To use all functions of this page, please activate cookies in your browser.
my.chemeurope.com
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
 My watch list
 My saved searches
 My saved topics
 My newsletter
Retention distanceRetention distance, or R_{D}, is a concept in thin layer chromatography, designed for quantitative measurement of equalspreading of the spots on the chromatographic plate and one of the Chromatographic response functions. It is calculated from the following formula:
Additional recommended knowledge
Theoretical considerationsThe coefficient lies always in range <0,1> and 0 indicates worst case of separation (all R_{f} values equal to 0 or 1), value 1 indicates ideal equalspreading of the spots, for example (0.25,0.5,0.75) for three solutes, or (0.2,0.4,0.6,0.8) for four solutes. This coefficient was proposed as an alternative to earlier approaches, such as deltaRf, deltaRf product or MRF (Multispot Response Function). Besides its stable range, the advantage is a stable distribution as a random variable, regardless of compounds investigated. In contrast to the similar concept called Retention uniformity, R_{d} is sensitive to R_{f} values close to 0 or 1, or close to themselves. If two values are not separated, it is equal to 0. For example the R_{f} values (0,0.2,0.2,0.3) (two compounds not separated at 0.2 and one at the start ) result in R_{D} equal to 0, but R_{U} equal to 0.3609. When some distance from 0 and spots occurs, the value is larger, for example R_{f} values (0.1,0.2,0.25,0.3) give R_{D} = 0.4835, R_{U} = 0.4066. CalculationThe calculation of the R_{D} requires some operations and is quite difficult to perform in spreadsheets. The following implementations may help. They take the vector of R_{f} values, returning the single R_{D} value. The R (programming language)/SPLUS implementation: rd < function (x) { x < sort(x) n < length(x) d < diff(c(0,x,1)); pd < prod(d); rd < ((n+1)^(n+1)*pd)^(1/n); return(rd); } The GNU Octave/Matlab implementation: function res = rd(x) x = sort(x); n = length(x); d = diff([0 x 1]); pd = prod(d); res = ((n+1).^(n+1).*pd).^(1./n); endfunction The Scilab implementation: function res = rd(x) x = gsort(x,"g","i"); n = length(x); d = diff([0 x 1]); pd = prod(d); res = ((n+1).^(n+1).*pd).^(1./n); endfunction See alsoReferences


This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Retention_distance". A list of authors is available in Wikipedia. 