In an air displacement micropipettor, the tip is typically used with which piston configuration?

• A. A disposable tip and a reusable piston
• B. A reusable tip and a disposable piston
• C. Both tip and piston disposable
• D. Both tip and piston reusable

Answer: (A)

In air displacement micropipettors, the part that actually contacts the liquid is the disposable tip, while the internal piston remains inside the instrument and is designed for repeated use. The tip is replaced with each sample to prevent cross-contamination and to accommodate different liquid viscosities and volumes. The piston, along with its seals, is a precision mechanism that should stay in good condition and be calibrated, so it’s reused rather than discarded.

Using a disposable tip with a reusable piston therefore best balances contamination control and instrument precision. Replacing the piston with every draw would be wasteful and unnecessary, while reusing tips or pistons that contact samples would increase contamination risk and wear.