Octapole collision cell

The performance characteristics of this analyzer are quite remarkable with mass accuracies of <2 ppm at a resolving power of 60 000 using an external calibration 5 and of <1 ppm with internal calibration.76 As such, it has attracted the attention of analysts and instrument developers alike. New features have included ETD (see Section 9.10.3.2.5) and options for higher energy collisions in the C-trap or in an additional octapole collision cell.77... 

The particularity of the LTQ orbitrap instrument is the possibility to operate the orbitrap and the LIT independently. Because high resolution requires longer transient time, further data can already be collected in the LIT at the same time. As an example accurate mass measurements of the precursor ion can be performed in the orbitrap while MS and MS spectra are recorded with the LIT. One other specificity of the system is that collision-induced dissociation can also be performed in the octapole collision cell. 

After nearly 10 years of solving real-world application problems, the practical capabilities of both hexapole and octapole collision cells using KED are fairly well understood. It is clear that the majority of applications are being driven by the demand for routine multielement analysis of well-characterized matrices, where a rapid sample turnaround is required. This technique has also been promoted by the vendors as a fast, semiquantitative tool for unknown samples. The fact that it requires very little method development, just one collision gas and one set of tuning conditions, makes it very attractive for these kinds of applications. ... 

H2 has been shown to be effective for the reduction of the intensities of polyatomics (ArO" ", ArH" " for Ca and Fe) in work with dry aerosols, as in laser ablation ICP-MS [620]. It has been shown to be generally useful, as demonstrated by Feld-mann et al. [621] with a hexapole system. Helium was also found to be useful for the dissociation of ArO+ and Ar, the latter interfering in the determination of Se and its species [622]. As shown for a hexapole system, the ion energies also are relevant for the effectiveness of the removal of interferents in He/H2 filled cells [623]. Apart from a hexapole, octapole collision cells have also been used, where H2 addition was found to be effective for Ar, ArO, and Ax reduction, and He for ArO+ reduction, but not for ArH or ArJ reduction [624]. In their work on laser ablation ICP-MS, Hattendorf and Gunther also mentioned that Ne was useful as a... 

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... 

Another important application of a linear quadrapole is operation in the RF-only mode, i.e., where the DC voltage is zero. In this mode, all ions with m/z between a low-mass and high-mass cut-off are transmitted. RF-only quadrapoles (or hexapole or octapole) are used as an ion guide between API sources and mass analysers (Ch. 5.4.5) and as collision cells in various MS-MS instruments. 

HCD Collision Cell C-Trap Octapole Split Lens... 

It should also be noted that the RF-only quadrupoles (as well as the related RF-only hexapoles and octapoles) can be operated as ion lenses, often referred to as RF-only ion guides or simply ion guides. RF-only quadrupoles (denoted as lower case q , nonitalicized, to distinguish them from the closely related quadrupole mass filters Q) also act as efficient collision cells for collision induced dissociation in triple quadrupole analyzers (QqQ, Section 6.4.3) and hybrid tandem quadrupole-time of flight instruments (QqTOF, Section 6.4.7). Discussion of these devices must be postponed imtil the principles of all hnear quadrupoles have been considered (Section 6.4.2). 

Fig. 2.4 Triple quadrupole MS, QQQ, where Q1 and Q3 indicate scanning quadrupoles and Q2 indicates the collision cell consisting of either an RF-only quadrupole, hexapole, or octapole. In some hybrid instruments Q3 is replaced by either a TOF or a linear quadrupole ion trap. (See text for more details and references for further reading)...

More recently, Yamanaka and Fryer showed the use of collision/reaction cell technology ICP-MS to determine elements at the trace and macro levels in various plant materials. They demonstrated that by using both helium and hydrogen gases in an octapole-based collision cell, they could determine ppm levels of Cr, Cu, and Fe... 

However, the use of highly reactive gases such as ammonia and methane can lead to more side reactions and potentially more interferences unless the by-prodncts from these side reactions are rejected. The way around this problem is to ntilize a lower-order multipole, such as a quadrupole, inside the reaction/collision cell and nse it as a mass discrimination device. The advantages of using a quadrupole are that the stability boundaries are much better defined than a hexapole or an octapole, so it is relatively straightforward to operate the quadrupole inside the reaction cell as a mass or bandpass filter. Therefore, by careful optimization of the quadrupole electrical fields, unwanted reactions between the gas and the sample matrix or solvent, which could potentially lead to new interferences, are prevented. This means that every time an analyte and interfering ions enter the reaction cell, the bandpass of the... 

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. 

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