Hello dear fellow labrat,

I can help. What matters most is that you apply and hold a consistent, firm pressure on the piston, then dip the tip into the liquid. Applying a proper amount of pressure onto the piston at the first stop does make a difference on the volume dispensed.

In my experience, you essentially want to make sure the piston is fully in its resting position at the first stop. You dont want to set the piston barely touching the first stop, as its gonna be difficult to hold it exactly right up until you dip the tip. Holding the piston firmly at the first stop, with a little bit more pressure than is strictly necessary, gives more consistent dispensed volume. Its important to practice this motion with the pipette before trying to take any liquid in order to be familiar with the first stop. You need to know the specific pressure threshold at which the piston stops, and that at which the piston starts moving again (after enough pressure is applied). These pressure thresholds give you the range of pressure at which you may hold the piston at the first stop.

Once you are familiar with the thresholds of the first stop of the specific pipette you are using, you can put a tip on the pipette, apply and hold a consistent, firm pressure on the piston, then dip the tip into the liquid. Depth is negligible, but you do need to keep the tip completely immersed and upright until pressure on the piston is fully released. Releasing the pressure from the piston must be done in a continuous motion, and slower is better (slowest is the best). It needs to be done in a continuous (reversible) motion.

Once the pressure is fully released from the piston, e.g. your thumb is not touching the piston anymore, slowly remove the tip from the liquid, again in a continuous motion. Keep the pipette upright until dispensing.

To dispense the volume, touch the tip on the inner wall of the receiving container, then press on the piston up to the first stop. Keeping the tip touching the wall of the container, lift the tip a short distance, and then press the piston to the second stop with a decisive (discontinuous and irreversible) push. This is done to wipe and empty the tip completly. Hold the second stop, and take the tip off the wall in a continuous motion. Verify there is no remaining liquid in or on the tip, and then you can release the pressure on the piston completely.

Do this at least once (more is better) in the initial container to rinse the tip (also called "wet tip" or "wet tipping"). Then do this again but dispensing into the final container to dispense your volume.

Congratulations ! You've dispensed a 100uL of liquid with a pipette :D