Chromatography Forum

It depends.

There are numerous chromatography overviews and resources linked up in the sticky section of these forums. Do your homework there. The link Tom previously provided should cover this as well.

The slightly longer answer is that it depends on what type of chromatography you are talking about.

As a *very* broad generalization:

In "reversed-phase" (ironically, the most popular type) increasing the polarity of the mobile phase increases retention.

In "normal-phase", increasing the polarity of the mobile phase decreases retention.

We can explain much of what goes on at the "boy scout merit-badge" level by the old saying "Like dissolves like and like sticks to like."