Normal phase (NP) stationary phases have been the first phases for chromatography and that is why their properties of polarity were determined as ’’normal’’. The stationary phase of a NP column has polar properties and is commonly used with nonpolar solvents as hexane or heptane. The other way round a reversed phase (RP) column has covalent charcteristics and is used with more polar eluents, like mixtures of acetonitrile and water.
