Ultra-High Performance Liquid Chromatography a milestone in the evolution of LC in that columns packed with <2µm particles, used with instrumentation capable of handling the resulting high back pressures, make possible extremely fast and efficient separations. UHPLC is a very powerful tool for today’s practicing chromatographer, as it can significantly increase the efficiency of a chromatographic separation. In addition, the wider range of usable flow rates makes high speed separations possible.
Effect on efficience
The lower the particle size, the higher column efficience is (see graph below). With particle size decrease the column back pressure increases significantly. This leads to ultra high pressure of longer LC columns. It means that we cannot use 1,9µm UHPLC column the same lenth like 5µm column (eg. 250 mm long column). In the end we have lower or similar column efficieny as we have with standard HPLC columns. The main benefit of the UHPLC columns is the analysis run time, not the efficiency.
If you need to increase efficiency, look at phase chemistry first. In this case look at stationary phase list.