Octopole configuration

The octopole configuration is similar to the quadrupole and hexapole in affording a good ion guidance system in its all-RF mode. The poles are connected in two pairs of four nonadjacent rods, and each pair is connected to an RF voltage supply, 180° out of phase with each other. The octopole is even more efficient than the hexapole as an ion guide. 

Fig. 3. Schematic diagram of the guided ion beam tandem mass spectrometer, double octopole configuration. Pumping speeds are shown. Ion sources available are listed and the microwave discharge source is shown. Adapted from [9]...

Fig. 8. Schematic drawing tandem mass spectrometer in Z configuration for coaxial infrared laser excitation. Aperture lenses have been omitted for clarity. Comptonents (a) Nozzle, (b) skimmer, (c) electron gun, (d) and (i) quadrupole mass filter, (e) and (g) quadrupole deflector, (f) octopole ion guide, (h) CO2 laser, (j) ion conversion dynode, and (k) secondary eiectron multiplier. ...

DCIM-MS has been coupled to liquid chromatography (LC) for analyzing complex peptide samples [36], Peptides eluting from the LC column were analyzed on an IMS-Q-TOF mass spectrometer. The ions generated from the source were accumulated in an ion trap and injected periodically into the drift tube. After mass analysis by the quadrupole, ions were subjected to collision-induced dissociation (CID) within an octopole collision cell and the product ions were analyzed by a TOF analyzer. Using this instrumental configuration, the urinary proteome [37], the Drosophila melano-gaster head proteome [38], and the human plasma proteome [39] have been analyzed. While many additional measurements, compared to standard mass spectrometry-based proteomics experiments, were obtained (for example, collision cross-sections), these were not used to improve upon protein identification results. 

The orbitrap mass analyzer is an ion trap device that provides high accuracy and resolution mass measurement without the need of a magnetic field, (Hu et al. 2005 Zubarev and Makarov 2013) and thus it is more accessible in terms of lab requirements, and initial and operating costs. Some consider it to be the gold standard mass spectrometer for proteomic-based measurements (Mitchell 2010). The orbitrap mass analyzer is usually found in a hybrid configuration interfaced with a linear ion trap mass analyzer and transfer octopoles and C-trap (Fig. 2.5) (Senko et al. 2013). 

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