A complete pipetting cycle involves steps such as pipette tip installation, volume setting, liquid aspiration and dispensing, and tip removal. Each step requires adherence to specific operating procedures.

1. Tip Installation

   For a single-channel pipette, insert the pipette vertically into the tip, lightly press, and rotate slightly left and right to secure it.

   For a multi-channel pipette, align the first channel with the first tip, insert it at an angle, and slightly shake it front and back to secure it.

   Avoid repeatedly tapping the pipette to ensure tip airtightness. Prolonged use of this assembly method can cause components to loosen or even lead to the knob for adjusting the scale getting stuck.

2. Volume Setting

   When adjusting from a large volume to a small volume, rotate counterclockwise to the desired scale. When adjusting from a small volume to a large one, turn clockwise past the set volume before returning to the desired setting for optimal accuracy.

   Do not rotate the adjustment knob beyond the volume range to avoid damaging the pipette's internal mechanical components.

3. Aspiration and Dispensing

   Press the pipette button to the first stop for liquid aspiration. Ensure a steady and slow release, as overly rapid aspiration can cause liquid to be drawn into the pipette.

   During dispensing, press the button against the container wall, initially pressing to the first stop, pausing briefly, and then pressing to the second stop to expel any remaining liquid.

   • Aspirate liquids vertically.
   • For 5ml and 10ml pipettes, immerse the tip 5mm below the liquid surface, aspirate slowly, pause for 3 seconds below the liquid surface after reaching the desired volume, and then withdraw.
   • Slowly release the controller during aspiration to prevent rapid liquid entry into the pipette.

   When aspirating volatile liquids, rinse the tip 4-6 times to saturate the barrel chamber with vapor, preventing leakage.

4. Proper Placement of Pipette

   After use, hang the pipette vertically on a pipette stand, taking care not to let it fall. When the pipette tip contains liquid, never place it horizontally or upside down to avoid liquid backflow, which could corrode the piston spring.

   If not in use, set the pipette's volume to the maximum scale value to keep the spring in a relaxed state, protecting it.

5. Common Mistakes

   1. Repeatedly tapping the tip during assembly, making it difficult to remove and potentially damaging the pipette.
   2. Tilting the pipette during aspiration, leading to inaccurate pipetting and possible liquid entering the pipette handle.
   3. Rapidly releasing the thumb during liquid aspiration, inducing turbulent flow and liquid directly entering the pipette.
   4. Directly pressing to the second stop during liquid aspiration (follow the standard procedure outlined above).
   5. Using a large-range pipette for small sample volumes (choose a pipette with an appropriate volume range).
   6. Placing a pipette with residual liquid in a horizontal position (hang the pipette on a pipette stand).