Use of carbonyldiimidazole as a derivatization agent for the detection of pinacolyl alcohol, a forensic marker for Soman, by EI-GC-MS and LC-HRMS in official OPCW proficiency test matrices.

Pinacolyl alcohol (PA), a key forensic marker for the nerve agent Soman (GD), is a particularly difficult analyte to detect by various analytical methods. In this work, we have explored the reaction between PA and 1,1'-carbonyldiimidazole (CDI) to yield pinacolyl 1H-imidazole-1-carboxylate (PIC), a product that can be conveniently detected by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high-resolution mass spectrometry (LC-HRMS). Regarding its GC-MS profile, this new carbamate derivative of PA possesses favorable chromatographic features such as a sharp peak and a longer retention time (RT = 16.62 min) relative to PA (broad peak and short retention time, RT = 4.1 min). The derivative can also be detected by LC-HRMS, providing an avenue for the analysis of this chemical using this technique where PA is virtually undetectable unless present in large concentrations. From a forensic science standpoint, detection of this low molecular weight alcohol signals the past or latent presence of the nerve agent Soman (GD) in a given matrix (i.e., environmental or biological). The efficiency of the protocol was tested separately in the analysis and detection of PA by EI-GC-MS and LC-HRMS when present at a 10 µg/mL in a soil matrix featured in the 44th PT and in a glycerol-rich liquid matrix featured in the 48th Official Organization for the Prohibition of Chemical Weapons (OPCW) Proficiency Test when present at a 5 µg/mL concentration. In both scenarios, PA was successfully transformed into PIC, establishing the protocol as an additional tool for the analysis of this unnatural and unique nerve agent marker by GC-MS and LC-HRMS.

Analysis of Organophosphorus-Based Nerve Agent Degradation Products by Gas Chromatography-Mass Spectrometry (GC-MS): Current Derivatization Reactions in the Analytical Chemist's Toolbox.

The field of gas chromatography-mass spectrometry (GC-MS) in the analysis of chemical warfare agents (CWAs), specifically those involving the organophosphorus-based nerve agents (OPNAs), is a continually evolving and dynamic area of research. The ever-present interest in this field within analytical chemistry is driven by the constant threat posed by these lethal CWAs, highlighted by their use during the Tokyo subway attack in 1995, their deliberate use on civilians in Syria in 2013, and their use in the poisoning of Sergei and Yulia Skripal in Great Britain in 2018 and Alexei Navalny in 2020. These events coupled with their potential for mass destruction only serve to stress the importance of developing methods for their rapid and unambiguous detection. Although the direct detection of OPNAs is possible by GC-MS, in most instances, the analytical chemist must rely on the detection of the products arising from their degradation. To this end, derivatization reactions mainly in the form of silylations and alkylations employing a vast array of reagents have played a pivotal role in the efficient detection of these products that can be used retrospectively to identify the original OPNA.

Improving Quantification of tabun, sarin, soman, cyclosarin, and sulfur mustard by focusing agents: A field portable gas chromatography-mass spectrometry study.

Commercial gas chromatograph-mass spectrometers, one of which being Inficon's HAPSITE® ER, have demonstrated chemical detection and identification of nerve agents (G-series) and blistering agents (mustard gas) in the field; however most analyses relies on self-contained or external calibration that inherently drifts over time. We describe an analytical approach that uses target-based thermal desorption standards, called focusing agents, to accurately calculate concentrations of chemical warfare agents that are analyzed by gas chromatograph-mass spectrometry. Here, we provide relative response factors of focusing agents (2-chloroethyl ethyl sulfide, diisopropyl fluorophosphate, diethyl methylphosphonate, diethyl malonate, methyl salicylate, and dichlorvos) that are used to quantify concentrations of tabun, sarin, soman, cyclosarin and sulfur mustard loaded on thermal desorption tubes (Tenax® TA). Aging effects of focusing agents are evaluated by monitoring deviations in quantification as thermal desorption tubes age in storage at room temperature and relative humidity. The addition of focusing agents improves the quantification of tabun, sarin, soman, cyclosarin and sulfur mustard that is analyzed within the same day as well as a 14-day period. Among the six focusing agents studied here, diisopropyl fluorophosphate has the best performance for nerve agents (G-series) and blistering agents (mustard gas) compared to other focusing agents in this work and is recommended for field use for quantification. The use of focusing agent in the field leads to more accurate and reliable quantification of Tabun (GA), Sarin (GB), Soman (GD), Cyclosarin (GF) and Sulfur Mustard (HD) than the traditional internal standard. Future improvements on the detection of chemical, biological, radiological, nuclear, and explosive materials (CBRNE) can be safely demonstrated with standards calibrated for harmful agents.

