Weak affinity interactions among biomolecules have attracted more and more attentions for they play a significant role in organisms. However, it is difficult to characterize these interactions due to the limitation of the detection approaches. The biosensor based on total internal reflection imaging ellipsometry (TIRIE) is a real-time analysis method for biomolecular interaction detection with the advantages of high throughput and sensitivity. The interaction between tris and lysozyme (LZM), a typical example of weak affinity interactions, has been detected with TIRIE as a trial. Tris is immobilized on the gold thin film substrate to form the biosensing surface and then LZM as well as its negative controls is delivered to the tris-immobilized surface. The interaction process between tris and LZM is recorded by TIRIE biosensor to forma real-time curve and its dissociation constant is deduced as 7.6 x 10(-5) M, which is in agreement with the results in the reported work by other investigators. The results indicate that TIRIE biosensor is competent for weak affinity interaction analysis. (C) 2014 Elsevier B.V. All rights reserved.