Indirect fluorescence detection of aliphatic biogenic polyamines and diamines following chromatographic separation

Indirect fluorescence detection of amino sugars with the use of copper complexes of tryptophan and its analogues following high-performance liquid chromatographic separation

A simple, indirect fluorescence detection method has been developed for detecting specific mono-amino sugars (D-glucosamine, D-galactosamine, D-mannosamine) following chromatographic separation. The eluting amino sugars release L-tryptophan (L-Trp) from a copper-tryptophan complex which is introduced postcolumn. Analyte detection is based on measuring the increase in L-Trp fluorescence, which is quenched when complexed with copper. Two tryptophan analogues, 5-hydroxy-L-tryptophan (5-HTP) and DL-5-methoxytryptophan (5-MTP), were also evaluated as postcolumn reagents. 5-MTP was found to be a suitable alternative to L-Trp for the detection of these mono-amino sugars. Detection limits for D-glucosamine, D-galactosamine, and D-mannosamine are in the range of 0.15-0.30 nmol injected.

Non-derivatization approach to high-performance liquid chromatography-fluorescence detection for aminoglycoside antibiotics based on a ligand displacement reaction

An indirect fluorescence detection method has been developed for detecting the aminoglycoside antibiotics following chromatographic separation. This approach to detection is based on a displacement reaction between the aminoglycosides and a copper(II)-L-tryptophan (L-Trp) complex, Cu(L-Trp)2. The aminoglycosides, which contain multiple amino groups, have strong affinities for the Cu(II) ion and displace L-Trp from the Cu(L-Trp)2 complex. The resulting increase in L-Trp fluorescence, which is quenched when coordinated to Cu(II), is indicative of the presence of the aminoglycoside. Fluorescence titration data indicate that there is a stoichiometric ratio of 1:1 between the reaction of the aminoglycosides with Cu(L-Trp)2. This HPLC detection scheme is implemented postcolumn by mixing a buffered Cu(L-Trp)2 solution with the column eluent prior to detection. The aminoglycosides were separated with the use of a column packed with a polymeric strong cation-exchanger. Separation and detection variables were optimized and are discussed. The detection limits for the aminoglycosides tested ranged from 4.2 to 14.5 ng injected (S/N=3). A linear working curve was achieved for amikacin in the range of 29-586 ng for a six point linearity test. The developed separation and detection scheme was further tested by analyzing commercial pharmaceutical formulations of these antibiotics.