There is provided a method for thermally focusing the elution times of compounds of a liquid chromatography system comprising a pre-column and a separation column as well as to provide a liquid chromatography system, wherein the chromatographic separation of a mixture of substances is optimized. It also relates to packaged products obtained by packaging them in the packaging material that has been provided with one or more openings, in order to make it easy to open the package. One of at least two tables of constants is selected wherein each table of constants is capable of reducing the number of transformed data samples by a different factor.