Selective stationary phase for solid-phase microextraction analysis of sarin (GB)

Using metal complex ion-molecule reactions in a miniature rectilinear ion trap mass spectrometer to detect chemical warfare agents

The gas-phase reactions of a series of coordinatively unsaturated [Ni(L)n](y+) complexes, where L is a nitrogen-containing ligand, with chemical warfare agent (CWA) simulants in a miniature rectilinear ion trap mass spectrometer were investigated as part of a new approach to detect CWAs. Results show that upon entering the vacuum system via a poly(dimethylsiloxane) (PDMS) membrane introduction, low concentrations of several CWA simulants, including dipropyl sulfide (simulant for mustard gas), acetonitrile (simulant for the nerve agent tabun), and diethyl phosphite (simulant for nerve agents sarin, soman, tabun, and VX), can react with metal complex ions generated by electrospray ionization (ESI), thereby providing a sensitive means of detecting these compounds. The [Ni(L)n](2+) complexes are found to be particularly reactive with the simulants of mustard gas and tabun, allowing their detection at low parts-per-billion (ppb) levels. These detection limits are well below reported exposure limits for these CWAs, which indicates the applicability of this new approach, and are about two orders of magnitude lower than electron ionization detection limits on the same mass spectrometer. The use of coordinatively unsaturated metal complexes as reagent ions offers the possibility of further tuning the ion-molecule chemistry so that desired compounds can be detected selectively or at even lower concentrations.

Determination of chemical warfare agents and related compounds in environmental samples by solid-phase microextraction with gas chromatography

Solid phase microextraction (SPME) is an increasingly common method of sample isolation and enhancement. SPME is a convenient and simple sample preparation technique for chromatographic analysis and a useful alternative to liquid-liquid extraction and solid phase extraction. SPME is speed and simply method, which has been widely used in environmental analysis because it is a rather safe method when dealing with highly toxic chemicals. A combination of SPME and gas chromatography (GC) permits both the qualitative and quantitative analysis of toxic industrial compounds, pesticides and chemical warfare agents (CWAs), including their degradation products, in air, water and soil samples. This work presents a combination of SPME and GC methods with various types of detectors in the analysis of CWAs and their degradation products in air, water, soil and other matrices. The combination of SPME and GC methods allows for low detection limits depending on the analyte, matrix and detection system. Commercially available fibers have been mainly used to extract CWAs in headspace analysis. However, attempts have been made to introduce new fiber coatings that are characterized by higher selectivities towards different analytes of interest. Environmental decomposition of CWAs leads to the formation of more hydrophilic products. These compounds may be isolated from samples using SPME and analyzed using GC however, they must often be derivatized first to produce good chromatography. In these cases, one must ensure that the SPME method also meets the same needs. Otherwise, it is helpful to use derivatization methods. SPME may also be used with fieldportable mass spectrometry (MS) and GC-MS instruments for chemical defense applications, including field sampling and analysis. SPME fibers can be taken into contaminated areas to directly sample air, headspaces above solutions, soils and water.

Hand-portable gas chromatograph-toroidal ion trap mass spectrometer (GC-TMS) for detection of hazardous compounds

A novel gas chromatograph-mass spectrometer (GC-MS) based on a miniature toroidal ion trap mass analyzer (TMS) and a low thermal mass GC is described. The TMS system has an effective mass/charge (m/z) range of 50-442 with mass resolution at full-width half-maximum (FWHM) of 0.55 at m/z 91 and 0.80 at m/z 222. A solid-phase microextraction (SPME) fiber mounted in a simple syringe-style holder is used for sample collection and introduction into a specially designed low thermal mass GC injection port. This portable GC-TMS system weighs <13 kg (28 lb), including batteries and helium carrier gas cartridge, and is totally self-contained within dimensions of 47 x 36 x 18 cm (18.5 x 14 x 7 in.). System start-up takes about 3 min and sample analysis with library matching typically takes about 5 min, including time for column cool-down. Peak power consumption during sample analysis is about 80 W. Battery power and helium supply cartridges allow 50 and 100 consecutive analyses, respectively. Both can be easily replaced. An on-board library of target analytes is used to provide detection and identification of chemical compounds based on their characteristic retention times and mass spectra. The GC-TMS can detect 200 pg of methyl salicylate on-column. n-Butylbenzene and naphthalene can be detected at a concentration of 100 ppt in water from solid-phase microextraction (SPME) analysis of the headspace. The GC-TMS system has been designed to easily make measurements in a variety of complex and harsh environments.

Application of solid-phase microextraction in analytical toxicology

Solid-phase microextraction (SPME) is a miniaturized and solvent-free sample preparation technique for chromatographic-spectrometric analysis by which the analytes are extracted from a gaseous or liquid sample by absorption in, or adsorption on, a thin polymer coating fixed to the solid surface of a fiber, inside an injection needle or inside a capillary. In this paper, the present state of practical performance and of applications of SPME to the analysis of blood, urine, oral fluid and hair in clinical and forensic toxicology is reviewed. The commercial coatings for fibers or needles have not essentially changed for many years, but there are interesting laboratory developments, such as conductive polypyrrole coatings for electrochemically controlled SPME of anions or cations and coatings with restricted-access properties for direct extraction from whole blood or immunoaffinity SPME. In-tube SPME uses segments of commercial gas chromatography (GC) capillaries for highly efficient extraction by repeated aspiration-ejection cycles of the liquid sample. It can be easily automated in combination with liquid chromatography but, as it is very sensitive to capillary plugging, it requires completely homogeneous liquid samples. In contrast, fiber-based SPME has not yet been performed automatically in combination with high-performance liquid chromatography. The headspace extractions on fibers or needles (solid-phase dynamic extraction) combined with GC methods are the most advantageous versions of SPME because of very pure extracts and the availability of automatic samplers. Surprisingly, substances with quite high boiling points, such as tricyclic antidepressants or phenothiazines, can be measured by headspace SPME from aqueous samples. The applicability and sensitivity of SPME was essentially extended by in-sample or on-fiber derivatization. The different modes of SPME were applied to analysis of solvents and inhalation narcotics, amphetamines, cocaine and metabolites, cannabinoids, methadone and other opioids, fatty acid ethyl esters as alcohol markers, gamma-hydroxybutyric acid, benzodiazepines, various other therapeutic drugs, pesticides, chemical warfare agents, cyanide, sulfide and metal ions. In general, SPME is routinely used in optimized methods for specific analytes. However, it was shown that it also has some capacity for a general screening by direct immersion into urine samples and for pesticides and other semivolatile substance in the headspace mode.

