Structural Diversity of Zirconium Metal-Organic Frameworks and Effect on Adsorption of Toxic Chemicals.

While linkers with various conformations pose challenges in the design and prediction of metal-organic framework (MOF) structures, they ultimately provide great opportunities for the discovery of novel structures thereby enriching structural diversity. Tetratopic carboxylate linkers, for example, have been widely used in the formation of Zr-based MOFs due to the ability to target diverse topologies, providing a promising platform to explore their mechanisms of formation. However, it remains a challenge to control the resulting structures when considering the complex assembly of linkers with unpredicted conformations and diverse Zr6 node connectivities. Herein, we systematically explore how solvents and modulators employed during synthesis influence the resulting topologies of Zr-MOFs, choosing H4TCPB-Br2 (1,4-dibromo-2,3,5,6-tetrakis(4-carboxyphenyl)benzene) as a representative tetratopic carboxylate linker. By modulating the reaction conditions, the conformations of the linker and the connectivities of the Zr6 node can be simultaneously tuned, resulting in four types of structures: a new topology (NU-500), she (NU-600), scu (NU-906), and csq (NU-1008). Importantly, we have synthesized the first 5-connected Zr6 node to date with the (4,4,4,5)-connected framework, NU-500. We subsequently performed detailed structural analyses to uncover the relationship between the structures and topologies of these MOFs and demonstrated the crucial role that the flexible linker played to access varied structures by different degrees of linker deformation. Due to a variety of pore structures ranging from micropores to hierarchical micropores and mesopores, the resulting MOFs show drastically different behaviors for the adsorption of n-hexane and dynamic adsorption of 2-chloroethyl ethyl sulfide (CEES) under dry and humid conditions.

Simultaneous quantification of four metabolites of sulfur mustard in urine samples by ultra-high performance liquid chromatography-tandem mass spectrometry after solid phase extraction.

Four HD urinary metabolites including hydrolysis metabolite thiodiglycol (TDG), glutathione-derived metabolite 1,1'-sulfonylbis[2-S-(N-acetylcysteinyl)ethane] (SBSNAE), as well as the ß-lyase metabolites 1,1'-sulfonylbis[2-(methylsulfinyl)ethane] (SBMSE) and 1-methylsulfinyl-2-[2-(methylthio) ethylsulfonyl]ethane (MSMTESE) are considered as important biomarkers for short-term retrospective detection of HD exposure. In this study, a single method for simultaneous quantification of the four HD metabolites in urine samples was developed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The four urinary metabolites were simultaneously extracted from urinary samples using a solid phase extraction (SPE) method with high extraction recoveries for all four metabolites varied in the range of 71.1-103% followed by UHPLC-MS/MS analysis. The SPE is simple and high effective only requiring 0.1mL of urinary samples and 0.5h time consuming. The problem of previous co-elution of TDG and SBSNAE in UHPLC was well solved, and complete separation of TDG, SBSNAE, SBMSE and MSMTESE from SPE-processed urine matrix was obtained to increase specificity and sensitivity. A full method validation was performed for each analyte in urine matrix. The linear range of calibration curves for the four analytes were respectively from 0.50-500ngmL-1 for TDG and SBSNAE, 0.05-500ngmL-1 for SBMSE and MSMTESE with coefficient of determination value (R2) ≥0.990. The limit of detection was 0.25ngmL-1 for TDG and SBSNAE, 0.01ngmL-1 for SBMSE and MSMTESE spiked in normal urine. The intra/inter-day precision for each analyte at three QC levels had relative standard deviation (%RSD) of ≤10.3%, and the intra/inter-day accuracy ranged between 88.0-108%. This developed method allows for simultaneous and trace measurement of four HD urinary metabolites within one single determination with the lowest usage amount of urine samples over all previous methods This study provides a useful tool for early diagnosis and monitoring of HD poisoning for medical treatment with high confidence, avoiding the need for application of several analysis methods.

Development and comparison of HPLC and MEKC methods for the analysis of cyclic sulfur mustard degradation products.

