Adductomics: a promising tool for the verification of chemical warfare agents' exposures in biological samples.

Humans are constantly exposed to a wide range of reactive and toxic chemicals from the different sources in everyday life. Identification of the exposed chemical helps in the detection and understanding the exposure associated adverse health effects. Covalent adducts of proteins and DNA formed after xenobiotics exposure may serve as readily measurable indicators of these exposures. Measuring the exposed chemicals with focus on adducts resulting from the nucleophilic interactions with blood proteins is useful in the development of diagnostic markers. Particularly, the most abundant proteins such as albumin and hemoglobin acts as dominant scavengers for many reactive chemicals in blood and can serve as excellent diagnostic candidates to determine the type of chemical exposure. This review focuses on the potential application of an adductomics approach for the screening of bimolecular adducts of chemical warfare agents (CWAs). Recent incidents of CWAs use in Syria, Malaysia, and the UK illustrate the continuing threat of chemical warfare agents in the modern world. Detection of CWAs and their metabolites in blood or in other body fluids of victims depends on immediate access to victims. Concentrations of intact CWAs in body fluids of surviving victims may decline rapidly within a few days. Certain CWAs, particularly nerve agents and vesicants, form covalent bonds with certain amino acids to form CWA-protein adducts. Proteins that are abundant in the blood, including albumin and hemoglobin, may carry these adducts longer after the original exposure. We searched MEDLINE and ISI Web of Science databases using the key terms "adductomics" "adducts of CWAs," "CWAs adducts detection in the biological samples," "protein adducts of CWAs," alone and in combination with the keywords "detection" "intoxication" "exposure" "adverse effects" and "toxicity." We also included non-peer-reviewed sources such as text books, relevant newspaper reports, and applicable Internet resources. We screened bibliographies of identified articles for additional relevant studies including non-indexed reports. These searches produced 1931 citations of which only relevant and nonduplicate citations were considered for this review. The analysis of biomedical samples has several purposes including detecting and identifying the type of chemical agent exposed, understanding the biological mechanism, assists in giving adequate treatment, determining the cause of death and providing evidence in a court of justice for forensic investigations. Rapid advances in the mass spectrometry to acquire high-quality data with greater resolution enabled the analysis of protein and DNA adducts of xenobiotics including CWAs and place the rapidly advancing 'adductomics' next to the other "-omics" technologies. Adductomics can serve as a powerful bioanalytical tool for the verification of CWAs exposure. This review mostly describes the protein adducts for nerve agents and vesicants, outlines the procedures for measuring adducts, and suggests the evolving (or future) use of adducts in the detection and verification of CWAs.

Sex Difference in the Effect of Whole Body Heating on Cardiovascular Functions.

Cold pressor test (CPT) is a well-known method for evaluating non-baroreflex mediated autonomic cardiovascular functions in humans. It has been reported that autonomic cardiovascular response to CPT differs in males and females and that heat stress attenuates the increase in arterial blood pressure during CPT. Study has also indicated that heat stress attenuates the increase in arterial blood pressure during CPT. The present study assessed the autonomic cardiovascular reactivity in males and females during cold pressor test before and after whole body heating for 40 min. 20 healthy Indian males and 18 females participated in the study. The participants were exposed to 40°C dry bulb temperature and 40% relative humidity in a simulated thermal chamber. They performed CPT before and after heat stress and their beat to beat heart rate and blood pressure were recorded. It was observed that baroreflex sensitivity (BRS) was significantly lower in females during CPT before heat stress (p < 0.01) as well as after heat stress (p < 0.01). Moreover, following whole body heating, the BRS during CPT increased slightly in females but not in males. Stroke Volume (SV) increased significantly during CPT before heat stress in females from pre-heat baseline (82 ml/beat vs. 101 ml/beat) (p < 0.001) as well as during CPT after heat stress from post-heat baseline (75 ml/beat vs. 95 ml/ beat) (p < 0.01). SV increased significantly in males during CPT after heat stress only (p < 0.01) as compared to post-heat baseline (82.5 ml/beat vs. 94.5 ml/beat). Frequency domain analysis of heart rate variability indicated that during CPT, low frequency power in males was higher than females (p < 0.05) and high frequency power was higher in females than males (p < 0.05). This suggests that autonomic modulation of cardiovascular function during CPT in males is mediated mainly via sympathetic neural system and in females it is mediated via vagal system. LF/HF ratio during CPT was found to be significantly higher in males (2.54) than females (1.27) before heat stress (p < 0.01).

