Detection of low molecular weight toxins using optical phase detection techniques

Abstract Optical methods based on recording a phase shift of electromagnetic waves offer high sensitivity for detection of bio-reactions. The method of Total Internal Reflection Ellipsometry (TIRE), which records simultaneously two parameters Ψ and Δ related, respectively, to the amplitudes and phases of p- and s-components of polarized light, was exploited here for detection of mycotoxins (T-2, zearalanone, and aflatoxin). The TIRE direct label-free immunoassay enables detecting the above mycotoxins in sub-ppb concentrations in water as well as in food extracts. Further enhancement of sensitivity can be achieved with the use of SiO 2 /Si 3 N 4 /SiO 2 planar waveguides operating as polarization interferometers (PI).