Use of a hand-portable gas chromatograph-toroidal ion trap mass spectrometer for self-chemical ionization identification of degradation products related to O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX)

The chemical warfare agent O-ethyl S-(2-diisopropylaminoethyl) methyl phosphonothiolate (VX) and many related degradation products produce poorly diagnostic electron ionization (EI) mass spectra by transmission quadrupole mass spectrometry. Thus, chemical ionization (CI) is often used for these analytes. In this work, pseudomolecular ([M+H]⁺) ion formation from self-chemical ionization (self-CI) was examined for four VX degradation products containing the diisopropylamine functional group. A person-portable toroidal ion trap mass spectrometer with a gas chromatographic inlet was used with EI, and both fixed-duration and feedback-controlled ionization time. With feedback-controlled ionization, ion cooling (reaction) times and ion formation target values were varied. Evidence for protonation of analytes was observed under all conditions, except for the largest analyte, bis(diisopropylaminoethyl)disulfide which yielded [M+H]⁺ ions only with increased fixed ionization or ion cooling times. Analysis of triethylamine-d₁₅ provided evidence that [M+H]⁺ production was likely due to self-CI. Analysis of a degraded VX sample where lengthened ion storage and feedback-controlled ionization time were used resulted in detection of [M+H]⁺ ions for VX and several relevant degradation products. Dimer ions were also observed for two phosphonate compounds detected in this sample.     

Microcolumn liquid chromatography with thermionic detection of the enantiomers of O-ethyl S-2-diisopropylaminoethyl methylphosphonothioate (VX)

An improved interface for the on-line coupling of microcolumn liquid chromatography (micro-LC) with thermionic detection (TID) is described. Modifications have been made to enable separate adjustment of the eluent introduction and the detector flame temperature in order to improve the sensitivity and ease of use of the system. The micro-LC-TID was used for the chiral separation of the nerve agent O-ethyl S-2-diisopropylaminoethyl methylphosphonothioate (VX). Baseline separation for the enantiomers of VX was obtained on Chiralcel OD using 1% isopropanol in hexane as the eluent. The detection limit of VX using 60 nl injections is ca. 5 μg/ml (ppm range). However, when using large-volume injections (10 μl) the detection limit is ca. 25 ng/ml (ppb range).     

Gas Chromatographic Determination of O-Ethyl S-(N,N-Diisopropylamino) Ethyl Methylphosphonothiolate and O,O-Diisopropyl S-Benzyl Phosphorothiolate as Corresponding Phosphonofluoridate and Phosphorofluoridate

Abstract

A gas chromatographic method has been reported for the determination of phosphonothiolates and phosphorothiolates as corresponding phosphonofluoridates and phosphorofluoridates after reaction with AgF. The transformation reaction procedures and the chromatographic conditions were recommended for the model compounds, O-ethyl S-(N,N-diisopropylamino)ethyl methylphosphonothiolate (MESP) and O,O-diisopropyl S-benzyl phosphorothiolate (DPSP). The results obtained have shown that the recovery is 100+4.5% for determination of MESP in the range of 1.88-8.00 μg/ml (in benzene solution) and the relative standard deviations (RSD) are less than 2.12% for MESP and DPSP at the 3.18, 6.30 and 5.48 μg/ml level.     

Photoassisted reaction of chemical warfare agent VX droplets under UV light irradiation

A photoassisted reaction of O-ethyl S-[2-(diisopropylamino) ethyl] methylphosphonothioate (VX) droplets in air was carried out. The experimental results indicated that VX droplets could be easily and chemically transformed into other compounds under irradiation of a germicidal lamp over sufficient time. Quantum chemical calculation results demonstrated that UV light less than 278 nm wavelength could possibly initiate photoreaction of VX and that both P-S and P=O bonds in the VX molecule were lengthened. The identification of reaction products by gas and liquid chromatography mass spectroscopy and NMR revealed that the VX molecule in air under UV light irradiation could undergo isomerization of S-esters to O-esters, cleavage of P-S, S-C, and C-N bonds, and ozonation of tertiary amines.     

