Electric circuit, switchable

In modem ion trap mass spectrometry, weak higher-order multipole and/or dipole electric fields are always superimposed upon the quadrupole electric field. The weak superimposed higher-order multipole and/or dipole electric fields are found to enhance the mass spectral performance with respect to mass resolution, charge capacity, scan speed, and to chemical mass shift. In fact, all commercial ion trap mass spectrometers are non-linear ion traps [7-9]. In the Finnigan ion trap instrument, the positions of the two end-cap electrodes are stretched out from the theoretical positions to add the higher-order multipoles. In the Bruker ion trap, the profiles of the end-cap electrodes are crafted to create the superimposed higher-order multipoles. In the Varian 4000 ion trap, a dipole and higher-order multipoles are superimposed upon the quadrupole field by a switchable electric circuit [10],... 

The non-linear ion traps with stretched or modified electrode profiles have been discussed previously in detail. In 2004, Varian introduced the 4000 instrument with a new type of non-linear ion trap [9,10], in which a dipole and higher-order multipoles are superimposed upon the quadrnpole field by a switchable electric circuit, shown in Figure 15.2. 

Fig. 10 (A) Polarization curves of the biofuel cell with the pH-switchable 02-cathode obtained at different pH values generated in situ by the enzyme logic network (a) pH ca. 6, (b) pH ca. 4, (c) pH ca. 6. Inset The reversible changes of the open-circuit voltage produced by the cell at the variable pH. (B) Electrical power density generated by the biofuel cell on different load resistances at different pH values generated in situ by the enzyme logic network (a) pH ca. 6, (b) pH ca. 4, (c) pH ca. 6. Inset The reversible changes of the maximum power density produced by the biofuel cell at the variable pH, (C) The maximum power density produced by the biofuel cell as the function of different combinations of the input signals. (Adapted from ref. 76 with permission).

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