Laboratory Equipment & Techniques Flashcards

Which centrifuge type uses a fixed angle rotor where tubes are held at a constant angle during spinning?

Answer: Fixed-angle centrifuge

Fixed-angle rotors hold tubes at a set angle (typically 25–45°) throughout the run, causing particles to sediment along the tube wall.

When calibrating a spectrophotometer, which solution is used to set 100% transmittance (zero absorbance)?

Answer: The blank (reagent blank)

The reagent blank contains all reagents except the analyte and is used to zero the instrument, correcting for reagent color and background absorbance.

A laboratory thermometer reads 37.2°C when placed in a 37.0°C reference bath. This difference is best described as:

Answer: Systematic error (bias)

A consistent offset from the true value in one direction is systematic error (bias), which can often be corrected by calibration.

Which pipette type is designed to deliver a single fixed volume and is NOT adjustable?

Answer: Volumetric (transfer) pipette

Volumetric (transfer) pipettes are calibrated to deliver one precise fixed volume and offer the highest accuracy for that volume.

In a biosafety cabinet Class II Type A2, the percentage of air recirculated within the cabinet versus exhausted is approximately:

Answer: 70% recirculated, 30% exhausted

Class II Type A2 BSCs recirculate approximately 70% of air through HEPA filters and exhaust about 30% to the environment (via HEPA or hard-duct).

What does the term 'resolution' refer to when describing a centrifuge's performance?

Answer: Ability to separate two particles of different sedimentation rates

Resolution in centrifugation refers to how well the instrument can separate two populations of particles with different densities or sizes.

A Neubauer hemocytometer counting chamber has a depth of:

Answer: 0.1 mm

The standard Neubauer hemocytometer has a chamber depth of 0.1 mm, which is used in calculating cell counts per volume.