Method for the determination of species in solution with an optical wave-guide
First Claim
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1. A method of determining the presence of an analyte in solution, which comprises the steps of:
- (a) applying a film of a reactant to a surface of an optical waveguide 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;
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Abstract
An analyte in solution is made to react with a spectific reactant coated on the wave-guide thus modifying the optical properties thereof. The index of refraction of the wave-guide material is higher than that of the reaction medium which ensures that a light signal injected into said guide be carried by multiple total reflection, the distance of penetration of the evanescent wave associated with the totally reflected signal being of the same order of magnitude or greater than the thickness of the analyte-reactant product layer.
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17 Claims
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1. A method of determining the presence of an analyte in solution, which comprises the steps of:
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(a) applying a film of a reactant to a surface of an optical waveguide 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; - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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2. (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 reactant to form a layer of analyte-reactant product on said waveguide of a thickness less than λ
- ; and
(d) controlling the depth of penetration dp of said evanescent light component associated with said signal in said waveguide in accordance with the relation
space="preserve" listing-type="equation">dp=λ
/2π
(sin.sup.2 θ
-(n.sub.2 /n.sub.1).sup.2).sup.1/2so that said depth of penetration dp substantially matches or exceeds the thickness of said analyte-reactant 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.
- ; and
Specification