Evanescent-wave cavity ring-down spectroscopy for enhanced detection of surface binding under flow injection analysis conditions

In evanescent-wave cavity ring-down spectroscopy, one (or more) of the re°ections inside the cavity is a total internal re°ection (TIR) event. Only the evanescent wave associated with this TIR is being used for prob-ing the sample. This technique is therefore highly surface-speci-c and attractive for probing surface interactions, for example in °ow injection analysis (FIA). We show that is possible to do FIA using a °ow with 50 % of methanol in aqueous bu®er, enabling repeated measurements with-out contaminating the 45o BK7 Dove prism surface. The prism could be used for days without cleaning or realignment. Furthermore, prisms with di®erent coatings that are self-assembled to the silanol surface were used in cytochrome C adsorption studies.