In this study, novel, fast, and simple methods based on RP-HPLC and MEKC with DAD are developed and validated for the qualitative and quantitative determination of five cyclic sulfur mustard (HD) degradation products (1,4-thioxane, 1,3-dithiolane, 1,4-dithiane, 1,2,5-trithiepane, and 1,4,5-oxadithiepane) in water samples. The HPLC method employs a C18 column and an isocratic water-ACN (55:45, v/v) mobile phase. This method enables separation of all five cyclic compounds within 8 min. With the CE method, the baseline separation of five compounds was achieved in less than 11 min by applying a simple BGE composed of a 10 mM borate buffer and 90 mM SDS (pH 9.15). Both methods showed good linear correlation (R2 > 0.9904). The detection limits were in the range of 0.08-0.1 µM for the HPLC method and 10-20 µM for MEKC. The precision tests resulted in RSDs for migration times and peak areas less than 0.9 and 5.5%, respectively, for the HPLC method, and less than 1.1 and 7.7% for the MEKC method, respectively. The developed methods were successfully applied to the analysis of five cyclic HD degradation products in water samples. With the HPLC method, the LODs were lowered using the SPE for sample purification and concentration.

Solid-Phase Extraction of Sulfur Mustard Metabolites Using an Activated Carbon Fiber Sorbent.

A novel solid-phase extraction method using activated carbon fiber (ACF) was developed and validated. ACF has a vast network of pores of varying sizes and microporous structures that result in rapid adsorption and selective extraction of sulfur mustard metabolites according to the pH of eluting solvents. ACF could not only selectively extract thiodiglycol and 1-methylsulfinyl-2-[2-(methylthio)-ethylsulfonyl]ethane eluting a 9:1 ratio of dichloromethane to acetone, and 1,1'-sulfonylbis[2-(methylsulfinyl)ethane] and 1,1'-sulfonylbis- [2-S-(N-acetylcysteinyl)ethane] eluting 3% hydrogen chloride in methanol, but could also eliminate most interference without loss of analytes during the loading and washing steps. A sample preparation method has been optimized for the extraction of sulfur mustard metabolites from human urine using an ACF sorbent. The newly developed extraction method was applied to the trace analysis of metabolites of sulfur mustard in human urine matrices in a confidence-building exercise for the analysis of biomedical samples provided by the Organisation for the Prohibition of Chemical Weapons.

Iron phthalocyanine modified mesoporous titania nanoparticles for photocatalytic activity and CO2 capture applications.

An iron(II)phthalocyanine (Fepc) modified mesoporous titania (Fepc-TiO2) nanocatalyst with a specific surface area of 215 m(2) g(-1) has been synthesized by a hydrothermal method. Fepc-TiO2 degrades one of the highly toxic chemical warfare agents, sulfur mustard (SM), photocatalytically under sunlight with an exposure time of as low as 70 min. Furthermore, the mesoporous Fepc-TiO2 also captured 2.1 mmol g(-1) of CO2 at 273 K and 1 atm.

Iron oxide functionalized graphene nano-composite for dispersive solid phase extraction of chemical warfare agents from aqueous samples.

Present study deals with the preparation and evaluation of graphene based magnetic nano-composite for dispersive solid phase extraction of Chemical Weapons Convention (CWC) relevant chemicals from aqueous samples. Nano-composite, Fe3O4@SiO2-G was synthesized by covalently bonding silica coated Fe3O4 onto the graphene sheets. Nerve agents (NA), Sulfur mustard (SM) and their non-toxic environmental markers were the target analytes. Extraction parameters like amount of sorbent, extraction time and desorption conditions were optimized. Dispersion of 20 milligram of sorbent in 200mL of water sample for 20min. followed by methanol/chloroform extraction produced average to good recoveries (27-94%) of targeted analytes. Recoveries of real agents exhibited great dependency upon sample pH and ionic strength. Sarin produced maximum recovery under mild acidic conditions (56% at pH 5) while VX demanded alkaline media (83% at pH 9). Salts presence in the aqueous samples was found to be advantageous, raising the recoveries to as high as 94% for SM. Excellent limits of detection (LOD) for sulphur mustard and VX (0.11ngmL(-1) and 0.19ngmL(-1) respectively) proved the utility of the developed method for the off-site analysis of CWC relevant chemicals.