Subjective and objective convergence of the eyes at simulated altitude of 18,000 feet preceded by short-term exposure to heat stress.

Armed forces personnel including military aviators are quite often exposed concurrently to various environmental stressors like high environmental temperature and hypoxia. Literatures have suggested that exposure to one environmental stressor may modify the physiological response on subsequent exposure to same or different stressor. The present study was undertaken to investigate the impact of cross tolerance between two environmental stressors of aviation (heat and hypoxia) in ten healthy adult males in a simulated altitude chamber in a within subject experimental study. They were assessed for their convergence ability of the eyes at ground and at simulated altitude of 18,000 ft with or without pre-exposure to heat stress. Subjective convergence at simulated altitude of 18,000 ft did not show any improvement following pre-exposure to heat stress. Objective convergence was improved following pre-exposure to heat stress and was found to be 10.76 cm and 9.10 cm without and with heat stress respectively at simulated altitude of 18,000 ft. Improved objective convergence at high altitude as a result of pre-exposure to heat stress is indicative of better ocular functions. This might benefit aviators while flying at hypoxic condition.

Determination of alkyl alkylphosphonic acids by liquid chromatography coupled with electrospray ionization tandem mass spectrometry using a dicationic reagent.

A new analytical method based on liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) is proposed and validated for the identification and quantification of alkyl alkylphosphonic acids (AAPAs) in aqueous matrices. Retrospective detection and identification of degradation products of chemical warfare agents is important as an indicator of possible use of chemical warfare agents or of environmental contamination. A commercially available solution of 1,9-nonanediyl-bis-(3-methylimidazolium)bisfluoride (NBMI) allowed detection of AAPAs by positive mode electrospray ionization mass spectrometry by forming an adduct with AAPAs. MS/MS experiments using an ion trap analyzer were carried out for unambiguous identification of AAPAs. Different parameters were optimized in order to obtain both an adequate chromatographic separation and a high sensitivity using experimental design methodology. Quantification was done with matrix-matched calibration standards of AAPAs. The method was validated in terms of linearity (r(2) >0.982), intra- and inter-day precisions (RSD below 15%), and robustness. The method is sensitive enough for the determination of AAPAs in aqueous matrices, with limits of detection in the 1-5 ng mL(-1) range and limits of quantification in the 5-20 ng mL(-1) range. Finally, the method was successfully applied to determine these AAPAs in aqueous samples provided by the Organization for the Prohibition of Chemical Weapons during 26(th) and 29(th) official proficiency tests. The added advantage of this method is identification of low mass range analyte at high mass range, which obviates the background noise at low mass range.

µ-PADs for detection of chemical warfare agents.

Conventional methods of detection of chemical warfare agents (CWAs) based on chromogenic reactions are time and solvent intensive. The development of cost, time and solvent effective microfluidic paper based analytical devices (µ-PADs) for the detection of nerve and vesicant agents is described. The detection of analytes was based upon their reactions with rhodamine hydroxamate and para-nitrobenzyl pyridine, producing red and blue colours respectively. Reactions were optimized on the µ-PADs to produce the limits of detection (LODs) as low as 100 µM for sulfur mustard in aqueous samples. Results were quantified with the help of a simple desktop scanner and Photoshop software. Sarin achieved a linear response in the two concentration ranges of 20-100 mM and 100-500 mM, whereas the response of sulfur mustard was found to be linear in the concentration range of 10-75 mM. Results were precise enough to establish the µ-PADs as a valuable tool for security personnel fighting against chemical terrorism.

Detection and identification of alkylphosphonic acids by positive electrospray ionization tandem mass spectrometry using a tricationic reagent.

