Quiz 2

Question 1

What are the two principles that all chromatography techniques rely upon to separate a mixture of two or more compounds?

Answer 1

• Distribution of two phases, one stationary lone phase and one mobile phase (moving)

Question 2

A student used slurry packing to prepare and then loaded the sample for preparation. Give two essential pieces of advice to the student to assure efficient separation of the compounds into discrete bands.

Answer 2

• Never allow the column to dry (avoid formation of air bubbles or channels)
• add sample in as small of an area as possible

Question 3

All of the compounds in a mixture were a white solid or colorless liquid so the student collected 25 fractions from the column chromatography. Propose how the student would evaluate the purity of the fractions and decide which fractions to combine.

Answer 3

run a TLC (or GC) of each fraction to identify pure fractions and mixed fractions. Combine the pure fractions.

Also, visualize with I₂ chamber and UV.