Rapid Determination of Explosives and Narcotics Using a Multicapillary-Column Gas Chromatograph and an Ion-Mobility Spectrometer

A gas chromatograph for the rapid determination of explosives (2,4-dinitrotoluene, 2,4,6-trinitrotoluene, and pentaerythritol tetranitrate) and narcotics (heroin, cocaine hydrochloride, and crack) is described, and its analytical characteristics are presented. The instrument was equipped with a multicapillary column and an ion-mobility spectrometer as a detector.     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.     

Detection of explosives by ion mobility spectrometry

Ion mobility spectrometry is an effective method for detecting mine-explosive devices and explosive charges and for revealing objects and peoples who came into contact with explosives. This is because of the excellent analytical and performance characteristics of the corresponding instruments. In the present work, we described the objects to be detected, formulated the basic terms and definitions, considered the physicochemical basics of the separation of ions by their mobility in a gas under an electric field, and presented experimental data on the main analytical characteristics of spectrometers: their ability to identify analytes, resolution power, time to provide readings, sensitivity, and detection limit.     

Russian publications (1991–2010) devoted to ion mobility spectrometry

The physicochemical principles of ion mobility spectrometry are described; Russian publications issued between 1991 and 2010 and devoted to the development of the fundamentals and technical implementation of this method, its use for physicochemical research, and solving problems of analytical chemistry, safety, medicine, and ecology, are reviewed.     

Status of the front-end-electronics for the time-of-flight measurements at the MPD experiment

The preamplifier based on the ASIC NINO for the Time of Flight system (TOF) of MPD/NICA was developed and tested. The signal is read from both sides of the strip of the multi gap Resistive Plate Chamber (MRPC). In total there are around 14000 channels of electronics. To measure time of flight of secondary particles from collision of heavy ions on the collider NICA the Time over Threshold (ToT) method is used. According to the bench tests the preamplifier board showed stable work and good time resolution <10 ps for one channel. It was also tested at the test beam facility of the Nuclotron. The time resolution of the TOF detector which used the described preamplifier was reached ～42 ps.     

Current-conducting properties of paper consisting of multiwall carbon nanotubes

Electrical conductivity σ(T) of the paper consisting of multiwalled carbon nanotubes (MWCNTs) is studied in the temperature range 4.2-295 K, and its magnetoresistivity ρ(B) at various temperatures in magnetic fields up to 9 T is analyzed. The temperature dependence of the paper electrical conductivity σ(T) exhibits two-dimensional quantum corrections to the conductivity below 10 K. The dependences of negative magnetoresistivity ρ(B) measured at various temperatures are used to estimate the wavefunction phase breakdown length L _φ of conduction electrons and to obtain the temperature dependence L _φ = constT ^?p/2, where p ≈ 1/3. Similar dependences of electrical conductivity σ(T), magnetoresistivity ρ(B), and phase breakdown length L _φ(T) are detected for the initial MWCNTs used to prepare the paper.     

泥沙输运模拟综述——现状及其发展趋势

随着流体力学中数值方法的飞速发展,计算模型已经成为研究流体运动,泥沙输运和不同环境(诸如河流,湖泊及沿海地区)中相应污染物归趋过程等方面非常有吸引力的工具,在过去的30多年里,发展了许多计算水动力学/泥沙输运模型.文章追溯当前具有代表性的(一维、二维、三维)模型的发展历程,描述他们各自的特点,优势及局限,力图作为对模型方面感兴趣读者的第一指南,同时也为大家讨论模型的局限性,未来的发展趋势和研究需求方面搭建一个平台.给出了模型的表达,时空特性,水动力学和沉积物的耦合方式,处理非恒定流,推移质和悬移质,泥沙交换过程,泥沙类型(粘性或非粘性)及非均匀泥沙输运的能力.总结了不同模型的应用实例,读者可以运用这些例子作为研究模型设置,模型率定及模型验证的参考.给出了选择泥沙输运模型应遵循的原则,模型输入及率定方面存在的问题及改进的途径.探讨了现有水动力学/泥沙输运模型在处理复杂湍流,泥沙携带,流动与输沙耦合,非均匀泥沙,离散和扩散系数,河岸来沙处理等方面的局限性及改进的方向.最后,对基于多相流思想的泥沙输运模型及其它一些交叉性问题作了评述与展望.     

Coefficient of ion mobility versus electric field strength dependence in gases: Experimental determination

A technique for finding the electric field dependence of the coefficient of ion mobility in gases is suggested. For ions of 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, 1,3,5-trinitrobenzene, 1,3-dinitrobenzene, and dimethylmethylphosphonate, these dependences are taken in air by applying a variable periodic polarity-asymmetric specially shaped electric field. The accuracy of the technique suggested is estimated and compared with that of the conventional drift tube method.     

Qualitative analysis of trace constituents by ion mobility increment spectrometer

Ion mobility increment spectrometry (IMIS) is a high sensitive selective ionization technology for detection and identification of ultra-trace constituents, including toxic compounds, CW-agents, drugs and explosives in ambient air or liquid sample. Like an ion mobility spectrometry (IMS), this technology rests on sampling air containing a mixture of trace constituents, its ionization, spatial separation of produced ions and separated ions detection. Unlike IMS, ions of different types in IMIS are separated by ion mobility increment, α. Value α, is a function of the parameters: electric field strength and form, atmospheric pressure. To exclude the influence of these parameters on an α, the method of explosives identification by a standard compound was suggested. As a standard compound iodine was used. The relationship among the mobility coefficient increments equal to the relationship among the compensation voltage α_i/α_iodine=U_i/U_iodine is determined, where i are ions of 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, p-mononitrotoluene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene This relationship is practically independent of the above mentioned parameters in the range 25<E/N<90 Td. The limits of the relative error of this relationship are determined both from spectra of individual compounds and nitrocompound-iodine mixtures.