Backflushing the needle seat of the Agilent Vialsampler

Created by Max Schütte over 2 years ago | Last modified by Carlos Vargas 9 months ago

This Information Applies To: Agilent Infinity II Vialsamplers G7129A/B/C.

Issue:

High pressure in the Vialsampler is oftentimes due to a blockage in the needle seat assembly. The needle can pick up sample particulates or plugs from the vial caps when the Vialsampler is drawing the sample. When the valve switches back to mainpass, they are forced into the seat capillary and cause obstruction and high pressure.

Steps to follow:

To backflush the needle seat according to the following procedure, you need a pump with a manual purge valve. If you have a pump with an automatic purge valve, read the note below the article.

Turn on the pump flow rate to 3 mL/min through your CDS Software, Lab Advisor or through the Instant Pilot and open the purge valve. Set the injector to bypass mode (in Lab Advisor: under Instrument Control; in your CDS Software, right-clicking your instrument and selecting Set to bypass).
Using Lab Advisor (see How to Install Lab Advisor), go to the Service and Diagnostics section, click the Vialsampler, and click Injector Steps. Next, click Needle up for the Vialsampler to lift the needle (see Figure 1) up fully.

Figure 1. Lab Advisor Injector Steps - Needle Up
Remove the safety cover (see Figure 2), then lift and flip the wash port to the left into the service position (Figure 3).

Figure 2. Removal of the safety cover

Figure 3. Flipping the wash port into the service position

Warning: Avoid removing capillaries under high pressure, make sure to wear appropriate protective gear.
Disconnect the capillary in port 6 of the injection valve. Disconnect the seat capillary from port 5 in the injection valve and connect the needle seat capillary to port 6. The flow will go directly from the pump through the needle seat (make sure to work in bypass mode, use Figure 4 as a reference).

Figure 4. Injection valve ports, standard configuration. Connections:
1 - From pump
2 - To metering device
3 - Plug
4 - To waste
5 - From needle seat
6 - To analytical column

Keep the vialsampler in the Needle Up position.
Close the purge valve and take note of the pressure. To release the pressure, open the purge valve and then close it again for another pressure pulse. Repeat to flush out the blockage. Make sure to have paper towels ready to collect the mobile phase flow at the needle seat.
Once there is flow backwards through the seat capillary, open the purge valve.
Reinstall the needle seat capillary into port 5 and return the capillary that goes to the column to its original position on the injection valve (port 6). Flip back the wash port and reinstall the safety cover.
In Lab Advisor under Injector Steps, click Needle Into Seat and then Reset to finish the procedure (Figure 5).

Figure 5. Lab Advisor Injector Steps - Needle Into Seat + Reset
End the connection from Lab Advisor, and close Lab Advisor.
Open your CDS software and run the HPLC with normal flow rates. Make sure to work in mainpass mode.

If the pressure is still high after the backflush, you will need a new seat. If you need more help, contact your local Agilent Technologies Support representative.

Note: If you have a pump with an automatic purge valve, you may disconnect and take out the needle seat completely. Connecting its capillary directly to the waste outlet of the switching valve of the pump and setting the pump to purge, you may thus flush backwards through the seat.