By Anonymous on Monday, June 18, 2001 - 12:29 pm:
I have been working on a TLC method for phospholipid degradation products. The mobile phase is chloroform/methanol/water. Sometimes I get a change in Rf for only one of the compounds even though I have been using the same conditions. Does anyone know what may cause this?
By H W Mueller on Tuesday, June 19, 2001 - 01:16 am:
Do you get the Rf change of one substance when you apply ONE spot of a standard (a known) containing the different analytes. or do you get a different Rf in separate applications (maybe of an unknown?).
By Anonymous on Tuesday, June 19, 2001 - 04:40 pm:
I have two concentrations of one lyso-phospholipid standard. Only the Rfs for this standard move around from analysis to analysis. The Rfs for the other standards and samples are fairly constant.
By H W Mueller on Tuesday, June 19, 2001 - 11:56 pm:
If there is only one of the lyso´s of the standard with Rf variation than it must be unstable or have unfavorable (at least: Non-robust method) chromatographic conditions. Can´t think of anything else.
We got an unknown peak (RP-HPLC) in the derivatization of ascorbic acid with dinitrophenylhydrazine which was in a different place everytime we injected the soup. We called it the phantom peak. Is your standard well defined?
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