Durable carbon electrode

• US 6,592,730 B1
• Filed: 02/07/2000
• Issued: 07/15/2003
• Est. Priority Date: 02/07/2000
• Status: Expired due to Fees

• Current Assignee: American Sterilizer Company (Steris Corporation)
• Original Assignee: Steris Corporation
• Inventors: Kelsch, Daniel N., McVey, Iain F., Lewandowski, Jan J.
• Primary Examiner(s): Tung, T.
• Application Number:
  US09/499,479
• Time in Patent Office: 1,254 Days
• Field of Search: 204/400, 204/412, 204/294, 204/286.1, 204/297.01
• US Class Current: 204/412
• CPC Class Codes: A61L 2/186 Peroxide solutions
• CPC Class Codes: A61L 2202/11 Apparatus for generating biocidal substances, e.g. vaporisers, UV lamps

Abstract

An electrochemical analysis system includes a chamber (34) that defines a fluid receiving reservoir therein. A working electrode (40), a reference electrode (42), and a counter electrode (44) is mounted to the chamber. An electrochemical analysis circuit (38) applies appropriate voltages to the electrodes and reads appropriate currents from the electrodes to provide an indication of the peroxyacetic acid concentration in a sample. The working electrode includes a glassy carbon rod (60) which is surrounded by a compressible polymeric sleeve (64) and a metal sleeve (66). One end of the metal sleeve is swaged (68) to form a fluid tight compression seal with the insulating sleeve and the glassy carbon rod. An electrically conductive thermal extension joint between the glassy carbon rod and an electrically conductive rod (70) includes a bore (72) in the conductive rod in which the glassy carbon rod is slidably received and a compressed spring (74) in the bore.

Claims

1. A disinfectant/sterilant system comprising:

a chamber which receives an item to be disinfected or sterilized;

a pump for pumping a peroxyacetic acid antimicrobial solution into the chamber; and

an electrochemical analysis chamber fluidly connected to receive the peroxyacetic acid solution flowing to the chamber, the electrochemical analysis chamber including;

a chamber which defines a fluid receiving reservoir;

a plurality of measurement electrodes disposed in the reservoir to be in electrical contact with solutions received in the reservoir, at least one of the electrodes including a brittle carbon rod supported and sealed in a metallic sleeve comprising a stainless steel tube, a sleeve of electrically insulating material surrounding the brittle carbon rod, formed of an oxidant-resistant polymer, the insulating sleeve compressing at a force below a compression force which fractures the brittle carbon rod, the metal sleeve being compressed beyond its elastic limit around the insulating sleeve to form a compression fitting with the insulating sleeve and the brittle carbon rod; and

an analysis control system connected with the electrodes for conducting electrochemical measurements which are indicative of peroxyacetic acid concentration.

2. The system as set forth in claim 1 further including an electrical connector interconnected with the carbon rod.

3. The system as set forth in claim 2 wherein the electrical connector includes a metallic fitting which is supported by and electrically insulated from a second end of the metallic sleeve.

4. The system as set forth in claim 3 wherein a second end of the metallic sleeve is compressed against an insulator sleeve to support and form a fluid-tight seal with the electrical connector.

5. The system as set forth in claim 2 wherein the electrical connector includes:

an electrically conductive rod that is connected with the carbon rod by an electrically conductive thermal expansion connection assembly.

6. The system as set forth in claim 5 wherein the thermal expansion connection assembly includes:

a bore defined in the electrically conductive rod which is sized and shaped to receive the carbon rod slidably therein.

