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.

A high-resolution phosphorus-31 nuclear magnetic resonance (NMR) spectroscopic method for the non-phosphorus markers of chemical warfare agents.

A high-resolution phosphorus-31 nuclear magnetic resonance (NMR) spectroscopic method has been developed for detection, identification and quantification of non-phosphorus markers of toxic nerve agents (soman and V-class), vesicants (HD, HN-2, HN-3), and incapacitating agent (Bz). These analytes were converted to phosphorus-containing derivatives via phosphitylation reaction of their hydroxyl and sulfhydryl functions (using 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane). This was followed by (31)P{(1)H} and (31)P NMR analysis of these derivatives. The chemical shifts (δ) and coupling constants ((3)J(P-H)) of derivatives were used for their specific detection and identification. The method allowed clear distinction between the alcohols and thiols. The lower limits of detection of these analytes were found to be between 12 and 28 µg obtained from 128 transients of (31)P{(1)H} quantitative NMR experiments. Utility of the method was ensured by the detection and identification of triethanolamine present (at an original concentration of 5 µg/mL) in an aqueous sample from 28th OPCW Official Proficiency Tests.

Magnetic multi-walled carbon nanotubes assisted dispersive solid phase extraction of nerve agents and their markers from muddy water.

The multi-walled carbon nano-tubes (MWCNT) were magnetized with iron oxide nanoparticles and were characterized by SEM and EDX analyses. These magnetized MWCNT (Mag-CNT) were used as sorbent in dispersive solid phase extraction (DSPE) mode to extract nerve agents and their markers. Mag-CNT were dispersed in water and collected with the help of an external magnet. From Mag-CNT, the adsorbed analytes were eluted and analyzed by GC-FPD in phosphorus mode. DSPE was found to be advantageous over conventional solid phase extraction (SPE) in terms of operational simplicity, speed, handling of large sample volume and recoveries. Extraction parameters such as eluting solvent, sorbent amount, pH and salinity of aqueous samples were optimized. Optimized extraction conditions included 40 mg of Mag-CNT as sorbent, chloroform as eluent, pH 3-11 and salinity 20%. Under the optimized conditions, recoveries from distilled water ranged from 60 to 96% and were comparable in tap and muddy water. Limits of quantification and limits of detection of 0.15 ng/ml and 0.05 ng/ml, respectively, were achieved. Superiority of Mag-CNT over conventional C(18) SPE was also established.

Polyelectrolyte functionalized multi-walled carbon nanotubes as strong anion-exchange material for the extraction of acidic degradation products of nerve agents.

Extraction, enrichment and gas chromatography mass spectrometric analysis of degradation products of nerve agents from water is of significant importance for verification of Chemical Weapons Convention (CWC) and gathering forensic evidence of use of nerve agents. Multi-walled carbon nanotubes (MWCNTs) were non-covalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) to afford the cationic functionalized nano-tubes, which were used as solid-phase anionic-exchanger sorbents to extract the acidic degradation products of nerve agents from water. Extraction efficiencies of MWCNTs-PDDA were compared with those of mixed mode anion-exchange (HLB) and silica based strong anion-exchange (Si-SAX) cartridges. Optimized extraction parameters included MWCNTs-PDDA 12 mg, washing solvent 5 mL water and eluting solvent 3 mL of 0.1M aqueous HCl followed by 3 mL methanol. At 1 ng mL(-1) spiking concentration of mono- and di-basic phosphonic acids, MWCNTs-PDDA exhibited higher extraction efficiencies in comparison to Si-SAX and HLB. The limits of detection were achieved down to 0.05 and 0.11 ng mL(-1) in selected ion and full scan monitoring mode respectively; and limits of quantification in selected ion monitoring mode were achieved down to 0.21 ng mL(-1).

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.

Gas chromatography-electron ionization-mass spectrometry analysis of O,O'- dialkyl methylphosphonites for verification analysis of the Chemical Weapons Convention.

Gas chromatography-mass spectrometry (GC-MS) analysis of O,O'-dialkyl methylphosphonites (DAMPs) was carried out with a view to developing a database and understanding the mechanism of fragmentation. DAMPs are included in the list of schedule 2B4 chemicals of the Chemical Weapons Convention. GC-MS analysis of DAMPs and their deuterated analogs revealed that their fragmentations were dominated by α-cleavages, alkenyl radical loss and hydrogen rearrangements. Based on fragment ions of deuterated analogs and density functional theory calculations, the fragmentation routes were rationalized.

Application of high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy for the analysis of degradation products of V-class nerve agents and nitrogen mustard.

The detection and identification of the degradation products of nitrogen mustard and nerve agent VX by high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-UV-SPE-NMR) were demonstrated. The analytes selected for the study were N,N-dimethylaminoethanol (DMAE), N,N-diethylaminoethanol (DEAE), N,N-diisopropylaminoethanol (DIAE) and triethanolamine (TEA). Offline solid-phase extraction (SPE) followed by derivatization was applied to eliminate the interferents and make the analytes amenable for UV detection. Thereafter, chromatographically separated derivatives were trapped on on-line SPE cartridges. They were subsequently eluted and 1H NMR and COSY spectra were obtained. The overall detection limits of the LC-UV-SPE-NMR method for the mentioned analytes were found to be 18, 23, 25, and 32 mg/L respectively. Applicability of the method to real samples was demonstrated by the analysis of samples provided during the 22nd OPCW official proficiency test. The method gave reproducible NMR spectra devoid of intense background signals.