**15. Applications**

Ion exchange has proven to be one of the major methods of fractionation of labile biological substances. In the development of modern high performance media for purification, ion exchange chromatography has played a major role in the separation and purification of biomolecules and contributed sgnificantly to our understanding of biological processes. Analytical and preparative applications from the research laboratory. Ion exchange chromatography has played a role in the purificationof thousands of enzymes, and using modern matrices with optimized separation conditions gives extremely high recoveries. Normally the isoforms of an enzyme have approximately the same molecular weight. This makes their separation impossible by gel filtration. However, the small differences in charge properties resulting from altered amino acid composition enable the separation of isoenzymes using ion exchange chromatography. Ion exchange is frequently used for the purification of immunoglobulins.

Ion exchange chromatography also has many important applications in the field of industrial and pilot scale preparations. Many blood products such as albumin and IgG as well as the products of recombinant DNA technology, such as growth factors and pharmaceutically important enzymes are purified using this technique. Analytical applications of ion exchange chromatography are to be found in diverse areas such as quality control of purified products or process monitoring in biotechnology.

Other areas of application include food research where FPLC ion exchange can be used in the and in clinical research where ion exchange chromatography has been used in studies such as the relationship between post-partum depression and -endorphin secretion and the correlation of a chromatogram of the urine from patients exhibiting tubular proteinuria, due to acute pyelonephritis, severe burns or renal transplants, shows distinct peaks corresponding to 2-microglobulin, retinol binding protein and 1-acid glycoprotein.