The retrospective detection and identification of degradation products of chemical warfare agents are of immense importance in order to prove their spillage and use. A highly sensitive liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method--using an imidazolium-based tricationic reagent--was developed for the detection and identification of the anionic degradation products of nerve agents. A commercially available solution of 1,3-imidazolium-bis-(1-hexylbenzylimidazolium) trifluoride (IBHBI) formed adducts with alkylphosphonic acids (APAs), allowing detection of the APAs by positive mode ESI-MS. Tandem mass spectrometry was used for the unambiguous identification of the APAs. Parameters influencing the formation and stability of these adduct during mass spectrometric analysis, such as solvent composition, concentration of IBHBI, effect of pH and interferences by salts, were optimized. The absolute limits of detection (0.1 ng) for achieved for the APAs were better than those previously reported, and linear dynamic ranges of 10-2000 ng mL(-1) were achieved. The method was repeatable with a relative standard deviation ≤7.3%. APAs present in aqueous samples provided by the Organization for the Prohibition of Chemical Weapons during the 22(nd) and 24(th) Official Proficiency tests were detected and identified as IBHBI adducts. The added advantage of this method is that low-mass analytes are detected at higher mass, thus obviating the problem with background noise at low mass.

Dispersive solid-phase extraction for in-sorbent Fourier-transform infrared detection and identification of nerve agent simulants in analysis for verification of chemical weapon convention.

The combination of dispersive solid-phase extraction (DSPE) and Fourier-transform infrared (FTIR) spectroscopy is presented for detection and quantification of markers and simulants of nerve agents. Hydrophilic-lipophilic balance (HLB) sorbent was used for extraction and enrichment of organophosphonates from water. When the extraction efficiency of DSPE was compared with that of conventional solid-phase extraction (SPE), DSPE was more efficient. Extraction conditions such as extraction time, and type and quantity of sorbent material were optimized. In DSPE, extracted analytes are detected and quantified on the sorbent using FTIR as analytical technique. Absorbance in FTIR due to P-O-C stretching was used for detection and quantification. Infrared absorbance of different analytes were compared by determining their molar absorptivities (ε (max)). Quantitative analyses were performed employing modified Beer's law, and relative standard deviations (RSDs) for intraday repeatability and interday reproducibility were found to be in the range 0.30-0.90% and 0.10-0.80% respectively. The limit of detection (LOD) was 5-10 µg mL(-1). The applicability of the method was tested with an unknown sample prepared by mimicking the sample obtained in an international official proficiency test.

Multiwalled carbon nanotubes as efficient adsorbent for solid-phase extraction of chemical warfare agents and related chemicals from water.

Optimization of extraction and enrichment parameters of chemical warfare agents and their related chemicals from water are presented using multiwalled carbon nanotubes (MWCNTs) as solid-phase extractant. Selected analytes were O,O'-dialkyl alkylphosphonates, nerve agent and mustards. Extraction parameters, including sample volume, nature and volume of washing and eluting solvent, were optimized. Recoveries of analytes were determined by GC-MS and ranged from 81 to 104%. A comparison with C(18), hydrophilic-lipophilic balance and active carbon sorbents demonstrated the superiority of MWCNTs for non-toxic analogues of nerve agents. Optimized conditions involve 40 mg MWCNTs as the sorbent, 5.0 mL water as the washing solvent, 3 mL ethyl acetate as the eluent and sample loading of 10 mL water spiked at 0.1 µg/mL. The limits of detection (LOD) were achieved down to 1 and 0.05 ng/mL in full scan and selected ion-monitoring modes, respectively.

Application of cation-exchange solid-phase extraction for the analysis of amino alcohols from water and human plasma for verification of Chemical Weapons Convention.

The analysis of nitrogen containing amino alcohols, which are the precursors and degradation products of nitrogen mustards and nerve agent VX, constitutes an important aspect for verifying the compliance to the CWC (Chemical Weapons Convention). This work devotes on the development of solid-phase extraction method using silica- and polymer-based SCX (strong cation-exchange) and MCX (mixed-mode strong cation-exchange) cartridges for N,N-dialkylaminoethane-2-ols and alkyl N,N-diethanolamines, from water. The extracted analytes were analyzed by GC-MS (gas chromatography-mass spectrometry) in the full scan and selected ion monitoring modes. The extraction efficiencies of SCX and MCX cartridges were compared, and results revealed that SCX performed better. Extraction parameters, such as loading capacity, extraction solvent, its volume, and washing solvent were optimized. Best recoveries were obtained using 2 mL methanol containing 10% NH(4)OH and limits of detection could be achieved up to 5 x 10(-3) microg mL(-1) in the selected ion monitoring mode and 0.01 microg mL(-1) in full scan mode. The method was successfully employed for the detection and identification of amino alcohol present in water sample sent by Organization for Prohibition of Chemical Weapons (OPCW) in the official proficiency tests. The method was also applied to extract the analytes from human plasma. The SCX cartridge showed good recoveries of amino alcohols from human plasma after protein precipitation.

