In this paper, an adsorbent with dimethylamine ligand for endotoxin removal was prepared and used to study the adsorption isotherms of endotoxin and BSA. The results showed that as the introducing of endotoxin, the maximum adsorption capacity q(m) of BSA increased from 7.24 to 7.74 mg/mL and the apparent association constant K-A of BSA decreased from 14.06 to 11.48 mL/mg. The adsorption isotherms of BSA changed from Langmuir model to Multilayer model. All these gave the direct evidences to construct the adsorption process. By comparing adsorption isotherms of endotoxin with BSA, it was found that the apparent association constant K-A of endotoxin was much higher than that of BSA. (c) 2006 Elsevier Ltd. All rights reserved.