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Normal Phase Efficiency Indicators
Posted: Fri Dec 19, 2008 11:29 pm
by Douglas Rodenburg
Does anyone have indicator recommendations for normal phase efficiency measurements? I am looking for those that are "customary" or usual or generally recognized.
Thank you
Doug
Posted: Mon Dec 22, 2008 6:08 am
by tom jupille
toluene
Posted: Fri Jan 02, 2009 5:43 am
by XL
Tom,
When toluene is used as the efficiency indicator for a nomral phase column, what mobile phase is recommended for the test? If a normal phase mobile phase (high organic solvent) is used, toluene should elute close to the void in which case it won't be a good probe. It seems more reasonable to use a polar compound such as urea or uracil as probes for normal phase chromatography. Would you please elaborate on this? Thanks!
Posted: Sat Jan 03, 2009 12:32 am
by tom jupille
XL, remember that solvent strength in normal phase is the reverse of that in reversed-phase (i.e, water is a very strong solvent). In the event, a typical mobile phase would be a few percent dichloromethane (strong solvent) in hexane (weak solvent), with the percentage adjusted to give a reasonable k' (the exact value, obviously, will depend on the column).