Neuroprotective Effects of Galantamine on Nerve Agent-Induced Neuroglial and Biochemical Changes.

Neuroprotection from nerve agent such as soman-induced neural damage is a major challenge for existing drugs. Nerve agent exposure can cause many neural effects in survivors arising mainly due to acetylcholinesterase (AChE) inhibition or death within minutes. Unraveling the mechanisms underlying the nerve agent-induced multiple neurological effects is useful to develop better and safe drugs. The present study aimed to understand the molecular response during soman exposure and to evaluate the neuroprotective efficacy of galantamine on nerve agent-induced neurotoxic changes. mRNA expression studies using quantitative real-time PCR revealed significant changes in S-100ß, Gfap, c-fos, and Bdnf in the hippocampus and piriform cortex after soman (90 µg/kg, s.c) exposure. Immunoblot analysis showed acute soman exposure significantly increased the protein levels of neuroglial markers (S100-ß and GFAP); c-Fos and protein oxidation in discrete rat brain areas indicate their role in nerve agent-induced neurotoxicity. Induction of BDNF levels during soman exposure may indicate the recovery mechanisms activation. AChE was inhibited in the blood and brain up to 82% after soman exposure. Antidotal treatment with galantamine alone (3 mg/kg) and galantamine plus atropine (10 mg/kg) has protected animals from nerve agent-induced intoxication, death, and soman-inhibited AChE up to 45% in the blood and brain. Animal received galantamine displayed increased levels of neuroprotective genes (nAChRα-7, Bcl-2, and Bdnf) in the brain suggest the neuroprotective value of galantamine. Neuroglial changes, c-Fos, and protein oxidation levels significantly reduced after galantamine and galantamine plus atropine treatment indicate their potential antidotal value in nerve agent treatment.

Extraction of chemical warfare agents from water with hydrophilic-lipophilic balance and C18 cartridges: comparative study.

Efficient extraction of chemical warfare agents (CWAs) from water is essential before subjecting them to gas chromatographic and spectral analysis aiming towards verification of the Chemical Weapons Convention (CWC). It requires development of fast, reliable, simple and reproducible sample preparation of CWAs from water which is likely to be contaminated during deliberate or inadvertent spread of CWAs. This work describes development of a solid-phase extraction method using hydrophilic-lipophilic balance (HLB) cartridges for extraction of CWAs from water. The extraction efficiencies of HLB and C18 cartridges were compared and the results revealed that HLB sorbents performed better. Extracts were analyzed by gas chromatography-mass spectrometry. Extraction parameters, such as extraction solvent, its volume and rinsing solvent were optimized. Best recoveries of target analytes were obtained using 1mL methanol and limits of detection were achieved up to 0.05microg/mL with dichloromethane. Precision of the method was found to be less than 9.2% RSD.

Application of Doehlert design in optimizing the determination of degraded products of nerve agents by ion-pair liquid chromatography electrospray ionization tandem mass spectrometry.

A qualitative method was developed for the determination of degraded products of nerve agents by using ion-pair liquid chromatography electrospray ionization tandem mass spectrometry (IP-LC-ESI-MS(n)). Generally, alkylphosphonic acids (APAs) and O-alkyl alkylphosphonic acids (AAPAs) give deprotonated molecular ion [M-H](-) in negative mode. Interestingly, first time we obtained the molecular radical anion [M](.-) of phosphonic acids in negative mode by using tri-n-butyl amine as an ion-pairing agent. We interpreted this observation as an indication of electrochemical reduction of phosphonic acids in electrospray needle. Three variables such as sheath gas flow, electrospray needle voltage and pH of the mobile phase were investigated to enhance the molecular radical anion [M](.-) signal of each analyte. The Doehlert design was used to obtain the region in which the optimum value of such variables is simultaneously achieved. Limit of detection achieved was 0.5 microg mL(-1) for AAPAs and 10 microg mL(-1) for APAs. Excellent precision was observed with less than 8.61% RSD. Finally, the method was applied for the detection of ethyl methylphosphonic in aqueous extract of soil sample.