化学反应热诱导激光光偏转分析法研究

探讨了化学反应热诱导激光光偏转分析法的基本原理及各种影响因素。用此法成功地进行了溶液酸碱中和反应、氧化还原反应、络合反应、沉淀反应以及胃动力新药吗丁啡片剂中有效药成分多潘立酮的分析测定,取得了满意结果。该法仪器装置简单,测定线性范围宽,应用范围广。     

Medium effects on the ionization constants of some quinoline derivatives

Summary The deprotonation and acid ionization constants of some quinoline derivatives in aqueous organic solvents were determined. The organic solvents used include methanol and ethanol as amphiprotic solvents andDMF andDMSO as dipolar aprotic solvents. The obtainedpK ₁ andpK ₂ values are discussed with respect to the nature and the amount of the organic component. The high stabilization of the non-protonated form by dispersion forces and of the proton by its interaction with the solvent are the main factors responsible for the increase in the ionization constants of the protonated forms of the quinolines under investigation. On the other hand, H-bonding interactions (in addition to the electrostatic effect) seem to play the major role in determining the second acid-base equilibrium of 8-hydroxyquinoline. The deprotonation constants of the examined quinolines are correlated with their experimentally determined lone-pair ionization potential values.

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Lösungsmitteleffekte auf die Ionisationskonstanten einiger Chinolinderivate

Zusammenfassung Die Deprotonierungs- und Ionisationskonstanten einiger Chinolinderivate wurden in wäßrigen organischen Medien, darunter Methanol und Ethanol als amphiprotische undDMF undDMSO als dipolare aprotische Lösungsmittel, bestimmt. Die gemessenenpK ₁- undpK ₂-Werte werden im Hinblick auf die Art und Menge der organische Komponente diskutiert. Die hohe Stabilisierung der nichtprotonierten Form durch Dispersionskräfte und des Protons durch Wechselwirkungen mit dem Lösungsmittel sind die wesentlichen Faktoren, die für den Anstieg der Ionisationskonstanten der protonierten Formen der untersuchten Chinoline verantwortlich sind. Andererseits scheinen Wasserstoffbrückenbindungen — zusätzlich zum elektrostatischen Effekt — das zweite Säure-Basen-Gleichgewicht von 8-Hydroxychinolin entscheidend zu beeinflussen. Die Deprotonierungskonstanten aller untersuchten Chinoline werden mit ihren experimentell bestimmtenlone-pair-Ionisationspotentialen korreliert.

     

Identification of O-Isobutyl S-(2-Diethylaminoethyl) Methylthiophosphonate Chemical Neutralization Products in Bitumen–Salt Matrices

Products of the chemical neutralization of O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate, a VX Group warfare agent, in bitumen–salt matrices were studied by gas chromatography–mass spectrometry. Forty-four compounds were characterized by their electron impact ionization mass spectra and gas chromatographic retention indices on standard nonpolar polydimethylsiloxane phases; seven of these compounds were determined as derivatives. The structures of 26 compounds were identified, including structures of 24 O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate neutralization products. To solve this problem, chromatographic retention indices of unknown compounds were evaluated using reference data for their structural analogues. Partition coefficients in the binary heterophase hexane–octanol system were determined for the major components.     

计算机模拟在化学理论与实验教学中的应用

With the help of PHREEQC program,we introduced the application of computer simulation in theoretical and laboratory teaching of chemistry.Accordingly,reaction models for the chemical process of acid-base neutralization,complexation reaction,precipitation-dissolution equilibrium,and chemical kinetics were established.These models can greatly help the students understand chemistry,improve the teaching quality,enrich modern teaching methodology,develop students' creativity,and establish a scientific and efficient research method.     

