Chromatography Forum

I am analyzing a homologous series of tertiary amines with ELSD and HILIC column. On the one end of the series the analyte peak has been split for an unknown reason. Fractions of the peak are with same m/z and also NMR shows no impurities.

Does anybody has experience how analytes with different counter ions would behave with HILIC column and ELSD? In the mobile phase counter ion is most probably not attached to the analyte (as is the situation in the column), but during the nebulization phase the mobile phase evaporates, so are the counter ions back to the analyte? (counter ions are so small that they do not show any signal with mass spec.)

Thanks for your help!

The peak has already split by the time it gets to the detector. Ion recombination in the detector can't split the peak.

Try cutting your sample injection in half and see if that improves the situation.

Counter ions do typically separate independetly in HILIC. There is a recent example of HILIC with ELSD of both positive and negative ions in the most recent issue of LCGC.
http://www.lcgcmag.com/lcgc/article/art ... ?id=364379

Can there be a mismatch between your sample solvent (or ion strength) and your eluent?
Reducing the injection volume as Mark suggested can be a way around that (or an adjustment of the sample environment...).