Purification: A highly sophisticated sieve The purification process sorts the molecules in order to isolate them individually or in groups. Crude extracts are added to a liquid solution which draws the molecules through a purifying device. The molecules move along at different rates according to their physicochemical properties. At the end of the process, identical molecules are sorted into three groups based on their migration rate: the top, middle, and bottom fractions. The purified actives are the molecules contained in the middle fractions. The purification process thus removes undesirable molecules and concentrates the active content.