Contribution a l'etude du dosage par radioactivation du sourfre et du phosphore en tres faibles concentrations dans les metaux de tres haute purete (Aluminium,magnesium, cuivre,fer, nickel)

The chemical separation of sulphur and phosphorus from pure iron and nickel, is described. Sulphur has been determined first by irradiation in fast neutrons, then by irradiation in mixed fast and thermal neutrons. The two methods gave two different results; so, we were led to point out the same phenomenon asJ. Le Hericy had already pointed out for the determination of sulphur in copper. We found that the abnormal amounts of sulphur came from external contamination with chlorine since sulphur is then produced by the³⁵Cl(n, p)³⁵S reaction. The diffusion of³⁵S atoms (produced on the edge of the samples) explains that the concentration of sulphur decreases from the edge to the middle of the sample. We prepared samples of iron and nickel, artificially covered with ammonium chloride, and we studied the apparent concentration of sulphur as a function of the depth in these samples. Our experiences pointed out that the contamination in sulphur yielded by the (n, p) reaction, reaches very quickly the middle of the samples. This phenomenon limits the determination of sulphur by the³⁴S(n, γ)³⁵S reaction, in nickel and iron.      

Synthesis,Characterization and Mass Spectrometric Analysis of Cysteine and Valine Adducts of Sulphur Mustard

The synthetic standards for cysteine and valine adducts of sulphur mustard have been synthesized using 2-(2-chloroethylthio) ethanol (half-mustard). These adducts have been recognized as biomarkers for exposure to sulphur mustard. The adducts have been fully characterized using 1 H and 13 C NMR spectroscopy and mass spectrometric techniques.     

Radiation-thermal hydrodesulphurization of brown coal

The results of the investigation of radiation-thermal hydrodesulphurization of brown coal in presence of methane under accelerated electrons with a dose rate P=350 Gy/s in the intervals of temperatureT=200–500 °C, absorbed dose up to 60 kGy are presented. It has been established that at the more favourable conditions (T=400–450 °C,D>60 kGy) about 80% of sulphur is removed from the coal and in the solid product sulphur decreased up to 1.0–1.1%. In these conditions the selectivity of desulphurization processes iss=2.6–3.8 and energy consumption towards removal of sulphur isE=0.5–0.6 kW h/kg. The mechanism of selective activation by irradiation for the desulphurization process is discussed.     

Determination of a set of parameters for the molecular modelling of phosphorothioate DNA

Phosphorothioate DNAs, have emerged as a new class of potent drugs. They are obtained by the replacement of the anionic oxygens of the phophodiester backbone by sulphur. A set of parameters has been developed for the FLEX force field implemented in JUMNA 10.0 to take into account the influence of sulphur on the structure of the DNA double helix. The consistency of our parameters was tested by modelling a phosphorothioate oligomer namely d(GC)8. d(GC)8. Results, obtained on both R-p_S and S-p_S diastereoisomers, were compared to the phosphodiester counterpart and are in agreement with available experimental data. Thus, our set of parameters seems suitable for further molecular modelling of other phosphorothioate oligomers. Received: 15 July 1998 / Accepted: 8 September 1998 / Published online: 10 December 1998     

Methods for the analysis of thiodiglycol sulphoxide, a metabolite of sulphur mustard, in urine using gas chromatography-mass spectrometry.

Two methods have been developed for the analysis of thiodiglycol sulphoxide, a metabolite of sulphur mustard, in urine. The first method recovers thiodiglycol sulphoxide from urine by extraction from a solid absorbent tube and clean up on Florisil. In the second method thiodiglycol sulphoxide is reduced to thiodiglycol with acidic titanium trichloride prior to extraction. This method detects thiodiglycol, thiodiglycol sulphoxide, and their acid-labile esters, as the single analyte thiodiglycol. In both cases the recovered analytes were converted to the bis(pentafluorobenzoyl) derivative of thiodiglycol and detected by gas chromatography-mass spectrometry using negative ion chemical ionisation. The limits of detection were 1 ng per 0.5-ml sample of urine. Urine from five normal human subjects showed low background levels of thiodiglycol sulphoxide in the range 2-8 ng/ml. However, a sixth subject was found to be excreting levels of thiodiglycol sulphoxide as high as 36 ng/ml. The first method has been used in toxicokinetic studies of sulphur mustard and the second method is intended to be used for the retrospective confirmation of mustard poisoning in casualties of chemical warfare.     

