Detection of CrO4(2-) using a hydrogel swelling microcantilever sensor.

Hydrogels containing various mounts of tetraalkylammonium salts were used to modify microcantilevers for measurements of the concentration of CrO4(2-) in aqueous solutions. These microcantilevers undergo bending deflection upon exposure to solutions containing various CrO4(2-) concentrations as a result of swelling or shrinking of the hydrogels. The microcantilever deflection as a function of the concentration of CrO4(2-) ions is nearly linear in most concentration ranges. It was found that a concentration of 10(-11) M CrO4(2-) can be detected using this technology in a fluid cell. Other ions, such as Br-, HPO4(2-), and NO3-, have minimal effect on the deflection of this cantilever. The anions SO4(2-) and CO3(2-) could interfere with the CrO4(2-) detection, but only at high concentrations (> 10(-5) M). Such hydrogel-coated microcantilevers could potentially be used to prepare microcantilever-based chemical and biological sensors when molecular recognition agents are immobilized in the hydrogel.