Partition Chromatography

Partition chromatography is based on the differing solubility and hydrophobicity of the analytes in the stationary phase compared to the mobile phase. Analytes are separated based on their partitioning between the liquid mobile phase and a stationary phase.

Reversed Phase Liquid Chromatography (RPLC)

Reversed Phase Liquid Chromatography (RPLC) uses a polar mobile phase and a non-polar stationary phase. Silica-based materials in this category have a non-polar surface altered by attaching silanes with alkyl hydrocarbon tethers. In RPLC, the most polar compounds elute first, while the most non-polar compounds elute last.

Normal Phase Liquid Chromatography

Normal Phase Liquid Chromatography, on the other hand, uses a polar stationary phase and a nonpolar mobile phase. Stationary phases for Normal Phase Liquid Chromatography are usually silica-based, and there are also bonded normal phase materials. Organic moieties may include cyano and amino functional groups. In this chromatography, the least polar compounds elute first, and the most polar compounds elute last.

Hydrophilic Interaction Liquid Chromatography (HILIC)

Hydrophilic Interaction Liquid Chromatography (HILIC) is used for the retention and separation of problematic polar compounds. In HILIC mode, water acts as the strongest solvent to effectively elute analytes off the column, while the organic solvent acts as the weak solvent. This is opposite to reversed-phase chromatography.

Ion-exchange Chromatography

Ion-exchange chromatography separates solutes based on ionic charge. Retention in ion-exchange chromatography is determined by the pH of the eluent, the nature and ionic strength of the buffer, and temperature. Stationary phases for ion-exchange separations are classified by the nature and strength of the acidic or basic functions on their surfaces.

Size Exclusion Chromatography (SEC)

Size Exclusion Chromatography (SEC) separates analytes based on their size. SEC separates analytes based on their size by filtration through a gel in the SEC column containing spherical beads with pores of a specific size distribution. Small molecules enter the pores and their flow through the column is retarded according to their size, while large molecules cannot enter the pores and elute early with the mobile phase before small molecules.

Figure depicts the various types of chromatography alongside their respective subparts -