The organic solvent type can be varied to change retention and separation selectivity, much like reversed phase separations. Solvent strength (from weakest to strongest) for HILIC generally is tetrahydrofuran acetonitrile < isopropanol < ethanol < methanol < water, where water is the strongest elution solvent. Note that to further increase retention in HILIC, using another polar solvent such as methanol or isopropanol with water is sometimes is effective.  As such, acetonitrile is the preferred weak solvent in HILIC mode.

For optimum column efficiency and reproducibility, buffers in the range of 10 - 20 mM concentration or additives in the 0.5 % range are used in the mobile phase. 

Phosphate buffers are not recommended because of their poor solubility in high organic mobile phases, in addition to being incompatible with MS detection, where HILIC is commonly used.