Laboratory Instrumentation and Analytical Principles Flashcards

Which method is considered the gold standard for confirming a positive drug-of-abuse screen?

Answer: Gas chromatography-mass spectrometry

GC-MS separates compounds and identifies them by their unique mass spectra, giving definitive confirmation.

In reverse-phase HPLC, which combination of phases is used?

Answer: Nonpolar stationary phase, polar mobile phase

Reverse-phase HPLC uses a nonpolar (e.g., C18) column with a polar solvent, so nonpolar analytes are retained longer.

In thin-layer chromatography, a compound travels 3 cm while the solvent front travels 6 cm. What is its Rf?

Answer: 0.5

Rf = distance traveled by solute ÷ distance traveled by solvent = 3/6 = 0.5.

Which variables are needed to calculate the relative centrifugal force (g) of a centrifuge?

Answer: Rotor radius and revolutions per minute

RCF = 1.118 × 10^-5 × r × rpm², so it depends on rotor radius and speed.

In flow cytometry, forward scatter primarily reflects which cell property?

Answer: Cell size

Forward-scattered light is roughly proportional to cell size, while side scatter reflects granularity.

Hematology analyzers using the Coulter principle count cells by detecting what?

Answer: Changes in electrical impedance as cells pass through an aperture

Each cell passing through the aperture briefly raises resistance, and the pulse size is proportional to cell volume.

A mass spectrometer separates and identifies ions based on what property?

Answer: Mass-to-charge ratio (m/z)

Mass analyzers sort ions by their mass-to-charge ratio.