1) Retention time can be used to identify a compound in a mixture using gas chromatography. Which one of the following will not affect the retention time of a compound in a gas chromatography column?
A. concentration of the compound
B. nature of the stationary phase
C. rate of fl ow of the carrier gas
D. temperature of the column

Solution

2) Consider the following statements about a high-performance liquid chromatography (HPLC) column that uses a polar solvent and a non-polar stationary phase to analyse a solution:
Statement I – Polar molecules in the solution will be attracted to the solvent particles
by dipole-dipole attraction.
Statement II – Non-polar molecules in the solution will be attracted to the stationary phase by dispersion forces.
Statement III – Polar molecules in the solution will travel through the HPLC column more rapidly than non-polar molecules.
Which of these statements are true?
A. I and II only
B. I and III only
C. II and III only
D. I, II and III

Solution

3) A small sample of a purified ester mixture was passed through a gas chromatograph (GC) attached to a mass spectrometer.
The chromatogram showed two peaks, indicating that the ester mixture contained two different fatty acid methyl esters, A and B. The peak area of each compound and the mass-to-charge ratio of the molecular ion of each compound are shown in the following table. Assume that the charge on each molecular ion is +1.

a) What information about the relative amounts of the two methyl esters is provided by the chromatogram?

Solution