AACC AACC Laboratory Instrumentation & Technology 2 — Questions and Answers
Question 1: Which principle underlies the operation of an ion-selective electrode (ISE) used to measure electrolytes such as sodium and potassium?
- Amperometric current generation
- Selective membrane potential difference (Nernst equation) (Correct answer)
- Spectrophotometric absorbance change
- Immunochemical binding reaction
Correct answer: Selective membrane potential difference (Nernst equation)
ISEs generate a voltage across a selective membrane that is proportional to the logarithm of the ion activity, as described by the Nernst equation.
Question 2: What is the function of a monochromator in a spectrophotometer?
- To amplify the light signal
- To isolate a narrow band of wavelengths from a broadband light source (Correct answer)
- To convert photons into electrical current
- To mix the sample with reagent
Correct answer: To isolate a narrow band of wavelengths from a broadband light source
A monochromator uses a prism or diffraction grating to disperse light and select a specific wavelength range for the measurement.
Question 3: In point-of-care testing (POCT) devices, what type of calibration is typically used to ensure accuracy without full laboratory procedures?
- Multi-point external calibration
- Single-point or factory-embedded calibration with electronic verification (Correct answer)
- Blank-subtraction calibration only
- Full six-point linear calibration
Correct answer: Single-point or factory-embedded calibration with electronic verification
Most POCT devices use factory-set calibration encoded on cartridges or test strips, with single-point electronic verification rather than full wet chemistry calibration.
Question 4: Which component of an atomic absorption spectrophotometer (AAS) provides element-specific radiation for analyte measurement?
- Flame atomizer
- Hollow cathode lamp (HCL) (Correct answer)
- Monochromator grating
- Photomultiplier tube
Correct answer: Hollow cathode lamp (HCL)
The hollow cathode lamp emits the characteristic spectral lines of the element being measured, providing the specific wavelength needed for absorption.
Question 5: What is the Beer-Lambert law relationship used for in clinical spectrophotometry?
- Calculating osmolality from freezing point depression
- Relating analyte concentration to absorbance at a specific wavelength (Correct answer)
- Determining enzyme kinetics from reaction velocity
- Measuring zeta potential of colloidal particles
Correct answer: Relating analyte concentration to absorbance at a specific wavelength
Beer-Lambert law states that absorbance is directly proportional to analyte concentration and path length, forming the basis of quantitative spectrophotometric assays.
Question 6: In electrophoresis used for protein separation in clinical labs, what property primarily determines the migration rate of proteins?
- Protein color and turbidity
- Charge-to-mass ratio of the protein (Correct answer)
- Protein solubility in the buffer
- Temperature of the electrophoresis chamber
Correct answer: Charge-to-mass ratio of the protein
Proteins migrate through the gel matrix at rates determined by their charge-to-mass ratio under the applied electric field.
AACC AACC Laboratory Instrumentation & Technology 2
Which principle underlies the operation of an ion-selective electrode (ISE) used to measure electrolytes such as sodium and potassium?