Ion mobility spectrometry

Ion mobility spectrometry has become the most successful and widely used technology for the detection of trace levels of nitro-organic explosives on handbags and carry on-luggage in airports throughout the US. The low detection limits are provided by the efficient ionization process, namely, atmospheric pressure chemical ionization (APCI) reactions in negative polarity. An additional level of confidence in a measurement is imparted by characterization of ions for mobilities in weak electric fields of a drift tube at ambient pressure. Findings from over 30 years of investigations into IMS response to these explosives have been collected and assessed to allow a comprehensive view of the APCI reactions characteristic of nitro-organic explosives. Also, the drift tube conditions needed to obtain particular mobility spectra have been summarized. During the past decade, improvements have occurred in IMS on the understanding of reagent gas chemistries, the influence of temperature on ion stability, and sampling methods. In addition, commercial instruments have been refined to provide fast and reliable measurements for on-site detection of explosives. The gas phase ion chemistry of most explosives is mediated by the fragile CONO(2) bonds or the acidity of protons. Thus, M(-) or M.Cl(-) species are found with only a few explosives and loss of NO(2), NO(3) and proton abstraction reactions are common and complicating pathways. However, once ions are formed, they appear to have stabilities on time scales equal to or longer than ion drift times from 5-20 ms. As such, peak shapes in IMS are suitable for high selectivity and sensitivity.

Thermal decomposition processes were investigated for Bacillus Gram-positive spores. Thermogravimetry analysis (TGA) experiments at 200 K min −1 produced a temporal evolution of biochemicals from the spores. Qualitative and quantitative aspects such as peak resolution, peak ratios, peak positions, and temperature maxima are compared and contrasted in the thermal weight loss and differential thermogravimetry (DTG) curves for different Bacillus bacterial spores. The TGA experimental data were used to generate the activation energy and frequency factor Arrhenius equation parameters. These parameters were used to produce TGA and the negative of the first derivative of the TGA (−DTG) decomposition model curves, and the latter are compared to their respective bacterial experimental TGA and −DTG profiles for validation and modeling purposes. The thermal decomposition model is also shown to have application in the prediction of weight loss profiles at significantly higher heating rates than that from the laboratory TGA system. The model thermal decomposition profiles are applied in comparisons to the total ion chromatograms of Bacillus atrophaeus bacterial spores generated by an outdoors fielded pyrolysis-gas chromatography-ion mobility spectrometry (Py-GC-IMS) bioaerosol detection system. Pyrolysis at a high heating rate of 3300 K min −1 was used. The bioaerosol detection system provides very similar qualitative information to the TGA and −DTG experimental and model profiles.

Neural networks were trained using whole ion mobility spectra from a standardized database of 3137 spectra for 204 chemicals at various concentrations. Performance of the network was measured by the success of classification into ten chemical classes. Eleven stages for evaluation of spectra and of spectral pre-processing were employed and minimums established for response thresholds and spectral purity. After optimization of the database, network, and pre-processing routines, the fraction of successful classifications by functional group was 0.91 throughout a range of concentrations. Network classification relied on a combination of features, including drift times, number of peaks, relative intensities, and other factors apparently including peak shape. The network was opportunistic, exploiting different features within different chemical classes. Application of neural networks in a two-tier design where chemicals were first identified by class and then individually eliminated all but one false positive out of 161 test spectra. These findings establish that ion mobility spectra, even with low resolution instrumentation, contain sufficient detail to permit the development of automated identification systems.

Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the influence of an electrical field. The separation is affected by mass and charge but most particularly by shape (collision cross section). When coupled to MS, IMS-MS offers therefore a powerful tool for structural elucidation and isomer separation. Systematic studies aimed to compare and quantitate the effects of structural changes on drift time such as length and ramification of carbon chain, unsaturation, geometrical isomerism (cis/trans isomers for instance), cyclization and ring size are, however, scarce. Herein we used traveling wave ion mobility mass spectrometry (TWIM-MS) to systematically evaluate the relationship between structure and drift time. For that, a series of deprotonated carboxylic acids were used as model ions with a carboxylate " charge tag " for gas phase MS manipulation. Carboxylic acids showed a near linear correlation between the increase of carbon number and the increase of collision cross section (CCS). The number of double bonds changes slightly the CCS of unsaturated acids. No differences in drift time and no significant differences in CCS of cis-and trans-double bond of oleic and elaidic acids were observed. Cyclization considerably reduces the CCS. In cyclic carboxylic acids, the increase of double bonds and aromatization significantly reduces the CCS and the drift times. The use of a more polar-izable drift gas, CO 2, improved in some cases the separation , as for biomarker isomers of steranoic acids. The β-isomer (cis-decaline) has smaller CCS and therefore displayed lower drift time compared to the α-isomer (trans-decaline). Structural changes revealed by calculations were correlated with trends in drift times.

