Pump Operation
This section describes control of BASi pumps attached to the epsilon platform. If you have another brand of pump it may be used with epsilon hardware, but you will not be able to control it with this software.
Two screens control all pump operations: the Purge Options screen allows mobile phase or cleaning solutions to be automatically pumped through the system at a high flow rate; the Pump Schedule controls isocratic and gradient flows during normal operation. Refer to the pump manuals for specifics on pump operation and maintenance.
PURGE OPTIONS
A purge can be used to bring fresh mobile phase rapidly through the system. The pump will attempt to maintain a user-chosen pressure by varying the flowrate. If the chosen pressure limit is not reached (e.g., if the purge valve is open) the pump will increase flow to its maximum, 5 mL/min, and hold that flow rate for a user-chosen duration.
The PURGE OPTION screen can be accessed through the Method Menu or by clicking the <
To program a purge, enter the PURGE DURATION, MAX. PRESSURE, and SOLVENT % (enter percentages for bottles A and B; bottle C will be calculated as the remainder). INITIAL FLOW is the starting flow rate, and should generally be about 1/2 of the desired flow rate. For a purge through the purge valve it should be 2.5 mL/min; for a purge through a column it should be 1/2 of the usual flow rate of the column.
Start the purge by clicking on the PURGE button. During a purge, the RUN STATUS box displays elapsed time. The pump will stop when elapsed time reaches zero.
PUMP SCHEDULE
The PUMP SCHEDULE contains all the operating information for the pump, as well as pushbuttons for immediate-mode control. Note that your PUMP SCHEDULE may vary from the ones shown below, depending on the features of your pump.
The PUMP SCHEDULE is accessed through the Method Menu or by clicking the <
Two typical pump control screens are shown below. Gradient pumps will have the first type. Isocratic pumps can have either type, depending on the model.
MAXIMUM and MINIMUMPRESSURE are the safety limits for the pump. For most chromatography, we recommend a pressure minimum of 200 PSI and a maximum of 4000 PSI. If the pressure falls below the set minimum, or rises above the set maximum, the pump will stop and report the appropriate error.
FLOW RATE can be set from 0 to 0.5 mL/min in 0.01 mL increments, and from 0.5 to 5 mL/min in 0.1 mL increments.
SYNCHRONIZED START checkbox should be checked for gradient runs, and blank for isocratic runs. Synchronization ensures precise gradients by delaying the start of a run until a pre-set piston position has been reached.
GRADIENT SCHEDULE LISTBOX contains the pump instructions for a timed run. There must be at least two lines here: a 0.0 minute start line and an end line. Up to 10 lines may be entered in the gradient schedule; they will be automatically sorted by time. The first event must have time 0.0, and subsequent events must be at least 0.1 minutes apart. For each line of the listbox, enter the time and the percentages for bottles A and B (C is automatically calculated as the remainder). When bottle percentages differ between lines, the software will calculate the appropriate linear gradient between the two lines.
The chromatographic run will end at the longest time in any of the following modules: Pump, EC Detector, External Detector, PAD, or Switch Schedule.href="/manuals/LC_epsilonhref="index#operation">here for a review of the other Method screens.) If the pump's maximum time is shorter than another time in the Method, the pump will revert to its time 0.0 conditions after completing this schedule.
PUMP DURATION is the equivalent of the last line of the gradient schedule, for pumps that use the second type of control screen. This is a non-critical entry, generally set to the length of the chromatographic run, or shorter. When the specified time is reached, the pump's clock stops and the pump continues to run at the entered conditions.
EXEC and STOP pushbuttons are provided for manual control of the pump. EXEC puts the 0.0 time line into effect.
Note that a pump program cannot be initiated from the Pump Schedule; you must start a programmed run to begin the program.
MONITORING PUMP PRESSURE
Certain troubleshooting procedures require a printout of pump pressure over time. This can be easily achieved with a BASi pump by feeding the pump's pressure output into the epsilon system as an external detector.
Proceed as follows:
- Connect the 'Pressure' and 'Gnd' terminals on the back of the pump to either 'EXT-1' or 'EXT-2' and 'Gnd' on the back of the epsilon detector.
- Set the input voltage Range to 10 Volts.
- Modify the graph scaling so Full Scale Y is 10,000 and Label Y Units is PSI. Be careful to change the scaling only for the detector channel assigned to the pump.
- Start a run and collect data for 10 minutes.
