Question

14. The chromatogram below was prepared using HPL.C with a polar stationary phase and OCH CH:NH2), and pentanol (CsHiOH) polar mobile phase. (a) If the compounds in the sample were octanol (CsHi-OH), benzene (CHo), ethanolamine (H ( and please correlate the numbered peaks below with the compounds. (b) Please describe how you might improve the resolution of compounds 2 and 3 without changing the stationary phase. (8 points) 0.8 s 0.4 03 0.2 0.1 10 12 16 18 20 Time inn」

Answer 1

a)In HPLC, elution of order of solutes governed by polarity. The solutes with less polarity will elute first in presence of polar stationary phase as they spend proportionally lesser time in the column.

So, in the above condition

peak 1 indicates Benzene

peak 2 indicates Octanol

peak 3 indicates Pentanol

peak 4 indicates Ethanolamine

b) For better resolution of two solutes depends on the selectivity factor,$\alpha$ There are two common methods to increase $\alpha$, (i) add a reagent to a mobile phase which reacts with the solutes in secondary equilibrium reaction (ii) change the mobile phase.