Headspace-trap gas chromatography–mass spectrometry for determination of sulphur mustard and related compounds in soil

Methods for trace determination of sulphur mustard (HD) and some related cyclic sulphur compounds in soil samples have been developed using headspace-trap in combination with gas chromatography–mass spectrometry (GC–MS). Two quite different types of soil were employed in the method optimisation (sandy loam and silty clay loam). Prior to analysis, water saturated with sodium chloride was added to the samples, at a water to soil ratio of 1:1. A detection limit of 3 ng/g was achieved for HD, while the cyclic sulphur compounds 1,4-thioxane, 1,3-dithiolane and 1,4-dithiane could be detected at 0.2–0.7 ng/g. The methods were validated in the concentration range from the limit of quantification (LOQ) to hundred times LOQ. The within assay precision at fifty times LOQ was 6.9–7.3% relative standard deviation (RSD) for determination of the cyclic sulphur compounds, and 15% RSD for determination of HD. Recoveries were in the range of 43–60% from the two soil types. As the technique requires very little sample preparation, the total time for sample handling and analysis was less than 1 h. The technique was successfully employed for the determination of cyclic sulphur compounds in a sediment sample from an old dumping site for chemical munitions, known to contain HD degradation products.     

Fabrication of TiO2/Ti nanotube electrode and the photoelectrochemical behaviors in NaCl solutions

Titanium oxide nanotube electrodes were successfully prepared by anodic oxidation on pure Ti sheets in 0.5 wt.% NH₄F + 1 wt.% (NH₄)₂SO₄ + 90 wt.% glycerol mixed solutions. Nanotubes with diameter 40–60 nm and length 7.4 μm were observed by field emission scanning electron microscope. The electrochemical and photoelectrochemical characteristics of TiO₂ nanotube electrode were investigated using linear polarization and electrochemical impedance spectroscopy techniques. The open-circuit potential dropped markedly under irradiation and with the increase of Cl⁻ concentrations. A saturated photocurrent of approximately 1.3 mA cm⁻² was observed under 10-W low-mercury lamp irradiation in 0.1 M NaCl solution, which was much higher than film electrode. Meanwhile, the highest photocurrent in NaCl solution implied that the photogenerated holes preferred to combine with Cl⁻. Thus, a significant synergetic effect on active chlorine production was observed in photoelectrocatalytic processes. Furthermore, the generation efficiency for active chlorine was about two times that using TiO₂/Ti film electrode by sol–gel method. Finally, the effects of initial pH and Cl⁻ concentration were also discussed.     

Comparisons of an external magnetic field effect and chemical effect on X-ray <Emphasis Type="Italic">Kβ</Emphasis>/<Emphasis Type="Italic">Kα</Emphasis> intensity ratio and line-shape of some Chromium compounds

The effect of chemical composition and external magnetic field on the Kβ/Kα intensity ratio and line-shape of some chromium compounds have been investigated using the energy dispersive X-ray fluorescence analysis. The measurements were done using the 22.69 keV photon energy and energy dispersive Si(Li) semiconductor detector. The samples are located in the external magnetic field of intensities 0.6 T and 1.2 T. The experimental results obtained for B = 0 are compared with other experimental and theoretical values. The results have shown that the X-ray Kβ/Kα intensity ratios, chemical shifts, asymmetry indices and full widths at half maximum (FWHM) values can change when irradiation is conducted in a magnetic field.     

Determination of the sulphur content of a lunar sample by neutron capture gamma-ray spectrometry

The technique of prompt neutron capture gamma-ray spectroscopy has been used to determine sulphur concentrations in extraterrestrial materials. In particular an effort was made to resolve reported discrepancies in the sulphur assays for the lunar rock sample 70215. While the validity of chemical analysis techniques are often influenced by the chemical form of the sulphur, particularly when in low concentration, the method used here is independent of such effects. The lunar and a bulk Allende meteorite sample were analyzed for sulphur, iron and silicon. The latter material, being well documented, was analyzed in order to verify the techniques of measurement and the subsequent methods of data reduction. Based upon our measurements and the acceptance of the silicon and iron content of the lunar sample the sulphur content was found to be 1741±112 ppm by weight.     

Rapid radiochemical separations using and induction furnace: Determination of sulphur in rocks

The use of an induction furnace for rapid radiochemical separations in neutron activation analysis of rocks is discussed in general and the activation analysis of sulphur in geological samples is described as a specific application. After irradiation the sample is heated in an induction furnace in a flow oxygen. The expelled sulphur oxides are adsorbed onto activated charcoal and measured in the well of a sodium iodide detector. The 3102 keV peak of the 5 minute³⁷S is used for analysis. The separation time is seven minutes, the yield 99% and the detection limit 200 μg S. Results of the analysis of ores are presented.     

