Final answer:
The statement regarding reversed phase HPLC is True, where the mobile phase is more polar than the hydrophobic stationary phase. Advances like UHPLC have further improved the efficiency and speed of HPLC separations.
Step-by-step explanation:
The statement is True: Reversed phase HPLC uses a system in which the mobile phase is more polar than the stationary phase. In reverse phase HPLC, the stationary phase typically consists of silica particles coated with hydrophobic alkane chains, often referred to as C-18 columns.
Analytes with a higher affinity for this hydrophobic stationary phase will elute more slowly compared to those with a lower affinity.
The mobile phase is often a mixture of water with a less polar organic solvent like methanol, where the organic solvent component is adjusted to achieve the desired polarity and, hence, the selectivity for the compounds being separated.
For instance, when separating phosphatidylcholine compounds, their similar structures but varying hydrophobicity allows them to be separated based on their different interactions with the stationary and mobile phases.
More hydrophobic solutes will move slowly through the column due to stronger interactions with the hydrophobic stationary phase, leading to effective separation.
Advancements like ultra-high pressure liquid chromatography (UHPLC) have been developed to increase efficiency, resolution, and sensitivity while reducing analysis time by using columns packed with smaller particles capable of withstanding high pressures.
This application of UHPLC with pressures over 10,000 psi and particles smaller than 2 µm has been a significant achievement in liquid chromatography.