28
Shown below is a decrease in retention for cytosine on the four stationary phases as the column temperature
is increased. Linear van’t Hoff plots resulted from this study. Negative retention enthalpy values were obtained,
indicating an exothermic process of transferring cytosine from the mobile phase to the stationery phase.
0.0036
ln k
1/T (K)
1.00
10.00
0.0030
0.0032
0.0034
0.0028
Syncronis HILIC
Hypersil GOLD HILIC
Accucore HILIC
Hypersil GOLD Silica
Independently of its effect on the retention of test compounds, column temperature often positively affects the
chromatographic efficiency due to lower viscosity and higher diffusivity. Our study demonstrated lower back
pressures could be achieved when the temperature was raised, with average pressure dropping from 113
to 77 bar as the temperature was taken from 20 to 70 °C.
0.0036
ln k
1/T (K)
0.00
0.0030
0.0032
0.0034
0.0028
0.01
0.10
1.00
10.00
Syncronis HILIC
Hypersil GOLD HILIC
Accucore HILIC
Hypersil GOLD Silica
Van't Hoff plot for salicylic acid
Van't Hoff plot for cytosine
Mobile Phase:
90/10 acetonitrile/100 mM ammonium
acetate
Flow Rate:
1.0 mL/min
Inj.Volume:
5 µL
Detection:
228 nm
Mobile Phase:
90/10 acetonitrile/100 mM ammonium
acetate
Flow Rate:
1.0 mL/min
Inj.Volume:
5 µL
Detection:
248 nm
