Method of self-compensating a fiber optic chemical sensor

• US 5,094,958 A
• Filed: 08/30/1990
• Issued: 03/10/1992
• Est. Priority Date: 08/30/1990
• Status: Expired due to Fees

• Current Assignee: FiberChem, Inc.
• Original Assignee: FiberChem, Inc.
• Inventors: Klainer, Stanley M., Goswami, Kisholoy
• Primary Examiner(s): Lacey, David L.
• Assistant Examiner(s): Daley, Thomas E.
• Application Number:
  US07/575,165
• Time in Patent Office: 558 Days
• Field of Search: 436/166, 436/172, 436/805, 356/320, 356/408, 356/318, 356/250, 356/319, 250/227.23, 250/227.21, 250/227.28, 250/458.1, 250/461.2, 250/226, 350/96.29, 350/96.33
• US Class Current: 436/172
• CPC Class Codes: G01J 3/427 Dual wavelengths spectrometry
• CPC Class Codes: G01N 2021/6421 Measuring at two or more wavelengths
• CPC Class Codes: G01N 2021/6432 Quenching
• CPC Class Codes: G01N 2021/6434 Optrodes
• CPC Class Codes: G01N 2021/6441 with two or more labels
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 21/648 using evanescent coupling or surface plasmon coupling for the excitation of fluorescence
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B

Abstract

A chemical sensor, such as a fiber optic chemical sensor, is self-calibrated by measuring two output values which behave differently in response to an analyte, and forming a ratio between the two measured output values to cancel out effects of variations in external factors such as temperature variations, differences between coatings, light (illuminator) variations, fouling, bleaching, leaching or the like. An indicator material may be used which produces both fluorescence and phosphorescence, both monomer and aggregate emission or absorption bands, emission or absorption bands with or without an isosbestic point, emission peaks at one wavelength at two different excitation bands, or emission peaks at two wavelengths for excitation at two wavelengths.

Claims

1. A method of self-compensating a chemical sensor for variations in external factors when detecting oxygen, comprising:

forming the sensor with an indicator material of biacetyl which produces both fluorescence emissions at 450 nm and 490 nm and phosphorescence emissions at 518 nm and 570 nm, only the phosphorescence emissions of which are analyte specific;

exciting the indicator material at 420 nm to produce fluorescence and phosphorescence peaks at said wavelengths;

forming a ratio of a fluorescence peak intensity at 450 nm or 490 nm to a phosphorescence peak intensity at 518 nm or 570 nm;

determining oxygen changes from the ratio.

2. A method of self-compensating a chemical sensor for variations in external factors when detecting pH, comprising:

forming the sensor of an indicator material of a mixture of crystal violet and polyacrylic acid which is excitable at a first wavelength of 508 nm and second wavelength of 590 nm;

exciting the indicator material at the first and second wavelengths;

measuring emission intensity peaks of the indicator material at 635 nm and 740 nm when excited at the first and second wavelength;

forming a ratio of the emission intensity peaks at 635 nm and 740 nm when excited at the first and second wavelength;

determining pH changes from the ratio.

3. A method of self-compensating a chemical sensor for variations in external factors when detecting chlorine, comprising:

forming the sensor with an indicator material of congo red which produces an absorption spectra which has an isosbestic point at 560 nm and at 800 nm and absorption peaks at 500 nm and 650 nm;

exciting the indicator material to produce the absorption spectra;

forming a ratio of a peak intensity of the absorption spectra at 500 nm or 650 nm to the intensity at the isosbestic point at 560 nm or 800 nm;

determining chlorine changes from the ratio.

4. A method of self-compensating a chemical sensor for variations in external factors when detecting oxygen, comprising:

forming the sensor with an indicator material of a solution of pyrene in toluene which produces both a monomer emission band between 360-420 nm and an aggregate emission band between 440-640 nm which have different quenching rates for oxygen;

exciting the indicator material to produce the monomer and aggregate bands;

forming a ratio of a monomer band peak intensity at 390 nm to an aggregate band peak intensity at 480 nm;

determining oxygen changes from the ratio.

5. The method of claim 4 comprising forming the indicator material of a 10^-3 M solution of pyrene in toluene.

6. A method of self-compensating a chemical sensor for variations in external factors when detecting pH comprising:

forming the sensor of an indicator material of hydroxypyrenetrisulfonate which produces an emission intensity at a single wavelength of 570 nm which has a first peak in a first excitation band between 380-410 nm and a second peak in a second excitation band between 420-480 nm;

exciting the indicator material at the first and second excitation bands;

measuring emission intensity peaks at 570 nm when excited at the first and second excitation bands;

forming a ratio of the emission intensity peaks at 570 nm when excited at the first and second excitation bands;

determining pH changes from the ratio.