Facility monitoring of chemical warfare agent simulants in air using an automated, field-deployable, miniature mass spectrometer.

Vapors of four chemical warfare agent (CWA) stimulants, 2-chloroethyl ethyl sulfide (CEES), diethyl malonate (DEM), dimethyl methylphosphonate (DMMP), and methyl salicylate (MeS), were detected, identified, and quantitated using a fully automated, field-deployable, miniature mass spectrometer. Samples were ionized using a glow discharge electron ionization (GDEI) source, and ions were mass analyzed with a cylindrical ion trap (CIT) mass analyzer. A dual-tube thermal desorption system was used to trap compounds on 50:50 Tenax TA/Carboxen 569 sorbent before their thermal release. The sample concentrations ranged from low parts per billion [ppb] to two parts per million [ppm]. Limits of detection (LODs) ranged from 0.26 to 5.0 ppb. Receiver operating characteristic (ROC) curves are presented for each analyte. A sample of CEES at low ppb concentration was combined separately with two interferents, bleach (saturated vapor) and diesel fuel exhaust (1%), as a way to explore the capability of detecting the simulant in an environmental matrix. Also investigated was a mixture of the four CWA simulants (at concentrations in air ranging from 270 to 380 ppb). Tandem mass (MS/MS) spectral data were used to identify and quantify the individual components.

Locus-specific microemulsion catalysts for sulfur mustard (HD) chemical warfare agent decontamination.

The rates of catalytic oxidative decontamination of the chemical warfare agent (CWA) sulfur mustard (HD, bis(2-chlororethyl) sulfide) and a range (chloroethyl) sulfide simulants of variable lipophilicity have been examined using a hydrogen peroxide-based microemulsion system. SANS (small-angle neutron scattering), SAXS (small-angle X-ray scattering), PGSE-NMR (pulsed-gradient spin-echo NMR), fluorescence quenching, and electrospray mass spectroscopy (ESI-MS) were implemented to examine the distribution of HD, its simulants, and their oxidation/hydrolysis products in a model oil-in-water microemulsion. These measurements not only present a means of interpreting decontamination rates but also a rationale for the design of oxidation catalysts for these toxic materials. Here we show that by localizing manganese-Schiff base catalysts at the oil droplet-water interface or within the droplet core, a range of (chloroethyl) sulfides, including HD, spanning some 7 orders of octanol-water partition coefficient (K(ow)), may be oxidized with equal efficacy using dilute (5 wt. % of aqueous phase) hydrogen peroxide as a noncorrosive, environmentally benign oxidant (e.g., t(1/2) (HD) approximately 18 s, (2-chloroethyl phenyl sulfide, C(6)H(5)SCH(2)CH(2)Cl) approximately 15 s, (thiodiglycol, S(CH(2)CH(2)OH)(2)) approximately 19 s {20 degrees C}). Our observations demonstrate that by programming catalyst lipophilicity to colocalize catalyst and substrate, the inherent compartmentalization of the microemulsion can be exploited to achieve enhanced rates of reaction or to exert control over product selectivity. A combination of SANS, ESI-MS and fluorescence quenching measurements indicate that the enhanced catalytic activity is due to the locus of the catalyst and not a result of partial hydrolysis of the substrate.

Synergism of activated carbon and undoped and nitrogen-doped TiO2 in the photocatalytic degradation of the chemical warfare agents soman, VX, and yperite.

Efficient photocatalytic decomposition of chemical warfare agents is a process that may find application in emergency situations or for the controlled destruction of chemical warfare stockpiles. A series of heterogeneous photocatalysts comprising TiO2-activated carbon or N-TiO2-activated carbon composites exhibit excellent photocatalytic activity to effect the complete decomposition of yperite, soman, and VX in high concentrations. The remarkable photocatalytic activity arises from the synergism between adsorption on active carbon and photoactivity by titania. Nitridation makes the composite also active under visible-light irradiation.

Kinetics of adsorption of 2-chloroethylethylsulphide on Al2O3 nanoparticles with and without impregnants.

