AACC Laboratory Instrumentation & Technology Flashcards

Which principle underlies the operation of an ion-selective electrode (ISE) used to measure electrolytes such as sodium and potassium?

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.

What is the function of a monochromator in a spectrophotometer?

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.

In point-of-care testing (POCT) devices, what type of calibration is typically used to ensure accuracy without full laboratory procedures?

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.

Which component of an atomic absorption spectrophotometer (AAS) provides element-specific radiation for analyte measurement?

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.

What is the Beer-Lambert law relationship used for in clinical spectrophotometry?

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.

In electrophoresis used for protein separation in clinical labs, what property primarily determines the migration rate of proteins?

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.