Characterization of reaction variables

A microscale method of characterizing the strength of the affinity between a compound, or combination of compounds, and an immobilized ligand which have affinity for each other, comprising the steps of:

• (i) providing a microfluidic device comprising a microchannel structure comprising a reaction microcavity, said reaction microcavity comprising a solid phase to which the ligand is immobilized, wherein a) the microfluidic device comprises a substrate having an axis of symmetry and b) the microchannel structure is oriented radially relative to the axis of symmetry wherein the reaction microcavity is oriented at a larger radial distance from the axis of symmetry than a substructure delivering liquid to the reaction microcavity;
• (ii) introducing under flow conditions a sample containing the compound or combination of compounds into a reaction microcavity of the microchannel structure to form immobilized complexes of the compound or compounds with the ligand along the solid phase of the reaction microcavity, wherein the substrate is spun around its axis of symmetry to drive liquid within the microchannel structures;
• (iii) measuring the distribution of the formed complexes in the solid phase within said reaction microcavity along the flow direction of the solid phase, and
• (iv) determining the strength of the affinity between a compound, or combination of compounds, and the immobilized ligand based on the distribution of the formed complexes in the flow direction of the solid phase.