Extraction of acidic degradation products of organophosphorus chemical warfare agents. Comparison between silica and mixed-mode strong anion-exchange cartridges.

The analysis of alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs), the hydrolyzed products of nerve agents, constitutes an important aspect for verifying the compliance to the Chemical weapons convention (CWC). This work devotes on the development of solid-phase extraction method using polymeric mixed-mode strong anion-exchange (Oasis MAX) cartridges for extraction of AAPAs and APAs from water. The extracted analytes were analyzed by GC-MS under full scan and selected ion monitoring mode. The extraction efficiencies of MAX and silica-based anion-exchange cartridges were compared, and results revealed that MAX sorbents yielded better recoveries. Extraction parameters, such as loading capacity, extraction solvent, its volume, and washing solvent were optimized. Best recoveries were obtained using 1 mL of acidic methanol (0.1 M), and limits of detection could be achieved up to 5 x 10(-4) microg mL(-1) (in SIM) and 0.05 microg mL(-1) in full scan mode. The method was successfully employed for the detection and identification of alkylphosphonic acids present in soil sample sent by the Organization for Prohibition of Chemical Weapons (OPCW) in the official proficiency tests.

In situ derivatization hollow fiber mediated liquid phase microextraction of alkylphosphonic acids from water.

Alkylphosphonic acids (APAs), particularly the methyl-, ethyl-, isopropyl- and n-propyl-phosphonic acids are important markers of extremely toxic nerve agents. Hence, their detection and identification is of vital importance to verification of chemical weapons convention (CWC). Verification analysis of CWC requires development of fast, reliable, simple and reproducible sample preparation methods of water and soil samples. Present investigation is focused on the optimization of alkylation of APAs in water with subsequent extraction of alkylated acids by hollow fiber liquid phase microextraction (HF-LPME). This simple and sensitive sample preparation of APAs from water offered better recoveries in comparison to conventionally used extraction technique. Under optimized conditions, the APAs were detected at the concentration of 0.5-0.75 microg/mL with S/N ratio > or = 5, whereas the LODs for alkyl APAs (monobasic APAs) were achieved up to 0.1 microg/mL. The developed method was finally tested with water samples supplied in 19th official proficiency test conducted by the OPCW.

A simple and economical chemical neutralization method for the destruction of sulfur mustard and its analogues.

A simple and economical chemical neutralization method is developed against highly toxic chemical warfare agent's viz. sulfur mustard (SM), sesquimustard, and their homologues/analogous. The method involves treatment of chemical warfare agents with sodium in inert solvents. This destruction method of sulfur mustards release innocuous products via desulfurization reactions. The products were characterized by GC-MS technique. The method is suitable in particular, for bulk destruction of heel of mustard stockpiles.

Microemulsion mediated in situ derivatization-extraction and gas chromatography-mass spectrometric analysis of alkylphosphonic acids.

Detection and identification of environmental signatures of chemical warfare agents is an important aspect of verification program of Chemical Weapons Convention (CWC). Alkylphosphonic acids (APAs) are ultimate and persistent degradation products of nerve agents. Their identification in a sample submitted for off-site analysis infers possible indication of contamination with nerve agents. This paper describes the development of a new sample preparation method which involves 'in situ derivatization and extraction' (INDEX) of acids from water. Derivatization is performed by alkylation of APAs with alkylbromides in surfactant less microemulsion (SLME). The derivatized analytes were analyzed by gas chromatography coupled with mass spectrometry. The developed method involves simultaneous derivatization (alkylation) and extraction of acidic analytes mediated by surfactant less microemulsion. Various derivatization-extraction parameters such as solvent, reaction time and temperature, base and alkyl bromides were optimized. Pentyl bromide in the presence of potassium carbonate and diisopropylamine at 100 degrees C derivatized the selected acids efficiently. Kinetic data for alkylation of methylphosphonic acids and some carboxylic acids were obtained to assess their relative susceptibility for alkylation in microemulsion. Methylphosphonic acid and isopropyl methylphosphonic acid took 140-150 min to reach completion while carboxylic acids took 100 min to complete the reaction. INDEX could be successfully performed even in the presence of interfering Ca(2+) and Mg(2+) ions.

