Page 169 - Illustrated Pocket Dictionary of Chromatography

170 RISE TIME

The Rf factor is used in thin-layer chromatography to identify a peak based on its
migration up the plate. The method for calculating Rf is shown above.

rise time The time required for a detector output to go from
10Æ90% of the final detector output is termed the detector rise time.

robustness Refers to how effectively the analysis results remain
constant when operational variables (e.g., temperature, pH, mobile
phase composition [small changes], etc) are purposely changed in a
controlled fashion. A robust method produces results that are essen-
tially invariant under the type of variability that occurs from everyday
preparations and operation.
Rohrschneider polarity scale, P* Classifies nonpolar and polar
stationary phases used in GC by utilizing a logarithmic retention ratio
scale based on n-butane, b, and butadiene, bd:

b
b
P* = [ V p bd V p )) -( log( V u bd V u ))]
a log((