A variety of alkali cation emitters were developed as the ion source for ion mobility spectrometry. The cation emitters were constructed based on alkali ion graphite intercalation compounds (GICs). The compounds were prepared by fusing alkali salts with ground graphite. In order to produce alkali ions, the compounds were loaded on a filament and heated to red. Reactant ions of the form alk + ions were observed for the alkali salts NaCl, KCl·LiCl, CsCl and SrCl. In addition to Na + ions, K + ions were observed at the beginning of thermionic emission from Na-GIC. This is due to the low ionization potential of potassium that exists in trace amounts in sodium salts. In addition to the potassium ion, Na + was observed in the case of LiCl salt. The Na + and K + peaks originating from impurities totally disappeared after about 40 min. However, the thermionic emission of the main ion of the corresponding salt lasted for several days. No negative ions were observed upon reversing the drift field. Selected organic compounds (methyl isobutyl ketone, dimethyl sulfoxide, acetone and tetrahydrofuran) were also ionized via alkali cation attachment reaction. Distinct ion mobility patterns were observed for different substances using one type of alkali reactant ion. However, the ion mobility pattern for a given substance changed when a different alkali reactant ion was used. Ammonia and amines were not ionized when this source was used.

Ion mobility spectrometry (IMS) is an instrumental technique used successfully for the detection of wide range of organic compounds in the gas phase. In this paper, advances in using special substances called dopants for gases flowing through IMS detectors are reviewed. These substances influence the ion-molecule chemistry in sample ionisation region as well as change conditions for the drift of ions. Improved selectivity and sensitivity of detection can be obtained by the use of dopants. In some cases, especially when measurements are conducted in the presence of different substances disturbing detection, the use of dopants is indispensable.

The applications of ion mobility spectrometry (IMS) have grown exponentially beyond its uses for explosive, illicit drug and chemical warfare agent monitoring in recent years. Instrumental developments including new drift tube materials and ionization sources have enabled the manufacturing of more sophisticated and affordable IMS equipment for the advantageous analysis of samples with no pretreatment. The most recent applications of IMS include quality control and cleaning validation procedures in the pharmaceutical industry; determinations of contaminants in food samples; clinical analyses of biological fluids; environmental analyses of contaminants in gaseous, liquid and solid samples; and (bio)process quality control monitoring. Coupling IMS with MS n has enabled the analysis of very complex samples and the extraction of knowledge unavailable from isolated MS measurements, especially in the polymer and petroleomic industries.

Lucretius was the first philosopher of immanence. It is he and not Democritus or Epicurus who holds this title. If we want to understand the historical emergence of the concept of immanence, we should start by distinguishing its precursors in Greek atomism from its first complete incarnation in Lucretius. This way, we can see exactly what first defined and distinguished immanence from its past. Therefore in what follows I would like to make three, perhaps controversial, claims about the emergence of philosophical immanence. 1) Lucretius was not an atomist, 2) Greek atomism reintroduced transcendence, and 3) It is the primacy of motion in Lucretius that defines his philosophical immanence. Lucretius was not an atomist This thesis is as counterintuitive as it is straightforward. The first major difference between Lucretius and the earlier Greek atomists is precisely that—the atom. For Leucippus, Democritus, and Epicurus atoms are always in motion, but the atom itself remained fundamentally unchanged, indivisible, and thus internally static—even as it moved. Thus instead of positing discrete atoms as ontologically primary as both ancient Greek and later modern theories do, one of Lucretius's greatest novelties was to posit the movement or flow of matter as primary. Lucretius did not simply " translate Epicurus, " as the Greco-centric story goes; rather, he introduced the first immanent kinetic materialism in the West. For example, although the Latin word atomus (smallest particle) was available to Lucretius to use in his poem, he intentionally did not use it, nor did he use the Latin word particula or particle to describe matter. The English translations of " atom, " " particle, " and others have all been added to the text in translation based on a certain historical interpretation of it. The idea that Lucretius subscribed to a world of discrete particles called atoms is therefore both a projection of Epicureanism, who used the Greek word atomos, and a retroaction of modern scientific mechanism of the fifteenth century onto De Rerum Natura. Lucretius rejected entirely the notion that things emerged from discrete particles. To believe otherwise is to distort the original meanings of the Latin text as well as the absolutely enormous poetic apparatus he summoned to describe the flowing, swirling, folding, and weaving of the flux of matter. Although Lucretius rejected the term atomus, he remained absolutely true to one aspect of the original Greek meaning of the word, τομος (átomos, " indivisible "), from-(a-, " not ") + τέμνω (témnō, " I cut "). Being is not cut up into discrete particles, but is composed of continuous flows, folds, and weaves. Discrete " things " (rerum) are composed of corporeal flows (corpora) that move together (conflux) and fold over themselves (nexus) in a woven knot work (contextum). For Lucretius, things only emerge and have their being within and immanent to the flow and flux of matter in motion. Discreteness is an apparent product of continuous folded matter, uncut, undivided, and in motion and not the other way around.

