Collision / reaction cells

Collision/reaction cell technology (CCT/CRC) is a cheaper alternative for reducing the impact of interferences than is high-resolution magnetic sector ICP-MS. 

Quadrupole mass spectrometer with collision/reaction cell... 

An overview of commercial ICP mass spectrometers from different companies (quadrupole based ICP-MS with and without collision/reaction cell, double-focusing sector field instrumentation with single and multiple ion collectors, time-of-flight (ToF), ICP-ion trap-MS and non-commercial ICP-Fourier transform ion cyclotron resonance (FTICR) mass spectrometers is given in Figure 5.2. By using ion traps and FTICR mass spectrometers in ICP-MS isobaric interferences of atomic ions... 

Figure 5.3 Instrumental outline of a quadrupole-based ICP-MS without collision/reaction cell (Agilent 7500). (Reproduced by permission of Agilent.)...

The figures of merit of quadrupole-based ICP-MS, such as the precision of isotope ratio measurements and the detection limits, can be improved significantly, especially for elements which are difficult to determine due to the appearance of isobaric interferences (e.g., by the trace, ultratrace and/or isotope ratio measurements of Ca, Fe, S, As, I or Se).16-22 The occurrence of interference problem can be minimized by the insertion of a collision/reaction cell in ICP-MS as the result of defined collision induced reactions using selected collision/reaction gases or gas mixtures (such as H2, He, NH3, 02, CH4 and others). For each analytical problem, which is different, e.g., for U or... 

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 ...

Further applications of ICP-MS with a collision/reaction cell in trace, ultratrace analysis and isotope ratio measurements are described in Chapter 8.16 17 20 22 27 28... 

The figures of merit of several commercial quadrupole based ICP mass spectrometers with and without a collision/reaction cell, produced by different companies, are summarized in Table 5.1. 

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... 

More recently, the advent of the collision/reaction cell technology has revolutionised commercial quadrupole ICP-MS systems. A gas, such as hydrogen, helium or ammonia, is introduced into the reaction cell (placed inside the mass spectrometer and preceding the analyser quadrupole), where it reacts and dissociates or neutralises the polyatomic species or precursors. Through collision and reaction with appropriate gases in a cell, interferences... 

A multipole cell at pressures around 1 to 15 mtorr, placed between the sampler-skimmer interface and the mass spectrometer, can serve two functions reduce the kinetic energy of the ions to nearly thermal energies (<0.5 eV) and carry out reactions with analyte or background ions. Of particular interest for ICP-MS are reactions that would dramatically reduce spectral overlaps due to elemental or polyatomic ions. Two potentially undesirable processes must be considered for successful use of a collision-reaction cell. Scattering losses can be severe if the mass of the collision or reaction gas is high compared to that of the analyte ion... 

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. 

---