Decomposition reaction of organophosphorus nerve agents on solid surfaces with atmospheric radio frequency plasma generated gaseous species

The decomposition and detoxification of compounds are of great interest in environmental protection and defense-related areas. We report the generation of gaseous excited species by scanning atmospheric radio frequency (rf) plasma and their reactions with two representative organophosphorus nerve agents, paraoxon and parathion, deposited on solid surfaces. The excited gaseous species generated in the Ar and Ar/O2 plasma were identified as atomic oxygen, OH radical, and excited nitrogen molecule from optical emission spectroscopy analysis. The reaction of these species with paraoxon and parathion was monitored with reflection-absorption infrared spectroscopy and compared with the decomposition by UV irradiation and UV/ozone treatments. The decomposition products of the atmospheric rf plasma treatment were similar to those of the UV/ozone treatment. The atomic oxygen and excited OH species generated by the plasma appear to be responsible for the oxidation of paraoxon and parathion. The plasma-induced decomposition process was much faster and more efficient than the UV/ozone process. The complete detoxification of paraoxon and parathion upon a short time exposure to the Ar/O2 plasma was confirmed by the Drosophila melanogaster culture test.     

Smart hydrogel sensor for detection of organophosphorus chemical warfare nerve agents

A novel “turn-off” fluorescence, smart hydrogel sensor for detection of a nerve agent simulant has been developed and tested. The smart hydrogel chemosensor has demonstrated an extremely fast and select fluorescence quenching detection response to the Sarin simulant diethylchlorophosphate (DCP) in the aqueous and vapor phases. The fluorogenic sensor utilizes 6,7-dihydroxycoumarin embedded in an polyacrylamide hydrogel matrix as the fluorescent sensing material. The rapid fluorescence quenching of the smart hydrogel films could easily be observed with the naked eye using a hand-held UV light at λ = 365 nm which demonstrates their practical application in real-time on-site monitoring.     

A 'chemically-gated' photoresponsive compound as a visible detector for organophosphorus nerve agents

We describe a versatile and convenient visible detection method for organophosphorus compounds based on a colorless 'pro-photoresponsive' organic molecule that undergoes photochemical ring-closing to produce a colored isomer only after it reacts with vapors of the phosphorylating agent.     

Photonic crystal sensor for organophosphate nerve agents utilizing the organophosphorus hydrolase enzyme

We developed an intelligent polymerized crystalline colloidal array (IPCCA) photonic crystal sensing material which reversibly senses the organophosphate compound methyl paraoxon at micromolar concentrations in aqueous solutions. A periodic array of colloidal particles is embedded in a poly-2-hydroxyethylacrylate hydrogel. The particle lattice spacing is such that the array Bragg-diffracts visible light. We utilize a bimodular sensing approach in which the enzyme organophosphorus hydrolase (OPH) catalyzes the hydrolysis of methyl paraoxon at basic pH, producing p-nitrophenolate, dimethylphosphate, and two protons. The protons lower the pH and create a steady-state pH gradient. Protonation of the phenolates attached to the hydrogel makes the free energy of mixing of the hydrogel less favorable, which causes the hydrogel to shrink. The IPCCA’s lattice constant decreases, which blueshifts the diffracted light. The magnitude of the steady-state diffraction blueshift is proportional to the concentration of methyl paraoxon. The current detection limit is 0.2 μmol methyl paraoxon per liter.     

Synthesis and anticholinesterase activity of some new fluorogenic analogues of organophosphorus nerve agents

Eighteen new fluorogenic analogues of organophosphorus nerve agents were synthesised and characterised. They included analogues of tabun, sarin, cyclosarin, soman, VX, and Russian VX, with the 7-oxy-4-methylcoumarin or 7-oxy-4-(trifluoromethyl)coumarin leaving group. These analogues inhibited acetylcholinesterase (AChE) effectively in vitro and therefore have potential as tools for the identification of novel organophosphatases in biological systems. Analogues of VX and Russian VX with the 7-amino-4-methylcoumarin group, although poor AChE inhibitors, may have utility for screening enzyme libraries for phosphoramidases capable of cleaving P-N bonds.     

Selective enrichment of the degradation products of organophosphorus nerve agents by zirconia based solid-phase extraction

Selective extraction and enrichment of nerve agent degradation products has been achieved using zirconia based commercial solid-phase extraction cartridges. Target analytes were O-alkyl alkylphosphonic acids and alkylphosphonic acids, the environmental markers of nerve agents such as sarin, soman and VX. Critical extraction parameters such as modifier concentration, nature and volume of washing and eluting solvents were investigated. Amongst other anionic compounds, selectivity in extraction was observed for organophosphorus compounds. Recoveries of analytes were determined by GC-MS which ranged from 80% to 115%. Comparison of zirconia based solid-phase extraction method with anion-exchange solid-phase extraction revealed its selectivity towards phosphonic acids. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 4.3 and 8.5 ng mL(-1), respectively, in selected ion monitoring mode.     

Design and synthesis of an alpha,alpha-difluorophosphinate hapten for antibody-catalyzed hydrolysis of organophosphorus nerve agents

In a new approach to the safe neutralization of organophosphorus chemical weapons, we designed a hapten to elicit catalytic antibodies with phosphatase activity. Here we report the synthesis of this alpha,alpha-difluorophosphinate hapten 6. Various methods for the introduction of the key alpha,alpha-difluoromethyl feature into the phosphinate hapten are discussed. The best results were obtained with the electrophilic gem-difluorinating agent N-fluorobenzenesulfonimide.     

Cyclisation of dienes using phosphorus-centred radicals to form organophosphorus adducts

Reaction of various dienes with phosphites or related phosphorus hydrides, under free radical cyclisation conditions, affords cyclic organophosphorus adducts. This quick, mild and technically clean approach affords 5- and 6-ring carbocycles and heterocycles in good to excellent yield.     

