(a) Nonpolar aromatic compounds were separated by HPLC on an octadecyl (C18) bonded phase. The eluent was 65 vol% methanol in water. How would the retention times be affected if 90% methanol were used instead?
(b) Octanoic acid and 1-aminooctane were passed through the same column described in part (a), using an eluent of 20% methanol/80% buffer (pH 3.0). State which compound is expected to be eluted first and why.
CH3CH2CH2CH2CH2CH2CH2CO2H
Octanoic acid
CH3CH2CH2CH2CH2CH2CH2CH2NH2
1-Aminooctane