Polar embedded reversed Phase Columns: ACN vs. MeOH

[Koen Hollebekkers]

Is there a difference in effiency when polar embedded columns are used with ACN or MeOH, for the neutral model compounds?
I have the feeling that you have higher efficiency with ACN compared with MeOH.

[Uwe Neue]

It is probably not related to your column. In principle, you should always get a higher efficiency in acetonitrile compared to methanol. This is due to the lower viscosity of acetonitrile-water mixtures.

[Mark Tracy]

In general, acetonitrile mobile phases give better efficiency than methanol for neutral compounds. In large part this is reflective of the viscosity difference. I reviewed some lot test data for C18 and PolarAdvantage columns (in plates/meter):

C18 C18 PA PA
90% MeOH 96K 102K 91K 92K terphenyl
70% MeCN 111K 115K 110K 106K phenanthrene
difference 15K 13K 19K 14K

There is not much difference between C18 and PA, certainly not enough to get worried about.