4. Solvents

HPLC solvents are used as a mobile phase to move the analyzed mixture through the separation column (stationary phase).

 

There are two basic types of solvent systems. Each is matched with a corresponding type of stationary phase (column):

Normal Phase vs Reverse Phase System

a) Normal Phase = solvent system non-polar (hexane, toluene); matched with normal phase column

b) Reverse Phase = solvent system polar (water, methanol, acetonitrile); matched with a reverse-phase column

 

Modern HPLC systems are able to mix multiple solvents, hence the most common are:

Combination Solvents

a) Binary (2) Solvent System

b) Quaternary (4) Solvent System

 

Note: HPLC from CTInstruments uses a reverse-phase, binary solvent system for the analysis of cannabinoids. This system is pushed through the column in isocratic mode (uniformly mixed solvent, see later for explanation).