annually produced which, on the long term, may enter the environment. Compared with other individual BDE congeners, BDE 197 has the seventh highest application rate. Reductive debromination of BDE 197 can lead to four hepta-, 15 hexa-, 23 penta-, and 28 tetra-BDE isomers, respectively. This variety includes all known major BDEs of environmental concern (BDE 47, 85, 99, 100, 153, 154, and 183). The identification of BDE 197 in technical octaBDE DE-79 strongly suggests that research on the environmental fate of BDEs should include this key-BDE congener.     

Isotope shift measurements in titanium I

The use of an effusive beam of titanium atoms crossed with a CW single-mode tunable dye laser has allowed the high-resolution, Doppler-free study of the isotope shifts between⁵⁰Ti,⁴⁸Ti and⁴⁶Ti, for seven 3d ² 4s ² a³ F _J 3d ² 4s 4p z ⁵ D _J , visible transitions of Ti I. The measurements show without ambiguity the existence of a non-negligible field shift. Using the values of the nuclear radii of titanium (coming from muonic X-ray measurements), it is possible to determine the respective values of the field and mass shifts.     

Die Massenspektren der Pyrrolidide einiger aliphatisch-alicyclischer Carbonsäuren

The mass spectra of the pyrrolidides of some long-chain carboxylic acids with alicyclic residues attached to their ω-end are discussed and compared with the spectra of the corresponding esters. Fragmentation triggered by the pyrrolidide group generates a series of peaks, which clearly exhibits the size and the structure of the carbon chain.     

Trace analysis of metals in plant samples with inductively coupled plasma – mass spectrometry

An analytical method for the quantitative determination of Al, Ti, V, Cr, Co, Ni, Cu, Zn, Mo, Cd, Ti and Pb in plant samples by ICP-MS has been developed. Spectral interferences, plant matrix effects, precision and accuracy are discussed. Results are demonstrated for selected samples concerned with the mass balance of heavy metals after utilization of non-food vegetable materials in a power plant. Received: 7 January 1997 / Revised: 2 June 1997 / Accepted: 18 June 1997     

Isotope shift and hyperfine structure measurements in titanium I

High accuracy measurements of hyperfine structure due to⁴⁷Ti and⁴⁹Ti in the 3d ² 4s ² a ³ F ₂?3d ² 4s4p z ⁵ D ₁ absorption line at σ=18482.772 cm^?1 have been performed by use of a Doppler-free experiment, where a beam of titanium atoms is crossed by a CW single mode tunable dye laser. They have allowed for the determination of isotope shifts between⁴⁶Ti,⁴⁷Ti,⁴⁸Ti,⁴⁹Ti and⁵⁰Ti. By use of accurate values of mean square nuclear charge radii for the even isotopes, it has been possible to separate mass shifts from field shifts and to determine accurate values for the mean square nuclear charge radii of⁴⁷Ti and⁴⁹Ti. The field shift presents a marked odd-even staggering.     

Microwave-assisted extraction and accelerated solvent extraction with ethyl acetate-cyclohexane before determination of organochlorines in fish tissue by gas chromatography with electron-capture detection

Focused open-vessel microwave-assisted extraction (FOV-MAE), closed-vessel microwave-assisted extraction (CV-MAE), and accelerated solvent extraction (ASE) were used for extraction before determination of organochlorine compounds (polychlorinated biphenyls, DDT, toxaphene, chlordane, hexachlorobenzene, hexachlorocyclohexanes, and dieldrin) in cod liver and fish fillets. Wet samples were extracted without the time-consuming step of lyophilization or other sample-drying procedures. Extractions were performed with the solvent mixture ethyl acetate-cyclohexane (1 + 1, v/v), which allowed direct use of gel-permeation chromatography without solvent exchange. For FOV-MAE, the solvent mixture removed water from the sample matrix via azeotropic distillation. The status of water removal was controlled during extraction by measuring the temperature of the distillate. After water removal, the temperature of the distillate increased and the solvent mixture became less polar. Only the pure extraction solvent allowed quantitative extraction of the organochlorine compounds. For CV-MAE, water could not be separated during the extraction. For this reason, the extraction procedure for wet fish tissue required 2 extraction steps: the first for manual removal of coextracted water, and the second for quantitative extraction of the organochlorine compounds with the pure solvent. Therefore, CV-MAE is less convenient for samples with high water content. For ASE, water in the sample was bound with Na2SO4. The reproducibility for each technique was very good (relative standard deviation was typically <10%); the slightly varying levels were attributed to deviations during sample cleanup and the generally low levels.     

Synthese desdl-4-Amino-3-isoxazolidons sowie seinerd-Form,des natürlichen Cycloserins

Zusammenfassung Ausgehend vom Brom-dimethylacetal wird über dendl--Diphenylmethylenaminoxy--aminopropionsäureester (III) der bekanntedl--Aminoxy--aminopropionsäureester (II) gewonnen. In neu bearbeiteter Cyclisierungsreaktion wurdedl-Cycloserin (I) erhalten, dessen Stabilität in Abhängigkeit vom Medium studiert wurde. Der aus (III) durch optische Spaltung zugängliche (–)-drehende Antipode wurde in ähnlichem Synthesegang in natürlichesd-Cycloserin (I) übergeführt.