A piezoelectric immunosensor based on a competitive format was developed for determination of ochratoxin A (OTA) concentration. Surface modifications via two self-assembled monolayers (SAMs) were investigated respectively and a better result was obtained with the SAM of 16-mercaptohexadecanoic acid (16-MHDA). The quartz crystal microbalance (QCM)-based immunosensor was fabricated by immobilizing anti-OTA antibodies onto the surface of the 16-MHDA-modified electrode, and allowing competition between free OTA and that conjugated with BSA to occur. The assay exhibited a working range of 50-1000 ng/mL and a detection limit of 16.1 ng/mL. Studies of interference and matrix effects were performed to evaluate the feasibility of the developed immunosensor for the direct analysis of OTA in real samples. Recoveries were conducted at 50, 200, and 1000 ng/g and were determined to be in the range of 142%-76%. The OTA assay is specific. No cross-reactivates were observed with citrinin.
