Micro chemical analysis employing flow through detectors

• US 5,444,807 A
• Filed: 05/13/1994
• Issued: 08/22/1995
• Est. Priority Date: 03/29/1993
• Status: Expired due to Term

• Current Assignee: World Precision Instruments Inc.
• Original Assignee: World Precision Instruments Inc.
• Inventors: Liu, Su Y.
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Sanghavi, Hemang
• Application Number:
  US08/242,739
• Time in Patent Office: 466 Days
• Field of Search: 385/125, 385/12, 385/13, 385/123, 385/143, 250/227.25, 250/227.19
• US Class Current: 385/125
• CPC Class Codes: G01N 2021/0346 Capillary cells; Microcells
• CPC Class Codes: G01N 2030/746 detecting along the line of flow, e.g. axial
• CPC Class Codes: G01N 2035/1062 for testing the liquid while it is in the transfer device
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 30/74 Optical detectors measurement of intensity, velocity, spectral content, polarisation, or phase of infrared, visible or ultraviolet light G01J
• CPC Class Codes: G02B 6/032 with non solid core or cladding G02B6/02295 takes precedence

Abstract

The chemical properties of a flowing liquid analyte, the analyte comprising a solvent having an index of refraction which is the same as or closely approaches that of water, are determined by liquid chromatography or capillary electrophoreses wherein the analyte is caused to flow through an optical waveguide. The waveguide is a rigid capillary having a refrctive index of less than 1.33. Measurement light is launched axially into the analyte by inserting an optical fiber, coupled to a light source, into one end of the waveguide.

Claims

1. A method of detecting the presence of an analyte in a solvent stream, said method comprising the steps of:

fabricating a waveguide capillary from a fluorocarbon polymer having a refractive index of less than 1.33, the capillary having spatially displaced inlet and discharge ports;

delivering the solvent containing the dissolved analyte to the inlet port of the waveguide;

maintaining a pressure differential between the waveguide inlet and discharge ports whereby a solvent stream will flow through the waveguide and will form the light transmitting core thereof;

inserting the first end of a first optical fiber into the waveguide core at a point displaced from the flow path between the inlet and discharge ports, the optical fiber being in intimate contact with the solvent;

coupling a source of measurement light to the second end of the first optical fiber whereby light will be launched into the solvent stream flowing between the waveguide inlet and discharge ports; and

receiving and analyzing light resulting from the passage of light from the source through the waveguide.

2. The method of claim 1 wherein the attenuation of light resulting from absorbance by the analyte is to be determined, the waveguide defined flow path is linear along at least a part of its length and the measurement light is launched into the solvent stream along the axis of said linear flow path.

3. The method of claim 2 wherein the first end of the first optical fiber is located adjacent to and in registration with a first end of the linear flow path and the step of receiving and analyzing includes:

positioning the first end of a second optical fiber adjacent to and in registration with the second end of the linear flow path to collect light which has passed through the waveguide liquid core.

4. The method of claim 2 wherein the first end of the first optical fiber is located adjacent to and in registration with a first end of the linear flow path and the step of receiving and analyzing includes:

positioning a mirror in registration with and adjacent to the second end of the linear flow path to cause light coupled to the wave guide core to be reflected and twice traverse the length of the linear flow path;

collecting the reflected light received at the first end of the linear flow path with the first optical fiber; and

separating the received reflected light from the light from the source and thereafter analyzing the separated light.

5. The method of claim 1 wherein the solvent is selected from the group consisting of aqueous solutions and methanol.

6. The method of claim 3 wherein the solvent is selected from the group consisting of aqueous solutions and methanol.

7. The method of claim 4 wherein the solvent is selected from the group consisting of aqueous solutions and methanol.

8. The method of claim 1 wherein the fluorescence resulting from the excitation of the analyte by the measurement light is to be measured and the step of receiving and analyzing includes juxtapositioning a light sensitive detector to the waveguide defined flow path along at least a portion thereof intermediate the inlet and discharge parts.

9. The method of claim 8 wherein the step of fabricating the wave guide includes causing at least a portion of the core region thereof to have an axis which lies in a plane and wherein the step of juxtapositioning the light sensitive detector comprises locating the detector so that it is symmetrical with respect to a plane which is substantially parallel to the plane of the waveguide core region.

10. The method of claim 8 wherein the step of receiving and analyzing further comprises:

positioning a reflector on the opposite side of the waveguide with respect to the detector.

11. The method of claim 9 wherein the waveguide core defines a non-linear flow path between the inlet and discharge ports.

12. The method of claim 11 wherein the step of receiving and analyzing further comprises:

positioning a reflector on the opposite side of the waveguide with respect to the detector.

13. The method of claim 1 wherein the measurement light is either ultraviolet or in the visible spectrum.

14. The method of claim 1 wherein the solvent is the effluent from chromatography or electrophoresis.

15. A flow-through cell for use in the measurement of chemical properties of small volumes of fluid containing dissolved analytes, said cell comprising:

a rigid capillary tube, said tube having a core region which defines a flow path, said flow path having an axis, said tube having a wall which interfaces with said core region, said wall having an index of refraction which is less than 1.32;

means defining an inlet port for delivery of a fluid to be analyzed to said core region, said inlet port providing fluid communication with said core region;

means defining a discharge port in fluid communication with said core region, said discharge port being displaced from said inlet port along said flow path, fluid delivered to said core region through said inlet port flowing along said flow path and exiting said core region through said discharge port;

means for transmitting light energy into said core region whereby the fluid to be analyzed will function as the light conducting medium of a liquid core waveguide, the guided light being generally coaxial with said flow path; and

light receiving means.

16. The flow-through cell of claim 15 wherein said capillary tube is comprised of a fluorocarbon polymer.

17. The flow-through cell of claim 15 wherein said flow path is at least in part linear between said inlet and discharge ports and said light transmitting means comprises a first optical fiber which directly communicates with said core region at a first end of said linear flow path port.

18. The flow-through cell of claim 17 wherein said light receiving means comprises a second optical fiber which directly communicates with said core region at the second end of said linear flow path port.

19. The flow-through cell of claim 17 further comprising:

a mirror positioned adjacent to the second end of said linear flow path port, said mirror reflecting light back along said flow path to said light energy transmitting means; and

whereas said light receiving means comprises;

said first optical fiber; and

means for separating reflected light received at said first optical fiber from measurement light delivered to said first optical fiber.

20. The flow-through cell of claim 15 wherein said light receiving means comprises:

a light sensitive detector positioned along at least a portion of said flow path on a first side thereof and external of said tube.

21. The flow-through cell of claim 20 wherein said light receiving means further comprises:

reflector means positioned on the opposite side of said tube with respect to said detector, said reflector means being shaped and located to reflect light passing through the tube wall to said detector.