Collision / reaction cells hexapole

In addition to these collision/reaction cell instruments, since 2002 Thermo Fisher Scientific has been selling the XSeries ICP-MS with a hexapole collision cell (developed from ThermoElemental PQExel ICP-MS) as a bench top instrument on the analytical market. A special ion extraction system in Thermo s XSeries", ion optics together with a hexapole collision cell to minimize the interference problem in ICP-MS, provides the lowest background signals for ICP-QMS (< 0.5 cps). 

Figure 5.6 Experimental arrangement ofquadrupole based ICP-MS with collision/reaction cell with dual axis hexapole collision cell, Platform XS photograph of collision cell is shown at bottom (GV Instruments, Manchester) (Reproduced by permission of GV Instruments Ltd.)2 ...

Collision/reaction cell Agilent ceVcs2 octopole cell (ORS) Elan DRC II quadrupole dynamic reaction cell XSeries11 hexapole cell ( XS-Minus modus) Varian-820-MS using collision reaction interface... 

Turner et al. [114] described an ICP-MS with a hexapole transfer lens (Fig. 3.12a) in a tube that allows the pressure to be maintained. The cell was initially reported to contain He, although it is likely that H2 or H20 vapor was also in the cell and is now purposely added to the cell [115]. Ar2+, ArCl+, ArO+, and Ar+ signals were reduced relative to Se+, As+, Fe+, and Ca+, respectively. Detection limits for Fe, Ca, K, Se, and As near 10 parts per trillion (ppt) have been reported [115]. Recently, Beaty and Liezers [116] also described a collision-reaction cell at a pressure of 30 mtorr that reduced the ion kinetic energy spread as well as continuum ICP-MS background to less than 1 count/sec. Previously, Douglas and French had described the use of an rf-only quadrupole for collisional focusing and reduction of the ion kinetic energy spread [117]. 

Figure 12 (a) ICP-MS with hexapole collision-reaction cell similar to that used by Micromass, (b) ICP-MS with dynamic reaction cell as described by Perkin-Elmer Sciex. 

Collision-Reaction Cells. Perhaps the most exciting development regarding molecular ion removal in ICP-MS is the use of collision or reaction cells, introduced in Sec. 3.1.5. These rf-only quadrupole, hexapole, or octapole cells, typically operated at pressures around 10 mtorr, can provide two benefits The collision cell can be used to reduce the ion kinetic energy and to focus ions toward... 

S. Mazan, N. Gilon, G. Cretier, J. L. Rocca, J.-M. Mermet, Inorganic selenium speciation using HPLC-ICP-hexapole collision/reaction cell-MS, J. Anal. Atom. Spectrom., 17 (2002), 366-370. 

Hot water extracts analyzed by RP-HPLC [Nucleosil 120 A Cl8 colunm with 30 mmol L ammonium formate, pH 3.0, 5% (v/v) methanol] and IP HPLC (10 mM TBAA in the RP mobile phase) with on-line ICP-MS detection. Three nebulizers were tested (Meinhard, HHPN, MCN) and a hexapole collision reaction cell was used... 

Another way of rejecting polyatomic interfering ions and the products of secondary collisions/reactions is to discriminate them by mass. As mentioned previously, higher-order multipoles cannot be used for efficient mass discrimination because the stability boundaries are diffuse and sequential secondary reactions cannot be easily intercepted. The only way this can be done is to utilize a quadrupole (instead of a hexapole or octapole) inside the collision/reaction cell and use it as a selective bandpass (mass) filter. There are a number of commercial designs using this approach, so let us take a look at them in greater detail in order to better understand how they work and how they differ. 

The first commercial instrument to use this approach was called dynamic reaction cell (DRC) technology Similar in appearance to the hexapole and octapole collision/reaction cells, the DRC is a pressurized multipole positioned prior to the analyzer quadrupole. However, this is where the similarity ends. In DRC technology, a quadrupole is used instead of a hexapole or octapole. A highly reactive gas such as ammonia, oxygen, or methane is bled into the cell, which is a catalyst for ion-molecule chemistry to take place. By a number of different reaction mechanisms, the gaseous molecules react with the interfering ions to convert than into either an innocuous species different from the analyte mass or a harmless neutral species. The analyte mass then emerges from the DRC free of its interference and is steered into the analyza quadrupole for conventional mass separation. 

Based on a quadrupole ICP-MS, another technique, termed collision/reaction cell, has frequently been used to reduce polyatomic ion interferences. " These techniques provide simple, efficient, and low-cost methods in the face of many difficult interference problems. In these methods, ions to be analyzed first enter a radio-frequency-only multipole (e.g. a quadrupole, hexapole, or octapole), in which the analytes react with the collision/reaction gas, which is usually oxygen, ammonia, xenon, or methane, " to remove polyatomic interference or generate a new analyte ion of mjz showing less interference. The RP-only multipole does not separate ions like a traditional quadrupole, but it has profound influence on collisional focusing of ions, both of the energy and spatial distributions. An example of removing the polyatomic interference is shown below, which uses ammonia gas to reduce any "" Ar" " interference in the measurement of " Ca ... 

Because of the disparity of the reaction rates of the two neutralization reactions, the analyte can be efficiently determined after the introduction of ammonia as a reactive gas into the multipole. There are many excellent reviews about the development and applications of collision/reaction cell in ICP-MS. " In order to eliminate the new isobaric interferences produced by secondary reactions, two methods are commonly used in the commercial instrument the discrimination of kinetic energy or mass filtering. " The former mainly utilizes the post-cell kinetic energy discrimination (KED) to suppress transport of the produces of the side reactions to the analyte in the hexapole and octapole cell instruments. Whereas in the latter, the quadrupole cell has a capability to reduce the formation of the unwanted side product ions by selecting an appropriate mass bandpass. The details of the KED and bandpass approaches can refer to many excellent books and reviews. " " ... 

Dexter M. A., Reid H. J. and Sharp B. L. (2002) The effect of ion energy on reactivity and species selectivity in hexapole collision/reaction cell ICP-MS, J. Anal. At. Spectrom. 17 676-681. 

A new generation of quaclrupole-based ICP-MS instruments offer an ion focusing and molecular ion destruction device named hexapole, collision cell or dynamic reaction cell depending on the manufacturer [17]. This device increases the transmission and destroys molecular ions with varying efficiency. An example of molecular ions and their impact on the analysis of bromine is shown in Fig. 3-... 

I. Feldmann, N. Jakubowski, D. Stueuer, Application of a hexapole collision and reaction cell in ICP-MS. Part 1 instrumental aspects and operational optimisation, Fresenius J. Anal. Chem., 365 (1999), 415-421. 

J. Marchante-Gayon, C. Thomas, I. Feldmann, N. Jakubowski, Comparison of different nebulisers and chromatographic techniques for the speciation of selenium in nutritional commercial supplements by hexapole collision and reaction cell ICP-MS. J. Anal. Atom. Spectrom., 15 (2000), 1093-1102. 

Commercial yeast-based supplements Hot water extraction IP HPLC-ICP-MS with hexapole collision and reaction cell, hydraulic high pressure nebulizer... 

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