Alternative reagent ions for plasma chromatography

Proctor, C. J.; Todd, John F. J.

doi:10.1021/ac00275a010

Cited by 62 publications

(34 citation statements)

References 13 publications

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“…Later, Blyth (1983) used acetone for the selective detection of chemical warfare agents [2] and Spangler et al (1985) introduced the use of carbon tetrachloride for the selective detection of explosives [3]. In a comparative study of halogen containing dopants, Proctor and Todd found dichloromethane to be superior to dibromomethane, methyl iodide, acetic acid, dimethyl sulfide, and acetonitrile [4] for the detection of explosives. Eiceman et al (1995) selectively detected mixtures of volatile organic and organophosphorus compounds using acetone and dimethylsulfoxide reagent gases [5] and Meng et al (1995) used water, acetone, and dimethylsulfoxide reagent gases to provide specific ionization of indoor ambient atmospheres for volatile organic compounds [6].…”

Section: Introductionmentioning

confidence: 99%

Using a buffer gas modifier to change separation selectivity in ion mobility spectrometry

Fernandez‐Maestre

Hill

2010

International Journal of Mass Spectrometry

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The mobilities of a set of common α-amino acids, four tetraalkylammonium ions, 2,4-dimethyl pyridine (2,4-lutidine), 2,6-di-tert-butyl pyridine (DTBP), and valinol were determined using electrospray ionization-ion mobility spectrometry-quadrupole mass spectrometry (ESI-IMS-QMS) while introducing 2-butanol into the buffer gas. The mobilities of the test compounds decreased by varying extents with 2-butanol concentration in the mobility spectrometer. When the concentration of 2-butanol increased from 0.0 to 6.8 mmol m −3 (2.5×10 2 ppmv), percentage reductions in mobilities were: 13.6% (serine), 12.2% (threonine), 10.4% (methionine), 10.3% (tyrosine), 9.8% (valinol), 9.2% (phenylalanine), 7.8% (tryptophan), 5.6% (2,4-lutidine), 2.2% (DTBP), 1.0% (tetramethylammonium ion, TMA, and tetraethylammonium ion, TEA), 0.0% (tetrapropylammonium ion, TPA), and 0.3% (tetrabutylammonium ion, TBA). These variations in mobility depended on the size and steric hindrance on the charge of the ions, and were due to formation of large ion-2-butanol clusters. This selective variation in mobilities was applied to the resolution of a mixture of compounds with similar reduced mobilities such as serine and valinol, which overlapped in N 2 -only buffer gas in the IMS spectrum. The relative insensitivity of tetraalkylammonium ions and DTBP to the introduction of 2-butanol into the buffer gas was explained by steric hindrance of the four alkyl substituents in tetraalkylammonium ions and the two tert-butyl groups in DTBP, which shielded the positive charge of the ion from the attachment of 2-butanol molecules. Low buffer gas temperatures (100 °C) produced the largest reductions in mobilities by increasing ion-2-butanol interactions and formation of clusters; high temperatures (250 °C) prevented the formation of clusters, and no reduction in ion mobility was obtained with the introduction of 2-butanol into the buffer gas. Low temperatures and high concentrations of 2-butanol produced a series of ion clusters with one to three 2-butanol molecules in compounds without steric hindrance. Clusters of two and three molecules of 2-butanol were also visible. Ligand-saturation on the positive ions with 2-butanol molecules occurred at high concentrations of modifier (6.8 mmol m −3 at 150°C); when saturated, no further reduction in mobility occurred when 2-butanol was introduced into the buffer gas.

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Section: Introductionmentioning

confidence: 99%

Using a buffer gas modifier to change separation selectivity in ion mobility spectrometry

Fernandez‐Maestre

Hill

2010

International Journal of Mass Spectrometry

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“…Addition of Cl − , Br − , or I − ions leads to an enhanced ability to detect NO 3 −1 from fragmentation of explosive materials. (149) Qualitative identification of explosives by IMS has been reported by various researchers with a variety of very low detection limits. According to Cohen et al, (150) rapid explosive vapor detection by IMS is feasible down to 10 −14 parts by volume in air; other researchers report that laboratory detection limit is as low as 200 pg for common explosives (such as NG, PETN, RDX, and TNT) (16) and as low as 0.01 ppb or 1.0 pg for TNT vapor.…”

