organic modifier chemistry

[chembot]

THF, Methanol, and Acetonitrile are commonly used organic modifiers for reverse phased LC.

What is the order of the strength of these? Anyone know the chemistry behind this ordering?

Similarly, what is the order of the viscosity of these at ambient temp and what is the chemistry behind this ordering?

any insight to these would be very helpful.

[Consumer Products Guy]

THF is strongest (most non-polar), then ACN, then methanol.

[tom jupille]

In principle, non-polar = stronger

In practice, all three of these form non-ideal mixtures with water (i.e., the properties of the mixture are not the average of the properties of the components). The viscosity of water/methanol mixtures, for example, can be higher than the viscosity of either water or methanol by itself.

There is a bit more discussion in these two recent threads:

http://www.sepsci.com/chromforum/viewtopic.php?t=2525
http://www.sepsci.com/chromforum/viewtopic.php?t=6974