Antidepressants or thymoleptics are compounds that have impetus or moodenhancing effects. Most depressive diseases are caused by a decreasing level of biogenic amines (noradrenaline and serotonin) in the brain. Antidepressants inhibit the mechanism of inactivation of these amines, which leads to a higher concentration at the corresponding receptors. Many C18 columns show strong adsorption of basic compounds, especially biogenic amines, which frequently result into peak tailing, fronting, and poor resolution. However, the Zorbax SB-C18 column is a densely covered, sterically protected C18 column made with a special Zorbax silica support that reduces or eliminates strong adsorption of biogenic amines and other basic compounds (Figure 1).