Technical data

Agilent 1290 Infinity LC System Manual and Quick Reference 125
Appendix
6
Setting Up a Method using Edit Entire Method
•Stop Time defines the overall time for the separation or run and is sometimes
referred to as the ‘Run Time’ by some users. This is the time, counted in
minutes since the injection was made, that the run ends which means that
data acquisition will stop, the flow, composition and other system settings
will revert to the initial values for the method and the system will become
available to make the next injection. It should always be at least as long as
the last entry in the timetable or else the run will stop and revert to starting
conditions before the timetable events are complete. Stop Time can be set to
No Limit in which case the user must manually stop the run. While all the
system modules have Stop Time parameters, the Stop Time in the pump is
considered to be the master and the other modules will usually be set to
follow this value.
•Post Time defines a countdown period after the end of a run during which
the next injection is prevented. It allows time for the system to
re-equilibrate after a gradient run. For an isocratic method it can be set to
Off. For a gradient method the value can be determined experimentally by
observing the baseline behavior but typically will need time for the delay
volume of the system plus at least three to five column volumes to be
flushed through the system.
• Pressure Limits control the behavior of the pump regarding pressure. The
maximum pressure of the 1290 Infinity pump is 1200 bar but some columns
can only withstand lower pressure and by setting this value here the
column will be protected. The pump will generate an error condition if this
pressure is reached and any run in progress will be stopped and the pump
switched to standby mode with no flow. Information about the maximum
pressure for a particular column is supplied with the column. Agilent
ZORBAX RRHD columns are suitable for operation at 1200 bar. The Low
Pressure limit is ‘Off’ when the value is zero but at any other value the
pump will generate an error if the pressure goes below this value during
operation. This is used as an alternative safeguard when the column is not
inside a module with a leak sensor or in case the system is pumped dry. A
value of 10 to 20 bar is typical.