New capillaries should be conditioned before you use them.

1.Filter all solutions to be used on your capillary through a .45µ or 0.2µ syringe filter.
2.Treat the capillaries by running 0.1N NaOH solution through them on your CE unit.
3.Rinse the capillaries with CEwater or HPCE grade water for 5 minutes.
4.Final step is to run your buffer through it for 10 minutes before injection.

This procedure should be followed each day before new or old capillaries are used.