Determination of the trace element levels in atmospheric pollutants by neutron activation analysis

An investigation of the potentials of neutron activation analysis for the routine analysis of trace elements present in atmospheric pollutants is discussed. Various techniques including sequential air sampling, multiple neutron irradiation, high resolution γ-ray spectrometry, chemical isolation, high flux neutron irradiation and X-ray spectrometry have been employed to determine the levels of Pb, Al, V, I, Cl, Mn, Cu, Br, Na, La, Mo, Au, Cr, Fe, Ni, Se, Zn, Ag and Co in atmospheric pollutants. The results of the analysis of nearly two hundred samples collected from the Buffalo New York area during 1968–1969 are reported. Presented at the Fourth Annual Conference on Trace Substances in Environmental Health, University of Missouri, Columbia Missouri, USA (June, 1970).     

Specific and sensitive quantitation of 2,2'-dichlorodiethyl sulphide (sulphur mustard) in water, plasma and blood: application to toxicokinetic study in the rat after intravenous intoxication.

A sensitive and specific capillary gas chromatographic method has been developed to measure trace amounts of 2,2'-dichlorodiethyl sulphide (sulphur mustard) in environmental or biological samples. Sulphur mustard was isolated from water or plasma by a solid-phase extraction procedure and from blood by liquid-liquid extraction. The accuracy and precision of the methods were demonstrated using replicate analyses of spiked water, plasma or blood: within-run and between-run variabilities were less than 20%. These analytical methods were used to evaluate the rate of sulphur mustard degradation in water or plasma. Good linear calibration curves, with a detection limit of 45 ng/ml, were obtained for quantitation and determination of sulphur mustard in blood following its intravenous administration to rats. Initial toxicokinetic data were obtained.     

Control of the Properties of Carbon Nanotubes Synthesized by CVD for Application in Electrochemical Biosensors

Interest in carbon nanotubes (CNT) has grown at a very rapid rate in the last decade. Their interesting physical and chemical properties open attractive possibilities in many application areas. These properties depend on the process conditions during synthesis and on subsequent purification steps. Recent studies have demonstrated that CNT can promote the electron transfer of biomolecules. These exceptional properties make them attractive for use in electrochemical biosensors. Multi walled nanotubes have been synthesized by the Chemical Vapor Deposition (CVD) method using methane as a carbon source and Ni–Al₂O₃–SiO₂ as the catalyst. The influence of the variation of certain reaction parameters such as feed gas composition, catalyst mass, temperature and reaction time in the yield of the CVD process has been established. In addition, the structural and chemical characteristics of the CNTs have been studied and a purification process to eliminate the catalyst and amorphous carbon has been developed that involves a gaseous oxidative process and acid treatment. The efficiency of the purification step has been determined by analytical techniques. Atomic force microscopy, Raman scattering, thermogravimetric analysis, inductively coupled plasma atomic spectroscopy are the characterization techniques employed in this work.     

Analytical Study of β-Irradiated Antibiotics in the Solid State

This paper reports results of the study on the influence of β-irradiation on the physical and chemical properties of selected salts of β-lactam antibiotics in solid state (sodium salt: ampicillin, azlocillin, benzylpenicillin, carbenicillin and piperacillin; potassium salt of benzylpenicillin, ampicillin anhydricum, ampicillin trihydricum, amoxicillin trihydricum and bacampicillin hydrochloride). The source of irradiation was a linear accelerator of electrons, and the irradiation effects were checked on the basis of the following: determination of mass, melting point and water contrent, and spectrophotometric (UV, IR) chromatographic and thermal (DTG, DSC) studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal behaviour of the system Fe(NO3)3?·?9H2O–Bi5O(OH)9(NO3)4?·?9H2O–glycine/urea and of their generated oxides (BiFeO3)

Activated carbons (AC), particularly those containing sulphur, are effective adsorbents for mercury (Hg) vapour at elevated temperatures. Activated carbon-based technologies are expected to become a major part of the strategy for controlling mercury emission from coal-fired power plants. Understanding the mechanism of mercury adsorption on sulphur impregnated activated carbons (SIAC) is essential to optimizing activated carbons for better mercury removal efficiency and to developing technologies for the handling of the spent AC. In this work thermal analysis before and after mercury uptake was carried out for the SIAC prepared under various conditions from oil-sand petroleum coke using a simultaneous differential thermal analyzer. Samples were heated at 20°C min⁻¹ under nitrogen in the temperature range from ambient to 1000°C. The DSC curves suggest both endothermic and exothermic changes during heating. The endothermic processes were attributed to evaporation of moisture and other volatile components. The exothermic processes existed in a wide temperature range of 150–850°C likely due to the oxidation reactions between carbon and adsorbed oxygen, oxygen-containing surface groups. The enthalpies of liquid mercury interaction with SIAC at different Hg/AC mass ratio were also measured at 30, 40 and 50°C using a differential scanning calorimeter. The combination of thermal analysis and calorimetry techniques enabled confirmation that the interaction of mercury with SIAC involves both physical and chemical processes.     

