Investigation of the effect of pressure on retention of small molecules using reversed-phase ultra-high-pressure liquid chromatography.
The effect of inlet pressure on the retention of a series of low molecular weight acids, bases and neutrals, was investigated at constant temperature in reversed-phase liquid chromatography using a commercial ultra-high-pressure system (Waters UPLC instrument). For neutral compounds, relatively small increases in retention factor of up to approximately 12% for a pressure increase of 500bar were noted; the largest values were obtained for polar solutes, or solutes of higher molecular weight. Ionisable acids and bases gave much larger increases in retention with pressure, in some cases as high as 50% for a pressure increase of 500bar. Thus, such compounds could show increases in retention factor approaching 100% over the pressure range available in the commercial UPLC instrument. Due to these differential increases, significant selectivity effects can be obtained for mixtures of different types of solute merely by changing the pressure.
Centre for Research in Biomedicine, University of the West of England, Frenchay, Bristol BS16 1QY, UK.
Morgane M
MM
Fallas
Uwe D
UD
Neue
Mark R
MR
Hadley
David V
DV
McCalley
D000327:Adsorption; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D008970:Molecular Weight; D011312:Pressure