Tandem MS with Quadrupole Analyzers

Triple quadrupole mass spectrometers, QqQ, have almost become a standard analytical tool for LC-MS/MS applications, in particular when accurate quantitation is desired (Chap. 12). Ever since their introduction [124-126] they have continuously been improved in terms of mass range, resolution, and sensitivity (Fig. 4.38). [127-129] 

Note At first sight, there is no difference whether Qi or Q3 is switched to RF-only for MS mode. However, for El it seems better to operate Q3 in RF-only mode. Otherwise, the ion source would effectively extend up to the entrance of Q3 making fragment ions more abundant due to elongated time for dissociations. Soft ionization methods do not show such differences. 

2 Scan Modes for Tandem MS with Triple Quadrupole Instruments 

In triple quadrupole instruments Qi and Q3 are operated independently as MSI and MS2, respectively, making MS/MS a straightforward matter. The experimental setups for product ion, precursor ion, and neutral loss scanning are summarized in Table 4.3. 

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