Try the following tips:

1. It is generally better to have the sample solvent strength stronger that the mobile phase solvent, especially at the beginning of a gradient. In addition, Cogent TYPE-C™ silica hydride phases are less susceptible to peak distortions than HILIC. With the proper gradient, most compounds will give good peak shape.

2. Certain compounds like polyprotic acids and phosphate containing species have special considerations since they are can be affected by metal ions in the HPLC system. In this case you can follow a simple procedure for dealing with metal issues.

3. Make sure that your injection volume/concentration is not excessive. You can see the effects of unsuitable injection volumes here.