Expired air chemical analysis is investigated as a search and locate method for the early detection of entrapped people under the ruins of collapsed buildings after an earthquake. Fasting individuals were examined as a group that simulates the medical status of some of such victims. Exhaled air from seven fasting male monks (after 63 h) was analysed using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) analysis. Over 150 volatile organic compounds (VOCs) were identified and the 43 most frequent are presented. Acetone showed by far the highest "positive alveolar gradient". Other compounds included phenol, di-limonene, 2-pentanone, isoprene and acetaldehyde. Quantitative results showed a 30-fold increase of acetone concentration (5.8 ppmv) compared to control measurements of a volunteer. Breath acetone was also identified through a portable gas chromatography-ion mobility spectrometer showing possible, under certain conditions, effectiveness of the method in the field.

The use of solid-phase microextraction (SPME) coupled to ion mobility spectrometry (IMS) to detect precursor and degradation products of chemical warfare agents (CWAs) as soil contaminants was investigated. The development and characterization of a system to interface a thermal desorption solid-phase microextraction inlet with a hand held ion mobility spectrometer was demonstrated. The analytes used in this study were diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP), and dimethyl methylphosphonate (DMMP). Two SPME fibers with different stationary phases, 100 m polydimethylsiloxane (PDMS) and 65 m polydimethylsiloxane divinylbenzene (PDMS/DVB), were evaluated in this study to determine the optimal fiber and extraction conditions. Better results were obtained with the PDMS fiber. SPME-IMS offered good repeatability and detection of the precursor and degradation products in spiked soil at concentrations as low as 10 g/g. Sample analysis time was less than 30 min for all the precursor and degradation products.

We report a miniaturized excitation source for soft ionization of molecules based on a dielectric barrier discharge. An atmospheric plasma is established at the end of a 500 μm diameter capillary using He as buffer gas. The plasma jet which comes out of the capillary is dependent on the gas flow rate. The mechanism of the production of N 2 + outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated by spatially resolved spectroscopic measurements throughout the plasma. Possible application of such miniaturized plasmas is the ionization of gaseous compounds under atmospheric pressure as an alternative to traditional APCI (atmospheric pressure chemical ionization). The miniaturized plasma was applied as ionization source for ion mobility spectrometry where the common sources are radioactive, thus limiting the place of installation. First measurements of gaseous compounds with such a plasma ion mobility spectrometer with promising results showed detection limits comparable or even better than those obtained using common radioactive ionization sources.

Field asymmetric waveform ion mobility spectrometry (FAIMS) holds significant promise for post-ionization separations in conjunction with mass-spectrometric analyses. However, a limited understanding of fundamentals of FAIMS analyzers has made their design and operation largely an empirical exercise. Recently, we developed an a priori simulation of FAIMS that accounts for both ion diffusion (including anisotropic components) and Coulomb repulsion, and validated it by extensive comparisons with FAIMS/MS data. Here it is corroborated further by FAIMS-only measurements, and applied to explore how key instrumental parameters (analytical gap width and length, waveform frequency and profile, the identity and flow speed of buffer gas) affect FAIMS response. We find that the trade-off between resolution and sensitivity can be managed by varying gap width, RF frequency, and (in certain cases) buffer gas, with equivalent outcome. In particular, the resolving power can be approximately doubled compared to "typical" conditions. Throughput may be increased by either accelerating the gas flow (preferable) or shortening the device, but below certain minimum residence times performance deteriorates. Bisinusoidal and clipped-sinusoidal waveforms have comparable merit, but switching to rectangular waveforms would improve resolution and/or sensitivity. For any waveform profile, the ratio of two between voltages in high and low portions of the cycle produces the best performance. (J Am Soc Mass Spectrom 2005, 16, 2-12)

