Ion Mobility Detector Research Articles

Test method for vapor collection and ion mobility detection of explosives with low vapor pressure.

Ion mobility spectrometry (IMS) has been widely used for on-site detection of explosives. Air sampling method is applicable only when the concentration of explosive vapor is considerably high in the air, but vapor pressures of common explosives such as 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and pentaerythritol tetranitrate (PETN) are very low. A test method for analyzing the vapor detection efficiency of explosives with low vapor pressure via IMS was developed using artificial vapor and collection matrices. Artificial explosive vapor was produced by spraying an explosive solution in acetone. Fifteen collection matrices of various materials with woven or nonwoven structures were tested. Two arrangements of horizontal and vertical positions of the collection matrices were employed. Explosive vapor collected in the matrix was analyzed using IMS. Only three collection matrices of stainless steel mesh (SSM), polytetrafluoroethylene sheet (PFS), and lens cleansing paper (LCP) showed the TNT and/or RDX ion peaks at an explosive vapor concentration of 49 ng/L. There was no collection matrix to detect PETN vapor at or lower than 49 ng/L. For the PFS, TNT and RDX were detected at a vapor concentration of 49 ng/L. For the LCP, TNT and RDX were detected at vapor concentrations of 14 and 49 ng/L, irrespectively. The difference in the explosive vapor detection efficiencies could be explained by the adsorption and desorption capabilities of the collection matrices. The proposed method can be used for evaluating the vapor detection efficiency of hazardous materials with low vapor pressure.

High-performance liquid chromatography with electrospray ionization ion mobility spectrometry: Characterization, data management, and applications.

The combination of high-performance liquid chromatography and electrospray ionization ion mobility spectrometry facilitates the two-dimensional separation of complex mixtures in the retention and drift time plane. The ion mobility spectrometer presented here was optimized for flow rates customarily used in high-performance liquid chromatography between 100 and 1500μL/min. The characterization of the system with respect to such parameters as the peak capacity of each time dimension and of the 2D spectrum was carried out based on a separation of a pesticide mixture containing 24 substances. While the total ion current chromatogram is coarsely resolved, exhibiting coelutions for a number of compounds, all substances can be separately detected in the 2D plane due to the orthogonality of the separations in retention and drift dimensions. Another major advantage of the ion mobility detector is the identification of substances based on their characteristic mobilities. Electrospray ionization allows the detection of substances lacking a chromophore. As an example, the separation of a mixture of 18 amino acids is presented. A software built upon the free mass spectrometry package OpenMS was developed for processing the extensive 2D data. The different processing steps are implemented as separate modules which can be arranged in a graphic workflow facilitating automated processing of data.

A novel headspace sampler for field detection of chemical warfare agents and simulants connected to a commercial ion mobility detector

A rapid and simple sampling technique for use in conjunction with commercial ion mobility spectrometric detectors is described. The technique may be used for the detection of chemical warfare agents in the field. A plastic syringe with a steel needle was attached to the nozzle of the detector, and the syringe shortened to reduce the dead volume in the interface. After heating samples of protective clothing in closed headspace vials to 70 °C for three minutes, the detector with the syringe and needle (called HS-LCD) was used to penetrate the vial and the overpressure was transferred to the detector via the simple interface. The detector response was registered in realtime. To demonstrate the possibilities with this technique, the HS-LCD sampler was tested in the field at relatively low temperatures on pieces of protective clothing contaminated by the chemical warfare agent simulants methyl salicylate and dipropylene glycol methyl ether. A significant improvement in detector response was observed utilising this technique compared to using the detector to survey the material in the open air. This improvement is believed to increase with decreasing ambient temperature and with decreasing analyte volatility. A more comprehensive list of possible interferents should be tested in the future.

화학탐지 최적화를 위한 유동 및 압력 특성 연구

In terms of chemical detection performance related with chemical material sampling, this investigation shows optimized values, resulted from minimizing loss from air turbulence and other reasons when pressure changes on the basis of sampling flow rate Based on simulations and pressure control of the outside conditions it became possible to obtain ion mobility detection optimum values, and to derive standard pressure conditions that is appropriate for DMS characteristic.

