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Method for the determination of species in solution with an optical wave-guide

  • US RE33,064 E
  • Filed: 10/09/1987
  • Issued: 09/19/1989
  • Est. Priority Date: 09/18/1981
  • Status: Expired due to Term
First Claim
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1. A method of determining the presence .Iadd.and concentration .Iaddend.of an analyte in solution, which comprises the steps of:

  • (a) applying a film of a reaction to a surface of an optical waveguide .Iadd.core .Iaddend.having a refractive index n1 ;

    (b) .[.injecting a light signal of a wave length λ

    into said waveguide at one end thereof and measuring at another end of said waveguide a light signal modification resulting from an evanescent light component associated with said signal in said waveguide, said light signal being internally reflected at an angle θ

    of internal reflection.]. .Iadd.contacting said film with a solution of an analyte in a liquid phase of refractive index n2 less than n1, whereby said analyte reacts with said reaction to form an analyte/reactant reaction product layer at the surface of said waveguide core, .Iaddend.(c) .[.contacting said film with a solution of an analyte in a liquid phase of refractive index n2 less than n1 whereby said analyte reacts with said reactance to form a layer of analyte-reactant product on said waveguide of a thickness less than λ

    ; and

    .]. .Iadd.injecting a light signal of waveguide λ

    into said waveguide core at an input thereof, whereby said light signal is internally reflected through said waveguide core at an angle θ

    of internal reflection and evanescent wave component of said light signal interacts with said analyte/reactant product at the surface of said waveguide core which interaction results in a modification of said light signal representing presence and concentration of said analyte, .Iaddend.(d) controlling the depth of penetration dp of said evanescent .[.light.]. .Iadd.wave .Iaddend.component .[.associated with said signal in said waveguide.]. .Iadd.into said liquid phase .Iaddend.in accordance with the relation;

    ##EQU3## so that said depth of penetration dp substantially matches or exceeds the thickness of said .[.analyte-reactant.]. .Iadd.analyte/reactant .Iaddend.product layer .[.and the measurement in step (b) takes place while the reaction occurs without interference from spurious signals from the liquid phase surrounding said layer..]..Iadd., and(e) measuring at an output of the waveguide core said light signal modification while the reaction occurs without interference from spurious signals from the liquid phase surrounding said layer.Iaddend..

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