Laser Mass Spectrometry of Organophosphorus Pesticides and Related Compounds

Abstract

Laser mass spectra obtained for 20 organophosphorus (OP) compounds were systematically evaluated for groups containing analogous structural features. Variations in fragmentation can be understood based on simple organic reactions. While detailed mechanistic interpretations of the laser mass spectra (LMS) were not possible, the qualitative features in the LMS obtained from five compounds, not in the original set, could be predicted based on the characteristics of the other OP compounds studied. The success of the prediction lends credence to the qualitative models developed for rationalizing the LMS. A specific feature in the LMS of aromatic thionophosphates is a thiono-thiolo rearrangement. Detailed investigation into the phenomena involved comparison of LMS obtained from aromatic thionophosphates with spectra from electron impact, chemical ionization, field desorption, and secondary ion mass spectrometry. These results led to the conclusion that the rearrangement in laser mass spectrometry must occur during volatilization while the molecule/ion is in the “cloud” present immediately above the laser impact area.     

EFFECT OF ULTRAVIOLET RADIATION ON THE ENERGY METABOLISM OF THE CORNEAL EPITHELIUM OF THE RABBIT

The present research was directed at quantifying possible alterations in corneal epithelial metabolic activity secondary to in vivo exposure to ultraviolet radiation (UVR). Microfluorometric energy metabolite assays on microgram (microgram) sized, freeze-dried tissue samples were used as an in vitro means of assessing overall metabolic activity in the epithelium of control rabbit corneas and in the epithelium of UVR-exposed rabbit corneas 2 min after discontinuation of exposure. The specific assays were for glucose, glycogen, adenosine triphosphate (ATP), and phosphocreatine (PCr). The radiant exposures were kept constant at 0.05 J cm-2 for all UVR wavelengths utilized (290, 300, 310 and 360 nm). Experimental UVR exposure conditions served to increase epithelial glucose and glycogen concentrations. Although the epithelial ATP concentrations were unchanged, the epithelial PCr concentrations (a high energy phosphate bond reservoir) decreased as a result of UVR exposure. Overall, the data demonstrate a decrease in corneal epithelial metabolic activity, which may be wavelength-dependent, as a result of UVR exposure. It is suggested that immediate metabolic stress can be responsible for the pattern of epithelial cell loss seen in photokeratitis.     

Synthesis, characterization and DFT calculations of new ethynyl-bridged C60 derivatives

A new series of soluble C₆₀ derivatives for organic electronic application has been synthesized by ethynylation reaction using different electron-donating and electron-withdrawing groups of varying length.     

Influence of Traces of Water on Adsorption and Diffusion of Hydrocarbons in NaX Zeolite

Measurements have been performed on the influence of a small amount of water on adsorption properties of alkanes (C₃ to C₆) and olefins (C₃ and C₄) in NaX zeolite. Adsorption capacity and heat of adsorption have been measured by a Volume Step method. Kinetics has been measured by Thermal Frequency Response method and the results have been compared with the results obtained by PFG-NMR.It has been found that water reduces the adsorption capacity especially at low adsorbate concentration. The heat of adsorption is slightly reduced by water. The kinetics of alkanes is always reduced by the adsorbed water. On the contrary, the diffusion kinetics of olefins is improved or remains unchanged, depending of the sorbat concentration.     

Proton-induced grain boundary segregation in stainless steel

Abstract

A technique is developed which addresses the problem of irradiation assisted stress corrosion cracking of stainless steels in light water reactors using high energy protons to induce grain boundary segregation. These results represent the first grain boundary segregation measurements in bulk produced by proton irradiation of stainless steel. The technique allows the study of grain boundary composition with negligible sample activation, short irradiation time, rapid sample turnaround and at minimal cost. Scanning Auger electron microscopy is used to obtain grain boundary composition measurements of irradiated and unirradiated samples of ultra high purity (UHP) type 304L stainless steel and UHP type 304L steels with the additions of phosphorus (UHP + P) and sulphur (UHP + S). Results show that irradiation of all three alloys causes significant Ni segregation to the grain boundary and Cr and Fe away from it. Irradiation of the UHP + P alloy also results in segregation of P at the grain boundary from 5.3 to 8.7 at %, over 80 times the bulk value. No radiation-induced grain boundary segregation of S was measured in the UHP + S alloy. Results also indicate that the presence of P or S may enhance radiation-induced segregation of major alloying elements at the boundary. Comparison of irradiated and unirradiated regions of the UHP + P alloy indicate that while a prior thermal treatment segregates P to the grain boundary to 5.3 at %, the major element concentrations at the grain boundary are completely different from those under irradiation.     

Les deplacements chimiques carbone 13 des groupements methyles traites en termes d'interactions H/H,H/Me,Me/Me

The different conformations of the methyl groups for a series of saturated cyclic and linear hydrocarbons were analysed. From these results we were able to identify the different interactions H/H, H/Me, Me/Me and calculate the chemical shifts of the methyl group for a series of hydroxylated stereoisomers.     

The influence of superficial conduction on the magnetoresistivity of antimony

The difference between adiabatic- and isothermal-magnetoresistivity has been used to study the dependence of the superficial current in antimony monocrystals upon the condition of the surfaces of the sample.     

Short-Chain Branching in Polyethylene and Poly(vinyl Chloride) Using Pyrolysis Hydrogenation Gas Chromatography and 13C Nuclear Magnetic Resonance Analysis

This study compares the use of pyrolysis hydrogenation gas chromatography (PHGC) and ¹³C Fourier transform nuclear magnetic resonance (FTNMR) methods for the analysis of reference polyethylene (PE) samples, ethylene-α-olefin copolymers, and specially prepared poly(vinyl chloride) (PVC) samples which were reduced to their PE skeletal structures. The nature and relative quantities of the short branches along the polymer chains were determined using both techniques. Improved high-resolution PHGC data, obtained with a fused silica capillary separation column, gave results which were in satisfactory agreement with the ¹³C FTNMR data. This approach confirms that detailed microstructural information can be obtained with these methods by using carefully controlled experimental conditions and appropriate reference systems.