<Diagnostic:
Flow rate problems>
The column dead time (t0) provides a first-order
diagnostic for flow rate changes because t0 is determined entirely
by the flow rate and the internal volume of the column (Vm). Since it is unlikely
that column volume will change (unless the column itself has been
changed or a guard column/cartridge added), any change in t0 indicates a flow rate
change.
For isocratic
separations, further confirmation of a flow rate change is provided
if the retention times of all peaks (including t0) change by the same
percentage.
For gradient
separations, flow rate changes are often related to proportioning
problems which can be identified by the Gradient step-test.
Ref: LC-GC, 15(2) 112 (1997)
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