Detection of Chemical Weapon Nerve Agents in Bone by Liquid Chromatography-Mass Spectrometry.

A recently proposed model for the incorporation of xenobiotics of forensic interest into the human skeleton suggests nerve agent metabolites may incorporate into bone at relatively elevated concentrations based on their unique chemical properties. To test the hypothesis that nerve agent metabolites interact with bone, methods for the extraction, isolation and semi-quantitative detection of nerve agent metabolites (MPA, EMPA, IMPA, iBuMPA, CMPA and PMPA, corresponding to the nerve agents VX, Russian VX, sarin, cyclosarin and soman, respectively) from osseous tissue were developed using liquid chromatography-mass spectrometry with both quadrupole time-of-flight and triple quadrupole (QqQ) instruments. The optimized methods were validated on the QqQ instrument. Despite high ion suppression, the achieved limits of detection (5-20 pg/g for four analytes; 350 pg/g for the fifth analyte) were lower than many of those published for the same analytes in other biomatrices, including serum and urine. These methods were tested on the skeletal remains of minipigs exposed to the chemical weapon VX in vivo. The VX metabolite was detected in multiple minipig bone samples; to the authors' knowledge, this is the first time in vivo nerve agent exposure has been detected from bone. Further, detected concentrations and diaphyseal-to-epiphyseal area count ratios reflect animal exposure history. Although the results are limited, they are promising, indicating that nerve agent metabolites may interact with bone as a pharmacokinetic compartment and can be extracted from bone postmortem. Additional studies, assessing the effects of different agents, exposure pathways and taphonomic variables, are needed; however, these results suggest the method may be used with human bone to detect use of chemical weapons from postmortem biomatrices even well after a suspected attack. More general implications for both nerve agent toxicology and skeletal toxicology are also discussed.

"Covalent-Assembly"-Based Fluorescent Probe for Detection of a Nerve-Agent Mimic (DCP) via Lossen Rearrangement.

The highly selective and sensitive fluorescence "light-up" probe, 5'-(dimethylamino)-2'-formyl-N-hydroxy-[1,1'-biphenyl]-2-carboxamide(PTS), has been fabricated for the nerve-agent mimic diethyl chlorophosphate (DCP). The probe is designed by combining two novel strategies of "covalent assembly" and Lossen rearrangement. Formation of a phosphoryl intermediate from DCP and a hydroxamic acid group in PTS yields an isocyanate that quickly undergoes Lossen rearrangement to produce an aniline that condenses intramolecularly to a fluorescent phenanthridine system. PTS shows superior properties to probe DCP, such as rapid response (within 100 s), low detection limit (10.4 nM), specificity, and excellent linearity (R2 = 0.9993) in the range from 2 to 16 µM. More importantly, its application of detecting DCP vapor has also been achieved with satisfying results.

Methylation protocol for the retrospective detection of isopropyl-, pinacolyl- and cyclohexylmethylphosphonic acids, indicative markers for the nerve agents sarin, soman and cyclosarin, at low levels in soils using EI-GC-MS.