Analysis of gaseous toxic industrial compounds and chemical warfare agent simulants by atmospheric pressure ionization mass spectrometry

The suitability of atmospheric pressure chemical ionization mass spectrometry as sensing instrumentation for the real-time monitoring of low levels of toxic compounds is assessed, especially with respect to public safety applications. Gaseous samples of nine toxic industrial compounds, NH3, H2S, Cl2, CS2, SO2, C2H4O, HBr, C6H6 and AsH3, and two chemical warfare agent simulants, dimethyl methylphosphonate (DMMP) and methyl salicylate (MeS), were studied. API-MS proves highly suited to this application, with speedy analysis times (<30 seconds), high sensitivity, high selectivity towards analytes, good precision, dynamic range and accuracy. Tandem MS methods were implemented in selected cases for improved selectivity, sensitivity, and limits of detection. Limits of detection in the parts-per-billion and parts-per-trillion range were achieved for this set of analytes. In all cases detection limits were well below the compounds' permissible exposure limits (PELs), even in the presence of added complex mixtures of alkanes. Linear responses, up to several orders of magnitude, were obtained over the concentration ranges studied (sub-ppb to ppm), with relative standard deviations less than 3%, regardless of the presence of alkane interferents. Receiver operating characteristic (ROC) curves are presented to show the performance trade-off between sensitivity, probability of correct detection, and false positive rate. A dynamic sample preparation system for the production of gas phase analyte concentrations ranging from 100 pptr to 100 ppm and capable of admixing gaseous matrix compounds and control of relative humidity and temperature is also described.

Dynamic solid phase microextraction for sampling of airborne sarin with gas chromatography-mass spectrometry for rapid field detection and quantification

A portable dynamic air sampler and solid phase microextraction were used to simultaneously detect, identify, and quantify airborne sarin with immediate analysis of samples using a field portable gas chromatography-mass spectrometry system. A mathematical model was used with knowledge of the mass of sarin trapped, linear air velocity past the exposed sampling fiber, and sample duration allowing calculation of concentration estimates. For organizations with suitable field portable instrumentation, these methods are potentially useful for rapid onsite detection and quantification of high concern analytes, either through direct environmental sampling or through sampling of air collected in bags.

Walljet electrochemistry: quantifying molecular transport through metallopolymeric and zirconium phosphonate assembled porphyrin square thin films

By employing redox-active probes, condensed-phase molecular transport through nanoporous thin films can often be measured electrochemically. Certain kinds of electrode materials (e.g. conductive glass) are difficult to fabricate as rotatable disks or as ultramicroelectrodes-the configurations most often used for electrochemical permeation measurements. These limitations point to the need for a more materials-general measurement method. Herein, we report the application of walljet electrochemistry to the study of molecular transport through model metallopolymeric films on indium tin oxide electrodes. A quantitative expression is presented that describes the transport-limited current at the walljet electrode in terms of mass transport through solution and permeation through the film phase. A comparison of the film permeabilities for a series of redox probes measured using the walljet electrode and a rotating disk electrode establishes the accuracy of the walljet method, while also demonstrating similar precision for the two methods. We apply this technique to a system consisting of zirconium phosphonate assembled films of a porphyrinic molecular square. Transport through films comprising three or more layers is free from significant contributions from pinhole defects. Surprisingly, transport through films of this kind is 2-3 orders of magnitude slower than through films constructed via interfacial polymerization of nearly identical supramolecular square building blocks (Keefe; et al. Adv. Mater. 2003, 15, 1936). The zirconium phosphate assembled films show good size exclusion behavior. The details of the observed dependence of permeation rates on probe molecule size can be rationalized with a model that assumes that the walls of the squares are slightly tilted from a strictly vertical geometry, consistent with atomic force microscopy measurements, and assumes that the individual wall geometries are locked by rigid interlayer linkages.

Pesticide vapours in confined atmospheres. Determination of dichlorvos by SPME-GC-MS at the microg m(-3) level

A method based on SPME is described for assessing the gaseous dichlorvos concentration in confined atmospheres like a greenhouse after a pesticide application. Sampling was made by using SPME with PDMS fibres immersed into a 250 mL sampling flask into which air samples were dynamically pumped from the analysed atmosphere. Sampling duration was 40 min and samples were then analysed by GC-MS. Calibration was performed from a vapour saturated air sample and gas phase diluted samples, and this procedure afforded a curve with a regression coefficient (R2) higher than 0.98. The repeatability of these measurements was observed with an RSD of 2.5%. This analysis procedure was then applied for the determination of gaseous dichlorvos concentrations versus time, in the atmosphere of an experimental 8 m2 and 20 m3 greenhouse. The pesticide was sprayed according to real cultivation conditions and measurements were made from 2 up to 74 h after application affording observed concentrations in the range of decades and hundreds of microg m(-3) (corresponding limits of detection and quantification were found at the level of a few microg m(-3)).