Removing air bubbles from lines

Air bubbles do form in tubing over time so it is important to remove them before doing liquid handling. The first step to do this is to move the pipette tips to the waste station which is achieved by pressing the “Go to waste” button in Interactive Mode.

Figure 1: Wash station controller that shows that wash and waste pumps turning on/off also there are buttons for moving the pipette tips to the wash, waste and dry pad positions. The dry pad positions are recorded so tips go to different places

After the pipettes are in place then you manually push fluid in through them to get the air out of the lines. There is a manual perfusion setup for removing air bubbles from lines. There is a stopcock valve positioned between the PCV and the PCV peristaltic pump.

All of this is done in Interactive Mode

Figure 2: When the 4-way valve is in the close position, you fill up a syringe with fluid using the valve connected to the tubing coming out of the PCV. There you can draw fluid from the PCV then position the valve to other direction and push the fluid out towards the direction of the pipette tips. You keep doing this until all the bubbles are pushed out.

Figure 3: Valves are positioned to the close position. This moves the fluid (and air bubbles) from the line coming out of the PCV through the lines connected to the pipette tips

Here are steps for doing this:

1. Connect a syringe to the manual stopcock valve positioned in the line coming out of the pressure compensation vessel (PCV) and aspirate fluid out of the PCV into the syringe (remove any air out of the syringe).
2. Put the 4-way valves into the “close” position.
3. Position the manual stopcock valve so that you close the tube come from the PCV and open the tube going towards the pipettes and push the fluid through until you see no more air coming out of the pipettes. (You will need to reload the syringe a few times depending on how big it is before you start to see all the air coming out). Likely the waste station will fill up do you need to turn on the waste peristaltic pump to draw the excess liquid into the waste.
4. Each syringe from the 8-channel syringe pump probably needs to have the luer lock tubing removed (1 at a time and connected to the syringe that is used for drawing fluid out of the PCV). This is to remove some air trapped in the pipette loading module. This will drain out the fluid then next when filled the bubbles are cleared.

Figure 4: Position the 4-way valves to output so that you can clear the bubbles out of the line that connects the multichannel syringe pump to pipettes.

This will clear the lines from the PCV to the pipettes but you still need to get the air bubbles out between the syringes and valves. To do this, now you need to:

1. Position the corresponding valve into the output position.
2. Draw some fluid into the syringe connected to the manual valve that draws fluid from the PCV.
3. Disconnect the tubing from one of the multichannel syringes and put that end in a bottle and disconnect the corresponding tubing to pipette and attach the fluid filled syringe.
4. Perfuse until all air bubbles are out and attach to multichannel syringe pump first, put valve into bypass position, then attach the other end of tubing to the corresponding pipette.

Figure 5: To remove the bubbles coming out of the multichannel syringe pump to the pipettes. You need to fill up a syringe with fluid, disconnect the tubing from the pipettes, disconnect the corresponding tubing that is connected to one of the syringes in the multichannel syringe pump, connect that end to a fluid reservoir (like a bottle) then push bubbles out.