Which technique helps avoid air bubbles and inaccurate volumes when drawing up reagent into a micropipette?

• A. Submerge the tip entirely below the surface.
• B. Immerse the tip just below the liquid surface and release the plunger quickly.
• C. Pre-wet the tip, set the correct volume, and immerse the tip below the surface.
• D. Pre-wet the tip, set the correct volume, immerse the tip just below the liquid surface, slowly release the plunger to avoid bubbles, and keep the pipette vertical.

Answer: (D)

Controlling the liquid column to avoid air bubbles and ensure an accurate volume is achieved by pre-wetting the tip, setting the correct volume, immersing the tip just below the surface, releasing the plunger slowly, and keeping the pipette vertical. Pre-wetting reduces the liquid’s tendency to bead on the plastic walls, giving a more consistent uptake. Setting the volume calibrates the plunger movement to the exact amount you need. Immersing just below the surface places the tip at the liquid–air interface so the liquid is drawn up cleanly without pulling in air from above. Releasing the plunger slowly prevents turbulence and bubble formation that would distort the volume. Keeping the pipette vertical avoids tilting that can change the effective opening and lead to inconsistent aspiration. Submerging the tip completely, releasing the plunger quickly, or neglecting to pre-wet or maintain a vertical orientation can all increase bubbles or introduce volume errors.