Section: Ion Mobility Spectrometrymentioning

confidence: 99%

Laser‐ and Optical‐Based Techniques for the Detection of ExplosivesUpdate based on the original article by David L. Monts, Jagdish P. Singh and Gary M. Boudreaux,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd

Hummel

Dubroca

2013

Encyclopedia of Analytical Chemistry

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A wide variety of optical‐ and laser‐based techniques have been and are currently being investigated as means of identifying and characterizing explosive materials. These efforts are hampered by the very low volatility of explosive compounds at room temperature and their tendency to ignite at higher temperatures where their vapor pressures are beginning to reach a regime where the species can be readily detected. Traditional, condensed‐phase absorption spectroscopy (both infrared (IR) and ultraviolet/ visible (UV/VIS)) requires larger samples than are frequently available and, although useful as confirmatory techniques, do not provide signatures that enable unique identification of species. The choice of nontraditional techniques for analysis of explosive materials is dependent upon the amount of sample available, the sample matrix, and sample‐imposed constraints upon the measurement. Raman spectroscopy can identify and quantify condensed phase explosive materials, but the detection limit depends upon substrate, excitation wavelength, and illumination area: limits of detection (LODs) vary from 0.05 ng for 2,4,6‐trinitrotoluene (TNT) on glass to 10 µg for nitroglycerin (NG) on silica gel. The other detection techniques considered require volatilization of either the explosive compound itself or more often of characteristic decomposition products, such as NO, NO 2 , or N 2 O. Using IR irradiation, researchers have demonstrated that photoacoustic spectroscopy (PAS) has detection limits ranging from 0.55 ppb (parts per billion) for vapor‐phase NG with 9 mm excitation to 220 ppm (parts per million) for vaporphase 2,4‐dinitrotoluene (DNT) with 6‐µm excitation. IR laser differential absorption detection of dissociation products NO, NO 2 , and/or N 2 O can achieve detection limits of a few picograms. Laser‐induced fluorescence (LIF) detection of the photofragments (typically NO) of explosive compounds yields detection limits in the tens to hundreds of ppb (by weight) range. Low LODs can be achieved using ion detection techniques: resonance‐enhanced multiphoton ionization (REMPI) spectrometry is capable of LODs for detecting vapor‐phase explosives compounds in the hundredths to tens of ppb range; ion mobility spectrometry (IMS) has vapor‐phase detection limits for common explosive compounds of typically 200 pg, but for some species can be significantly lower: for example, 1 pg for TNT.

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“…Selecting a reactant molecule with a proton affinity higher than the interferent but lower than the product ion can eliminate common interferents. 4 Since ionization and analysis occur under atmospheric conditions, the formation of ion clusters is common. To avoid unwanted clustering in the ionization region, the counter flow gas needs to be dry.…”

Section: Ion Mobility Spectrometrymentioning

confidence: 99%

Instrument response measurements of ion mobility spectrometers in situ: maintaining optimal system performance of fielded systems

et al. 2005

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Ion Mobility Spectroscopy (IMS) is the most widespread detection technique in use by the military for the detection of chemical warfare agents, explosives, and other threat agents. Moreover, its role in homeland security and force protection has expanded due, in part, to its good sensitivity, low power, lightweight, and reasonable cost. With the increased use of IMS systems as continuous monitors, it becomes necessary to develop tools and methodologies to ensure optimal performance over a wide range of conditions and extended periods of time. Namely, instrument calibration is needed to ensure proper sensitivity and to correct for matrix or environmental effects. We have developed methodologies to deal with the semi-quantitative nature of IMS and allow us to generate response curves that allow a gauge of instrument performance and maintenance requirements. This instrumentation communicates to the IMS systems via a software interface that was developed in-house. The software measures system response, logs information to a database, and generates the response curves. This paper will discuss the instrumentation, software, data collected, and initial results from fielded systems.

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Alternative reagent ions for plasma chromatography

Cited by 62 publications

References 13 publications

Using a buffer gas modifier to change separation selectivity in ion mobility spectrometry

Using a buffer gas modifier to change separation selectivity in ion mobility spectrometry

Laser‐ and Optical‐Based Techniques for the Detection of ExplosivesUpdate based on the original article by David L. Monts, Jagdish P. Singh and Gary M. Boudreaux,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd

Instrument response measurements of ion mobility spectrometers in situ: maintaining optimal system performance of fielded systems

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