A cyclic neutron activation system using an isotopic neutron source for the measurement of short-lived isotopes

The design and construction of an activation analysis system using an isotopic neutron source which allows the measurement of prompt and delay gamma-rays, in conventional activation and cyclic activation modes, is briefly described with emphasis laid on its flexibility, transportability and low cost. Photon spectra obtained from the irrdiation of large samples under prompt, delay and cyclic conditions using both NaI(Tl) and Ge(Li) detectors are presented and described with respect to ‘in-vivo’ neutron activation analysis and the measurement of N, O, Na, P, Cl and Cd. It is pointed out that, despite the attractive possiblity of measuring Se in liver, ‘in-vivo’, by cyclic activation analysis, the system may potentially prove a very useful tool for industrial and other non-medical applications.     

Intercalation of Benzamide into Kaolinite

Well-crystallized kaolinite (K) was initially reacted at 60 degrees C with a water/dimethylsulfoxide (DMSO) mixture and the resulting intercalation derivative (K-DMSO) was characterized by powder X-ray diffractometry (PXRD), thermal analysis (simultaneous TG and DSC), and Fourier-transformed infrared spectroscopy (FTIR). Benzamide crystals were then melted with the K-DMSO derivative at 140 degrees C for 4 days, when a gradual displacement of DMSO by benzamide was observed within the interlayer spacing of the modified kaolinite. The resulting material, after extensive washing with acetone, was characterized and compared to the results obtained previously for the K-DMSO composite. Benzamide intercalation proceeded by gradual displacement of DMSO molecules until completion. The structural stabilization of the K-BZ derivative was explained through the establishment of hydrogen bonds between the carbonyl oxygen atoms of the intercalated benzamide and aluminol groups present at the surface of the kaolinite layer. The interlamellar spacing of K-BZ was shown to be possibly occupied by benzamide molecules that were located at a 68 degrees orientation in relation to the layer surface. Unlike most intercalation molecules such as DMSO, variations in the interplanar spacing of kaolinite were consistent with the nonkeying of any other part of the molecule between the aluminosilicate interlayers. Copyright 2000 Academic Press.     

Complexing effects in the solvent extraction of thallium(I) 2-mercaptobenzothiazole

Studies of the extraction of thallum(l) from aqueous solution in the absence and presence of aqueous complexing agents into chloroform containing 2-mercaptobenzothiazole are described. Fluoride, chloride, bromide, iodide, thiocyanair, cyanide, and sulfate were employed as aqueous complexing agents. A number of the participating species were identified and association constants are estimated.     

First Synthesis of 3-Mercapto-2(1H)-pyridinone, a Simple Disubstituted Pyridine Useful for Synthesis of the 4-Azaphenoxathiine Ring System and Its Novel Diazaphenoxathiine Analogs: 1,6-Diazaphenoxathiine and 2,6-Diazaphenoxathiine(1)

3-Mercapto-2(1H)-pyridinone (1) can be synthesized in three simple high-yielding steps from readily available 2-tert-butylthiazolo[4,5-b]pyridine (2). Its disodium salt condenses with o-chloronitrobenzene, 2-chloro-3-nitropyridine, and 3-chloro-4-nitropyridine 1-oxide to give respectively 4-azaphenoxathiine (10), 1,6-diazaphenoxathiine (12), and 2,6-diazaphenoxathiine 2-oxide (14) which reduces to 2,6-diazaphenoxathiine (15). The structures of these previously unreported azaphenoxathiine systems were confirmed by assignment of their respective (13)C NMR spectra.     

Thallium-205, carbon-13 and proton NMR parameters for some monomethylthallium(III) derivatives

Thallium-205, carbon-13 and proton NMR spectra have been determined for some monomethylthallium(III) derivatives CH₃TlX₂ (X  anion) permitting comparison of NMR parameters in the series CH₃TlX₂, (CH₃)₂TlX, (CH₃)₃Tl.     

Synthesis and properties of new ditertiary stibines based upon o-, m- or p-xylyl and m- or p-phenylene backbones and their complexes with tungsten, iron and nickel carbonyls

High yield syntheses for 1,2-, 1,3-, and 1,4-xylyl distibines (1,2-C6H4(CH2SbMe2)2, 1,3-C6H4(CH2SbMe2)2, 1,4-C6H4(CH2SbMe2)2, respectively) from Me2SbCl (conveniently made in situ from Me2PhSb and HClgas) and the appropriate di-Grignard are reported. The 1,3- and 1,4-phenylene distibines, 1,3-C6H4(SbMe2)2 and 1,4-C6H4(SbMe2)2, were made similarly. The new ligands have been characterised by mass spectrometry, 1H and 13C[1H] NMR spectroscopy, and by the preparation of methiodide derivatives. The crystal structures of 1,4-C6H4(CH2SbMe2)2 and [1,3-C6H4(CH2SbMe3)2]I2 have been determined. The synthesis of 1,2-C6H4(CH2SbPh2)2 has been achieved similarly in modest yield and the distibine converted into the tetra-iodo-derivative 1,2-C6H4(CH2SbPh2I2)2. The coordination modes available to these ligands have been probed by the synthesis and characterisation of complexes with nickel, iron and tungsten carbonyls. The crystal structure of [[Fe(CO)4]2[micro-1,3-C6H4(CH2SbMe2)2]] has been determined. The spectroscopic properties of these carbonyl derivatives have been compared with those of complexes of other antimony ligands, and in some cases with diphosphine and diarsine complexes, to probe the electronic properties of the new ligands.     

Identification of marker proteins for Bacillus anthracis using MALDI-TOF MS and ion trap MS/MS after direct extraction or electrophoretic separation

Direct extraction of bacterial vegetative cells or spores followed by matrix-assisted laser desorption ionization/time of flight mass spectrometry (MALDI TOF MS) has become popular for bacterial identification, since it is simple to perform and mass spectra are readily interpreted. However, only high-abundance proteins that are of low mass and ionize readily are observed. In the case of B. anthracis spores, small acid-soluble spore proteins (SASPs) have been the most widely studied. Additional information can be obtained using tandem mass spectrometry (MS-MS) to confirm the identity of proteins by sequencing. This is most readily accomplished using ion trap (IT) MS-MS. However, enzymatic digestion of these proteins is needed to generate peptides that are within the mass range of the ion trap. The use of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), or other forms of electrophoresis, allows one to focus on specific proteins of interest (e.g. the high mass exosporium glycoproteins BcIA and BcIB) that provide additional species- and strain-specific discrimination.