Spectroscopic analysis of chemical substances

• US 4,195,641 A
• Filed: 12/15/1977
• Issued: 04/01/1980
• Est. Priority Date: 12/15/1977
• Status: Expired due to Term

• Current Assignee: SCI Development Corporation
• Original Assignee: Alexander Spock, Larry W. Burton, Marc D. Rafal, William T. Joines
• Inventors: Burton, Larry W., Joines, William T., Rafal, Marc D., Spock, Alexander
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US05/860,983
• Time in Patent Office: 838 Days
• Field of Search: 356/85, 356/86, 356/311, 356/313, 356/417, 128/2 A, 128/2 E, 128/2 W, 128/2.1 R, 128/2.1 E, 128/632
• US Class Current: 600/346
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/4266 sweat secretion
• CPC Class Codes: A61B 5/441 Skin evaluation, e.g. for skin disorder diagnosis
• CPC Class Codes: G01N 21/66 electrically excited, e.g. electroluminescence

Abstract

An intense electric field is employed as the external source of energy in carrying to a spectroscopic analysis of a chemical composition. The substance to be analyzed is placed between an insulated conductive electrode and a ground reference. A high voltage is then applied to the electrode to generate an electric field of a predetermined intensity within the test sample. As a result of the energy absorbed, the constituents of the sample are caused to release their characteristic spectral emissions. These emissions are optically filtered to isolate the wavelength of interest which is passed to a light detector and registered on a photon counting system. The procedure is especially and uniquely applicable for conducting an in situ chemical analysis of human sweat, thus offering a valuable aid in the diagnosis of various medical abnormalities.

Claims

1. A method for carrying out a non-destructive, spectroscopic analysis of a chemical substance which comprises:

(a) positioning a test sample of the chemical substance to be analyzed between an insulated conductive electrode and a ground reference;

(b) stimulating the components of said chemical test sample to emit their characteristic optical spectra by establishing an electric field on and within said sample of at least 10⁶ volts per meter with said electric field being generated by the application of an appropriate potential to said insulated electrode;

(c) filtering the optical spectra emitted from said test sample to segregate for further processing those spectral emissions having a selective wavelength which identifies the chemical element of interest;

(d) detecting the emitted light energy at said selected wavelengths; and

(e) determining the intensity of said detected light energy as a measure of the concentration of said chemical element in said chemical substance.

2. The method according to claim 1 wherein a DC potential is applied to said insulated electrode to generate said electric field.

3. The method according to claim 1 wherein an AC potential having a frequency less than that at which electromagnetic resonance would be caused to occur in said chemical test sample is applied to said insulated electrode to generate said electric field.

4. A method for carrying out a chemical analysis of human sweat in situ which comprises:

(a) positioning an appendage of the human body such that a portion of the skin thereof is in contact with a glass-encapsulated, conductive electrode;

(b) stimulating the chemical constituents present in the sweat secreted from the intraepidermal sweat ducts to emit their characteristic optical spectra by establishing an electric field of at least 10⁶ volts per meter on said portion of skin in contact with said glass-encapsulated electrode, and wherein said electric field is generated by applying an AC potential of appropriate magnitude to said electrode with the frequency of the applied potential being less than that at which electromagnetic resonance would be caused to occur within the sweat being tested;

(c) filtering the optical spectra emitted from the sweat secreted from the intraepidermal ducts of the skin in contact with said glass-encapsulated electrode to isolate selective wavelengths which are identified with a particular chemical constitutent of interest in said sweat;

(d) detecting the emitted light energy at said selective wavelengths; and

(e) determining the intensity of said detected light energy as a measure of the concentration of said chemical constituent within said sweat.

5. The method according to claim 4 wherein a forearm of the human body is positioned such that a portion of the skin thereof is in contact with said glass-encapsulated electrode.

6. The method according to claim 4 wherein said selective wavelengths are those approximating 589 nanometers which is an emission characteristic of sodium.

7. An apparatus for conducting a non-destructive, spectroscopic analysis of a chemical substance which comprises:

(a) an electrode encapsulated with an electrical insulator;

(b) means for positioning a test sample between said insulated electrode and an electrical ground reference;

(c) power means for supplying said electrode with a voltage appropriate for generating an electric field on and within said test sample of at least 10⁶ volts per meter wherein the chemical constituents of said test samples are inducted to emit their characteristic optical spectra;

(d) an optical filter positioned proximate said electrode and disposed to receive the light emitted from said test sample;

(e) light sensor means disposed to receive the light emissions which are allowed to pass through said optical filter; and

(f) means connected to the output of said sensor means for registering a measurement of the intensity of the light emissions received by said sensor means.

8. The apparatus according to claim 7 wherein the electrode and its insulation are opaque and wherein said optical filter and light sensor means are disposed above said electrode in horizontal alignment with said test sample.

9. The apparatus according to claim 7 wherein said electrode is semi-transparent and said insulator is transparent and said filter is positioned to receive said light after it has passed through said electrode and the electrical insulation which envelops it.

10. An apparatus for performing a spectroscopic, chemical analysis of human sweat in situ which comprises:

(a) a conductive wire mesh electrode encapsulated in an electrical insulator consisting of transparent glass and wherein said glass-encapsulated electrode is adapted to support an appendage of the human body placed in contact with said glass insulation for analyzing the sweat secreted from the intraepidermal sweat ducts within the skin of said appendage;

(b) power means for supplying said electrode with an appropriate AC voltage for generating an electric field of at least 10⁶ volts per meter on the skin of said appendage in contact with the glass insulation of said electrode and wherein the frequency at which said voltage is applied is less than that at which electromagnetic resonance would be caused to occur within the sweat being tested, and wherein as a result of the absorption of energy from the electric field the chemical constituents of said sweat are induced to emit their characteristic spectra;

(c) an optical filter positioned beneath said electrode and disposed to receive the light emitted from said sweat after said light has passed through said wire mesh electrode and the transparent glass insulation in which said electrode is encapsulated;

(d) light sensor means disposed to receive the light emissions which are allowed to pass through said optical filter; and

(e) means connected to the output of said sensor means for registering a measurement of the intensity of the light emissions received by said sensor means.

11. The apparatus according to claim 10 wherein said glass insulation has an electrical conductivity of between 0.1 and 0.001 times the conductivity of the skin in contact therewith.