Serotonin determination using electrochemical

The determination of catecholamines requires a highly sensitive and selective assay procedure capable of measuring very low levels of catecholamines that may be present. In past years, a number of methods have been reported for measurement of catecholamines in both plasma and body tissues. A few of these papers have reported simultaneous measurement of more than two catecholamine analytes. One of them utilized Used UV for endpoint detection and the samples were chromatographed on a reversed-phase phenyl analytical column. The procedure was slow and cumbersome because ofdue to the use of a complicated liquid-liquid extraction and each chromatographic run lasted more than 25 min with a detection Umit of 5-10 ng on-column. Other sensitive HPLC methods reported in the literature use electrochemical detection with detection limits 12, 6, 12, 18, and 12 pg for noradrenaline, dopamine, serotonin, 5-hydroxyindoleace-tic acid, and homovanillic acid, respectively. The method used very a complicated mobile phase in terms of its composition while whilst the low pH of 3.1 used might jeopardize the chemical stability of the column. Analysis time was approximately 30 min. Recently reported HPLC methods utilize amperometric end-point detection. 

F. Mashige, Y. Matsushima, C. Miyata, R. Yamada, H. Kanazawa, I. Sakuma, N. Takai, N. Shinozuka, A. Ohkubo and K. Nakahara, Simultaneous determination of catecholamines, their basic metabolites and serotonin in urine by high-performance liquid chromatography using a mixed-mode column and an eight-channel electrochemical detector, Biomed. Chromatogr, 9, 221-225 (1995). 

Serotonin In blood serotonin is predominantly located in the platelets, with levels in plasma being 100-fold lower. Most analysts interested in serotonin measurements have concentrated on determining serotonin in whole blood or platelet rich plasma. The presence of monoamine oxidase enzymes in blood necessitates the use of an enzyme inhibitor, e.g., pargyline to prevent the conversion of serotonin to 5-HIAA prior to analysis. Similar chromatographic conditions to those used for catecholamines can be used, e.g., CIS reversed-phase columns and electrochemical detection at an oxidation potential of -I-0.75 V or fluorescence detection. Sample... 

Patel, B.A. Arundell, M. Parker, K.H. Yeoman, M.S. O Hare, D. Simple and rapid determination of serotonin and catecholamines in biological tissue using high performance hquid chromatography with electrochemical detection. J. Chromatogr. B, 2005, 818, 269-276. 

Ponzio, F., and Jonsson, G., 1979, A rapid and simple method for the determination of picogram levels of serotonin in brain tissue using liquid chromatography with electrochemical detection,/. Neurochem. 32 129-132. 

Note however that histamine is a non-volatile amine and hence recourse is to explore in solution and apply an extraction protocol (such as liquid-liquid extraction) from the sample matrix. Electrochemical approaches have involved the use of boron-doped diamond electrodes which are reported to be superior to GC electrodes due to diamond s higher sensitivity, stability and reproducibility.Diamond is demonstrated to be the best electrode material for the detection of histamine, possessing high sensitivity, even at high oxidation potentials, and for the detection of serotonin, which fouls other electrodes such as GC after oxidation. High stability and remarkable detection limits for the determination of histamine (with serotonin also explored) via amperometry are reported to be possible.Table 16.3 provides a thorough overview of the electrochemical approaches for sensing histamine. 

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