DETERMINATION OF TETRAHYDROBIOPTERIN AND ITS ANALOGS IN BIOLOGICAL SAMPLES BY MICROBORE LIQUID-CHROMATOGRAPHY

Tetrahydrobiopterin and seven of its analogues (neopterin, xanthopteri n, biopterin, pterin, tetrahydropterin, 6-methyltetrahydropterin, and 6-methylpterin) were separated on a 1 x 150 mn C-18 microbore column. These analytes were detected by dual-electrode amperometry and UV abso rption. Both a conventional glassy carbon electrode and an interdigita ted array microelectrode were used. Low fmol amounts of xanthopterin, tetrahydropterin, tetrahydrobiopterin and 6-methyltetrahydropterin cou ld be determined by electrochemical detection in the oxidative mode, b ut pmol amounts of the other analogues were determined by electrochemi cal detection in the reductive mode and with UV detection. Catecholami nes and their metabolites do not interfere with the determination of t etrahydrobiopterin and its analogues in biological samples. The develo ped method was explored for the determination of tetrahydrobiopterin i n samples of human urine and rat tissue (brain, liver, and kidney).