In this work for the first time, simultaneous analysis of caffeine and theophylline was done by ion mobility spectrometry (IMS) only, without a powerful separation technique (e.g., HPLC). Ion mobility spectrometry with low cost, inexpensive maintenance and very fast analysis makes an attractive technique for the simultaneous determination of the caffeine and theophylline in foodstuff samples and biological matrices. In this study, the extraction protocol using molecular imprinted polymer-solid phase extraction (MIP-SPE) was successfully used to directly extract caffeine and theophylline from real samples. The results obtained provided the detection limits of 0.2 and 0.3 lg mL À1 for caffeine and theophylline, respectively. The linear dynamic range of about two orders of magnitude was obtained for these compounds. Also, the proposed method was used to analyse various real samples of green tea and spiked human plasma, and the obtained results confirmed the capability of ESI-IMS for simultaneous detection of caffeine and theophylline.

We have applied high-field asymmetric waveform ion mobility spectrometry (FAIMS) to the analysis of the phosphopeptides APLpSFRGSLPKSYVK, APLSFRGpSLPKSYVK, and APLSFRGSLPKpSYVK. The peptides have identical amino acid sequences and differ only in the site of phosphorylation. The results show that FAIMS is capable of at least partially separating these species. Separation was confirmed by coupling FAIMS with high-resolution electron transfer dissociation (ETD) mass spectrometry. Phosphorylation is retained on the ETD peptide fragments thereby allowing assignment of the site of the modification. Co-eluting phosphopeptides which differ only in the site of modification are frequently observed in liquid chromatography/tandem mass spectrometry phosphoproteomics experiments, and therefore these proof-of-principle results have implications for the application of FAIMS in that field. Copyright © 2009 John Wiley & Sons, Ltd.

The general principles and the technical implementations of traditional time-offlight ion mobility spectrometers and analyzers with field dependent mobilities were reviewed in our last article in this journal. Recent advances in instrumentation and new applications since 2006 are highlighted in this review. In addition to traditional applications as military chemical-agent detector, ion mobility techniques became more and more popular for different purposes. While ion mobility spectrometry was solely used as vapor sensor in the past decades, further developments in ionization techniques (especially electrospray ionization) permit now the routine use for the analysis of liquid samples. The coupling of ion mobility spectrometry with selective sample preparation techniques such as molecular imprinted polymers, the coupling with chromatographic techniques, the use of dopants and the application of selective ionization sources led to an expanded number of applications in industrial and environmental analysis with complex sample matrices due to an improved selectivity in comparison with traditional stand-alone spectrometers. Furthermore, new developments in hyphenated techniques, especially ion mobility -mass spectrometry couplings, resulted in an increased number of new applications for the analysis of biomolecules, pharmaceutical samples and in clinical diagnostics.

Ion mobility spectrometry (IMS) is an electrophoretic technique that allows ionised analyte molecules to be separated on the basis of their mobilities in the gas phase. The technique has found widespread application as a detector, most noticeably for chemical warfare agents on the battlefield and for explosives and narcotics at ports and airports. The application of IMS to structural studies of small molecules has also been recognised since the advent of the technique in the 1970s. The coupling of IMS with electrospray (ESI) and MALDI ion sources has opened up exciting possibilities for the study of the conformations and structures of a wide range of biomolecules in the gas-phase, including proteins, peptides and oligonucletoides. This tutorial review discusses the principles, instrumentation and applications of IMS for the elucidation of molecular structural characteristics.

The human breath contains indicators of human health and delivers information about different metabolism processes of the body. The detection and attribution of these markers provide the possibility for new, non-invasive diagnostic methods. In the recent study, ion mobility spectrometers are used to detect different volatile organic metabolites in human breath directly. By coupling multi-capillary columns using ion mobility spectrometers detection limits down to the ng/L and pg/L range are achieved. The sampling procedure of human breath as well as the detection of different volatiles in human breath are described in detail. Reduced mobilities and detection limits for different analytes occurring in human breath are reported. In addition, spectra of exhaled air using ion mobility spectrometers obtained without any pre-concentration are presented and discussed in detail. Finally, the potential use of IMS with respect to lung infection diseases will be considered.

