CMLA Laboratory Equipment Operation & Maintenance 2 — Questions and Answers
Question 1: What is the correct procedure when a centrifuge becomes unbalanced during operation?
- Add more weight to the heavier side
- Stop the centrifuge immediately and rebalance the tubes (Correct answer)
- Continue running at a lower speed
- Remove the lightest tube only
Correct answer: Stop the centrifuge immediately and rebalance the tubes
An unbalanced centrifuge must be stopped immediately to prevent mechanical damage and potential injury from vibration or rotor failure.
Question 2: Which maintenance task should be performed on a microscope's objective lenses after each use?
- Submerge in 70% ethanol for 5 minutes
- Clean with lens paper and approved lens cleaner (Correct answer)
- Wipe with paper towels to remove debris
- Rinse with tap water
Correct answer: Clean with lens paper and approved lens cleaner
Lens paper with approved cleaner prevents scratching the optical glass while removing oil and debris from objective lenses.
Question 3: A laboratory refrigerator storing reagents reads 12°C instead of the required 2–8°C. What is the first action?
- Transfer specimens to a cooler with ice
- Adjust the thermostat and document the temperature excursion (Correct answer)
- Discard all contents immediately
- Call the manufacturer
Correct answer: Adjust the thermostat and document the temperature excursion
The thermostat should be adjusted and the excursion documented so that reagent integrity can be assessed per laboratory protocol.
Question 4: What is the purpose of running a blank when using a spectrophotometer?
- To calibrate the wavelength selector
- To zero the instrument against the solvent baseline (Correct answer)
- To verify lamp alignment
- To test cuvette integrity
Correct answer: To zero the instrument against the solvent baseline
A blank containing all reagents except the analyte zeroes the instrument so absorbance readings reflect only the substance being measured.
Question 5: When calibrating an analytical balance, which of the following is critical?
- The balance must be running for at least 10 seconds
- External certified calibration weights must be used on a level, vibration-free surface (Correct answer)
- The balance door must remain open during calibration
- Calibration is only needed annually
Correct answer: External certified calibration weights must be used on a level, vibration-free surface
Certified weights on a level, stable surface ensure the balance reads accurately across its full measurement range.
Question 6: Which of the following describes proper autoclave loading to ensure effective sterilization?
- Pack items tightly to maximize load capacity
- Leave space between items to allow steam penetration (Correct answer)
- Wrap all items in aluminum foil
- Place all items in sealed containers
Correct answer: Leave space between items to allow steam penetration
Steam must contact all surfaces, so items must be spaced to allow full penetration throughout the load.
Question 7: How should a pipette calibration be verified after maintenance?
- Pipette colored dye and visually inspect volume
- Perform gravimetric testing by weighing dispensed distilled water (Correct answer)
- Aspirate and dispense air to check resistance
- Test with a graduated cylinder
Correct answer: Perform gravimetric testing by weighing dispensed distilled water
Gravimetric testing using distilled water's known density is the standard method for verifying pipette volume accuracy.
CMLA Laboratory Equipment Operation & Maintenance 2
What is the correct procedure when a centrifuge becomes unbalanced during operation?