A practical and efficient protocol for the derivatization and detection by GC-EI-MS of isopropyl-, pinacolyl- and cyclohexylmethylphosphonic acids, key diagnostic degradation products of the nerve agents sarin, soman and cyclosarin respectively, in six different types of soil matrices is presented. The method involves the in situ conversion of the phosphonic acids to their respective methyl esters using trimethyloxonium tetrafluoroborate when present in the soils at low levels (10 µg g-1) without any prior extractions or soil preparation. The soils employed in our study were Nebraska EPA soil, Georgia soil, silt, Virginia type A soil, regular sand and Ottawa sand and were chosen for their vast differences in composition and physical features. Appealing attributes of the protocol include its rapidity (t < 30 min), mildness (ambient temperature), and practicality that includes the production of the phosphonic methyl esters that can be easily detected by GC-EI-MS and corroborated with the instrument's internal NIST spectral library or the Organisation for the Prohibition of Chemical Weapons (OPCW) central analytical database (OCAD v.21_2019). The overall efficacy of the protocol was then tested on a soil sample featured in the 44th OPCW PT that our laboratory participated in. After preparing the soil so as to give pinacolyl methylphosphonic acid at a 5 µg g-1 concentration, the acid was successfully methylated and detected by GC-EI-MS. The protocol's performance mirrors that of the universally employed diazomethane protocol but accomplishes this without any of the explosive hazards and time consuming reagent preparation commonly associated with it.

Chromo-Fluorogenic Detection of Soman and Its Simulant by Thiourea-Based Rhodamine Probe.

Here, we introduced a novel thiourea-based rhodamine compound as a chromo-fluorogenic indicator of nerve agent Soman and its simulant diethyl chlorophosphate (DCP). The synthesized probe N-(rhodamine B)-lactam-2-(4-cyanophenyl) thiourea (RB-CT), which has a rhodamine core linked by a cyanophenyl thiosemicarbazide group, enabled a rapidly and highly sensitive response to DCP with clear fluorescence and color changes. The detection limit was as low as 2 × 10-6 M. The sensing mechanism showed that opening of the spirolactam ring following the phosphorylation of thiosemicarbazides group formed a seven-membered heterocycle adduct, according to MS analysis and TD-DFT calculations. RB-CT exhibited high detecting selectivity for DCP, among other organophosphorus compounds. Moreover, two test kits were employed and successfully used to detect real nerve agent Soman in liquid and gas phase.

Aqueous extraction followed by derivatization and liquid chromatography-mass spectrometry analysis: A unique strategy for trace detection and identification of G-nerve agents in environmental matrices.

A highly sensitive method for the detection and identification of sarin (GB), soman (GD) and cyclosarin (GF) chemical warfare agents (CWAs) in environmental outdoor and indoor matrices such as soil, asphalt, linoleum, formica, concrete and cloth was developed. The method incorporates derivatization of the G-type nerve agent extracts with 2-[(dimethylamino)methyl]phenol (2-DMAMP), followed by LC-ESI(+)-MS/MS analysis. Four LC-amenable extraction solvents were explored in terms of their extraction efficiency and the reaction rate of the derivatizing agent. The reaction time, temperature and derivatization reagent amount were optimized. The optimal procedure was found to be extraction with water by agitation (2 min), followed by the addition of 2-DMAMP directly into the injection vial and stirring for 5 min prior to LC-ESI(+)-MS/MS analysis, without any other pretreatment. The method was applied to real-world samples and exhibited very low detection limits (LODs) of 0.8-20 pg/cm2 in asphalt, linoleum, cloth, formica and concrete and 4 pg/g in soil. The newly developed method demonstrated significantly superior sensitivity compared to conventional GC-MS- and LC-MS-based methods for the identification of G-nerve agents and allowed the determination of both G-nerve agents and their hydrolysis products within a single LC-MS/MS run. The proposed methodology may be practical for verifying contaminated matrices collected in the battlefield or terror scenes in forensic investigations where trace level analysis is required.

Use of Hupresin To Capture Red Blood Cell Acetylcholinesterase for Detection of Soman Exposure.

