The invention is a method of purifying a propylene glycol monoalkyl ether containing carbonyl impurities which comprises contacting the propylene glycol monoalkyl ether stream in the liquid phase with a carbon adsorbent, and recovering a purified propylene glycol monoalkyl ether product. The purification method improves product quality and reduces the amount of carbonyl impurities in the propylene glycol monoalkyl ether.