In the present paper, we describe a new on-line SPE system where molecular imprinting, fiber-optic detection and flow injection analysis were combined for the first time. This new system has been applied for the on line detection of 4-nitrophenol (4-NP). Initially, molecularly imprinted polymers (MIP) have been prepared for the selective extraction of 4-NP using 4-vinylpyridine and ethylene glycol dimethacrylate as functional and cross-linking monomers, respectively. Selective extraction was achieved using the designed MIP with 97% of recovery on imprinted polymer and 10% on control polymer. The system provided a high degree of accuracy, with RSDs varying between 0.7 and 1.39%. In respect of accuracy, reproducibility, and rapidity, this system is comparable with HPLC. In short, the system allows simple, fast, and accurate analyte determination with the possibility of future automation.

Using atmospheric pressure nitrogen corona discharge electron attachment ion mobility spectrometry (APNCD-EA-IMS), the rate constants of electron attachment to 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and ␣,␣,␣-trichlorotoluene have been determined at ambient temperature as a function of the average electron energy in the range from 0.35 to 0.65 eV based on the experimental measurements of the negative ion mobility spectra. The rate constants are in the order of magnitude of ∼10 −9 cm 3 molecule −1 s −1. The ability of the dichlorobenzene isomers to capture the electrons has been found to decrease following the order of 1,2-chlorobenzene, 1,3-chlorobenzene and 1,4-chlorobenzene, which is different from previously reported results in the literature. For electron attachment to 1,2,4-trichlorobenzene and ␣,␣,␣-trichlorotoluene, the experimental measurements show that ␣,␣,␣-trichlorotoluene has a higher rate constant than 1,2,4-trichlorobenzene.

Ion mobility spectrometry (IMS), using standalone instrumentation and hyphenated with mass spectrometry (IM-MS), has recently undergone significant expansion in the numbers of users and applications, particularly in sectors outside its established user base; predominantly military and security applications. Although several IMS reference standards have been proposed, there are no currently universally recognised reference standards for the calibration and evaluation of mobility spectrometers. This review describes current practices and the literature on chemical standards for validating IMS systems in positive and negative ion modes. The key qualities and requirements an 'ideal' reference standard must possess are defined, together with the instrumental and environmental factors such as temperature, electric field, humidity and drift gas composition that may need to be considered. Important challenges that have yet to be resolved are also identified and proposals for future development presented.

In this paper, we demonstrate that humidity is a crucial parameter for analysis of aromatic compounds of low polarity with planar differential ion mobility spectrometry. Utilization of polar modifiers which are usually applied for the improvement of separation ability of DMS based systems does not improve the separation of aromatic compounds. Moreover, the peak area of the model compounds decreases with the increase of the modifier (water vapors and 2-propanole) concentration. The influence of the polar modifiers on the DMS separation ability was proven on examples of the six aromatic compounds (BTEX, 1,2,4-trimethylbenzene (TMB), and naphthalene) and one aliphatic compound (hexane). The influence of the modifier concentration on the compensation voltage, peak area, and peak width was investigated and discussed. The strong influence of the proton affinity of analytes on the peak area in the measurements with modifiers was demonstrated. Some notable aspects of the formation of the reactant ion positive are demonstrated and discussed.

The successful air sampling and detection of cocaine, methylenedioxymethylamphetamine (MDMA), and marijuana using SPME-IMS achieved by targeting their volatile markers (methyl benzoate, piperonal, and terpenes, respectively) is presented. Conventional methods of direct air sampling for drugs are ineffective because the parent compounds of these drugs have very low vapor pressures, making them unavailable for headspace sampling. Instead of targeting the parent drugs, IMS was set at the optimal operating conditions (determined in previous work) in order to detect their volatile chemical markers. SPME is an effective and rapid air sampling technique for the preconcentration of analytes which is especially useful in confined spaces such as cargo containers, where the volatile marker compounds of drugs can be found in sufficient concentrations. By sampling the air using a 100 μm polydimethyl siloxane (PDMS) SPME fiber for as little as one minute, enough mass of the targeted volatile markers in the headspace of a quart-sized metal paint can (gallon, ∼1101 cm 3 ) which contained sub-gram quantities of the drug samples was recovered for IMS detection. Additionally, several potentially interfering compounds found in goods commonly shipped in cargo containers were tested individually as well as in mixtures with the drugs. No peak interferences were observed for MDMA or marijuana, and minimal peak interferences were found for cocaine.

