Mobile phases in HPLC are often prepared as aqueous solutions with a variety of additives to prepare a buffer of a suitable pH range. Psilocybin is an organic zwitterionic compound and rests preferentially in one state over the other depending on the pH of the eluent (or diluent). In neutral pH deionized water, for example, psilocybin presents itself as a bimodal absorption representing a ratio of charge states present in solution.