We have been learning about HPLC and GC machines, and discussing the various types of columns, and I felt that everything was pretty clear and obvious. However, something from yesterday made me a bit confused, so I am hoping for some clarity. If you have a polar stationary phase, and you want the mobile phase to travel through the column faster, you want to up the polarity of the mobile phase. But why is that? It seemed to me like it would be the opposite, as two polar phases would "grip" each other, and actually make it travel slower. I thought that this would most certainly be the case in something like an open tube column, where a polar mobile phase would have much more interaction with a polar stationary phase. Can someone shed some light on this, please? I am having trouble wrapping my head around it. Thanks.