Try the following tips:
1. It is generally better to have the sample solvent strength stronger than 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 phases would be. With the proper gradient, most compounds will produce 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. If you use a Cogent Column phosphoric acid (PA), you should dedicate that column to that method since HPLC columns are altered once PA has been used in it. For these compounds you may want to consider using our metal free coated stainless steel columns.
3. Make sure that your injection volume/concentration is not excessive. You can see the effects of unsuitable injection volumes HERE.