Positive displacement micropipettors are described as using which configuration?

• A. Reusable tip and disposable piston
• B. Disposable tip and reusable piston
• C. Disposable tip and disposable piston
• D. Reusable tip and reusable piston

Answer: (A)

In positive displacement micropipettors, the liquid sample is in direct contact with the piston as it moves, so keeping the contact surfaces clean is essential for accuracy and preventing carryover. To achieve that, both the tip and the piston are designed to be disposable with each use. Replacing both components ensures no residues from previous samples affect the next transfer and allows reliable handling of challenging liquids.

If the tip were reusable, remnants could alter the volume or contaminate later samples. If the piston were reusable, residues or solvents could change displacement or introduce cross-contamination. Disposable tip and disposable piston mitigate these issues and maintain precision across a wide range of liquids.