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. Author manuscript; available in PMC: 2017 Sep 1.
Published in final edited form as: Proteomics. 2016 Aug 24;16(18):2435–2443. doi: 10.1002/pmic.201600113

Figure 1. An example of ion optics and the concept of a DC offset.

Figure 1

A DC voltage gradient is applied to sequential multipoles and lenses that compose the optics of the mass spectrometer, which all serve to focus and propel ions from the ion source through to the mass analyzer (from left to right). This gradient is increasingly negative, so as to propel positively charged ions (symbolized here by the red sphere with a positive sign) through the optics and towards the mass analyzer, with a final decrease in negative voltage to slow the ions down just enough so they can be captured in the trap. MP = multipole.