7
Troubleshooting
Irreproducible Retention Times
90
Accela Pump Hardware Manual
Thermo Scientific
Occasionally, a valve might freeze closed if it hasn’t been used for an extended period of time.
To open the valve, insert the valve tool (stainless steel wire) into the valve inlet and push the
floating piston away from the valve seat, as described in
“Servicing the Proportioning Valves”
on
page 77
.
Blocked Check Valve
Insufficient flow rate can also be a result of a blockage in one or both check valves. In this case,
clean the LDA by flushing it the appropriate solvents, as described in
“Cleaning the LDA
Components without Disassembling the LDA”
on
page 56
.
Irreproducible Retention Times
There are many reasons for retention time problems. Some of the more common causes are as
follows:
• An old or damaged column
• Inconsistent stationary phase (Was a new column installed?)
• A validated method that lacks robustness
• Changes in mobile phase composition
• Temperature fluctuations
• Pump problems
If you suspect the pump to be responsible, replace the column with a flow restrictor and run a
step gradient, as described in
“Testing the Pump Proportioning”
on
page 46
.
Contamination of the proportioning valves is likely to cause inaccuracy in the steps. Clean the
LDA by flushing it with the appropriate solvents, as described in
“Cleaning the LDA
Components without Disassembling the LDA”
on
page 56
.
