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

Claim 3

The method of claim 1, characterized in that said penetration depth is such that the electric field E at this depth Z is at least 0.1 Eo and preferably Eo/3, Eo being the electric field at zero depth.

Claim 4

The method of claim 1, characterized by the steps of contacting a section of the waveguide core coated with a thin film of the reactant specific to the analyte with a solution of said analyte thereby enabling said analyte to react with said reactant of said film and to form the reaction product layer, observing as a function of time the corresponding modification of the parameter of the light travelling through the core at the output of said core as the result of the reaction product layer formation and correlating the rate data so obtained with corresponding standard reference rate data obtained in a similar manner from calibrating samples of said analyte, the waveguide core used being non porous.

Claim 5

The method of claim 1, characterized by the steps of coating a section of the waveguide core with a reference quantity of the analyte to be determined, injecting light into an input of said section, contacting said lit section with the analyte solution while adding beforehand or simultaneously thereto a reference amount of the reactant for causing the latter to competitively react with the analyte in the solution and said reference quantity on the section, observing as a function of time the corresponding light parameter modification at an output of said section as the result of said reaction between the reactant and said reference quantity and comparing the rate data so obtained with standard reference rate data obtained in a similar manner from calibrating samples or solutions of said analyte, the waveguide core used being non porous.

Claim 6

The method of claim 3, in which there is added to the solution a tracer quantity of pure analyte in labelled form, the presence of said label in the reaction product layer on the waveguide core causing the said light parameter modification, the magnitude of said modification being in direct relation with the ratio of labelled analyte to analyte in the solution.

Claim 7

The method of claim 3, characterized by the steps of using a waveguide core with a coating of the reactant in excess of that stoichiometrically needed for binding the analyte in the solution to be determined, contacting said coated waveguide core with the solution for totally binding any analyte contained in the solution, adding to the solution a reference amount of analyte in pure labelled form to react with the still unused excess of reactant, the presence of said label in the reaction product causing the said modification, the magnitude of said modification being in direct proportion to the ratio of the labelled analyte to the analyte originally in the solution.

Claim 8

The method of claim 3, characterized in that the analyte contained in the solution possesses more than one binding site for specifically binding at least two kinds of reactants, and by the steps of contacting said waveguide core coated with the first kind of reactant with said solution, adding a reference quantity of the second kind of reactant for causing said second kind to bind to a second binding site of said analyte, the light parameter modification being the result of the binding of said second kind to the said second binding site of the analyte bonded by its first binding site to said first kind of reactant on the waveguide core.

Claim 13

The method of claim 10, characterized in that the waveguide core is a single-mode or multi-mode optical fiber core.

Claim 14

The method of claim 11, characterized in that a multi-mode fiber is used, and comprising the steps of using modes sufficiently shallow, with regard to the fiber axis, to ensure total reflection and sufficiently steep to ensure a high linear density of light signal coating interaction sites.

Claim 15

The method of claim 11, characterized in that the waveguide core is a multi-mode fiber and in that the modes are selected with an initial reflecting angle close to the critical angle, whereby in the course of the reaction a slight change of the refractive index n 2 that occurs due to the growing of the reaction product layer will result in partial or total refraction of the light outside the core.

Claim 16

An apparatus for carrying out the method of claim 1, comprising: -a light source (8; 43; 70; 107), -an optical waveguide (1; 41; 71; 101) having a core section which may be exposed to a solution containing an analyte to be measured, said core section having a refractive index n, higher than the refractive index n 2 of said solution and carrying a coating of a reactant specific to the analyte, -optical elements (9, 10, 11; 47-52; 70; 105) arranged to inject light from said light source into said waveguide so as to enable propagation of the injected light through the core section by multiple internal total reflection at a reflection angle 0, -light detecting means (12; 58; 78; 124) arranged to receive light emerging from said waveguide and to convert it to an electrical signal reflecting a modification which a parameter of the injected light may have suffered in response to the penetration of the propagating light into a reaction product layer forming on the surface of the core section as a result of a reaction between the reactant and the analyte, -circuit means (13, 14; 55; 61, 62; 81-86; 115-117) for determining, from said electrical signal, data representative of said reaction, the apparatus being characterised in that, -the optical elements (9, 10, 11; 47-52; 70; 105) are arranged to inject said light into said waveguide (1; 41; 71; 101) at a front face thereof extending transversely to the direction of light propagation inside the waveguide, -the light detecting means (12; 58; 78; 114) are arranged to collect said light emerging from the waveguide at a rear face thereof also extending transversely to the direction of light propagation, and -the ratio n l /n 2 and 8 are so selected that the depth z to which the electric field of the evanescent waves, occurring outside the core section due to the total reflection of the light guided inside, penetrates into the surroundings of the core section matches or exceeds the thickness of said reaction product layer.

Claim 17

The apparatus of claim 15, characterized in that the waveguide is in the form of a plate (41; 71) or a fiber (1; 101) of refractive index in the range of about 1.4 to about 3.5.

Claim 18

The apparatus of claim 15, characterized in that the modified light emerges as fluorescent or partly absorbed light.

Claim 19

The apparatus of claim 15, characterized in that the waveguide is in the form of a spirally coiled optical fiber.

Claim 20

The apparatus of claim 16, characterized in that a counterplate (42; 72) is arranged in non-touching close parallel relationship with the waveguide plate (41; 71), the reaction taking place in the space provided between said plates, the reaction medium being held in place by capillary forces.