Solid Supported Liquid–Liquid Extraction of Chemical Warfare Agents and Related Chemicals from Water

Solid-supported liquid–liquid extraction was optimized to extract the chemical warfare agents and their non-toxic analogues from water. The developed method was compared to the conventionally used liquid–liquid extraction. This method yielded high recoveries (70–80%) of non-toxic analogues of chemical warfare agents and good recoveries (65–75%) of the nerve agent sarin and Lewisite-III. The limits of detection of non-toxic analogues of CWAs, and toxic sarin and Lewisite-III, in selected ion monitoring and full scan mode, varied from 0.01 to 0.5 μg mL^?1 and 0.1 to 1.0 μg mL^?1 respectively.     

A DFT study on regioselectivity in the [2 + 2] photocycloaddition of 6-amino-2-(3′-thienoyl)-1,4-benzoquinone and ethylene

DFT-B3LYP studies have been used to understand the realm of [2 + 2] photocycloaddition reactions that lead to the formation of four-membered cyclobutane derivatives. Regioselectivity in these reactions has been explored for the typical system 6-amino-2-(3′-thienoyl)-1,4-benzoquinone and ethylene. The results favor initial attack of ethylene on quinonoid carbon C5 rather than any other position.     

Gas chromatography/mass spectrometric analysis of methyl esters of N,N-dialkylaminoethane-2-sulfonic acids for verification of the Chemical Weapons Convention

This paper describes the synthesis and gas chromatography/electron ionization mass spectrometric (GC/EI-MS) analysis of methyl esters of N,N-dialkylaminoethane-2-sulfonic acids (DAESAs). These sulfonic acids are important environmental signatures of nerve agent VX and its toxic analogues, hence GC/EI-MS analysis of their methyl esters is of paramount importance for verification of the Chemical Weapons Convention. DAESAs were prepared by condensation of 2-bromoethane sulfonic acid with dialkylamines, and by condensation of dialkylaminoethyl chloride with sodium bisulfite. GC/EI-MS analysis of methyl esters of DAESAs yielded mass spectra; based on these spectra, generalized fragmentation routes are proposed that rationalize most of the characteristic ions.     

Microsynthesis and electron ionisation mass spectrometric analysis of chemical weapons convention (CWC)-related O,O-dialkyl-N,N-dialkylphosphoramidates

The paper describes microsynthesis and GC/EIMS analysis of O,O-dialkyl-N,N-dialkylphosphoramidates (DADAPs). DADAPs belong to schedule 2B6 category of chemical weapons convention (CWC), as they are important markers of the chemical warfare agent Tabun and its analogues. The study was undertaken to develop a spectral database of DADAPs for verification of CWC. The reported synthetic strategy can be adopted to prepare several analogues of DADAPs simultaneously and rapidly during official proficiency tests, for the unambiguous identification of analytes within a short period. Based on the EIMS data of more than 60 compounds, fragmentation routes are proposed which explain the formation of most of the characteristic fragment ions. Subtle differences in EIMS of isomeric DADAPs are discussed to facilitate their identification.     

Micro-synthesis and electron ionization mass spectral analysis of O-alkyl N,N-dialkylphosphoramidocyanidates

This communication describes microsynthesis and GC/MS analysis of O-alkyl N,N-dialkylphosphoramidocyanidates (ADAPCs), which are analogues of chemical warfare agent, Tabun. The study was undertaken with a view to develop spectral data base of ADAPCs for verification purpose of Chemical Weapons Convention (CWC). Reported microsynthetic approach has advantages over traditional synthesis in terms of efficiency, synthetic waste, and exposure to toxic chemicals. GC/MS analysis of variety of these compounds (ADAPCs) was performed. Based on the obtained mass spectra of structurally diverse ADAPCs, the fragmentation routes are proposed, which explains most of the characteristic ions.     

Structural aspects of crown complexes with alkali and alkaline earth cations. Benzo-15-crown-5 as a discriminating macrocycle

X-ray structural results have been reviewed for the related M^z+ L _z ^– -B15C5 complexes where M^z+=Li⁺ to Cs⁺ and Mg²⁺ to Ba²⁺, L^–=2,4,6-trinitrophenolate (Picrate or Pic) and 3,5-dinitrobenzoate (Dnb), and B15C5=benzo-15-crown-5. These results combined with those for come MX_z-B15C5 (X=NCS^–, I^–, NO ₃ ^– , ClO ₄ ^– , BPh ₄ ^– ) complexes have revealed that B15C5 is a useful macrocycle with regard to the within-the-group and between-the-groups discriminations of M^z+ in the solid state.     