Toxicity from acute exposure to nerve agents and organophosphorus toxicants is due to irreversible inhibition of acetylcholinesterase (AChE) in the nervous system. AChE in red blood cells is a surrogate for AChE in the nervous system. Previously we developed an immunopurification method to enrich red blood cell AChE (RBC AChE) as a biomarker of exposure. The goal of the present work was to provide an alternative RBC AChE enrichment strategy, by binding RBC AChE to Hupresin affinity gel. AChE was solubilized from frozen RBC by addition of 1% Triton X-100. Insoluble debris was removed by centrifugation. The red, but not viscous, RBC AChE solution was loaded on a Hupresin affinity column. Hemoglobin and other proteins were washed off with 3 M NaCl, while retaining AChE bound to Hupresin. Denatured AChE was eluted with 1% trifluoroacetic acid. The same protocol was used for 20 mL of RBC AChE inhibited with a soman model compound. The acid denatured protein was digested with pepsin and analyzed by liquid chromatography tandem mass spectrometry on a 6600 Triple-TOF mass spectrometer. A targeted method identified the aged soman adduct on serine 203 in peptide FGESAGAAS. It was concluded that Hupresin can be used to enrich soman-inhibited AChE solubilized from 8 mL of frozen human erythrocytes, yielding a quantity sufficient for detecting soman exposure.

Coupling Activity-Based Detection, Target Amplification, Colorimetric and Fluorometric Signal Amplification, for Quantitative Chemosensing of Fluoride Generated from Nerve Agents.

The G-class nerve agents, which include sarin, soman, and cyclosarin, react readily with nucleophilic reagents to produce fluoride. Thus, a chemosensing protocol has been designed for these agents that pairs the nucleophilic reactivity of oximates for generating fluoride with an autoinductive target amplification reaction to amplify the quantity of fluoride for facile colorimetric and fluorescent optical quantification. The chemosensing protocol was demonstrated by using the nerve agent surrogate diisopropyl fluorophosphate (DFP) and benzaldoxime as the nucleophile. Autoinductive fluoride amplification responds to fluoride released from DFP by amplifying the fluoride concentration and a yellow reporter molecule. The reporter is a conjugated oligomer with a nominal repeating unit that originates from 4-aminobenzaldehyde. Exposure of the amplified fluoride to a fluoride-specific ratiometric fluorescent reporter provides a fluorescent readout, in which three fluorophores are generated per fluoride. Both colorimetric and fluorescent readouts enable quantitative assays with low micromolar limits of detection for fluoride resulting from DFP. More importantly, this work demonstrates the successful merging of multiple complex reactions for achieving selective, sensitive, and quantitative chemosensing.

Analysis of Nerve Agent Metabolites from Hair for Long-Term Verification of Nerve Agent Exposure.

Several methods for the bioanalysis of nerve agents or their metabolites have been developed for the verification of nerve agent exposure. However, parent nerve agents and known metabolites are generally rapidly excreted from biological matrixes typically used for analysis (i.e., blood, urine, and tissues), limiting the amount of time after an exposure that verification is feasible. In this study, hair was evaluated as a long-term repository of nerve agent hydrolysis products. Pinacolyl methylphosphonic acid (PMPA; hydrolysis product of soman) and isopropyl methylphosphonic acid (IMPA; hydrolysis product of sarin) were extracted from hair samples with N,N-dimethylformamide and subsequently analyzed by liquid chromatography-tandem mass spectrometry. Limits of detection for PMPA and IMPA were 0.15 µg/kg and 7.5 µg/kg and linear ranges were 0.3-150 µg/kg and 7.5-750 µg/kg, respectively. To evaluate the applicability of the method to verify nerve agent exposure well after the exposure event, rats were exposed to soman, hair was collected after approximately 30 days, and stored for up to 3.5 years prior to initial analysis. PMPA was positively identified in 100% of the soman-exposed rats (N = 8) and was not detected in any of the saline treated animals (N = 6). The hair was reanalyzed 5.5 years after exposure and PMPA was detected in 6 of the 7 (one of the soman-exposed hair samples was completely consumed in the analysis at 3.5 years) rat hair samples (with no PMPA detected in the saline exposed animals). Although analysis of CWA metabolites from hair via this technique is not appropriate as a universal method to determine exposure (i.e., it takes time for the hair to grow above the surface of the skin and typical analysis times are >24 h), it complements existing methods and could become the preferred method for verification of exposure if 10 or more days have elapsed after a suspected exposure.

A Rapid and Sensitive Strip-Based Quick Test for Nerve Agents Tabun, Sarin, and Soman Using BODIPY-Modified Silica Materials.

