[STM]

Hello everyone,

Please I need suggestions on how to separate two very similar triphenyl phosphine compounds (A and B) on Reverse-phase (LC-18) HPLC column with Fluorescence detector. The names are quite big and I cant supply the structures here. In A, a phenyl group in triphenyl phosphine has been replaced  by a swallowed-tail perylene derivative compound. A is oxidized to B by Hydrogen peroxide. The only difference between A and B is the formation of phosphine oxide bond in B which is absent in A. Every other functional group in A and B are the same.

I have tried Acetonitrile : water (60:40) and Methanol: water (60:40) but no separation. I am presently using Acetonitrile: Water (90:10) but the two compounds seem to be coming out at about the same retention time thereby making it difficult to differentiate since both A and B have same excitation and emission wavelength.

I need suggestions on how I can explore this little difference (the additional phosphine oxide bond in B) to effect there separation on HPLC.

[sjb]

Hello everyone,

Please I need suggestions on how to separate two very similar triphenyl phosphine compounds (A and B) on Reverse-phase (LC-18) HPLC column with Fluorescence detector. The names are quite big and I cant supply the structures here. In A, a phenyl group in triphenyl phosphine has been replaced  by a swallowed-tail perylene derivative compound. A is oxidized to B by Hydrogen peroxide. The only difference between A and B is the formation of phosphine oxide bond in B which is absent in A. Every other functional group in A and B are the same.

I have tried Acetonitrile : water (60:40) and Methanol: water (60:40) but no separation. I am presently using Acetonitrile: Water (90:10) but the two compounds seem to be coming out at about the same retention time thereby making it difficult to differentiate since both A and B have same excitation and emission wavelength.

I need suggestions on how I can explore this little difference (the additional phosphine oxide bond in B) to effect there separation on HPLC.

Do you have to do this via HPLC? What sort of quantity are you talking - can an acid:base treatment work?

[STM]

@SJB: Yes it is important I do this via HPLC because I need to monitor both at nanomolar concentration in the cause of my reaction and it takes HPLC to achieve separation and quantification at such low concentration.

[Arkcon]

The quickest idea I can come up with is switching column chemistry, but I don't know if that's where you want to go with this.  You might get a good separation with a phenyl-column, but switching to normal phase would also work, but that requires more extreme changes.

I'm guessing SJB: meant if you wanted to switch to GC, for the sensitivity you need, if thes compounds are GC-volatile.  It seems to me like that's the typical method for this sort of analysis.

[sjb]

I'm guessing SJB: meant if you wanted to switch to GC, for the sensitivity you need, if thes compounds are GC-volatile.  It seems to me like that's the typical method for this sort of analysis.

Hi Arkcon, no, I wasn't thinking about that sort of thing at all, though now you mention it this also seems like a good idea. I was thinking more along the lines of an acid may form the phosponium ion and be (more) water soluble and so effect a separation that way. However, if we're talking nM concentrations that may not be that effective.