Microanalysis of serotonin by high pressure liquid chromatography with electrochemical detection.

Serotonin (5-HT) analysis by high pressure liquid chromatography with electrochemical detection (HPLC-ED) has been designed to perform micro assays below the picogram range. We demonstrated that the oxidation potential of 5-HT was tightly linked to the pH of the buffer used as eluent phase. The electrochemistry of 5-HT in pH 4.00 acetate buffer and in pH 6.80 phosphate buffer allowed quantification down to 2 x 10(-18) g. The oxidization current was linked to the 5-HT amount added. The electrochemical response of 5-HT was different for low amounts in the 10(-18) g range and for amounts above the picogram range. Two curves were obtained according to the electrochemical response of 5-HT: the first one was for the 10(-18) g range and the second one was for the picogram range and above. It thus appeared between concentration ranges that assays are not be feasible. This method has been used to analyse 20 microns frozen slices of rat spinal cord. These data open new insights into scarce quantification of 5-HT without the use of radio-elements.