The cosmetic and pharmaceutical industries are continuously demanding fast, efficient, cost-effective analytical methods to monitor production processes and assure end-product quality. The presence of residual reagents or impurities formed during a synthetic process can have an adverse impact on product quality, assurance of which requires using increasingly sensitive analytical methods to facilitate the detection and/or determination of toxic compounds with potentially hazardous effects on consumer's health. In this work, we assessed the potential of ion mobility spectrometry (IMS) for the detection and quantitation of dimethylaminopropylamine (DMAPA) residues in stearamidopropyldimethylamine (SAPDA) production samples. The influence of instrumental variables including solvent, solution drying time, injected volume and volatilization temperature was examined. The ensuing analytical method takes less than 1 min per analysis and uses only a few microlitres of sample. The calibration curve was linear over the DMAPA concentration range 0.030-0.500 g mL −1 . The proposed method was validated for use in control processes. The complex plasmagram for amidoamines allows the origin of cosmetic oils to be easily, expeditiously identified. Based on the results, IMS holds great promise for the qualitative and quantitative determination of the studied amide and various others in cosmetic products.

Normal and cyclic alkanes and alkenes form stable gas-phase ions in air at atmospheric pressure from 40 to 200 "C when moisture is below 1 ppm. Ionization of alkanes in a 63Ni source favored charge transfer over proton transfer through pathways involving [M -IIf and [M -3]+ ions. Ion mobility spectra for alkanes showed sharp and symmetrical profiles while spectra for alkenes suggested fragmentation. Ion identifications were made by using mass spectrometry, and ionization pathways were supported by using deuterated analogs of alkanes and alkenes. Alkanes were ionized seemingly through a hydrogen abstraction pathway and did not proceed through an alkene intermediate. New methods for interpretation of mobility spectra utilizing ion mobility spectrometry, atmospheric pressure chemical ionization mass spectrometry, chemical ionization mass spectrometry, and ion mobility spectrometry-mass spectrometry data were demonstrated. (J Am Sot Mass Spectrom 2994, 5, 177-185)

The electrodynamic ion funnel has enabled the manipulation and focusing of ions in a pressure regime (0.1 to 30 Torr) that has challenged traditional approaches, providing the basis for much greater mass spectrometer ion transmission efficiencies. The initial ion funnel implementations aimed to efficiently capture ions in the expanding gas jet of an electrospray ionization source and radially focus them for efficient transfer through a conductance limiting orifice. We review the improvements in fundamental understanding of ion motion in ion funnels, the evolution in its implementations that have brought the ion funnel to its current state of refinement, as well as applications of the ion funnel for purposes such as ion trapping, ion cooling, low pressure electrospray, and ion mobility spectrometry.

The radial distribution of ions at atmospheric pressure in the drift region of two ion mobility spectrometers of dissimilar dimensions was determined using a concentric ring detector, a detector with annulus design, and metallic and non-metallic blocking rings. The radial density profile of ions at the detector plate exhibited a maximum off-center beyond which ion density declined rapidly. The intensity at the center was roughly 40% less than the maximum, which to some extent reflects the ion density profile in the source. A hole in the detector plate center with diameter of 3 mm or less did not measurably affect ion intensities measured at the detector, while incremental enlargement of the hole caused a considerable decline in intensity. Finally, the radial broadening of the ions throughout their transit in the drift region suggested that diffusion alone could not account for the observed results.

Groundwater can be contaminated when e.g. gasoline tanks leak. Due to sampling and lab analysis, groundwater monitoring is time consuming and expensive. The technologies developed for rapid on-site analysis of gasoline contaminated groundwater face the technical limitation to distinguish the gasoline from complex matrices. In the present study the fingerprint identification of volatile organic components (VOCs) in gasoline contaminated groundwater using gas chromatography (GC) differential ion mobility spectrometry (DMS) is investigated. Groundwater was spiked with five sorts of gasoline (one reformulated gasoline, gasoline without additives and three different brand gasoline collected on petrol stations) and analyzed by GC-DMS. Seven VOCs (benzene, toluene, ethyl benzene, m-xylene, p-xylene, o-xylene, 1,2,4-trimethylbenzene) were identified by GC mass spectrometry (GC-MS) as well as by GC-DMS and selected as markers. The semi-quantitative determination of the selected compounds was achieved. The limits of detection of the GC-DMS are 46.42 ng for benzene, 1.13 ng for toluene, 1.80 ng for ethylbenzene, 0.22 ng for m-xylene, 1.13 ng for p-xylene, 0.61 ng for o-xylene and 0.37 ng for 1,2,4-trimethylbenzene, respectively. These results reveal the feasibility of GC-DMS for on-site monitoring of contaminated groundwater.

