HPLC and UHPLC

High performance liquid chromatography (HPLC: High Performance Liquid Chromatography) is an umbrella term for various liquid chromatographic separation techniques with enormous efficiency. This is achieved by using columns with very small, defined particles, which make it possible to separate many substances in a relatively short time. HPLC refers to the use of stationary phases with a particle size of 3 to around 10 µm. The maximum back pressure is 400 bar.

UHPLC (Ultra High Performance Liquid Chromatography) uses even smaller particles. These are in the order of magnitude of around 1 to <3 µm. This results in an increase in back pressure, which in UHPLC is a maximum of 1000 to 1500 bar.

The advantages of UHPLC over conventional HPLC generally lie in its higher efficiency and separation performance. Due to the small particles, the flow rates can be increased to a certain extent without any loss of separation performance. As a result, analysis times can be drastically reduced. The use of small inner column diameters also enables high solvent savings to be achieved.

The disadvantages of UHPLC are that the general costs for equipment, columns and their maintenance are higher.

The stationary phases for (U)HPLC are usually based on silica gel as the base material. Various polymers, metal oxides or pure carbon can also be used. The properties of the stationary phases can be specifically modified and adapted due to the wide range of modification options for these base materials, so that a number of separation techniques can be used for (U)HPLC.

These are: