
Chapter 7 PSD Analysis
7-44 PerSeptive Biosystems
7
7.4.3 Observing the Effects of Grid Voltage%
Adjusting Grid Voltage% affects resolution.
In this section
In this section, you will:
• Understand the function of Grid Voltage% in focusing ions
• Observe the impact of Grid Voltage% on higher and lower
mass ions
NOTE: For typical applications, use the Grid Voltage% in
the standard .BIC file provided. This section is a
demonstration of the impact of Grid Voltage%.
Effect of Grid
Voltage% on
product ion
resolution
The resolution of an ion is affected by the amount of time it
spends in the reflector. After an ion is accelerated and is
velocity-focused (ions of the same mass align in time), it
defocuses as it moves down the flight tube. When an ion
spends an equal amount of time refocusing in the reflector,
resolution is optimized (Figure 7-14).
Figure 7-14 Ion Focusing
From source
Point of initial focus
Focused higher mass ion
Unfocused lower mass ion
Unfocused mid-mass ion
6 µsec
8 µsec
10 µsec
10 µsec
10 µsec
Flight tube
Reflector
10 µsec
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