Detection of gunpowder stabilizers with ion mobility spectrometry

This study is the first reported ion mobility detection of ethyl centralite and diphenylamine (DPA) smokeless gunpowder stabilizers, together with the nitroso and nitro derivatives of diphenylamine. First, the applicability of the ion mobility spectrometry (IMS) for the substances of interest was determined. The existence of numerous peaks, both in positive and negative modes, clearly demonstrates the success of these experiments. All mono and di-nitro derivatives of DPA tested were detected with this method. Unfortunately, many of the ions generated were not accurately identified. However, reduced mobility constants representative of each ion generated under defined operating conditions could be used for purpose of compound identification.The method was then successfully tested on real gunpowder samples.By the use of IMS, we managed to establish a rapid, simple and sensitive screening method for the detection and identification of smokeless gunpowder organic components.

Ion mobility spectrometry

The invention relates to the field of ion mobility detection, in particular to an ion mobility spectrometry. The ion mobility spectrometry comprises a silicon base plate, wherein an ion source, a mobility tube, a detection electrode and an airflow driver are sequentially arranged on the upper surface of the silicon base plate, a cover body is arranged on the silicon base plate and packages the ion source, the mobility tube, the detection electrode and the airflow driver in the cover body, the outlet of the ion source is connected with the inlet of the mobility tube, and the detection electrode and the airflow driver are sequentially arranged the outlet of the mobility tube. The ion mobility spectrometry utilizes a voltage control medium to block the action of a discharging circuit, further controls air flow sped in the mobility tube, and accordingly obtains ion injection rate accurately. Therefore, the resolution ratio of the ion mobility spectrometry is improved and can be improved to be about 90.

Breath analysis and monitoring by membrane extraction with sorbent interface.

An analytical system consisting of a sampling chamber, membrane extraction module, sorbent trap and gas chromatograph with flame ionization or ion mobility detector was used for on-line monitoring of the composition of the last 250 mL portion of human expired breath. The sampling chamber consisted of a tube fitted with check valves on both ends to allow the air to pass through during expiration, but not to return or allow mixing with ambient air. The last portion of breath was held in the chamber at the end of breath expiration. The organic components in the trapped breath were transferred to the carrier gas by permeation through the membrane in the extraction module and were concentrated in the sorbent trap before introduction as a sharp plug on the front of chromatographic column. Moisture in the breath did not penetrate the membrane to a substantial degree. This system was used to investigate presence of acetone as a biologically important marker of human health as well as exposure to volatile compounds.

Improved supercritical fluid chromatography-ion mobility spectrometry interface

This article describes the construction and performance of a restrictor . heater for interfacing an ion mobility detector IMD to a supercritical fluid chromatograph. In this interface design, an independent heating system controlled . the temperature of the supercritical fluid chromatography SFC column restrictor up to 3258C. The performance of this direct SFC)IMD interface was evaluated by separating and detecting test compounds that do not contain chromophore groups and cannot be detected by UVrvisible detection methods. Polydimethylsilicone .PDMS oligomers with molecular weights larger than 4000 amu were efficiently separated and detected when the restrictor was heated to 3258C. Overall detector sensitivity and chromatographic resolution were improved with the novel interface. Q 1999 John Wiley & Sons, Inc. J Micro Sep 11: 251)257, 1999

Surface Ionization Ion Mobility Spectrometry

A surface ionization (SI) source was designed and constructed for ion mobility spectrometry (IMS). Compared with a conventional (63)Ni source, the surface ionization source is as simple and reliable, has an extended dynamic response range, is more selective in response, and does not have regulatory problems associated with radioactive ionization sources. The performance of this SI-IMS was evaluated with several different classes of compounds. Triethylamine was employed for studying the behavior of the ionization source under different source conditions and gaseous environments. Amines, tobacco alkaloids, and triazine herbicides were also investigated. Picogram level detection limits were achieved for target compounds with a response dynamic range of 5 orders of magnitude. Selective monitoring by IMS was also demonstrated. While the surface ionization source does not have the universality of response that is obtained with a (63)Ni ionization source, it is an excellent nonradioactive alternative for the ionization and ion mobility detection of those compounds to which it responds.