Test strips that in combination with a portable fluorescence reader or digital camera can rapidly and selectively detect chemical warfare agents (CWAs) such as Tabun (GA), Sarin (GB), and Soman (GD) and their simulants in the gas phase have been developed. The strips contain spots of a hybrid indicator material consisting of a fluorescent BODIPY indicator covalently anchored into the channels of mesoporous SBA silica microparticles. The fluorescence quenching response allows the sensitive detection of CWAs in the µg m(-3) range in a few seconds.

Hydrophilic interaction liquid chromatography-tandem mass spectrometry methylphosponic and alkyl methylphosphonic acids determination in environmental samples after pre-column derivatization with p-bromophenacyl bromide.

Once exposed to the environment organophosphate nerve agents readily degrade by rapid hydrolysis to the corresponding alkyl methylphosphonic acids which do not exist in nature. These alkyl methylphosphonic acids are finally slowly hydrolyzed to methylphosphonic acid. Methylphosphonic acid is the most stable hydrolysis product of organophosphate nerve agents, persisting in environment for a long time. A highly sensitive method of methylphosphonic acid and alkyl methylphosphonic acids detection in dust and ground mixed samples has been developed and validated. The fact that alkyl methylphosphonic acids unlike methylphosphonic acid did not react with p-bromophenacyl bromide under chosen conditions was discovered. This allowed simultaneous chromatographic separation and mass spectrometric detection of derivatized methylphosphonic acid and underivatized alkyl methylphosphonic acids using HILIC-MS/MS method. Very simple sample pretreatment with high recoveries for each analyte was developed. Methylphosphonic acid pre-column derivate and alkyl methylphosphonic acids were detected using tandem mass spectrometry with electrospray ionization after hydrophilic interaction liquid chromatography separation. The developed approach allows achieving ultra-low detection limits: 200 pg mL(-1) for methylphosphonic acid, 70 pg mL(-1) for ethyl methylphosphonic acid, 8 pg mL(-1) for i-propyl methylphosphonic acid, 8 pg mL(-1) for i-butyl methylphosphonic acid, 5 pg mL(-1) for pinacolyl methylphosphonic acid in the extracts of dust and ground mixed samples. This approach was successfully applied to the dust and ground mixed samples from decommissioned plant for the production of chemical weapons.

Measurement of breakthrough volumes of volatile chemical warfare agents on a poly(2,6-diphenylphenylene oxide)-based adsorbent and application to thermal desorption-gas chromatography/mass spectrometric analysis.

To establish adequate on-site solvent trapping of volatile chemical warfare agents (CWAs) from air samples, we measured the breakthrough volumes of CWAs on three adsorbent resins by an elution technique using direct electron ionization mass spectrometry. The trapping characteristics of Tenax(®) TA were better than those of Tenax(®) GR and Carboxen(®) 1016. The latter two adsorbents showed non-reproducible breakthrough behavior and low VX recovery. The specific breakthrough values were more than 44 (sarin) L/g Tenax(®) TA resin at 20°C. Logarithmic values of specific breakthrough volume for four nerve agents (sarin, soman, tabun, and VX) showed a nearly linear correlation with the reciprocals of their boiling points, but the data point of sulfur mustard deviated from this linear curve. Next, we developed a method to determine volatile CWAs in ambient air by thermal desorption-gas chromatography (TD-GC/MS). CWA solutions that were spiked into the Tenax TA(®) adsorbent tubes were analyzed by a two-stage TD-GC/MS using a Tenax(®) TA-packed cold trap tube. Linear calibration curves for CWAs retained in the resin tubes were obtained in the range between 0.2pL and 100pL for sarin, soman, tabun, cyclohexylsarin, and sulfur mustard; and between 2pL and 100pL for VX and Russian VX. We also examined the stability of CWAs in Tenax(®) TA tubes purged with either dry or 50% relative humidity air under storage conditions at room temperature or 4°C. More than 80% sarin, soman, tabun, cyclohexylsarin, and sulfur mustard were recovered from the tubes within 2 weeks. In contrast, the recoveries of VX and Russian VX drastically reduced with storage time at room temperature, resulting in a drop to 10-30% after 2 weeks. Moreover, we examined the trapping efficiency of Tenax TA(®) adsorbent tubes for vaporized CWA samples (100mL) prepared in a 500mL gas sampling cylinder. In the concentration range of 0.2-2.5mg/m(3), >50% of sarin, soman, tabun, cyclohexylsarin, and HD were recovered, whereas <1% of VX and Russian VX were recovered in the same concentration range. The results indicate that CWA vapors, with the exception of VX and Russian VX, can be measured by an on-site collection procedure using the Tenax(®) TA resin tubes, followed by a subsequent TD-GC/MS analysis.

