L. De Boni et al., Experimental observation of light-induced solitary waves of analyte bands in capillary electrophoresis, ELECTROPHOR, 20(12), 1999, pp. 2493-2500
The phenomenon of electrophoresis in free solution has been studied theoret
ically down to the molecular level for decades. In addition, intermolecular
photo-induced proton transfer reactions, which occur in a wide class of mo
lecules (phenols and aminoarenes) as well as proteins (green fluorescent pr
otein), were also studied extensively. However, the study of the effect of
light-induced electrophoretic mobility changes of the analytes in electroph
oresis was begun only recently. In the present work, capillary zone electro
phoresis was chosen as the environment to measure the magnitude of these el
ectrophoretic mobility shifts induced by light. Background electrolytes (ru
nning electrolytes) with high refractive indices were developed, allowing t
he capillary to work like an optical fiber. The experimental conditions for
obtaining stable coupling and guided laser light along the liquid core are
discussed. Experimental evidence of band compression is observed, leading
to a solitary wave behavior of the analyte band (2-naphthol). These solitar
y waves result from competition between thermal diffusion (dispersion mecha
nism) and a nonlinear (band compression) effect due to the combined electro
phoresis phenomenon and absorption of guided light by the molecules of the
band (which are subjected to a "reversible intermolecular proton transfer r
eaction" as one of their decay routes). The possibilities of applying this
effect to different methods and techniques are also discussed.