Determination of soman and VX degradation products by an aspiration ion mobility spectrometry

An aspiration type ion mobility spectrometry (IMS) has been used to determine chemical warfare agent (CWA) degradation products from liquid samples. This technique is based on ion mobility which depends on the molecular weight, charge and shape. With this method, it is possible to measure the mobility distribution of positive and negative ion clusters simultaneously in six different electrodes. Each measuring electrode determines a different portion of the ion mobility distribution formed within the cell’s radioactive source. The strongest responses for all CWA degradation products and 2-propanol were seen in the order of sixth, fifth and second channels. On the basis of projection calculation, the fingerprints for 2-propanol and soman (GD; pinacolyl methylphosphonofluoridate) and VX o-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate) degradation products can be separated from each other. The detection levels for ethyl methylphosphonate (EMPA), pinacolyl methylphosphonate (PMPA), and ethylphosphonic acid (EPA) were 37.2 (37.2 μg/ml), 54.1 (54.1 μg/ml) and 55.1 ppm (55.1 μg/ml), respectively. However, the separation efficiency between different CWA degradation products was quite poor. The projections of these compounds were between 0.9976 and 0.9989, and this means that these fingerprints were identical. Thus, it is only possible to get one profile for all these degradation products of soman and VX. The data provided show that IMS is suitable as a simple technique for screening of CWA degradation products.     

乳酸-溴酸钾-硫酸锰-硫酸-丙酮体系的B-Z振荡反应

This paper presents a study of the concentration range of reactant of oscillation reaction in α-hydroxy-propionic acid-KBrO3-MnSO4-H2SO4-propanone system. The special feature of the reaction is a damped oscillation. A section of the damped oscillation wave is similar to a spindle. Effects of many factors on the oscillation have been examined. The period and amplitude as function of the initial concentration of each reactant have been studied. It was found that mumbers, period and amplitude of each section of damped oscillation and preoscillatory time depend on the initial concentrations of the reactants.     

On-Demand Activation of Transesterification by Chemical Amplification in Dynamic Thiol-Ene Photopolymers

Chemical amplification is a well-established concept in photoresist technology, wherein one photochemical event leads to a cascade of follow-up reactions that facilitate a controlled change in the solubility of a polymer. Herein, we transfer this concept to dynamic polymer networks to liberate both catalyst and functional groups required for bond exchange reactions under UV irradiation. For this, we exploit a photochemically generated acid to catalyse a deprotection reaction of an acid-labile tert-butoxycarbonyl group, which is employed to mask the hydroxy groups of a vinyl monomer. At the same time, the released acid serves as a catalyst for thermo-activated transesterifications between the deprotected hydroxy and ester moieties. Introduced in an orthogonally cured (450 nm) thiol-click photopolymer, this approach allows for a spatio-temporally controlled activation of bond exchange reactions, which is crucial in light of the creep resistance versus reflow ability trade-off of dynamic polymer networks.     

Hydrodynamic Instabilities Driven by Acid-base Neutralization Reaction in Immiscible System

The hydrodynamic instabilities driven by an acid-base neutralization reaction, in contact along a plane interface, placed in a Hele-Shaw cell under the gravitational field are reported.The system consists of the heavier aqueous tetramethyle-ammonium hydroxide below the lighter layer of organic phase with propionic acid as reacting specie. The effect of chemical composition on hydrodynamic instabilities during interfacial mass transfer accompanied by a neutralization reaction is investigated. Depending on the initial concentration of the reacting species, Marangoni convection in the form of roll cells or trains of waves is observed. Mach-Zehnder interferometer is used to measure the change in base concentration at the time of instability formation. The results show that the instabilities resulted from the convection flow are more efficient to the mechanism of mass transfer and can drastically alter pattern formation in the system.     

线形碳元素簇合物的成键性质

在ab initio 3-21G水平上, 用能量梯度法优化了线性碳元素簇合物C_n~e(n为成簇原子个数, e为电荷)的平衡几何结构. 所得的电离势随成簇原子个数的改变, 呈现出不同程度的奇偶交替变化趋势. 在ab initio计算基础上, 用Boys方法, 对其占据正则分子轨道进行定域化变换, 得到了它们的定域分子轨道. 对定域分子轨道性质的分析表明, 线性碳元素簇合物中, 主要键型有双中心σ和π健, 双中心弯键和三中心香蕉健, 以及多中心σ和π健. 这种键型的多样化可视为小元素簇的成健特征. 此外, 通过对其成键性质的分析, 讨论了线性碳元素簇的稳定性. 对于小碳元素簇, 化学键的共轭性对其稳定性具有十分显著的作用.     