A B S T R A C T The marked increase in international terror in recent years requires the development of highly efficient methods to detect trace amounts of explosives at airports, border crossings and check points. The preferred analytical method worldwide is the ion mobility spectrometry (IMS) that is capable of detecting most explosives at the nano-gram level. Sample collection for the IMS analysis is based on swabbing of a passenger's belongings to collect possible explosive residues. The present study examines a wide range of issues related to swab-based particle collection and analysis, in the hope of gaining deeper understanding into this technique that will serve to improve the detection process. The adhesion of explosive particles to three typical materials, plastic, metal and glass, were measured using atomic force microscopy (AFM). We found that a strong contribution of capillary forces to adhesion on glass and metal surfaces renders these substrates more promising materials upon which to find and collect explosive residues. The adhesion of explosives to different swipe materials was also examined. Here we found that Muslin, Nomex ® and polyamide membrane surfaces are the most promising materials for use as swipes. Subsequently, the efficiency of multiple swipe use – for collecting explosive residues from a glass surface using Muslin, Nomex ® and Teflon™ swipes – was examined. The study suggests that swipes used in about 5–10 " sampling and analysis cycles " have higher efficiency as compared to new unused swipes. The reason for this behavior was found to be related to the increased roughness of the swipe surface following a few swab measurements. Lastly, GC-MS analysis was employed to examine the nature of contaminants collected by the three types of swipe. The relative amounts of different contaminants are reported. The existence and interference of these contaminants have to be considered in relation to the detection efficiency of the various explosives by the IMS.

The aim of the present study was to evaluate the suitability of ion mobility spectrometry (IMS) for the detection of human urine as an indication of human presence during urban search and rescue operations in collapsed buildings. To this end, IMS with a radioactive ionization source and a multicapillary column was used to detect volatile organic compounds (VOCs) emitted from human urine. A study involving a group of 30 healthy volunteers resulted in the selection of seven volatile species, namely acetone, propanal, 3-methyl-2-butanone, 2-methylpropanal, 4-heptanone, 2-heptanone and octanal, which were detected in all samples. Additionally, a preliminary study on the permeation of urine volatiles through the materials surrounding the voids of collapsed buildings was performed. In this study, quartz sand was used as a representative imitating material. Four compounds, namely 3-methyl-2-butanone, octanal, acetone and 2-heptanone, were found to permeate through the sand layers during all experiments. Moreover, their permeation times were the shortest. Although IMS can be considered as a potential technique suitable for the detection, localization and monitoring of VOCs evolved from human urine, further investigation is necessary prior to selecting field chemical methods for the early location of trapped victims.

Gas chromatography mass spectrometry (GC-MS) was employed to determine the chemical composition of essential oil obtained from Eucalyptus globulus and Trachyspermum ammi. The essential oil obtained from leaves of Eucalyptus globulus and from seeds of Trachyspermum ammi by Clevenger apparatus. Chemical composition of the essential oils of E. globulus and T. ammi was analyzed by Gas chromatography – Mass spectrometry. Four main compounds in E. globulus were identified as Eucalyptol, Methyl –salicylate, Thymol, Para- cymene. 1, 8-cineole was found to be the main compound of E. globulus essential oil. Thymol, gamma- terpinene, para- cymene, beta- pinene were the main compounds of T. ammi oil and traces amount of beta myrcene, alpha- thujne, alpha- pinene, alpha- terpinene, carvacrol compounds of T. ammi were identified by GC-MS. Thymol was the main compound of T. ammi oil. The antifungal activity of E. globulus and T. ammi oils were screened against Trichophyton mentagrophytes and Epidermatophyton floccosum by using disc diffusion and modified micro dilution method. T. ammi oil shows highest inhibition zone in comparison to E. globulus oils and references antibiotics i.e. Clotrimazole and Ketoconazole.

A conventional ion mobility spectrometry (IMS) was used to study atmospheric pressure evaporation of seven pure imidazolium and pyrrolidinium ionic liquids (ILs) with [Tf 2 N], [PF 6 ], [BF 4 ] and [fap] anions. The positive drift time spectra of the as-received samples measured at 220 • C exhibited close similarity; the peak at reduced mobility K 0 = 1.99 cm 2 V −1 s −1 was a dominant spectral pattern of imidazolium-based ILs. With an assumption that ILs vapor consists mainly of neutral ion pairs, which generate the parent cations in the reactant section of the detector, and using the reference data on the electrical mobility of ILs cations and clusters, this peak was attributed to the parent cation [emim]. Despite visible change in color of the majority of ILs after the heating at 220 • C for 5 h, essential distinctions between spectra of the as-received and heated samples were not observed. In negative mode, pronounced peaks were registered only for ILs with [fap] anion.

