Talk:Retardation factor
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Retardation factor (Rf) is only used in planar chromatography. Retention factor is mainly used in column chromatography (gas or liquid chromatography). I am planning on writing a page on terminology in chromatography which will address this.Xenofonos (talk) 21:49, 3 April 2008 (UTC)
Retardation/retention and column/planar chromatography[edit]
The definition and notation for retardation factor match that of the IUPAC definition for planar chromatography, but the use of retention factor doesn't seem to match.
- Retardation factor in planar chromatography, Rf: ratio of spot travel to mobile phase travel.[1]
- Retention factor in column chromatography, k: residence time in stationary phase compared to mobile phase.[2]
- Retardation factor in column chromatography, R: fraction of the sample in the mobile phase at equilibrium given by R=1/(k+1)[3]
Original reference: Ettre, L. S. (1993), "Nomenclature for chromatography (IUPAC Recommendations 1993)", Pure and Applied Chemistry, 65: 819, doi:10.1351/pac199365040819. Ettre notes that R=Rf in the ideal case.
The IUPAC Gold Book has no entry for retention factor in planar chromatography. Is the use of retention factor as in the article standard? --Kkmurray (talk) 02:30, 15 October 2008 (UTC)
- The Roberts/Gilbert/Martin undergrad lab text uses "retention factor" (and no other term) to describe Rf for TLC. DMacks (talk) 02:37, 15 October 2008 (UTC)
- Skoog/Holler/Crouch (6th ed. p. 150) uses both retardation factor and retention factor to describe TLC separations and gives the relationship as R=1/(k+1). I haven't seen anything that equates retardation and retention factor. Am I missing something, or is the statement in the first sentence of the article equating the two incorrect? --Kkmurray (talk) 21:09, 15 October 2008 (UTC)
- Sounds like either "they're different things technically, but equal in the ideal case" or else an entrenched incorrect usage (possibly based on only considering ideals?). So we shouldn't say that they are "the same" (and can even explain the difference since they're inter-related), but do have to acknowledge that both terms are used for Rf itself. DMacks (talk) 21:15, 15 October 2008 (UTC)
- Skoog/Holler/Crouch (6th ed. p. 150) uses both retardation factor and retention factor to describe TLC separations and gives the relationship as R=1/(k+1). I haven't seen anything that equates retardation and retention factor. Am I missing something, or is the statement in the first sentence of the article equating the two incorrect? --Kkmurray (talk) 21:09, 15 October 2008 (UTC)
NOTE: Irrespective of the above discussion: it is curious that there seems to be no consensus in the literature about how to write Rf: while the "R" is usually written as capital letter in italics, "f" can be written as small letter, subscript, either in italics or NOT in italics; sometimes it is written as "F" (capital letter, subscript, in italics). —Preceding unsigned comment added by 134.130.101.232 (talk) 15:50, 14 April 2009 (UTC)
Column chromatography[edit]
This section doesn't seem to make sense. It's saying that retardation factor and retention factor are different things, whereas the rest of the article says they are the same thing. Plus, the link "retention factor" (which is implied to be at least somewhat different, given the different notation) simply redirects to this same document. If the terms have different uses in column chromatography, that should probably be more clear. Arc de Ciel (talk) 03:12, 19 October 2009 (UTC)