SENSITIVE DETERMINATION OF (-)-ISOPROTERENOL AND DIHYDROXYPHENYL)-2-[(3,4-DIMETHOXYPHENETHYL)AMINO] ETHANOL (T-0509), A CARDIOTONIC AGENT, IN RAT PLASMA UTILIZING A FULLY AUTOMATED CATECHOLAMINE ANALYZER

(-)-Isoproterenol (ISO), used as bronchodilator, and yphenyl)-2-[(3,4- dimethoxy-phenethyl)amino]ethanol (T-0509), a new cardiotonic agent, w ere determined in rat plasma (only 25 muL) using a fully automated cat echolamine (CA) analyser that includes in-line pre-extraction of CAs, coupled with an HPLC-ethylenediamine condensation reaction and a perox yoxalate chemiluminescence detection system (HPLC-ED-PO-CL). The chrom atographic conditions were: precolumn, SERUMOUT-CEX; buffer for delive ring CAs in the precolumn, 10 mm potassium phosphate buffer (pH 7.5)/e thanol (92 + 8, v/v) (1 mL/min); precolumn clean-up solution, 4% phosp horic acid/acetonitrile (50 + 50, v/v) (I mL/min); analytical column, TSKgel ODS-80Ts, 250 x 4.6 mm i.d.; eluent, 75 mm potassium acetate bu ffer (pH 3.2)/50 mm potassium phosphate buffer (pH 3.2)/acetonitrile ( 83.6 + 4.4 + 12, v/v/v for ISO and 76 + 4 + 20 v/v/v for T-0509) (1 mL /min); fluorogenic reagent solution, 105 mm ED and 175 mm imidazole in acetonitrile/ethanol (90 + 10, v/v) (0.25 mL/min); chemiluminogenic r eaction solution, 0.25 mm TDPO, 150 mm hydrogen peroxide and 110 mm TF A in dioxane/ethyl acetate (50+50, v/v) (1.4 mL/min). Colterol, ydroxy phenyl)-2-[(1,1-dimethyl)ethylamino]ethanol, (+/-)-N-t-butylnorepineph rine was used as an internal standard (IS) for ISO, and enyl)-2-[(3,4, 5-trimethoxyphenethyl)aminolethanol, yphenethyl-aminomethyl)-3,4-dihyd roxybenzylalcohol (T-1583) for T-0509. The detection limits for ISO an d T-0509 were 1.3 and 0.9 fmol on injection, respectively.