Analytical chromatography, reflecting the composition of the sample, seeks efficient separation and high sensitivity without the need to collect specific fractions, and eluates are usually disposed of as waste liquids. In preparative chromatography, however, the maximum amount of product must be produced in the minimum amount of time in order to save investment and operating costs. Due to the difference in purpose, there are major differences in the optimisation of the operating parameters chosen for preparative chromatography and analytical chromatography, including column size, packing, flow rate, operating pressure, injection volume, product purity, product recovery and chromatographic separation effectiveness. The former requires the smaller the injection volume, while the latter requires the column to be overloaded in order to increase the preparation volume. There are two types of column overloading, one is "mass overloading", where a smaller injection volume is maintained and the injection concentration is increased, and the other is "volume overloading", where a smaller injection concentration is maintained and the injection volume is increased. In preparative chromatography, mass overloading is generally considered to be preferable. In preparative chromatography separations, both separation and column efficiency decrease as the degree of mass overloading increases. However, operating with mass overload can increase the preparative volume provided that the separation can be achieved.