Flavin mononucleotide for indirect laser-induced fluorescence detection ofanions separated by capillary electrophoresis

Flavin mononucleotide (FMN), also known as riboflavin-5'-phosphate, has bee n characterized as an indirect laser-induced fluorescence (LIF) detection r eagent for inorganic anions, organic acids, anionic surfactants and polypho sphates after separation by capillary electrophoresis (CE). FMN provides a good wavelength match for laser excitation at 488 nm, is readily soluble in aqueous or aqueous/organic solutions, and unlike fluorescein provides stro ng fluorescence at both acidic and basic pH values. Analyte peaks due to a loss in FMN fluorescence are generated at weakly alkaline pH values as expe cted, but peak direction is switched at more alkaline pH values such as 8.6 or 9.0. A separation of 21 inorganic anions and organic acids is possible in about 20 min using the indirect LIF mode using 10 mu M FMN with 2 mM die thylenetriamine as the electroosmotic flow suppressor. Detection limits for these analytes are in the 10-20-mu g/l range without any required preconce ntration. The use of methanol improves resolution and facilitates the simul taneous separation of aliphatic/aromatic surfactant standard mixtures or co mmercial shampoos in less than 20 min. (C) 1999 Published by Elsevier Scien ce BN. All rights reserved.