Identification of chemical warfare agents from vapor samples using a field-portable capillary gas chromatography/membrane-interfaced electron ionization quadrupole mass spectrometry instrument with Tri-Bed concentrator.

A field-portable gas chromatograph-mass spectrometer (Hapsite ER system) was evaluated for the detection of chemical warfare agents (CWAs) in the vapor phase. The system consisted of Tri-Bed concentrator gas sampler (trapping time: 3s(-1)min), a nonpolar low thermal-mass capillary gas chromatography column capable of raising temperatures up to 200°C, a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump for data acquisition, and a personal computer for data analysis. Sample vapors containing as little as 22µg sarin (GB), 100µg soman (GD), 210µg tabun (GA), 55µg cyclohexylsarin (GF), 4.8µg sulfur mustard, 390µg nitrogen mustard 1, 140µg of nitrogen mustard 2, 130µg nitrogen mustard 3, 120µg of 2-chloroacetophenone and 990µg of chloropicrin per cubic meter could be confirmed after Tri-Bed micro-concentration (for 1min) and automated AMDIS search within 12min. Using manual deconvolution by background subtraction of neighboring regions on the extracted ion chromatograms, the above-mentioned CWAs could be confirmed at lower concentration levels. The memory effects were also examined and we found that blister agents showed significantly more carry-over than nerve agents. Gasoline vapor was found to interfere with the detection of GB and GD, raising the concentration limits for confirmation in the presence of gasoline by both AMDIS search and manual deconvolution; however, GA and GF were not subject to interference by gasoline. Lewisite 1, and o-chlorobenzylidene malononitrile could also be confirmed by gas chromatography, but it was hard to quantify them. Vapors of phosgene, chlorine, and cyanogen chloride could be confirmed by direct mass spectrometric detection at concentration levels higher than 2, 140, and 10mg/m(3) respectively, by bypassing the micro-concentration trap and gas chromatographic separation.

Chiral separation of G-type chemical warfare nerve agents via analytical supercritical fluid chromatography.

Chemical warfare nerve agents (CWNAs) are extremely toxic organophosphorus compounds that contain a chiral phosphorus center. Undirected synthesis of G-type CWNAs produces stereoisomers of tabun, sarin, soman, and cyclosarin (GA, GB, GD, and GF, respectively). Analytical-scale methods were developed using a supercritical fluid chromatography (SFC) system in tandem with a mass spectrometer for the separation, quantitation, and isolation of individual stereoisomers of GA, GB, GD, and GF. Screening various chiral stationary phases (CSPs) for the capacity to provide full baseline separation of the CWNAs revealed that a Regis WhelkO1 (SS) column was capable of separating the enantiomers of GA, GB, and GF, with elution of the P(+) enantiomer preceding elution of the corresponding P(-) enantiomer; two WhelkO1 (SS) columns had to be connected in series to achieve complete baseline resolution. The four diastereomers of GD were also resolved using two tandem WhelkO1 (SS) columns, with complete baseline separation of the two P(+) epimers. A single WhelkO1 (RR) column with inverse stereochemistry resulted in baseline separation of the GD P(-) epimers. The analytical methods described can be scaled to allow isolation of individual stereoisomers to assist in screening and development of countermeasures to organophosphorus nerve agents.

Selective chromo-fluorogenic detection of DFP (a Sarin and Soman mimic) and DCNP (a Tabun mimic) with a unique probe based on a boron dipyrromethene (BODIPY) dye.

