纸层析实验中的Rf

Rf is also known as the retardation factor.
Chromatography is used in the separation of a mixture of fluids (for this explanation,liquids are used).
Let me explain the rudimentary method:paper chromatography.
1.Draw a pencil line on a piece of rectangular filter paper,and put a dot of liquid on the line.
2.Dip one end of stationary phase in a moving phase (eg pure water or ethanol will suffice).
3.Due to different absorption properties and solubilities of each constituent,each liquid will move up the paper at different rates,effectively separating them.
4.The retardation factor,a measure of absorption,is calculated by Rf = (distance travelled by unknown) / (distance travelled by solvent)
Each substance has a specific Rf value,and is useful for scientists to identify them using their unique Rf values.This allows us to study what is contained in a mixture (eg in the study of the constituents of the coloured pigments making up chlorophyll).
This is what a paper chromatogram looks like.
It is the distance travelled by the sample or analyte divided by distance travelled by the solvent front in chromatography.
试样经层析后可用比移值（Rf）表示各组成成分的位置（比移值=原点中心至色谱斑点中心的距离与原点中心至流动相前沿的距离之比）,由于影响比移值的因素较多,因此一般采用在相同实验条件下对照物质对比以确定其异同.