The elutopic series lists solvents in order of their power to carry a given compound through stationary phase (e.g. silica gel). The order of solvents runs in the order of their polarity. The series is useful when selecting a solvent for a particular separation where more polar compounds will normally require a more polar solvent. The solvent for a chromatographic separation will usually be specified in the script however a good starting point for a new separation is one with medium polarity such as dichloromethane or acetone.