
Chapter 6 Acquiring Mass Spectra
6-24 PerSeptive Biosystems
6
Prompt fragments
Prompt fragments appear in the spectrum at masses that
correspond to the theoretical masses of the fragments,
because they are formed in the source.
PSD fragments
PSD fragments appear in the spectrum at masses slightly
higher than the theoretical masses of the fragments because
they are formed after the source, but travel at the same speed
as the precursor until they reach the reflector. Because they
have lower kinetic energy than the precursor, they separate in
mass from the precursor in the reflector.
6.3.3 Parameters Affecting
Resolution and Signal-to-Noise Ratio
Parameters
affecting
resolution
These parameters have a primary impact on resolution:
• Delay Time
• Guide Wire Voltage%
• Grid Voltage%
• Digitizer Bin size and Input Bandwidth
For more information on optimizing resolution, Section 5.4.3,
Optimizing Resolution.
Parameters
affecting
signal-to-noise
ratio
These parameters have a primary impact on signal-to-noise
ratio:
• Accelerating Voltage
• Guide Wire Voltage%
• Shots/Spectrum
• Digitizer Input Bandwidth
• Low Mass Gate
For more information on optimizing signal-to-noise, see
Section 5.4.4, Optimizing Signal-to-Noise Ratio.
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