User`s guide

Chapter 7 PSD Analysis
7-18 PerSeptive Biosystems
7
Differences from
regular analysis
When operating in PSD mode, note the following differences
from analysis in non-PSD mode:
• Higher laser intensity—In non-PSD mode, you use a
laser intensity that yields acceptable performance without
fragmentation. You need a higher laser intensity to
generate PSD fragments.
• Higher Grid Voltage% and shorter Delay Time—A
higher Grid Voltage% and shorter Delay Time generates
a sharper ion packet at the position of the Precursor Ion
Selector, and improves fragment ion resolution.
• Sample consumed more quickly—Higher laser
intensities ionize and consume sample more quickly than
lower laser intensities used in non-PSD mode.
• Different calibration used—PSD analysis uses a
different calibration function to correctly determine the
masses of PSD fragment ions. For information, see
Section 7.1.4, Mass Calculation for Fragment Ions.
• Acquisition of multiple spectra at different Mirror
Ratio settings to create a single composite
spectrum—To correctly focus fragments with different
mass ranges, collect PSD segment spectra with different
Mirror Ratio settings. The Data Explorer software
“stitches” the segments together to create a composite
spectrum. For information, see the
Data Explorer
Software User’s Guide
, Chapter 8, Viewing
Voyager PSD Data.