Cs and Cm are equilibrium concentrations in the stationary and mobile phases. Which expression defines distribution constant K?

• Cs + Cm
• Cs / Cm
• Cm / Cs

Which pair describes the phases used in chromatography?

• Two flowing phases that react with each other
• A stationary phase and a flowing mobile phase
• A stationary phase and an empty vacuum chamber

An unretained marker is used to measure the hold-up or dead time tM.

In a linear partition model, k = 4 and Vs/Vm = 0.2. Calculate distribution constant K.

With constant mobile-phase composition, temperature and flow, tM is 2 minutes and tR is 8 minutes. Calculate retention factor k.

Two analytes have k values of 1 and 4 on the same column under the same conditions. In the linear partition model, which has the larger K?

• The analyte with k = 4
• The analyte with k = 1
• Both have equal K values

For peaks with the same retention time, larger plate number N corresponds to a narrower peak. The plates are hypothetical equilibrium stages.

A less polar stationary phase lowers an analyte's measured K from 10 to 2. Linear partitioning applies and Vs/Vm stays fixed. What happens to k?

• It becomes five times as large
• It remains unchanged by the swap
• It becomes one fifth as large