A student researcher performed a chromatographic separation ofcaffeine and aspartame with methanol as the mobile phase using aC–18 column. The retention times for methanol (tm) , caffeine (tc), and aspartame (ta) were 41.8 s , 96.3 s , and 143.8 s ,respectively.
What is the selectivity factor (relative retention), α , forthis column?
α=
Calculate the hypothetical retention times for caffeine andaspartame if their retention factors were reduced by 28.0% . Assumethe mobile phase retention time (tm=41.8 s) remains constant.
tcaffeine=
staspartame=
Select the statements that correctly describe the outcome if thepartition coefficient for caffeine (Kc) were to decrease.
The retention time of caffeine would increase.
The retention time of caffeine would decrease.
Caffeine would spend a greater amount of time in the mobilephase.
The retention factor of caffeine would decrease.
The retention factor of caffeine would increase.
The retention time and retention factor of caffeine would notchange.
