CPC Chemical Instrumentation & Calibration 3

Question 1

In HPLC, what is the van Deemter equation used to describe?

Accepted Answer

The dependence of column plate height on mobile phase linear velocity

Answer

The van Deemter equation (H = A + B/u + Cu) describes how band broadening (plate height H) varies with mobile phase velocity, identifying optimal flow rate.

Question 2

Which phenomenon causes baseline drift in a differential refractometer (RI) detector during gradient HPLC elution?

Accepted Answer

Changes in mobile phase composition alter the bulk refractive index

Answer

RI detectors respond to the overall refractive index of the column effluent; solvent composition changes during gradient elution cause continuous baseline drift.

Question 3

In FTIR spectroscopy, what is the function of the Michelson interferometer?

Accepted Answer

To generate an interferogram by combining beams with varying path difference

Answer

The Michelson interferometer splits the IR beam, introduces a variable path difference with a moving mirror, and recombines the beams to create an interferogram that is Fourier-transformed into a spectrum.

Question 4

What does the term 'linearity of calibration' mean in method validation?

Accepted Answer

The ability of the method to produce responses proportional to analyte concentration over a defined range

Answer

Linearity demonstrates that instrument response is directly proportional to analyte concentration across the working range, typically verified by the coefficient of determination (R²).

Question 5

Which mass spectrometry ionization technique is most suitable for intact large biomolecules like proteins?

Accepted Answer

Electrospray ionization (ESI)

Answer

ESI is a soft ionization technique that produces multiply charged intact molecular ions from large polar biomolecules without fragmentation.

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CPC Chemical Instrumentation & Calibration 3