Analysis of chemical warfare agents in organic liquid samples with magnetic dispersive solid phase extraction and gas chromatography mass spectrometry for verification of the chemical weapons convention.

A simple, sensitive and low temperature sample preparation method is developed for detection and identification of Chemical Warfare Agents (CWAs) and scheduled esters in organic liquid using magnetic dispersive solid phase extraction (MDSPE) followed by gas chromatography-mass spectrometry analysis. The method utilizes Iron oxide@Poly(methacrylic acid-co-ethylene glycol dimethacrylate) resin (Fe2O3@Poly(MAA-co-EGDMA)) as sorbent. Variants of these sorbents were prepared by precipitation polymerization of methacrylic acid-co-ethylene glycol dimethacrylate (MAA-co-EGDMA) onto Fe2O3 nanoparticles. Fe2O3@poly(MAA-co-EGDMA) with 20% MAA showed highest recovery of analytes. Extractions were performed with magnetic microspheres by MDSPE. Parameters affecting the extraction efficiency were studied and optimized. Under the optimized conditions, method showed linearity in the range of 0.1-3.0µgmL(-1) (r(2)=0.9966-0.9987). The repeatability and reproducibility (relative standard deviations (RSDs) %) were in the range of 4.5-7.6% and 3.4-6.2% respectively for organophosphorous esters in dodecane. Limits of detection (S/N=3/1) and limit of quantification (S/N=10/1) were found to be in the range of 0.05-0.1µgmL(-1) and 0.1-0.12µgmL(-1) respectively in SIM mode for selected analytes. The method was successfully validated and applied to the extraction and identification of targeted analytes from three different organic liquids i.e. n-hexane, dodecane and silicon oil. Recoveries ranged from 58.7 to 97.3% and 53.8 to 95.5% at 3µgmL(-1) and 1µgmL(-1) spiking concentrations. Detection of diethyl methylphosphonate (DEMP) and O-Ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX) in samples provided by the Organization for Prohibition of Chemical Weapons Proficiency Test (OPCW-PT) proved the utility of the developed method for the off-site analysis of CWC relevant chemicals.

Magnetic hydrophilic-lipophilic balance sorbent for efficient extraction of chemical warfare agents from water samples.

Magnetic hydrophilic-lipophilic balance (MHLB) hybrid resin was prepared by precipitation polymerization using N-vinylpyrrolidone (PVP) and divinylbenzene (DVB) as monomers and Fe2O3 nanoparticles as magnetic material. These resins were successfully applied for the extraction of chemical warfare agents (CWAs) and their markers from water samples through magnetic dispersive solid-phase extraction (MDSPE). By varying the ratios of monomers, resin with desired hydrophilic-lipophilic balance was prepared for the extraction of CWAs and related esters of varying polarities. Amongst different composites Fe2O3 nanoparticles coated with 10% PVP+90% DVB exhibited the best recoveries varying between 70.32 and 97.67%. Parameters affecting the extraction efficiencies, such as extraction time, desorption time, nature and volume of desorption solvent, amount of extraction sorbent and the effect of salts on extraction were investigated. Under the optimized conditions, linearity was obtained in the range of 0.5-500 ng mL(-1) with correlation ranging from 0.9911-0.9980. Limits of detection and limits of quantification were 0.5-1.0 and 3.0-5.0 ng mL(-1) respectively with RSDs varying from 4.88-11.32% for markers of CWAs. Finally, the developed MDSPE method was employed for extraction of analytes from water samples of various sources and the OPCW proficiency test samples.

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.

Differentiation of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) with egg surface morphology and morphometrics using scanning electron microscopy.

Aedes aegypti and Aedes albopictus are potential arboviral vectors leading to high human fatality worldwide. Efforts in the present study were made to differentiate the eggs of A. aegypti and A. albopictus morphologically and morphometrically using scanning electron microscopy (SEM). Morphometrically, these species' eggs were 48.48% significantly different of the 33 attributes including egg dimensions, micropylar apparatus, dimensions and density of outer chorionic cells (OCCs), tubercles and width of exochorionic network. In comparison to A. aegypti eggs, A. albopictus eggs were significantly smaller and more tapered at the posterior end; however, the micropylar disc of A. aegypti was wider and had incomplete circular sectors whereas it was a narrower polygon without sectors in A. albopictus. These species were also significantly different with regards to OCC which enclose both large central and small peripheral tubercles. Specifically, the exochorionic networks in A. aegypti were interwoven, reticulated and extensively wide whereas they were narrow, prominent and solid-wall-like in A. albopictus. This feature may strengthen A. albopictus eggs against desiccation, when they are laid in containers. The morphometrical and morphological analysis of the egg's attributes of A. aegypti and A. albopictus may be helpful in understanding egg biology as well as in species confirmation.

Surface morphology and morphometric analysis of sensilla of Asian tiger mosquito, Aedes albopictus (Skuse): an SEM investigation.

BACKGROUND & OBJECTIVES: The sensilla and sensory mechanism play a significant role in hostseeking and oviposition behaviour of mosquitoes, which enable them to transmit various diseases to humans. Aedes albopictus (Skuse) has emerged as a major vector of Chikungunya virus in the recent epidemics in most parts of southern India. Studies on the sensory structures of dengue vector, Aedes aegypti (Linn) are comprehensive; whereas information on the sensillary systems of Asian tiger mosquito, Ae. albopictus is inadequate. Therefore, the present study has been carried out to observe various types of sensilla located on the antenna, maxillary palp, labial palp, tarsi and ovipositor of Ae. albopictus using scanning electron microscopy. METHODS: The antennae, maxillary palpi, labellum, tarsi and ovipositor of 10 different female mosquito of Ae. albopictus were fixed individually in 2.5% glutaraldehyde solution, washed twice and dehydrated with ascending grades of ethanol. Samples were cleared with xylene, air-dried, mounted on stubs, gold coated in an ion-sputtering unit and the sensilla were viewed between 5 and 10 KV using FEI-Quanta 400-EDAX scanning electron microscope. ANOVA revealed significant differences in the morphometric features of various sensilla. RESULTS: In the antenna Sensilla trichoidea are numerously distributed in all flagellar segments revealed four distinct subtypes. Two types of grooved peg sensilla were observed. Sensilla coeloconica was observed in the terminal flagellum of antenna and tarsomeres with large variation in diameter. Sensilla chaetica are distributed throughout the body and revealed greater variation in morphology and morphometric parameters. INTERPRETATION & CONCLUSION: The significant difference among various types of sensilla would possibly reveal their functions. The porous sensilla are olfactory and contact chemoreceptors while the aporous sensilla would play the role of mechanoreception. Sensilla coeloconica on the antenna, tarsus showed major differences with Ae. aegypti. The ovipositor sensilla revealed three types of chaetica arranged in rows but has not been reported earlier with other mosquito species.