Multiply charged ions resolving isotopic patterns

With external ion sources it became feasible to interface any ionization method to the QIT mass analyzer. [171] However, commercial QITs are chiefly offered for two fields of applications i) GC-MS systems with El and Cl, because they are either inexpensive or capable of MS/MS to improve selectivity of the analysis (Chap. 12) and ii) instruments equipped with atmospheric pressure ionization (API) methods (Chap. 11) offering higher mass range, and some 5-fold unit resolution to resolve isotopic patterns of multiply charged ions (Fig. 4.47). [149,162,172,173]... 

The most effective technique to deal with complex spectra due to multiply charged ions is to achieve the full separation between signals corresponding to different charge states and to resolve their isotopic patterns. Beyond a molecular weight of about 2000 u this requires high-resolving mass analyzers. 

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