USE OF 4-(N,N-DIMETHYLAMINOSULPHONYL)-7-FLUORO-2,1,3-BENZOXADIAZOLE AS A LABELING REAGENT FOR PEROXYOXALATE CHEMILUMINESCENCE DETECTION AND ITS APPLICATION TO THE DETERMINATION OF THE BETA-BLOCKER METOPROLOL IN SERUM BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Fluorogenic reagents having a benzofurazan moiety, viz., 4-(N,N-dimethylaminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F), 7-fluoro-4-nitro-2,1,3-benzoxadiazole and 4-(aminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole, were compared for the sensitive analysis of their derivatives by high-performance liquid chromatography with peroxyoxalate chemiluminescence detection. Of the proline derivatives, DBD-proline was the most sensitive with a detection limit of 2 fmol. The optimum concentrations of bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate and H2O2 for the post-column reaction were 0.5 and 75 mmol dm-3 respectively, and amino acids and beta-blockers derivatized with DBD-F were detected in the range 0.2-40 fmol (signal-to-noise ratio = 3) using the proposed method. The lower detection limit of metoprolol (a beta-blocker having an isopropylamino group) spiked in serum was 0.8 ng ml-1 using 20-mu-l of serum (signal-to-noise ratio = 5).