The phenomenon of ion mobility (IM), the movement/transport of charged particles under the influence of an electric field, was first observed in the early twentieth Century and harnessed later in ion mobility spectrometry (IMS). There have been rapid advances in instrumental design, experimental methods and theory together with contributions from computational chemistry and gasphase ion chemistry which have diversified the range of potential applications of contemporary IMS techniques. Whilst IMS-mass spectrometry (IMS-MS) has recently been recognized for having significant research/applied industrial potential and encompasses multi-/cross-disciplinary areas of science, the applications and impact from decades of research are only now beginning to be utilised for 'small molecule' species. This review focuses on the application of IMS-MS to 'small molecule' species typically used in drug discovery (from 100 to 500 Da) including an assessment of the limitations and possibilities of the technique. Potential future developments in instrumental design, experimental methods and applications are addressed. The typical application of IMS-MS in relation to small molecules has been to separate species in fairly uniform molecular classes such as mixture analysis, including metabolites. Separation of similar species has historically been challenging using IMS as the resolving power, R, has been low (from 3-100) and the differences in collision cross-sections that could be measured have been relatively small, so instrument and method development has often focused on increasing resolving power. However, IMS-MS has a range of other potential applications that are examined in this review where it displays unique advantages, including: determination of small molecule structure from drift time, 'small molecule' separation in achiral and chiral mixtures, improvement in selectivity, identification of carbohydrate isomers, metabonomics, and for understanding the size and shape of small molecules. This review provides a broad but selective overview of current literature, concentrating on IMS-MS, not solely IMS, and small molecule applications.

Correlations between the dimensions of a 2-D separation create trend lines that depend on structural or chemical characteristics of the compound class and thus facilitate classification of unknowns. This broadly applies to conventional ion mobility spectrometry (IMS)/mass spectrometry (MS), where the major biomolecular classes (e.g., lipids, peptides, nucleotides) occupy different trend line domains. However, strong correlation between the IMS and MS separations for ions of same charge has impeded finer distinctions. Differential IMS (or FAIMS) is generally less correlated to MS and thus could separate those domains better. We report the first observation of chemical class separation by trend lines using FAIMS, here for lipids. For lipids, FAIMS is indeed more independent of MS than conventional IMS, and subclasses (such as phospho-, glycero-, or sphingolipids) form distinct, often non-overlapping domains. Even finer categories with different functional groups or degrees of unsaturation are often separated. As expected, resolution improves in He-rich gases: at 70% He, glycerolipid isomers with different fatty acid positions can be resolved. These results open the door for application of FAIMS to lipids, particularly in shotgun lipidomics and targeted analyses of bioactive lipids.

The use of ion mobility mass spectrometry has grown rapidly over the last two decades. This powerful analytical platform now forms an attractive prospect for comprehensive analysis of many different molecular species, including chemically complex biological molecules. This paper describes the application of IM-MS to the study of peptides. We focus on three different ion mobility devices that are most frequently found in tandem with mass spectrometers. These are instruments using linear drift tubes (LDT), those using travelling wave ion guides (TWIGS) and those employing high field asymmetric ion mobility spectrometry (FAIMS). Each technique is described. Examples are given on the use of IM-MS for the determination of peptide structure, the study of peptides that form amyloid fibrils, and the study of complex peptide mixtures in proteomic investigations. We describe and comment on the methodologies used and the outlook for this developing analytical technique.

The validation of a qualitative ion mobility spectrometry (IMS) procedure for the detec- tion of trace amounts of heroin and cocaine is presented. The limit of detection (heroin 1 ng, cocain 0.2 ng) of the apparatus, the limit of decision (heroin 3 ng, cocaine 0.5 ng) and the robustness were determined by dosing a methanolic standard onto a filter and

In this research, selective separation and determination of phenazopyridine (PAP) is demonstrated using molecular imprinted polymer (MIP) coupled with electrospray ionization ion mobility spectrometry (ESI-IMS). In the non-covalent approach, selective MIP produced using PAP and methacrylic acid (MAA) as a template molecule and monomer, respectively. The created polymer is utilized as a media for solidphase extraction (SPE), revealing selective binding properties for the analyte from pharmaceutical and serum samples. A coupled MIP-IMS makes it possible to quantitize PAP in the range of 1-100 ng mL −1 and with a 0.2 ng mL −1 detection limit. Furthermore, the MIP selectivity is evaluated by application of some substances with analogous and different molecular structures to that of PAP. This method is successfully applied for the determination of PAP in pharmaceutical and serum samples.