High-resolution 2-DE for resolving proteins, protein adducts and complexes in plasma

A 2-DE system has been devised in which proteins are first separated in their native state followed by separation according to mass under denaturing conditions (Nat/SDS-PAGE). Hydrophilic properties of the gel and the presence of dihydroxybisacrylamide in the first dimension allowed a good resolution for high-molecular-weight proteins and maintained interactions. With this method 252 plasma spots have been resolved and 140 have been characterized by MS as isoforms of 60 proteins, a relevant part of which (12) were not detected by traditional 2-D gels or by other nondenaturing 2-D techniques. The list includes complement factors (C4d, C7), coagulation factors (coagulation factor II, fibrin beta), apolipoproteins (apolipoprotein B) and cell debris (vinculin, gelsolin, tropomyosin, dystrobrevin beta, fibrinectin I). Nat/SDS PAGE also allowed separation of nicked forms of albumin, Apo B100 and alpha2-macroglobulin and showed the presence of atypical albumin adducts corresponding to post-translational and oxidation products. Our system provides therefore new tools for resolving proteins, protein aggregates and complexes and amplifies the potentiality of traditional electrophoretic analysis.     

Determination of urea in blood plasma by enzyme-pH electrode

Combination of gel-entrapped urease with a pH electrode can be used to measure plasma urea, provided that the response is related to an auxiliary pH electrode. The response time is 1–3 min and electrodes can be used for up to one week. Good correlation was obtained for routine samples with a spectrophotometric diacetyl monoxime method (y = 0.952x + 0.224, r = 0.996).     

Determination of trimecaine metabolites in blood plasma by capillary isotachophoresis

A method is proposed for the determination of trimecaine (diethylglycylmesidide) and its de-ethylated metabolites (monoethylglycylmesidide and glycylmesidide) in blood plasma by capillary isotachophoresis. The deproteinated plasma is extracted into chloroform after alkalinization and the total solids in the organic layer are dissolved in acidified 25% 2-propanol. Subsequent isotachophoretic analysis is performed in an operational system consisting of potassium acetate buffer (pH 4.75) as the leading and beta-alanine as the terminating electrolyte. The order of the zones corresponds to the molecular weights of the separated compounds. The recovery of all substances of interest is 55% and the limit of determination is 0.05 micrograms of each substance in 1 ml of plasma.     

Development of a surface acoustic wave gas sensor for organophosphorus nerve agents employing lanthanide compounds as the chemical interface

The results of a study dealing with surface acoustic wave gas sensors for organophosphorus compounds such as nerve agents are described. Several lanthanum coordination compounds were applied as the chemical interface. The various sensors prepared were challenged with both the nerve agent sarin and the simulant dimethyl methylphosphonate. Many aspects were studied, such as sensitivity, selectivity, reversibility and response rate as well as the effect of temperature and structural features. Detection limits down to 0.1 ppm were found. Response rates require further improvement. Degradation phenomena were observed which in some cases yielded irreversible responses. The selectivity for organophosphorus compounds was found to be promising.     

Determination of homocysteine and other low-molecular-weight amino thiols in blood plasma

A current approach to determining low-molecular-weight amino thiols (cysteine, homocysteine, and glutathione) in model samples and blood plasma is considered. Procedures for determining 2–100 μM homocysteine in blood plasma with the use of microcolumn chromatography and capillary electrophoresis were developed. Photometric and fluorimetric detection techniques were used to identify amino thiols. Monobromobimane and 5-iodoacetamidofluorescein were used as labels. Mass spectrometry was used to confirm the structures of test amino thiol derivatives.     

Determination of methotrexate in human blood plasma by adsorptive stripping voltammetry

The use of adsorptive stripping voltammetry to measure sub-micromolar concentrations of methotrexate in plasma has been investigated. A simple clean-up procedure has been developed in which methotrexate is extracted from blood plasma with Amberlite XAD-2, which is a non-ionic resin, and eluted with methanol. Recovery for plasma analysis was 80%.     

Determination of trace formaldehyde in blood plasma by resonance fluorescence technology

A novel method for the determination of trace formaldehyde in blood plasma has been established by using resonance fluorimetry technique. It was based on the fact that oxidation of pyronine Y by potassium bromate was catalyzed by formaldehyde in sulfuric acid. When the wavelength interval was at Δλ = 0 nm, it was found that the decreased intensity (ΔF) of resonance fluorescence at 574.6 nm was proportional to the concentration of formaldehyde in the range of 1.27 × 10⁻² to 2.28 μg mL⁻¹. The limit of detection and the average recovery for formaldehyde were 3.80 ng mL⁻¹ and 101.6% (n = 6), respectively. The present method had been applied to the determination of trace formaldehyde in blood plasma, and the obtained results were in good agreement with those obtained by the resonance light scattering method.     

Determination of organophosphorus pesticides by thin-layer chromatography

Analysis for 13 common organophosphorus pesticides by thin-layer chromatography is described; 17 solvent systems were examined. With channel thin-layer chromatography, linear calibration graphs were obtained for the range 1-10 mug.     

Determination of organophosphorus compounds by dye-assisted chromatography

The application of dye-assisted reversed-phase liquid chromatography for the determination of several organophosphorus compounds is demonstrated for mobile phases containing 10^?4 M Brilliant Green in a mixed solvent of water and methanol, acetonitrile and 1,4-dioxane. This method, based on the interaction between a dye and analyte molecules, offers good detection limits for compounds which have weak chromophores. Detection limits are in the submicrogram range for aromatic pesticieds, and in the low microgram range for non-chomophoric aliphatic compounds.