Alumina nanoparticles in the size range of 2-30 nm and surface area 375 m(2)/g were synthesized using aerogel route and then characterized using N(2)-BET, SEM, TEM, XRD, FTIR and TGA techniques. Thereafter, these were impregnated with reactive chemicals and tested for their potential by conducting studies on kinetics of adsorption of 2-chloroethylethylsulphide (2-CEES) under static conditions. Kinetics was studied using linear driving force and Fickian diffusion model. The kinetics parameters such as equilibration constant, equilibration capacity, diffusional exponent and adsorbate-adsorbent interaction constant were also determined. AP-Al(2)O(3) with 10% impregnation of MoVPA (V(3)) and NaOH showed the maximum (574 mg/g) and minimum (88 mg/g) uptake of 2-CEES among impregnated systems respectively. All impregnated systems except NaOH impregnation showed the values of diffusional exponent to be <0.5, indicated the diffusion mechanism to be Fickian, whereas AP-Al(2)O(3) with and without NaOH impregnation showed the diffusional mechanism to be anomalous. Hydrolysis and dehydrohalogenation reactions (identified using GC/MS technique) were found to be the route of degradation of 2-CEES.

Optimisation of solvent desorption conditions for chemical warfare agent and simulant compounds from Porapak Q using experimental design. Part 2: Extraction of sulphur mustard from steel and glass Porapak tubes.

The vesicant chemical warfare (CW) agent sulphur mustard remains a hazard to personnel involved in demilitarisation activities. Sampling tubes containing Porapak Q are used to measure personal exposure to sulphur mustard vapour. Presented here is an evaluation of the solvent desorption parameters employed to remove sulphur mustard from steel and glass tubes containing Porapak Q. Statistical experimental design was used to elucidate the influence of solvent type, tube type, solvent volume and sonication time on sulphur mustard recovery. The order of increasing recovery was established as iso-octane < hexane = isopropyl alcohol. The same degree of sulphur mustard is recovered on both steel and glass tubes using hexane or isopropyl alcohol, with hexane exhibiting quantitative recovery. The sorbent mass (50 mg) should be increased when using steel tubes as breakthrough has been demonstrated. Given the inert nature of hexane towards sulphur mustard, its favourable chromatographic properties for splitless injection, and its greater recoveries, this solvent should be used for elution of Porapak Q tubes for quantitative analysis of sulphur mustard.

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.

Reactions of sulphur mustard on impregnated carbons.

Activated carbon of surface area 1100 m2/gm is impregnated with 4% sodium hydroxide plus 3% Cr(VI) as CrO3 with and without 5% ethylene diamine (EDA), 4% magnesium nitrate and 5% ruthenium chloride by using their aqueous solutions. These carbons are characterized for surface area analysis by BET conventional method and exposed to the vapours of sulphur mustard (HD) at room temperature (30 degrees C). After 24 h, the reaction products are extracted in dichloromethane and analyzed using gas chromatography and mass spectrometry (GC-MS). Hemisulphur mustard, thiodiglycol, 1,4-oxathiane are observed to be the products of reaction between sulphur mustard and NaOH/CrO3/C system, whereas on NaOH/CrO3/EDA/C system HD reacted to give 1,4-thiazane. On Mg(NO3)2/C system it gave hemisulphur mustard and thiodiglycol. On RuCl3/C system it degraded to divinyl sulphone. Residual sulphur mustard is observed along with reaction products in all systems studied. Reaction mechanisms are also proposed for these interesting surface reactions. Above-mentioned carbons can be used in filtration systems for protection against hazardous gases such as sulphur mustard.

Supercritical fluid extraction of chemical warfare agent simulants from soil.

Chemical warfare agent simulants are efficiently recovered from 2-ppm spikes in 1 g of Rocky Mountain Arsenal Standard Soil using methanol-carbon dioxide (5:95) at 300 atm for 2 min at 60 degrees C. Recoveries (n = 3) were 79 +/- 23% for dimethylmethylphosphonate, 93 +/- 14% for 2-chloroethylethyl sulfide, 92 +/- 13% for diisopropylfluorophosphate and 95 +/- 17% for diisopropylmethylphosphonate. Recoveries are higher than, but less precise than those achieved from a 5-min ultrasonic micro-scale extraction using methanol. Much less laboratory waste is generated than the current standard organic solvent extraction method (33 g of soil shaken with 100 ml of chloroform).