Enhancement of Fluorescence in Thin-Layer Chromatography Induced by the Interaction between n-Alkanes and an Organic Cation

• Published in: Analytical chemistry (Washington) Vol. 72; no. 8; pp. 1759 - 1766
• Main Authors: Cossío, Fernando P, Arrieta, Ana, Cebolla, Vicente L, Membrado, Luis, Domingo, María P, Henrion, Patrick, Vela, Jesús
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-04-2000
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Fluorescence; Other chromatographic methods; Pentacyclic compound; MO method; Fluorescence detector; Organic cation; Coating material; Frontier orbital; Aliphatic compound; Molecular dynamics method; Theoretical study; Molecular interaction; Ionic interaction; Thin layer chromatography; Separation method; Analysis method; Alkane; Molecular association; Oxygen nitrogen heterocycle
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac991302q

Fluorescence enhancement of a broad variety of solutes has been used extensively in TLC although no thorough explanation has been proposed. In this work, 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 sulfate. 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 interaction between alkanes and berberine sulfate is responsible for the enhancement of fluorescence produced by alkanes. Computational results suggest that the surrounding alkane molecules provide an apolar environment to the berberine cation, thus enhancing the intensity of the fluorescence signal. This proposed explanation has been tested by extending the fluorescence determination to other compounds. These include biologically interesting saturated and unsaturated fatty acids, steroids and derivatives, prostaglandins, ceramides, galactocerebrosides, as well as terpenes, and polypropylene glycols. In addition, according to the proposed explanation, the properties required for alternative impregnants to berberine are discussed.