Abstract: Biochemical Assay Methods. There is described a method for determining a value that allows the effect that a compound has on a target to be compared with the effect that another compound has on the target, which method comprises adding the compound, at a concentration which continuously varies with time, to a flow of the target. The method can be carried out using a microfluidic system.

Abstract: A microfluidic system comprising: at least one microfluidic channel, the inner surface of which is fluorinated or fluorous; and a pump for supplying a flow of an aqueous medium containing chemical reagents or assay components to said microfluidic channel. Preferably, the apparatus further comprises a supply of a non-aqueous medium which is compatible with the surface of the microfluidic channel but immiscible with the aqueous medium, such as a perfluorocarbon solvent, for forming a sheath around the flowing aqueous medium whereby the aqueous medium is suspended away from the surface of the microfluidic channel. Also provided are methods for carrying out a chemical reaction or a biological assay in the microfluidic systems of the subject matter disclosed herein.