Analytical determination of nicotine in tobacco by supercritical fluid chromatography–ion mobility detection

A preliminary investigation using supercritical fluid chromatography–ion mobility detector (SFC–IMD) to analyze the nicotine contained in tobacco was carried out. Nicotine in commercially available cigarettes and tobacco leaves was extracted into chloroform and determined by an IMD after SFC separation. The detection limit was at the picogram level for nonselective monitoring and the subnanogram level for nicotine selective detection. This system provided a simple analytical method for the analysis of nicotine and other alkaloids in tobacco. Compared to currently utilized methods, the SFC–IMD provided advantages of high sensitivity, nicotine specific detection and lower instrumentation cost. The potential of combining online supercritical fluid extraction with SFC–IMD for analysis of alkaloids in tobacco was demonstrated.

Application of an ion mobility detector in radiation stimulated plasma chemistry

Fast electrons emitted by a beta radiation source produce ion pairs between a two eletrode arrangement full with argon or nitrogen at ambient pressure. Ions created there were identified with the help of an ion mobility spectrometer. The production of reactive species by field accelerated electrons was studied in argon.

Quantification of mammalian lignans in biological fluids using gas chromatography with ion mobility detection

A method is presented to quantify selected mammalian lignans in human physiological fluids by gas chromatography (GC) coupled with ion mobility spectrometry (IMS). The use of IMS following GC permitted the selective and sensitive measurement of 2,3-bis(3-hydroxybenzyl)butane-1,4-diol ( i.e., enterodiol) and trans-2,3-bis(3-hydroxybenzyl)-γ-butyrolactone ( i.e., enterolactone) concentrations in urine and plasma following dietary supplementation with whole wheat/flaxseed bread high in mammalian lignan precursors. Following six weeks of flaxseed feeding, urinary and plasma levels of enterodiol and enterolactone were elevated, exceeding the amounts found at baseline by a factor of 3–5. The approach to mammalian lignan methodology presented herein provides novel analytical phytochemical procedures for assessing the impact of lignan consumption in human health and disease.

Comparison of a pulsed electron capture detector and a Fourier transform ion mobility detector after capillary supercritical fluid chromatography

A commercial electron capture detector and an ion mobility detector were interfaced to a supercritical fluid chromatograph (SFC). The ion mobility detector (IMD) was operated in the negative ion collection mode wherein analyte molecules of high electron affinity form negatively charged ions in the detector, producing an ECD-like response. Responses of the two detectors were compared using pressure programmed SFC with carbon dioxide as the mobile phase. A mixture of nine chlorinated pesticides (Lindane, DDT, DDE, BHC, Endrin, Heptachlor, Endosulfan, Dieldrin and Chloropicrin); a mixture of six polycyclic aromatic hydrocarbons (naphthalene, acenaphthalene, dimethylnaphthalene, pyrene, phenanthrene, and fluoranthene); two polychlorinated biphenyls (Aroclor 1248 and Aroclor 1260), and a bean extract containing the chlorinated fungicide Captan were chromatographed as test compounds. In all cases pressure programming of the carbon dioxide mobile phase resulted in an increasing baseline signal as pressure increased with the ECD while a stable baseline was observed with the IMD. These investigations demonstrated the potential of negative mode IMD as a useful alternative for the sensitive and selective SFC detection of compounds amenable to electron capture detection.

Photoemissive ionisation source for ion mobility detectors

A combination of a photoemissive ionisation source coupled to an ion mobility detector has been developed which utilises a pulsed light source thereby eliminating the need for an ion injection gate. Factors influencing the performance of this negative ion detector have been investigated. With air as the sample and drift gas streams, the performance of the detector is comparable to conventional designs employing radioactive ionisers.

Evaluation of an ion mobility detector for supercritical fluid chromatography with solvent-modified carbon dioxide mobile phases

An ion mobility detector (IMD) was evaluated for open tubular column supercritical fluid chromatography (SFC) when organic solvent-modified supercritical CO2 was used as mobile phase. It was found that the SFC/IMD interface design in which the SFC capillaray restrictor was directly inserted into the ionization region of the IMD was not acceptable because of low sensitivity that resulted from the effect of the modifier on detector temperature and mechanism of detection. A new interface utilizing a heated nebulizer gas to provide heat to the restrictor and to minimize the formation of ion clusters, and a bent nozzle for enhancing the ionization efficiency of the solute in the IMD ion source are described. Using 5% acetonitrile in CO2, the minimum detectable quantity (S/N=3) for pyrene was improved from 25.2 ng to 2.1 ng with the new detector design. This compares to a minimum detectable quantity of 0.1 ng when using neat CO2 as mobile phase. The use of molecular connectivity calculations to predict the drift times of selected analytes is also successfully demonstrated.

