Double-incident angle technique for surface plasmon resonance measurements

A new double-incident angle technique for surface plasmon resonance measurement is described. It is based on differential measurements at two chosen incident angles where the slopes are steepest and the reflectance changes are the biggest. The technique is as simple and robust as the conventional SPR detection measuring the reflected intensities using convergent light beam, but it has the advantage of being nonsensitive to variations of the resonance width and providing a higher sensitivity. Different concentrations of NaCl solutions are used to test the method. Compared with traditional single-incident angle method, sensitivity of this new method is improved by approximately 59%. It can be applied in genomics, proteomics, medical diagnostics, and many other fields of science and industry where a real time ultra-sensitive analysis of adsorption or of analyte-receptor binding is of interest.