The most popular method for purification of proteins and charged molecules is called Ion exchange chromatography. Conversely, in anion exchange chromatography, negatively charged molecules are attracted to a positively charged solid support. In cation exchange chromatography positively charged molecules are attracted to a negatively charged solid support. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field.