Troubleshooting Amplifier Reset

Issue Description 

The volume of the pump is approximately 600 μL, so once this volume has been pumped then a reset is expected. The Alerts log contains the time when the reset occurred, so the volume pumped can be easily calculated. For example, if the reset message appears every 3 hours and the flow rate is 3 μL/min, the pumped volume is:

3 hours * 60 minutes / hour = 180 minutes * 3 uL/min = 540 μL

This is close to the expected pump volume, as the pump does not completely empty before refilling. If however, the flow rate is only 1 μL/min, then the pumped volume is only 180 μL and this is too little! Natural resets often occur over the weekend when the high-flow pump is in idle flow.

Note that the pumps refill at the beginning of each sample run so there should never be a reset on a nano-flow channel, as the pump volume is too great for any reasonable natural reset to occur. At 300 nL/min, the pump can flow for 2000 hours without refilling!

There are three main causes of an unexpected Amplifier Reset: air in the pump, a faulty check valve or an internal leak. This document will describe only the “air in the pump” scenario, as the other causes of an Amplifier Reset require a service call.

To remove air in the pump: The method for removing air in the pump depends on the model LC. If the model is a low-pressure system, then follow Method A. If the model is high-pressure system, then follow Method B.

The difference between the two model types can most easily be determined by the mobile phase containers. If the mobile phases are stored in large bottles (usually 250 mL-1L), then the system is most likely a high-pressure system. Common names for high-pressure systems are “Ultra” and “ekspert”.

If the mobile phases are stored in vertical burettes with a stopcock on the bottom of the burette, then the system is most likely a low-pressure system. Common names for low-pressure systems are “nanoLC”, “Classic” and “Tempo”.

Method A (for low-pressure systems)

1. Locate the “pump priming tool” that was supplied with the system. This is a long piece of PEEK tubing with a union attached. See Figure 1

Figure 1 – Mobile phase priming tool

2. Identify the burette on the channel where the Amplifier Reset occurs
3. Insert the pump priming tool in to the burette
4. Open the Eksigent software
5. Click System > Mobile Phases > More. See Figure 2
6. Using the channel selector at upper right, select the channel where the Amplifier Reset occurs

In the Purge Settings section, enter 20

Figure 2 – Mobile phase window with the channel selector circled, and the Purge Settings group indicated with an arrow

7. Place a check mark in the appropriate Side
8. Click Purge Now
9. While the pump is purging, gently depress the pump priming tool to compress the check valve
10. Hold the priming tool down for a few purge cycles
11. Remove the prime tool to allow the remaining purges to complete

Depressing the check valve during the purge cycle allows air to escape out the top of the pump.

Method B (for high-pressure systems)

1. Open the Eksigent software
2. Click System > Mobile Phases > More. See Figure 2
3. Using the channel selector at upper right, select the channel where the Amplifier Reset occurs
4. In the Purge Settings section, enter 20
5. Place a check mark in the appropriate Side
6. Click Purge Now

The system will purge the pump, removing any air bubbles that may cause an Amplifier Reset.

Resolution 

Method A and B were described as a resolution to fix and amplifier reset issue.