Characterization of VX on concrete using ion trap secondary ionization mass spectrometry

The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methyl phosphonothiolate) was analyzed on the surface of concrete samples using an ion trap secondary ion mass spectrometer (IT-SIMS). It was found that VX could be detected down to an absolute quantity of 5 ng on a concrete chip, or to a surface coverage of 0.0004 monolayers on crushed concrete. To achieve these levels of detection, the m/z 268-->128 ion fragmentation was measured using MS2, where m/z 268 corresponds to [VX + H]+, and 128 corresponds to a diisopropylvinylammonium isomer, that is formed by the elimination of the phosphonothiolate moiety. Detection at these levels was accomplished by analyzing samples that had been recently exposed to VX, i.e., within an hour. When the VX-exposed concrete samples were aged, the SIMS signature for intact VX had disappeared, which signaled the degradation of the compound on the concrete surface. The VX signature was replaced by ions which are interpreted in terms of VX degradation products, which appear to be somewhat long lived on the concrete surface. These compounds include ethylmethylphosphonic acid (EMPA), diisopropyl taurine (DIPT), diisopropylaminoethanethiol (DESH), bis(diisopropylaminoethane) disulfide [(DES)2], and a particularly tenacious compound that may correspond to diisopropylvinylamine (DIVA), or an isomer thereof. It was found that the thiolamine-derived degradation products DIPT, DESH, and (DES)2 were removed with isopropyl alcohol extraction. However, the DIVA-related degradation product was observed to strongly adhere to the concrete surface for longer than one week. Although quantitation was not possible in this set of experiments, the results clearly show the rapid degradation of VX on concrete, as well as the surface sensitivity of the IT-SIMS for intact VX and its adsorptive degradation products.     

基于混酸回流制备碳点的中和过程

Carbon dots (C dots) are relatively novel carbon nanomaterials that have attracted significant interest due to their unique photoluminescence, good biocompatibility, and stability. The preparation methods of C dots was usually summarized into "top-down" and "bottom-up", and mixed acid reflux is a top-down strategy that can be used to synthesize C dots, during which neutralization is a necessary step that can significantly influence the properties and potential applications of the final product. Previously, this research area mainly focused on tuning the properties of C dots by changing the starting materials and/or varying the reaction conditions; the influence of the reagents used during neutralization has been largely ignored. As the previously reported C dots prepared by mixed acid reflux were obtained from different starting materials under varied conditions, a meaningful comparison is difficult. Herein, yellow-emitting C dots were prepared by mixed acid-refluxing a carbon-rich material derived from fullerene carbon soot. For the same batch of as-prepared C dots, the influences of four reagents, i.e., NaOH, Na₂CO₃, K₂CO₃, and NH₃·H₂O, during neutralization on the structures and photoluminescence of the resulting C dots were investigated in detail. The results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clearly showed that the reagent used during neutralization can affect the degree of dissociation of the acidic functional groups on the C dots. This is further supported by examination of the C dot/surfactant mixtures where subtle changes in the phase behavior were observed. Structural changes of the C dots cause variations in their surface states, ultimately altering the optical characteristics, including UV-vis absorption and fluorescence. Among the treated C dots, the sample prepared with Na₂CO₃ showed the strongest emission under the same excitation wavelength, while that prepared with NH₃·H₂O exhibited a distinct red shift (~8 nm) in the emission curve. The results presented herein provide clear evidence that neutralization reagent selection is important for optimizing the properties of the resulting C dots obtained by mixed acid reflux. In addition, the photoluminescence of the C dots can be influenced by their counterions, providing a novel method for tuning the properties of C dots while explaining their behavior in saline solutions. In short, the basicity of the neutralizing reagent and the type of counterions affect the structure of the C dots surface, which brings different performances. This work reminds researchers that it is necessary to use the type of neutralizing reagent as an experimental condition when preparing C dots in the future.     

