Catecholamines and their metabolites.

The research on biosynthesis, physiology, pharmacology, regulation and degradation of catecholamines has continuously increased for more than 50 years. This is not unexpected because of the fact that catecholamines are involved in so many life processes such as nerve conduction, blood circulation and hormone regulations in health and disease. This demands that methods for their determination should be improved, and in fact during the years a number of analytical methods have been published. About 20 years ago radioenzyme techniques with thin-layer chromatographic (TLC) separation of radiolabelled catecholamine derivatives were developed which greatly contributed to our knowledge of physiological concentrations of catecholamines in biological media, particularly in plasma and brain. Radioimmune methods were successful for analysis of a number of analytes, but for catecholamines radioimmunoassays developed slowly. We believe that the greatest potential for radioimmunochemical methods lies in their ability to localize catecholamines and metabolites at the cellular and subcellular levels. With the advent of gas chromatographic-mass spectrometric (GC-MS) and high-performance liquid chromatographic (HPLC) procedures analysis of catecholamines improved greatly., The equipment for GC-MS is expensive and requires technical skillfulness, but in experienced hands a lot of new biological data have emerged. An outstanding quality with GC-MS is that the method offers the ability to identify unknown compounds and is relatively free from interferences from extraneous compounds. In comparison with GC-MS, HPLC is versatile and has gained a widespread use. Applications for research in the catecholamine field are numerous. In general, the sensitivity and specificity are satisfactory with HPLC, but it should be borne in mind that a number of pitfalls can obscure the results. This involves both sample handling, clean-up and chromatographic procedures. At present, HPLC is the most expanding field in chromatographic determination of catecholamines and their metabolites. This is particularly the case for HPLC with electrochemical detection which has revolutionized our analytical potential in this field. These chromatographic procedures continue to develop. The prerequisites for further improved methods such as capillary zone electrophoresis and combined HPLC-MS are at hand and hopefully will soon come into more general use for analysis of catecholamines in biological samples.