BACE Basic Laboratory Equipment Use 2 — Questions and Answers
Question 1: What is the correct procedure for calibrating a micropipette before use?
- Pipette a known volume of water and weigh it on an analytical balance to verify accuracy (Correct answer)
- Run the pipette at full speed for 5 minutes to warm up the mechanism
- Check that the plunger moves smoothly with no resistance
- Rinse the tip three times with the solution before dispensing
Correct answer: Pipette a known volume of water and weigh it on an analytical balance to verify accuracy
Gravimetric calibration — pipetting water and weighing it — uses the known density of water (1.0 g/mL) to verify that the delivered volume matches the set volume.
Micropipette calibration uses gravimetric analysis: set the pipette to a known volume, aspirate distilled water, dispense onto a tared analytical balance, and record the weight. Since water at 20°C has a density of approximately 0.9982 g/mL, the mass in grams closely equals the volume in mL. SOP typically requires calibration at three volumes per pipette range.
Question 2: A centrifuge rotor becomes unbalanced during a spin. What is the most immediate risk?
- Sample contamination from aerosols
- Mechanical failure, rotor damage, or injury from rotor failure (Correct answer)
- Overheating of the centrifuge motor
- Loss of temperature control in the samples
Correct answer: Mechanical failure, rotor damage, or injury from rotor failure
An unbalanced rotor generates enormous centrifugal forces that can cause catastrophic rotor failure, potentially destroying the centrifuge and injuring nearby personnel.
At 10,000-30,000 rpm, even small imbalances create massive vibration and stress on the rotor. Catastrophic rotor failure can eject fragments through the centrifuge lid at lethal velocity. Always balance tubes opposite each other within 0.1 g, use rotor-matched balancing tubes, and never run a centrifuge with an odd number of tubes unless a balance tube is added.
Question 3: Which type of balance should be used when accurately weighing 50 mg of a reagent for a critical buffer preparation?
- A top-loading balance with 0.1 g readability
- An analytical balance with 0.0001 g (0.1 mg) readability (Correct answer)
- A triple beam balance
- A platform scale with 1 g readability
Correct answer: An analytical balance with 0.0001 g (0.1 mg) readability
An analytical balance with 0.1 mg readability provides the precision needed for accurately measuring small quantities like 50 mg.
For reagent quantities below 1 g, analytical balances (0.1 mg readability) are required to achieve acceptable accuracy. For 50 mg, a 0.1 g balance has a potential error of up to 200% of the target. Analytical balances must be leveled, warmed up, calibrated with certified weights, and used with draft shields to prevent air current errors.
Question 4: What is the proper disposal procedure for used sharps (needles, scalpel blades) in a biotechnology laboratory?
- Place in regular trash after recapping the needle
- Dispose in a rigid, puncture-resistant sharps container (Correct answer)
- Wrap in several layers of paper and place in biohazard bag
- Return to the central supply department for reprocessing
Correct answer: Dispose in a rigid, puncture-resistant sharps container
Sharps must be disposed of in rigid, puncture-resistant sharps containers to prevent needlestick injuries and comply with OSHA bloodborne pathogen standards.
OSHA's Bloodborne Pathogen Standard mandates that contaminated sharps be placed immediately in closable, puncture-resistant, leak-proof sharps containers. Recapping needles is prohibited. Sharps containers must be replaced when 3/4 full, then treated as regulated medical waste. Never bend, break, or otherwise manipulate contaminated sharps by hand.
Question 5: When using a vortex mixer, what is the appropriate technique for mixing a small volume (100 µL) in a microcentrifuge tube?
- Set vortex to maximum speed and hold tube sideways in contact with the spinning platform
- Press the tube bottom against the vortex pad at a slight angle at medium-low speed (Correct answer)
- Place tube in a tube rack and turn the vortex to continuous mode
- Invert the tube several times by hand instead since vortexing is not appropriate for small volumes
Correct answer: Press the tube bottom against the vortex pad at a slight angle at medium-low speed
For small volumes, pressing the tube bottom onto the vortex pad at an angle at medium speed creates a whirlpool inside the tube without risk of tube breakage or splashing.
For microcentrifuge tubes with small volumes, use medium speed with gentle downward pressure at a slight angle to create vortex flow inside the tube. High speed risks tube cap popping open, contents spraying, or tube fracture. For very sensitive samples (enzymes, DNA), use brief pulses rather than continuous vortexing. Always spin down briefly after vortexing to collect contents at the tube bottom.
Question 6: What does the abbreviation 'GLP' stand for in the context of laboratory equipment use and data recording?
- General Laboratory Procedure
- Good Laboratory Practice (Correct answer)
- Graduated Liquid Protocol
- Government Laboratory Policy
Correct answer: Good Laboratory Practice
GLP stands for Good Laboratory Practice — a set of quality principles governing how non-clinical laboratory studies are planned, performed, monitored, recorded, and reported.
Good Laboratory Practice (GLP) is a formal system (OECD Principles, FDA 21 CFR Part 58) that ensures the quality and integrity of non-clinical laboratory safety studies. Under GLP, all equipment must be calibrated, maintained, and documented; raw data must be recorded contemporaneously; procedures must follow written SOPs; and data must be archived.
BACE Basic Laboratory Equipment Use 2
What is the correct procedure for calibrating a micropipette before use?