N,N′-dichloro-bis[2,4,6-trichlorophenyl]urea (CC2) and suspending agents used for the preparation of decontamination formulation against chemical warfare agents

N,N′-dichloro-bis[2,4,6-trichlorophenyl]urea, known as CC2, is used as a reactive chemical decontaminant of mustard agents. The present study was undertaken to establish the compatibility of CC2 with a number of commonly used suspending agents, using thermoanalytical techniques viz., thermogravimetry (TG) and differential scanning calorimetry (DSC) with the support of Fourier transform infrared spectroscopy (FTIR). The results demonstrated the applicability of TG and DSC as a fast screening tool for analysing the compatibility of drug with excipients at the early stages of a preformulation process. Methylcellulose, hydroxypropylcellulose, and betaine were found to be compatible with CC2.     

Preliminary observations on the copolymerisation of acceptor monomer:donor monomer systems under microwave irradiation

The mechanistic rationalisation of specific ‘microwave effects’ previously reported in a range of chemical reactions suggests that they may be observable in the freeradical copolymerisation of comonomer pairs capable of forming donor-acceptor complexes. Polymerisation under microwave irradiation is carried out for several comonomer pairs with weak donor-acceptor interactions, and no acceleration in rate or change in degree of alternation attributable to changes in propagation are observed. An increase in reaction rate of 150–200 % is observed for all systems, with trends in molecular weight suggesting this was due to an increase in radical flux. This is consistent with earlier reports of rate enhancement for free-radical polymerisations using the initiator 2,2′-azobis-isobutyronitrile, and it is proposed that microwave irradiation may reduce the amount of geminate radical recombination.     

Evaluation and optimization of electron capture dissociation efficiency in fourier transform ion cyclotron resonance mass spectrometry

Electron capture dissociation (ECD) efficiency has typically been lower than for other dissociation techniques. Here we characterize experimental factors that limit ECD and seek to improve its efficiency. Efficiency of precursor to product ion conversion was measured for a range of peptide (∼15% efficiency) and protein (∼33% efficiency) ions of differing sizes and charge states. Conversion of precursor ions to products depends on electron irradiation period and maximizes at ∼5–30 ms. The optimal irradiation period scales inversely with charge state. We demonstrate that reflection of electrons through the ICR cell is more efficient and robust than a single pass, because electrons can cool to the optimal energy for capture, which allows for a wide range of initial electron energy. Further, efficient ECD with reflected electrons requires only a short (∼500 μs) irradiation period followed by an appropriate delay for cooling and interaction. Reflection of the electron beam results in electrons trapped in or near the ICR cell and thus requires a brief (∼50 μs) purge for successful mass spectral acquisition. Further electron irradiation of refractory precursor ions did not result in further dissociation. Possibly the ion cloud and electron beam are misaligned radially, or the electron beam diameter may be smaller than that of the ion cloud such that remaining precursor ions do not overlap with the electron beam. Several ion manipulation techniques and use of a large, movable dispenser cathode reduce the possibility that misalignment of the ion and electron beams limits ECD efficiency.     

The influence of sunflower and mustard leaf extracts on the germination of mustard seeds

The extracts from sunflower and mustard leaves were separated using SPE-Columns. The mustard seeds were germinated on water (24 h) and subsequently on crude extracts or separate fractions. The heat production rate was measured by isothermal calorimetry at 21°C and changes in seed cotyledons by FT-Raman spectroscopy. Crude extracts strongly inhibited seed germination. The water and ‘methanol’ fractions of mustard and sunflower extracts have a similar influence on the pattern of heat efflux. FT-Raman spectroscopy showed that extracts caused changes in cotyledons mainly in the content of fatty acids, carotenoids and flavonoids. Isothermal calorimetry and Raman spectroscopy are useful for the study of allelopathic interactions.     

High resolution prompt (n,γ) spectroscopy using a down hole logging tool

A down-hole logging tool is described utilising a 5 Ci²⁴¹Am–Be neutron source and intrinsic germanium gamma-ray detector. The tool was used to measure the prompt gamma-ray response from the irradiation of 4 well characterised coal samples. The correlation between the count-rate into the 2380 keV line arising from sulphur and the sulphur concentration as determined by chemical analysis is described. A depression in the count rate into the sulphur peak of interest is modelled using the neutron transport code ANISN and compares well with measurement. The influence of borehole diameter and the presence of borehole fluid upon logging performance is assessed.