Hollow fiber-mediated liquid-phase microextraction of chemical warfare agents from water.

Unambiguous detection and identification of chemical warfare agents (CWAs) and related compounds are of paramount importance from verification point of view of Chemical Weapons Convention (CWC). It requires development of fast, reliable, simple and reproducible sample preparation of CWAs from water which is likely to be contaminated during deliberate or inadvertent spread of CWAs. This work describes development of hollow fiber liquid-phase microextraction (HF-LPME) method for efficient extraction of CWAs (such as sarin, sulfur mustard and their analogues) from water followed by gas chromatography-mass spectrometric analysis. Extraction parameters, such as organic solvent, agitation, extraction time, and salt concentration were optimized. Best recoveries of target analytes were achieved using 1 microL trichloroethylene as extracting solvent, 1000 rpm stirring rate, 15 min extraction time, and 30% NaCl. Excellent precision was observed with less than 7.6% RSD. The limit of detection by HF-LPME was achieved up to 0.1 microg/L at 30% salt concentration.

Gas chromatography electron ionization mass spectrometric analysis of trimethylsilyl derivatives of bis(2-hydroxyethylthio)alkanes and bis(2-hydroxyethylsulfonyl) alkanes.

This communication describes GC-MS analysis of bis(trimethylsilyl) (bis-TMS) derivatives of bis(2-hydroxyethylthio)alkanes (BHETAs) and bis(2-hydroxyethylsulfonyl) alkanes (BHESAs) which are important markers of sulfur mustard class of chemical warfare agents. The study was undertaken with a view to develop spectral database of these compounds for verification analysis of Chemical Weapons Convention (CWC). Based on the obtained mass spectra of bis-TMS derivatives of BHETAs and BHESAs, the fragmentation routes are proposed, which explain most of the characteristic ions.

Enhanced nucleophilic reactivity of hydroxamate ions in some novel micellar systems for the cleavage of parathion.

The reactivity of three alpha-nucleophiles, i.e. N-phenylbenzohydroxamate, benzohydroxamate and salicylhydroxamate ions towards cleavage of p-nitrophenyldiethyl phosphorothioate (Parathion) is considerably enhanced in the presence of cationic surfactant, i.e. cetyltrimethylammonium bromide. The esterolytic properties of N-phenylbenzohydroxamate ion for parathion have also been examined in two novel surfactants, viz. cetyltriphenylphosphonium bromide and cetyldimethyl ethanol ammonium bromide. The cetyldimethyl ethanol ammonium bromide is more reactive. The rate-surfactant profiles have been fitted with pseudophase model.

On-matrix derivatisation-extraction of precursors of nitrogen- and sulfur-mustards for verification of chemical weapons convention.

Development and refinement of sample preparation protocols for retrospective detection and identification of chemical warfare agents (CWAs) and their markers is of paramount importance from verification point of view of chemical weapons convention (CWC). Precursors of nitrogen- and sulfur-mustards (NMPs and SMPs) are polar adsorptive markers of vesicant class of CWAs. Their detection in a given environmental sample may imply past contamination with mustards. For the efficient extraction of NMPs and SMPs from soil, on-matrix derivatisation-extraction (OMDEX) method was developed and optimized. The method involved trifluoroacetylation of analytes on soil itself, followed by extraction with suitable solvent. The extracted samples were analyzed by gas chromatography-mass spectrometry (GC-MS). This virtually single-step sample preparation offered better recoveries of NMPs and SMPs in comparison to conventionally used extraction, evaporation and derivatisation. The best recoveries of analytes were obtained with acetonitrile by OMDEX method. Dynamic linearity range of trifluoroacetylated (TFA) derivatives of NMPs and SMPs was 1-12 microg/L in GC-MS analysis in SIM mode. Repeatability and reproducibility of this technique containing 5 and 10 microg analytes/gm soil was <3.3% and <4.6%, respectively. OMDEX technique was finally applied for the detection of TFA derivatives of NMPs in the soil sample supplied in 16th official proficiency test conducted by OPCW in October 2004.