[pat.smith.01628]

The following conditions for analysis of Warfarin:

 Column:
— size: l =  0.25 m, Ø = 4.0 mm;
— stationary phase: spherical nitrile silica gel for chromatography R (5 µm);
— temperature: 30 °C.
Mobile phase:  glacial acetic acid R, acetonitrile R, water R (1:25:75 V/V/V)

Normal-phase or reverse-phase chromatography??

[Archer]

Are you asking if nitrile modified silica gel is normal-phase or reverse-phase?

As far as I am aware the nitrile modification is R = attached to {Silica sphere}-O-Si(CH₃)₂-R so in nitrile modified silica R = is in place of R = from a standard C18 modified silica.
 
Look up the definition of "Normal Phase" and see if the Nitrile modified silica fits.

[Arkcon]

Short modifiers (ie. cyano, or nitrile) on columns can be either normal phase or reverse phase.  You can tell what you're getting by what eluent you're using, and the nature of your analyte, and when it comes off.  Using that info, what can you say about your system?

[Kate]

Short modifiers (ie. cyano, or nitrile) on columns can be either normal phase or reverse phase.  You can tell what you're getting by what eluent you're using, and the nature of your analyte, and when it comes off.  Using that info, what can you say about your system?

Ok, so based on that I'd say it's normal phase, because the eluent is polar and less polar compounds will be retained longer in the column.

[Arkcon]

I was hoping the original poster would make the logical leap needed, but OK.  It does however depend on how well retained the analyate is -- does it come off early or late?  is it preceded by more non-polar or polar things?

[Archer]

I think the term "reversed phase" is redundant now as there are so many different column types which don't simply reverse the elution order of that observed with silica gel.

To me you have "normal phase" which is just silica then you have modified stationary phases.

This thread is a bit like askiing whether cyclodextrin modified silica with hexane /isopropanol is normal or reversed phase Chromatography.

[Arkcon]

Yeah, but people just look at me funny when I call it "abnormal phase"