Enhancement of fluorescence in thin-layer chromatography induced by the interaction between n-alkanes and an organic cation

Fluorescence enhancement of a broad variety of solutes has been used extens ively in TLC although no thorough explanation has been proposed. In this wo rk, we try to understand it and explore new applications to which it can be put. In this way, alkanes can be quantitatively determined by fluorescence scanning densitometry using silica gel plates impregnated with berberine s ulfate. Molecular simulation and analysis of molecular orbitals allows this phenomenon to be explained in this case and lays the groundwork to explain fluorescence enhancements produced by other molecules. A ion-molecule inte raction between alkanes and berberine sulfate is responsible for the enhanc ement of fluorescence produced by alkanes. Computational results suggest th at the surrounding alkane molecules provide an apolar environment to the be rberine cation, thus enhancing the intensity of the fluorescence signal. Th is proposed explanation has been tested by extending the fluorescence deter mination to other compounds. These include biologically interesting saturat ed and unsaturated fatty acids, steroids and derivatives, prostaglandins, c eramides, galactocerebrosides, as well as terpenes, and polypropylene glyco ls. In addition, according to the proposed explanation, the properties requ ired for alternative impregnants to berberine are discussed.