Effect of drop size on the degradation of VX in concrete

The effect of drop size on the degradation rate of VX, O-ethyl S-[2-(diisopropylamino)ethyl]methylphosphonothioate, in fresh concrete has been examined using (31)P NMR. Drops of neat VX, ranging in size from 4 microL to 0.2 microL, applied to small concrete coupons (8 mm x 15 mm) were observed to degrade at different rates, with the 1 microL and smaller drops reacting in less than 4 days, and the larger droplets reacting in less than 11 days. Additionally, 4 microL VX predissolved in hexane to evenly spread it over the concrete coupon likewise reacted faster, degrading in less than 5 days. The fresh concrete, less than 2 months old, exhibited significantly faster VX degradation for all drop sizes than that observed for "aged" concrete in a previous study where VX persisted for months. The enhanced reactivity of the "fresh" concrete for VX was maintained for at least a 1-year period. The pH of water containing crushed "fresh" and "aged" concrete was 10.0 and 9.0, respectively. The higher pH of the "fresh" concrete is one reason for its enhanced reactivity toward VX. An additional contribution to the enhanced reactivity of the "fresh" concrete is suggested by the increased mobility of its sorbed VX as evidenced by its significantly narrower peak in (31)P NMR spectra.     

Cobalt as chemical modifier to improve chromium sensitivity and minimize matrix effects in tungsten coil atomic emission spectrometry

Cobalt is used as chemical modifier to improve sensitivity and minimize matrix effects in Cr determinations by tungsten coil atomic emission spectrometry (WCAES). The atomizer is a tungsten filament extracted from microscope light bulbs. A solid-state power supply and a handheld CCD-based spectrometer are also used in the instrumental setup. In the presence of 1000 mg L⁻¹ Co, WCAES limit of detection for Cr (λ = 425.4 nm) is calculated as 0.070 mg L⁻¹; a 10-fold improvement compared to determinations without Co modifier. The mechanism involved in such signal enhancement is similar to the one observed in ICP OES and ICP-MS determinations of As and Se in the presence of C. Cobalt increases the population of Cr⁺ by charge transfer reactions. In a second step, Cr⁺/e⁻ recombination takes place, which results in a larger population of excited-state Cr atoms. This alternative excitation route is energetically more efficient than heat transfer from atomizer and gas phase to analyte atoms. A linear dynamic range of 0.25–10 mg L⁻¹ and repeatability of 3.8% (RSD, n = 10) for a 2.0 mg L⁻¹ Cr solution are obtained with this strategy. The modifier high concentration also contributes to improving accuracy due to a matrix-matching effect. The method was applied to a certified reference material of Dogfish Muscle (DORM-2) and no statistically significant difference was observed between determined and certified Cr values at a 95% confidence level. Spike experiments with bottled water samples resulted in recoveries between 93% and 112%.     

The Volumetric Study of the Forced Hydrolysis of the Beryllium(II) Cation in the Aqueous Solution

The volume change of the forced hydrolysis of the beryllium cation has been investigated by dilatometry and potentiometry methods. An equilibrium scheme has been proposed and the volume effects of the individual stages have been determined relative to the volume change of the neutralization reaction. It has been shown that the hydrolytic polymerization of the beryllium cation leads to a decrease of the solution volume compared with the neutralization reaction. Such behavior is a unique feature of the beryllium cation.     

Molecularly imprinted polymers for chemical agent detection in multiple water matrices

In the past few years concerns over the possibility of terrorist actions against domestic and military water supplies has become paramount. Antibodies, peptides, and enzymes have been used as molecular recognition elements in chemical sensors; however, such devices often have storage and operational stability issues that limits their success. Molecularly imprinted polymers (MIPs), have been successfully demonstrated an alternative in pesticide applications [A.L. Jenkins, R. Yin, J.J. Jensen, Analyst 126 (2001) 798-802]. The MIP materials possess selective molecular recognition properties that are complementary to the analyte in the shape and positioning of functional groups. These polymers have high selectivity and affinity constants while maintaining excellent thermal and mechanical stability. In this study, direct imprinting of chemical agents EA2192, VX, sarin, and soman (the “G” agents), was performed and the limits of detection calculated. The ability of these sensors to work in various water matrices including tap, deionized and reverse osmosis water with residual chlorine was also evaluated. Typical detection limits for these MIP sensors are approximately 50 ppt with wide linear dynamic ranges (ppt-ppm). Sensor response time is approximately 15 min.     

Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate

The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO₃⁻ compound and its H₂PO₄⁻-intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO₄²⁻ caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO₄²⁻ and H₂PO₄⁻. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.