The invention discloses a process for removing specific impurities of
diphenhydramine citrate. The identification is as follows: a graph is a related substance (HPLC) graph of a
diphenhydramine citrate crude product, and the
impurity is named as an
impurity I when Rt is equal to 15.567 min; the
impurity removal method comprises the following steps: dissolving a
diphenhydramine citrate crude product in a
solvent, heating and dissolving, cooling the
system to 40-55 DEG C, growing crystals for more than 3 hours, cooling to 0-30 DEG C, crystallizing for 2-3 hours, and filtering to obtain a diphenhydramine citrate fine product; wherein the
mass volume ratio of the crude product to the
solvent is 1g: (8-12) ml, and the
solvent is 95%
ethanol. The impurity I is disclosed, identified and confirmed for the first time, and a basis is provided for setting an impurity limit. The diphenhydramine citrate is refined by adopting a
crystal growing method, the refining effect is good, the removal rate of impurities I and other impurities is high, the operation is simple, and the method is particularly suitable for industrial production.