| abstract |
A method of assaying for an analyte in a fluid sample comprises detecting the presence of the analyte by determining the resulting change in refractive index at a solid optical surface in contact with the sample, which change is caused by the analyte involving or influencing the binding or release of a refractive index enhancing species to or from, respectively, the optical surface. According to the invention, the determination is performed with light having a wavelength at or near the maximum of the negative derivative of the absorptivity with respect to wavelength of said refractive index enhancing species to obtain maximum sensitivity. |