Trapping devices

Another powerftil class of instmnientation used to study ion-molecule reactivity is trapping devices. Traps use electric and magnetic fields to store ions for an appreciable length of time, ranging from milliseconds to thousands of seconds. Generally, these devices mn at low pressure and thus can be used to obtain data at pressures well below the range in which flow tubes operate. 

To satisfy the Resource Conservation and Recovery Act (1977) and its amendment for hazardous and solid waste (1984), the 80(K) Series Methods have been designed to analyze solid waste, soUs, and groundwater. In particular, methods 8240/8260 require the use of a purge-and-trap device in conjunction with packed or capillary GC/MS, respectively, for the analysis of purgeable organic compounds. Methods 8250/8270 concern analyses for the less-volatile bases, neutrals, and acids by GC/MS after extraction from the matrix by an organic solvent. 

Target compounds are specified for each Series Method. Volatile compounds that need to be analyzed can be extracted from the matrix by a purge-and-trap device. 

Rapid scanning mass spectrometers providing unit resolution are routinely used as chroaatographic detectors. Ion separation is accomplished using either a magnetic sector, quadrupole filter or ion trap device. Ions can also be separated by time-of-flight or ion cyclotron resonance mass analyzers but these devices are not widely used with chromatograidiic inlets and will not be discussed here [20]. 

Applications Off-line GC-FTIR using a trap device has been used for the determination of a wide range of polymer additives (with highest boiling constituents below 250 °C) in amounts down to 0.01 % with an accuracy of 5 to 10% [207]. According to Haslam el al. 208], the... 

With the site-selective hole injection and the hole trapping device established, the efficiency of the hole transport between the hole donor and acceptor, especially with respect to the distance and sequence dependence, were examined. Our experiments showed that hole transport between two guanines was extremely inefficient when the intervening sequence consisted of more than 5 A-T base pairs [1]. Hole injection into the DNA n-stack using photoexcited dCNBPU was accompanied by the formation of dCNBPU anion radical. Therefore, hole transport would always compete with the back electron transfer (BET). To minimize the effect of BET, we opted for hole transport between G triplets, that are still lower in oxidation potential than G doublet. With this experimental system, we researched the effect of the bridging sequence between two G triplets on the efficiency of hole transport [2]. 

A booby trap device which may be activated by a pull wire or by tilting of object to which applied, such as luggage, door handle, or hinged cover of box. 

Note Here, we are going beyond the domain of the classical mass spectro-metric time scale (Chap. 2.7). In ion trapping devices, ions are stored for milliseconds to seconds, i.e., 10 -10 times longer than their lifetimes in beam instruments. 

Ion trapping devices are sensitive to overload because of the detrimental effects of coulombic repulsion on ion trajectories. The maximum number of ions that can be stored in a QTT is about 10 -10, but it reduces to about 10 -10 if unit mass resolution in an RF scan is desired. Axial modulation, a sub-type of resonant ejection, allows to increase the number of ions stored in the QIT by one order of magnitude while maintaining unit mass resolution. [160,161] During the RF scan, the modulation voltage with a fixed amplitude and frequency is applied between the end caps. Its frequency is chosen slightly below V2 of the fundamental RF frequency, because for Pz < 1, e.g., = 0.98, we have z = (0 + 0.98/2) = 0.49 x... 

Bianchi AP, Varney MS, Phillips J. 1991. Analysis of industrial solvent mixtures in water using a miniature purge-and-trap device with thermal desorption and capillary gas chromatography-mass spectrometry. J Chromatogr 557(l-2) 429-439. 

Because of the differences in the construction of various purge and trap devices, actual recoveries may vary significantly from those shown in Figure 3 and Table I. Therefore it is required that individual investigators determine recoveries of compounds to be measured as a function of flow rate with their apparatus. Operation in the optimum flow rate range will assure maximum sensitivity and precision for the compounds measured. 

Ion trap/TOF This combination is advantageous because it enables the MS" capabilities of an ion trap with the high mass accuracy and speed of a TOF analyzer. The ion trap can either be a conventional hyperbolic Penning-type device or a linear trap device. Below we describe the deployment of the former type ion trap/TOF for explosives detection. 

Regeneration time As a gas trapping device, the cryopump must be regenerated after a certain period of operation. Regeneration involves the removal of condensed and adsorbed gases from the cryopanels by heating. The regeneration can be run fully or only partially and mainly differs by the way in which the cryopanels are heated. 

Another form of head space analysis uses a purge trapping device to trap volatile impurities. In this technique a gas, e.g. helium, is bubbled through the sample which is dissolved in suitable solvent (usually water) and the volatile impurities are thus stripped from the solution and passed in the stream of gas through a polymeric adsorbant where they become trapped and thus concentrated. The stream of gas is then switched so it passes in reverse direction through the polymeric trap, which is heated to desorb the trapped volatiles and the gas stream is then diverted into the GC. This type of procedure is used in environmental analysis to concentrate volatiles in water which are present at low levels. 

Pulverized oil shale is the main fuel for Estonian power stations, and atmospheric emissions therefrom have been studied in detail by Aunela et al. (1995), Hasanen et al. (1997), and Jalkanen (2000). The main emissions are acidic or greenhouse gases (SO2, NOx, CO2) and large amounts of airborne particulate matter that escape the trapping devices in the smoke stack (i.e., the part of fly ash <50 xm in diameter). 

Trapping Device Experiments. The system used to collect the organic compounds extracted from the aqueous stream was, in most cases, a series of glass U-tubes held at —76 °C. That temperature represented a practical lowest limit to prevent deposition of solid carbon dioxide. During the course of this program, it became evident that, for many compounds, complete mass balances were not being achieved. The trapping system appeared to be a likely source of such losses because many of the compounds studied had a finite vapor pressure at —76 °C. An effluent C02 stream saturated with these... 

Trapping a sample as it elutes from the column followed by some other identification or classification technique is often utilized with gas chromatographic analysis. The most common trapping devices are the cold trap, the gas scrubber (gas washing bottle), the evacuated bulb, and the adsorbent postcolumn. 

Booby Trap. Devices which are installed to operate against personnel in territory surrendered to the enemy are called booby traps. They are designed to function by themselves and to harass or destroy individuals or small groups of the enemy. The same device may be used for either an antipersonnel... 

P. Mela, A. van der Berg, Y. Fintschenko, E.B. Cummings, B.A. Simmons and B. J. Kirby, The zeta potential of cyclo-olefin polymer microchannels and its effects on insulative (electrodeless) dielectrophoresis particle trapping devices, Electrophoresis, 26 (2005) 1792-1799. 

Dorfman, K.D., Brenner, H., Modeling DNA electrophoresis in microfluidic entropic trapping devices. Biomed. Microdevices 2002, 4(3), 237-244. 

Elemental mass spectrometry has undergone a major expansion in the past 15-20 years. Many new a, elopments in sample introduction systems, ionization sources, and mass analyzers have been realized. A vast array of hybrid combinations of these has resulted from specific analytical needs such as improved detection limits, precision, accuracy, elemental coverage, ease of use, throughput, and sample size. As can be seen from most of the other chapters in this volume, however, the mass analyzers used to date have primarily been magnetic sector and quadrupole mass spectrometers. Ion trapping devices, be they quadrupole ion (Paul) [1] traps or Fourier transform ion cyclotron resonance (Penning) traps, have been used quite sparingly and most work to date has concentrated on proof of principal experiments rather that actual applications. 

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