Theoretical studies on the stereochemical course of 1,3‐dipolar cycloaddition of azomethine ylides derived from indol‐2,3‐dione and thiazolidine‐4‐carboxylic acid

1,3‐Dipolar cycloadditon of azomethine ylides with different dipolarophiles leads to the formation of novel heterocyclic spiro compounds having two or more chiral centers. The theoretical studies (HF/3–21G) on the 1,3‐dipolar cycloaddition reaction between ethene and azomethine ylide A4 derived from isatin and thaizolidine‐4‐carboxylic acid, indicates that the energy barrier for this addition is about ～ 8 kcal/mol higher than that in simplest azomethine ylide A1 . HF/3–21G studies on a series of azomethine ylides A2 and A3 suggested that the increased barrier is mainly due to stabilization of azomethine ylides arising from aromatic indol nucleus. Semi‐empirical studies indicate that the cycloaddition is streocontrolled as the transition states corresponding to only the stericlly allowed paths could be located on the potential energy surface.     

The effects of high-energy ion irradiations on the I–V characteristics of silicon NPN transistors

The silicon NPN rf power transistors were irradiated with different linear energy transfer (LET) ions such as 50?MeV Li³⁺, 80?MeV C⁶⁺ and 150?MeV Ag¹²⁺ ions in the dose range of 1–100?Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (ΔI_B), DC current gain (h_FE), displacement damage factor (K) and output characteristics were systematically studied before and after irradiation. The ion irradiation results were compared with ⁶⁰Co-gamma irradiation result in the same dose range. A considerable increase in base current (I_B) and a decrease in h_FE and I_CSat were observed after irradiation. The degradation in the electrical parameters was comparably very high for Ag¹²⁺ ion-irradiated transistor when compared to other ion-irradiated transistors, whereas the degradation in the electrical parameters for Li³⁺ and C⁶⁺ ion-irradiated transistors was comparable with gamma-irradiated transistor. The isochronal annealing study was conducted on the 100?Mrad irradiated transistors up to 500°C to analyze the recovery in different electrical parameters. The h_FE and other electrical parameters of irradiated transistors were almost recovered after 500°C for 50?MeV Li³⁺, 80?MeV C⁶⁺ ion and ⁶⁰Co-gamma-irradiated transistors, whereas for 150?MeV Ag¹²⁺ ion-irradiated transistor, the recovery in electrical characteristics is not complete.     

Comparison of 1 MeV electron,Co-60 gamma and 1 MeV proton irradiation effects on silicon NPN transistors

The total dose effects of 1?MeV electrons on the dc electrical characteristics of silicon NPN transistors are investigated in the dose range from 100?krad to 100?Mrad. The different electrical characteristics such as Gummel characteristics, excess base current (ΔI_B), dc current gain (h_FE), transconductance (g_m), displacement damage factor (K) and output characteristics were studied in situ as a function of total dose. A considerable increase in base current (I_B) and a decrease in h_FE, g_m and I_CSat was observed after 1?MeV electron irradiation. The collector–base (C–B) junction capacitance of transistors was measured to estimate the change in the effective carrier concentration. After 1?MeV electron irradiation, a considerable degradation in capacitance was observed. The plot of (1/C²) versus voltage shows that the effective carrier concentration and built-in voltage (V_bi) increase marginally upon 1?MeV electron irradiation. The results of 1?MeV electron irradiation were compared with 1?MeV proton and Co-60 gamma irradiation results in the same dose range. The degradation for 1?MeV electron and Co-60 gamma-irradiated transistors was significantly less when compared to 1?MeV proton-irradiated transistor. The 1?MeV proton, 1?MeV electron and Co-60 gamma-irradiated transistors were subjected to isochronal annealing to analyze the recovery of the electrical parameters.     

Asymptotic solution of a non-linear wave motion in an electron plasma

The theory of high-frequency waves has been used to calculate first and second-order asymptotic solutions for the propagation of non-linear waves in a cylindrical symmetric flow of an electron plasma. The behaviour of acceleration waves and weak shock waves has been analysed through these solutions and Whitham's rule for a weak shock wave on any wavelet has been confirmed through the first-order solution. The appearance of a weak shock wave on any wavelet has been determined and its strength, the location, and the speed of propagation have been found from the asymptotic solution presented in this paper. © 1997 by B. G. Teubner Stuttgart–John Wiley & Sons Ltd.