Chromatography Forum

Posted: **Wed Dec 01, 2004 1:51 am**

Can anyone define Rf value? I would really appreciate it.

Posted: **Wed Dec 01, 2004 3:25 am**

In thin layer chromatography or paper chromatography, Rf ("ratio of fronts") is the migration distance of a spot divided by the migration distance of the solvent front (both measured from the origin of the spot). If you want to relate it to other forms of liquid chromatography, Rf = 1/(1+k')

Posted: **Thu Dec 02, 2004 1:53 am**

I'm calculating my Rf value as follows:
distance dye traveled divided by the distance the solvent traveled

Posted: **Thu Dec 02, 2004 6:02 am**

that's correct.

Posted: **Sun Dec 05, 2004 9:00 pm**

What does your calculation mean? It really confuses me.

Posted: **Mon Dec 06, 2004 8:43 am**

Here's a tutorial on HPLC. It explains what k' is.

http://www.lcresources.com/resources/getstart/

Posted: **Mon Dec 06, 2004 9:34 pm**

ratio of fronts....... I like that.......

I learned that Rf meant....

Factor of retardation back in them olden days.

Posted: **Fri Dec 31, 2004 11:55 pm**

ratio of fronts....... I like that.......

I learned that Rf meant....

Factor of retardation back in them olden days.

Retention factor.

Analyte retention time / distance in HPLC or TLC is sensitive to the geometry of the column, run time, etc, . The retention factor (Rf) is a value for a compound that describes it's chromatography independantly of run, column length, etc. This value is useful for making comparisions while Rt is not.

Posted: **Fri Jan 07, 2005 2:52 am**

What is Rt?

Posted: **Fri Jan 07, 2005 3:03 am**

Rt=Retention time

Posted: **Fri Jan 07, 2005 3:52 am**

what is retention used for?
What category would it be used in the most?
What catetgory would it be used mainly for?

Posted: **Fri Jan 07, 2005 6:39 am**

No, we're not going to do your homework for you.

Go through the tutorial here to find the answers:

http://www.lcresources.com/resources/getstart/