ELECTROCHEMICAL OXYGEN DEMAND SYSTEM

• US 3,676,321 A
• Filed: 07/27/1970
• Issued: 07/11/1972
• Est. Priority Date: 07/27/1970
• Status: Expired due to Term

• Current Assignee: John P. Cummings, Richard E. Berg
• Original Assignee: John P. Cummings, Richard E. Berg
• Inventors: Cummings, John P., Berg, Richard E.
• Primary Examiner(s): Tung, T.
• Application Number:
  US05/058,254
• Time in Patent Office: 715 Days
• Field of Search: 204/1T,195R,195B
• US Class Current: 204/406
• CPC Class Codes: G01N 33/1806 biological or chemical oxygen demand (BOD or COD)
• CPC Class Codes: G01N 33/1893 using flow cells

Abstract

A method and system for the determination of organic and inorganic waste products present in aqueous samples, the arrangement including cell means for receiving a flow of an aqueous sample therethrough with means for delivering a predetermined quantity of a water soluble electrolyte into said sample prior to passing through said cell. Heating means are provided for maintaining the sample at a predetermined temperature level as it passes through said cell. The cell includes a plurality of space electrodes including a reference electrode, an indicating electrode, and a common electrode in circuit with said reference and indicating electrodes. A first circuit is coupled to the reference and common electrodes and a unipolar electrical signal is impressed thereacross, the magnitude being sufficient for aqueous electrolysis, A second circuit means is coupled to said indicating and common electrodes and delivers a scanning signal of a programmed potential magnitude with periodic increases and decreases in respect to time, the peak magnitude of said scanning signal being less than that required for aqueous electrolysis. Readout means are arranged in series with said indicating and common electrodes for determining the current flow through said second circuit means in response to the scanning signal. The system is also useful for the determination of carbon monoxide in gaseous atmospheres.

Claims

1. In a system for the determination of the electro-activity of ingredients present in aqueous samples:

a. cell means for receiving an aqueous sample containing a supporting electrolyte and electro-active components undergoing determination;

b. a plurality of spaced electrodes including a reference electrode, an indicating electrode, and a common electrode, each electrode being disposed within said cell and in contact with said sample;

c. first circuit means coupled to said reference electrode and common electrode for impressing a unipolar electrical signal thereacross of a magnitude sufficient for aqueous electrolysis, and adapted to deliver a current of constant magnitude;

d. second circuit means coupling said common electrode to said indicating electrode;

e. signal generating means in said second circuit means for applying a unipolar scanning signal across said indicating electrode and said common electrode, said scanning signal having a programmed potential magnitude with predetermined increases and decreases with time; and

f. electrical current read-out means in said second circuit means and in series with said common electrode and said indicating electrode for detErmining the current flow through said second circuit means in response to said scanning signal.

2. The system as defined in claim 1 being particularly characterized in that means are provided for maintaining said aqueous sample at a substantially constant temperature.

3. The system as defined in claim 1 being particularly characterized in that heating means are provided for maintaining said sample at a certain predetermined temperature.

4. The system as defined in claim 1 being particularly characterized in that means are provided for passing a fluid sample undergoing determination through said cell.

5. The system as defined in claim 1 being particularly characterized in that means are provided for moving a gaseous fluid sample containing an electro-active component through said cell.

6. The system as defined in claim 1 being particularly characterized in that said indicating electrode and common electrode are spaced apart by a predetermined distance and wherein said reference electrode and said common electrode are spaced apart by a distance which is greater than said predetermined distance.

7. In a system for the substantially continuous determination of electro-activity of ingredients present in aqueous samples:

a. cell means for receiving a flow of an aqueous sample with means for delivering and discharging the flow of said sample to and from said cell;

b. means delivering a predetermined quantity of a water soluble electrolyte into said sample for maintaining said electrolyte in said sample at a predetermined concentration level;

c. a plurality of spaced electrodes including a reference electrode, an indicating electrode, and a common electrode, each electrode being disposed within said cell and in contact with said sample;

d. heating means for maintaining said sample at a certain predetermined temperature level within said cell;

e. first circuit means coupled to said reference electrode and common electrode for impressing a unipolar electrical signal thereacross of a magnitude sufficient for aqueous electrolysis, and adapted to deliver a current of constant magnitude;

f. second circuit means coupling said common electrode to said indicating electrode;

g. signal generating means in said second circuit means for applying a unipolar scanning signal across said indicating electrode and said common electrode, said scanning signal having a programmed potential magnitude with predetermined increases and decreases with time; and

h. electrical current read-out means in said second circuit means and in series with said common electrode and said indicating electrode for determining the current flow through said second circuit means in response to said scanning signal.

8. The system as defined in claim 7 being particularly characterized in that said spaced electrodes are arranged along a predetermined line.

9. The system as defined in claim 8 being particularly characterized in that said indicating and common electrode are spaced apart by a predetermined distance and wherein said reference electrode and said common electrode are spaced apart by a distance which is greater than said predetermined distance.

10. The system as defined in claim 7 being particularly characterized in that said signal generating means in said second circuit means is coupled to a source of electrical energy and is adapted to apply a unipolar scanning signal of a magnitude less than that required for aqueous electrolysis.

11. The system as defined in claim 7 being particularly characterized in that each of said electrodes consists of a precious metal.

12. The system as defined in claim 11 wherein each of said electrodes consists essentially of platinum.

13. The system as defined in claim 9 being particularly characterized in that said distance between said reference electrode and said common electrode is twice said predetermined distance.

14. The system as defined in claim 7 being particularly characterized in that said sCanning signal has a peak amplitude less than about 2.5 volts.

15. The system as defined in claim 7 being a particularly characterized in that said indicating electrode and common electrode are spaced apart by a certain predetermined distance, and wherein said reference electrode and said common electrode are spaced apart by a distance which is greater than said predetermined distance.