Why does Ni and Fe ions have different Rf values?
In chromatography, a retardation factor (Rf) (also known as retention factor) is a ratio defined as follows: Rf= migration distance of substance/migration distance of solvent front For example, if particular substance in an unknown mixture travels 2.5 cm and the solvent front travels 5.0 cm, the retention factor would be 0.5. An Rf value will always be less than 1 since the solvent front always travels farther than does the substance under investigation. An Rf value is characteristic for any given compound (provided that the same stationary and mobile phases are used). It can provide corroborative evidence as to the identity of a compound. If the identity of a compound is suspected but not yet proven, an authentic sample of the compound, or standard, is spotted and run on a TLC plate side by side (or on top of each other) with the compound in question. Note that this identity check must be performed on a single plate, because it is difficult to duplicate all the factors which influence
