Repeller voltage

Increasing the sample size or decreasing the repeller voltage may increase the relative abundance of the M + 1 ion. If the sample pressure is very high, dimers also may be produced. 

Figure 2. Rate constant k for production of HEH+ from H2-He mixtures plotted as a function of repeller voltage...

Figure 3. Plot of NeH +/Ne + as a function of Ne + relative intensity at various repeller voltages...

Figure 9. Dependence of the ratio of CH + ions to total ions in the methane mass spectrum on the pressure of methane in the mass spectrometer ion source for different values of source repeller voltage...

Fragmentation occurs because the repeller voltage increases the kinetic energy of the ions, not only making collision-induced dissociation (CID) more likely but also allowing endothermic ion-molecule and solvent-switching reactions to occur. 

The molecular ion peaks of aliphatic nitriles (except for acetonitrile and propionitrile) are weak or absent, but the M + 1 peak can usually be located by its behavior on increasing inlet pressure or decreasing repeller voltage (Section 2.5). A weak but diagnostically useful M - 1 peak is formed by loss of an a hydrogen to form the stable ion RCH—C=N,+ <—> RCH=C=N+. 

Figure 3. Repelling voltage curves for an electrosprayed 0.01 wt % solution of 51,000 amu polystyrene in two parts acetone to one part benzene by volume (4)...

Similar results obtained with lysozyme (a protein of molecular weight 14,600) in a 75% ethanol-25 % water solution are shown in Figure 5. The vertical bars indicate the repelling voltage required to stop singly charged monomers, dimers, and trimers of lysozyme traveling at the calculated beam velocity of 754 meters/sec. Sharp dropoffs are seen to... 

Figure 5. Repelling voltage curves for electrosprayed solution of lysozyme (molecular weight 14,600) in three parts ethanol to one part water by volume. Curve 4 is the repelling voltage curve for electrosprayed solvent only, drawn to the same scale (7).

These voltages repel the ions inside the linear trap, and this repulsion is higher when the ions are closer to the ends. Ions are thus repelled towards the centre of the quadrupole if the same repelling voltages are applied at each end. Thus, the ion cloud will be squeezed at the centre of the quadrupole if the applied voltages are symmetrically applied, but can be located at closer to one end if the repelling voltage at that end is smaller. 

N-C Hj-morphine as internal standard. The internal standard was added to 10 ml urine, the urine buffered to pH 8.5 and extracted with chloroform isopropanol (4 1). The extraction residue was trimethylsilylated by adding 25 ul of N,0-bis(trimethylsilylJacetamide and heating at 60°C for about 1 h. About 2 ul was analyzed on a 3 % 0V-17 column at 230°C coupled direct to a Finnegan 1015 quadrupole mass spectrometer equipped with a chemical ionization source, which was operated at an ionizing energy of 100 eV, an ion repeller voltage of 0 V and a filament emission of 300 uA. The mass spectrometer was interfaced with a System Indus-... 

The rate coefficients, k, for reactions (100) and (101) measured as a function of repeller voltage by Friedman et al. [161, 162] are shown in Fig. 18. As can be seen, both curves have a characteristic energy... 

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