Purification Solution - Developer's Guide 81
Calibration Procedures
6
System Configuration and Delay Time Calibration
• Decrease the volume of tubing between the splitter and the detector(s) in
the make-up flow path.
After one or more solutions have been applied, repeat the fraction collector
delay calibration from the beginning.
Insufficient MSD-to-FC delay time
The minimum required delay time for MSD triggered collection either 5 sec or
6 × (MSD cycle time), whichever is the higher.
The reasons for insufficient MSD-to-FC delay time could be the following:
• The volume of delay tubing in front of the FC is too low.
• The MSD cycle time is too high.
• The make-up flow is too low for the applied preparative flow. There are
limitations to the combinations of preparative and make-up flows; see the
example in “System Configuration and Delay Time Calibration” on page 70.
• The volume of tubing between the splitter and detector(s) is too high.
The following suggestions are options for increasing the MSD-to-FC delay time,
but each of them has a certain disadvantage (given in parentheses) so
consider the most suitable way for the given situation:
• Optimize the MSD cycle time in the MSD method (a cycle time higher than
0.83 sec will increase the required delay volume limit):
• Use only one polarity if suitable (requires detailed knowledge of
collected compounds).
• Optimize peakwidth parameter: decrease it until MSD signal noise is still
acceptable.
• Decrease the MW range or increase the MW step size if suitable: typically,
it will not directly decrease the cycle time but it allows further
decreasing of the peakwidth parameter (a short MW range hides
potential contaminants).
• Consider using the MSD (ultra)fast mode, which enables a lower cycle
time.
• Performing MSD maintenance can also help in optimization of the noise
level.
• Use a longer delay coil in front of the FC (a higher coil volume causes more
dispersion, so use coils with a reduced dispersion rate such as knitted coils;
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