Microsecond analysis of transient molecules using bi-directional capillary electrophoresis.

We demonstrate the feasibility for minimizing electrophoretic analysis times of transient chemical species by inducing nascent, oppositely charged photochemical products to migrate in opposite directions from their point of creation. In this approach, separate probe sites are positioned within an electrophoretic channel both upfield and downfield from a photoreaction site formed by high-numerical-aperture optics, with positively charged (and in some cases neutral) components migrating toward one probe site and negatively charged species migrating in the opposite direction, toward the second probe site. As a proof-of-concept, fluorescent photoproducts of the hydroxyindoles, 5-hydroxytryptamine (serotonin), 5-hydroxytrptophan, and 5-hydroxyindole-2-carboxylic acid, are formed within a geometrically modified capillary and are transported electrophoretically and electroosmotically to probe sites several micrometers away. Although it is possible to detect all components in a single channel, or to use a two-cha...