Electron capture ion mobility spectrometry for the selective detection of chlorinated and brominated species after capillary gas chromatography

AbstractThis paper reports the first investigation of electron capture ion mobility spectrometry as a detection method for capillary gas chromatography. In previous work with negative ion mobility detection after gas chromatography, the principal reactant ion species were O2− or hydrated O2− due to the presence of oxygen in the drift gas. These molecular reactant ions have a mobility similar to chloride and bromide ions, which are the principal product ions formed by most halogenated organics via dissociative ion‐molecule reactions. Oxygenated reactant ions thus interfere with the selective detection of chloride and bromide product ions. A recently described ion mobility detector design efficiently eliminated ambient impurities, including oxygen, from infiltrating the ionization region of the detector; consequently, in the negative mode of operation, the ionization species with N2 drift gas were thermalized electrons. Thermalized electrons have a high mobility and their drift time occupies a region of the ion mobility spectrum not occupied by chloride, bromide, or other product ions. The result was improved selectivity for halogenated organics which ionize by dissociative electron capture. This was demonstrated by the selective detection of 4,4′‐dibromobiphenyl from the components of a polychlorinated biphenyl mixture (Aroclor 1248).

Ion mobility detection following liquid chromatographic separation

AbstractCoronaspray ion mobility spectrometry was used in sample detection following reversed‐phase liquid chromatographic separation. Samples were introduced by coronaspray using a fused silica transfer line that was inserted through a stainless steel needle. Ion mobility spectra and chromatographic responses via monitoring of reactant‐ion depletion in the software second gate mode were shown for esters of para‐hydroxy benzoic acid, isomers of nitroaniline, and a mixture of acetaminophen, caffeine, and phenacetin.

Detection limits of an ion mobility detector after capillary gas chromatography

AbstractA method for setting gating parameters is presented that maximizes response in ion mobility detection following capillary gas chromatography. The method requires knowledge of the drift times of the product ion or ions of interest and the drift times of the reactant ions. These values are obtainable from ion mobility spectra captured after capillary gas chromatography.The capillary insertion distance into the ion source and the presence or absence of an aperture grid were also found to have considerable effect on chromatographic response. Under optimized conditions, minimum detectable limits of <1 fmol/s are reported for tributylamine, phenyl sulfide, and tributyl phosphate. These values demonstrate significant improvements over reported detection limits of organics by the flame ionization detector and sulfur‐containing species by the flame photometric detector. The values show slight improvement over those reported for detection of nitrogen and are comparable to those reported for detection of phosphorus‐containing species by the thermionization detector.

Ion mobility detection of polydimethylsilicone oligomers following supercritical flui chromatographic separation

A mixture of polydimethylsilicones (Dow Corning 200), average molecular weight 2000 a.m.u., was separated by simultaneous density and temperature-programmed supercritical fluid chromatography and detected by ion mobility detection. Ion mobility spectra were captured by Fourier transform ion mobility spectrometry. Using information from these spectra it was possible to selectively detect a single compound in the complex mixture. A detector temperature investigation demonstrated that, for the efficient transfer of high-molecular-weight compounds from the column to the detector, the interface to the detector must be heated. Using a 50 μm I.D. column, a Guthrie-type restrictor and a detection temperature of 250°C, as many as 70 oligomers were separated and detected.

Selective detection of underivatized 2,4-dichlorophenoxyacetic acid in soil by supercritical fluid chromatography with ion mobility detection.

A simplified procedure was developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) in soils. Soil samples were separated by supercritical fluid chromatography after extraction without derivatization and without the use of column chromatography for cleanup. Interferences in the chromatographic separation were eliminated by using a tunably selective ion mobility detector. An atmospheric pressure ion formed by the free acid was selectively monitored so the detector could monitor 2,4-D in the presence of other electron-capturing compounds. For a randomly chosen soil sample, the level of 2,4-D detected was estimated at 500 ppb.