Chromatography Forum

Hi everybody!

I have a big, big problem! Can you help me to find some stability indicating method hplc for quantitative analysis of allantoins impurities in losions and creams. I tried using amino column and hilic silica column, but I did not get satisfactorily results, because I didn't see impurities and peaks of allantoin and urea get out together.

Thank you!
Best regards
Mila

Hi Mila -

This looks to be a difficult assay. Allantoin and urea
on Unison UK-Silica:

http://www.silvertonesciences.com/files/TI249E.pdf
http://www.silvertonesciences.com/files/TI178E.pdf

A quick search on google came up with an article where
the authors used an NH2 phase and 70:30 acetonitrile:water.

Did you try an NH2 phase? What did your chromatogram look like?

Dear Mila,

Today you may find several HILIC columns commercially available, most being either plain silica, or amino phases. These columns have limitations as the strong ionic interactions will contribute substantially to the separation mode. This is well described in recent studies, and below is two good references in comparing HILIC columns.

Retention Behavior of Small Polar Compounds on Polar Stationary Phases in Hydrophilic Interaction Chromatography
Y. Guo, S. Gaiki
J. Chromatogr. A, 1074 (2005) 71-80

Investigating the Effect of Chromatographic Conditions on Retention of Organic Acids in Hydrophilic Interaction Chromatography Using a Design of Experiment
Y. Guo, S. Srinivasan, S. Gaiki
Chromatographia, 66 (2007) 223-229

To obtain a different selectivity, you should aim at using a bonded phase, and I would suggest our zwitterionic phases as it gives a much different selectivity than all other HILIC phases.

Being a permanent zwitterion, it is charged yet neutral overall, which allows the use of much lower ionic strength in the mobile phase due to weak electrostatic interactions which is contrast to the strong interactions obtained with the two other alternatives.

Being a permanent bonded zwitterion, it is pH independent allowing the use of experimental conditions set for the analyte rather than for the column.

I would suggest you check in at our website for further reading or contact me via www.sequant.com

Looks like this has to be repeated: If you can´t use the ideal pH and/or ion concentration in your mobile phase, then the ZIC-HILIC does indeed show strong pH dependence.