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The reactivities of three reagents, 4-(N,N-dimethylaminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F), 4-( a m i nosu I p honyl)-7-f I uoro-2,1,3-benzoxadiazo le (ABD-F) and 4-(f I uorosu I p honyl)-7-p henoxy-2,1,3-benzoxadiazole (PBD-S02F), towards thiols and amines were compared. All three reacted with thiol compounds to give derivatives which fluoresced at ca. 51 5 n m (excitation at ca. 388 nm). However, the PBD-SOZ derivatives were not very stable. The rate of reaction of DBD-F with proline was faster than that of PBD-SOZF or ABD-F. The three reagents and their hydrolysates exhibited extremely low fluorescence. The fluorescence intensities of the proline derivatives synthesised were higher in neutral and acidic solutions than i n alkaline solution. The strength of the fluorescence intensities was in the order PBD-S02-proline > DBD-proline > ABD-proline a t all pH values tested. The mean values of the maximum wavelengths of DBD-proline, ABD-proline and PBD-SOz-proline were 596 n m (Aex, = 466 nm), 602 n m (Aex, = 466 nm) and 566 n m (Aex. 453 nm), respectively.Of the three reagents, DBD-F seemed to be applicable to the determination of amino acids. Nine amino acid derivatives of DBD-F were separated by reversed-phase high-performance liquid chromatography and detected with fluorescence at 590 nm (Aex. = 450 nm). The detection limits were in the sub-picomole range.

FI uorogenic reagents for a Ide hydes and ketones, viz., 4-am i nosu I p honyl-7-hyd razino-2,1,3-benzoxadiazole (ABD-H) and 4-( N,N-dimethylaminosulphonyl)-7-hydrazino-2,1,3-benzoxadiazole (DBD-H) and also purified 4-hydrazin0-7-nitro-2,1,3-benzoxadiazole hydrazine ( NBD-H.NHzNHz) were synthesised. These reagents are not fluorescent; however, their reaction products with aldehydes and ketones fluoresce at wavelengths from 548 to 580 nm with excitation from 450 to 470 nm. Both ABD-H and DBD-H exhibited similar reactivity and were more reactive than NBD-H.NH2NH2. The respective pseudo-first-order reaction rate constants for the production of the hydrazone of propionaldehyde with ABD-H, DBD-H and NBD-H.NH2NH2 were 8.9 x 10-2,7.2x 10-2 and 4.2 x 10-2 min-1 (the reaction was carried out in 0.0025% trifluoroacetic acid in acetonitrile a t room temperature, 22 "C). The detection limits using the manual method (i.e., measurement of fluorescence intensity) for the hydrazones of aldehydes and ketones with ABD-H, DBD-H and NBD-H.NHzNHz were in the V M range. The substrate blank fluorescence with ABD-H was half of that with DBD-H and NBD-H.NH2NHz. The reaction products were separated and analysed by reversed-phase high-performance liquid chromatography (HPLC) with spectrofluorimetric detection. The detection limits for propionaldehyde were 1040, 120 and 35.0 fmol with ABD-H, DBD-H and NBD-H.NHzNH2, respectively, and those for heptan-4-one were 2690, 560 and 673 fmol, respectively. Of the three reagents, DBD-H is recommended for the sensitive detection of ketones and NBD-H.NHzNHz for the detection of aldehydes. The detection limits for aldehydes and ketones by HPLC were in the sub-pmol to pmol range. Keywords : Flu0 rog en ic reagents for aide h ydes and ketones; 4-am in osulp ho n yl-7-h ydrazino-2, I, 3-benzoxadiazo le; 4-(N , N -dime t h ylaminosulp h on y1)-7-h ydrazino -2, I, 3-benzoxadiazole; 4-h ydrazino-7-nitro-2,1,3-benzoxadiazole h ydrazine; hig h-performance liquid chromatography Paper Of013881

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