Radiofrequency -only mode

Comparison of triple-quadrapole and Q-TOF use in these type of studies was reported [22]. While similar sensitivity can be achieved, the selectivity of the Q-TOF is better due to its high resolving power, thereby minimizing isobaric interferences. Bateman et al. [23] reported a novel mode of operation of a (J-TOF instrument for precursor-ion analysis of phosphoproteins. The first-stage quadrapole is operated in radiofrequency-only mode, serving as a wide-band ion-transmission... 

Figure 16.23—Triple quadrupote MS MS instrument. In the triple qnadrupole arrangement, the middle quadrupole is used as a collision chamber. It is operated in the radiofrequency voltage mode only, where it will transmit all masses. A gas pressure introduced in the second quadrupole is responsible for collision activation. Triple quadrupole instruments can conduct all three types of MS — MS analysis described above.

In the conventional measuring mode the sample stays in the NMR tube, and thus in the radiofrequency Helmholtz coil all of the time. In the continuous-flow mode it resides within the NMR detection coil only for a distinct time of some few seconds (Figure 1.2). This residence time t is dependent upon the volume of the detection cell and the employed flow rate (Table 1.1). For example, a detection volume of 120 jjlI, together with a flow rate of 0.5ml/min, results in a residence time of 14.4 s, while with a detection volume of 8 jjlI the residence time is only 0.96 s. A shorter residence time t within the NMR measuring coil results in a reduction of the effective lifetime of... 

The triple quadrupole (QqQ) mass spectrometer is comprised of two linear mass hlters, Q1 and Q3, and a radiofrequency (RE) only quadrupole, q2, as shown in Eigure 4.5(a). The QqQ analyzer is capable of MS and MS-MS scans and is commonly coupled to an ESI source for proteomic analysis. Each of the three quadrupoles consists of four linear rods that have a high voltage RE potential (I to 3 MHz) and a DC potential applied to them. A triple quadrupole instrument performs three types of MS-MS scan modes precursor, product, and neutral loss. The RF/DC... 

In inductively coupled plasma mass spectrometry (ICP-MS), atomization and ionization are achieved in a radiofrequency argon plasma at atmospheric pressure. Since a seminal publication in 1980 [19], ICP-MS has become one of the most frequently employed methods of elemental MS (Chap. 7.3 in [3], Chap. 4 in [6], Chap. 5 in [7]). The wide acceptance of ICP-MS is due to its comparatively robust, yet versatile sampling mode. An ICP not only offers high ionization efficiency for elements of low IE, e.g., 98% for IE = 1 eV, it is still applicable to nonmetals such as P and even Cl (ionization efficiency is 1% for IE = 13 eV). 

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