A novel colorimetric probe (P4) for the selective differential detection of DFP (a Sarin and Soman mimic) and DCNP (a Tabun mimic) was prepared. Probe P4 contains three reactive sites; i.e. (i) a nucleophilic phenol group able to undergo phosphorylation with nerve gases, (ii) a carbonyl group as a reactive site for cyanide; and (iii) a triisopropylsilyl (TIPS) protecting group that is known to react with fluoride. The reaction of P4 with DCNP in acetonitrile resulted in both the phosphorylation of the phenoxy group and the release of cyanide, which was able to react with the carbonyl group of P4 to produce a colour modulation from pink to orange. In contrast, phosphorylation of P4 with DFP in acetonitrile released fluoride that hydrolysed the TIPS group in P4 to yield a colour change from pink to blue. Probe P4 was able to discriminate between DFP and DCNP with remarkable sensitivity; limits of detection of 0.36 and 0.40 ppm for DCNP and DFP, respectively, were calculated. Besides, no interference from other organophosphorous derivatives or with presence of acid was observed. The sensing behaviour of P4 was also retained when incorporated into silica gel plates or onto polyethylene oxide membranes, which allowed the development of simple test strips for the colorimetric detection of DCNP and DFP in the vapour phase. P4 is the first probe capable of colorimetrically differentiating between a Tabun mimic (DCNP) and a Sarin and Soman mimic (DFP).

Detection of nerve agents using proton transfer reaction mass spectrometry with ammonia as reagent gas.

The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS.

Organophosphorus pesticide and ester analysis by using comprehensive two-dimensional gas chromatography with flame photometric detection.

Thirty-seven phosphorus (P)-containing compounds comprising organophosphorus pesticides and organophosphate esters were analyzed by using comprehensive two-dimensional gas chromatography with flame photometric detection in P mode (GC × GC-FPD(P)), with a non-polar/moderately polar column set. A suitable modulation temperature and period was chosen based on experimental observation. A number of co-eluting peak pairs on the (1)D column were well separated in 2D space. Excellent FPD(P) detection selectivity, responding to compounds containing the P atom, produces clear 2D GC × GC plots with little interference from complex hydrocarbon matrices. Limits of detection (LOD) were within the range of 0.0021-0.048 µmol L(-1), and linear calibration correlation coefficients (R(2)) for all 37 P-compounds were at least 0.998. The P-compounds were spiked in 2% diesel and good reproducibility for their response areas and retention times was obtained. Spiked recoveries were 88%-157% for 5 µg L(-1) and 80%-138% for 10 µg L(-1) spiked levels. Both (1)tR and (2)tR shifts were noted when the content of diesel was in excess of 5% in the matrix. Soil samples were analyzed by using the developed method; some P-compounds were positively detected. In general, this study shows that GC × GC-FPD(P) is an accurate, sensitive and simple method for P-compound analysis in complicated environmental samples.

Evaluation of in vitro absorption, decontamination and desorption of organophosphorous compounds from skin and synthetic membranes.

Chemical warfare agents, such as soman, and pesticides, such as chlorpyrifos, dichlorvos or malathion, are toxic organophosphorous compounds (OPCs) that are readily absorbed by the skin. Decontamination using solvents or surfactants may modify the cornified layer - the skin's main barrier against xenobiotic penetration. Thus, effective skin decontamination with fewer side effects is desired. We determined the membrane absorption, decontamination and desorption of toxic OPCs using human skin and synthetic membrane (cuprophane, cellulose acetate, methyl ethyl cellulose, acetophane and nylon) models, and estimated the efficacy of adsorptive powders (bentonite and magnesium trisilicate) at inhibiting this transfer. Using validated flow-through and static diffusion cell and HPLC methods, we found that the transfer of OPCs depends on their membrane affinity. The chlorpyrifos transfer decreased with a decrease in the membrane hydrophilicity, and that of malathion across hydrophilic membranes was less than half of that across hydrophobic membranes. We reliably modeled the toxicant transfer through the skin and synthetic membranes as first-order kinetic and/or square root law transfer processes, suggesting a potential application of synthetic membranes for predicting percutaneous absorption of OPCs. All tested adsorptive powders, applied either alone or as mixtures, significantly reduced the toxicant amount transferred across all membrane models, suggesting a potential therapeutic application with fewer later undesired effects on intact skin.