7. The system as set forth in claim 1 wherein the metallic sleeve is a second electrode.

8. The system as set forth in claim 1 wherein the carbon is an amorphous carbon.

9. A disinfectant/sterilant system comprising:

a chamber which receives an item to be disinfected or sterilized;

a pump for pumping a peroxyacetic acid antimicrobial solution into the chamber; and

an electrochemical analysis chamber fluidly connected to receive the peroxyacetic acid solution flowing to the chamber, the electrochemical analysis chamber including;

a chamber which defines a fluid receiving reservoir, and

a plurality of measurement electrodes disposed in the reservoir to be in electrical contact with solutions received in the reservoir, at least one of the electrodes including a carbon rod supported and sealed in a metallic sleeve, an electrically conductive rod interconnected with the carbon rod by an electrically conductive thermal expansion connection assembly, the thermal expansion connection assembly including;

a bore defined in the electrically conductive rod which is sized and shaped to receive the carbon rod slidably therein,

a spring disposed in the bore of the rod in a compressed state to make frictional contact with the electrically conductive rod and the carbon rod; and

an analysis control system connected with the electrodes for making electrochemical measurements which are indicative of peroxyacetic acid concentration.

10. The system as set forth in claim 9 wherein the insulating sleeve is formed from an oxidant resistant polymer.

11. The system as set forth in claim 9 wherein the carbon is an amorphous glassy carbon.

12. An electrochemical analyzer comprising:

an electrochemical cell which defines a fluid receiving reservoir;

a plurality of measurement electrodes disposed in the reservoir to be in electrical contact with solutions received in the reservoir, at least one of the electrodes being a carbon electrode including;

a brittle, carbon rod, an electrically conductive rod supporting an end of the carbon rod,

a metallic sleeve, the carbon rod being supported and sealed in the metallic sleeve,

a first sleeve of electrically insulating material surrounding the carbon rod which compresses at a force below a compression force which fractures the carbon rod, the metallic sleeve being compressed around the first insulating sleeve to form a compression fitting with the first insulating sleeve and the carbon rod; and

a second sleeve of electrically insulating material, the metallic sleeve being compressed around the second insulating sleeve, whereby an electrically insulating, fluid-tight seal is formed with the electrically conductive rod; and

an analysis control system connected with the electrodes for reading at least one of voltages and currents therefrom which are indicative of a concentration of a target composition.

13. The electrochemical analyzer as set forth in claim 12 further comprising a thermal expansion connection assembly interconnecting the electrically conductive rod and the carbon rod, said connection assembly including:

a bore defined in the electrically conductive rod which is sized and shaped to receive the carbon rod slidably therein.

14. The electrochemical analyzer as set forth in claim 12 wherein the measurement electrodes further include:

a reference electrode; and

a counter electrode.

15. The electrochemical analyzer as set forth in claim 14 wherein the metallic sleeve is the counter electrode.

16. The analyzer as set forth in claim 12 wherein the carbon is made of an amorphous carbon.

17. The analyzer as set forth in claim 16 wherein the carbon is a glassy carbon.

18. An electrochemical analyzer comprising:

an electrochemical cell which defines a fluid receiving reservoir;

a plurality of measurement electrodes disposed in the reservoir to be in electrical contact with solutions received in the reservoir, at least one of the electrodes including;

a carbon rod supported and sealed in a metallic sleeve, an electrically conductive rod interconnected with the carbon rod by an electrically conductive thermal expansion connection assembly, the thermal expansion connection assembly including;

a bore defined in the electrically conductive rod which is sized and shaped to receive the carbon rod slidably therein, and

a spring disposed in the bore of the rod in a compressed state to make electrical contact between the electrically conductive rod and the carbon rod; and

an analysis control system connected with the electrodes.

19. An electrode comprising:

a rod of carbon;

a compressible insulating sleeve surrounding the carbon rod, the compressible insulating sleeve compressing at a pressure lower than a compressive pressure at which the carbon rod fractures;

a ductile sleeve having a first end which surrounds the insulating sleeve, the first end of the ductile sleeve being compressed, compressing the insulating sleeve and providing a fluid-tight seal between the ductile sleeve, the insulating sleeve, and the carbon rod;

an electrical connector interconnected with the carbon rod and supported by a second end of the ductile sleeve, the electrical connector including an electrically conductive element that is directly connected with the carbon rod by an electrically conductive thermal expansion connection assembly.

20. The electrode as set forth in claim 19 wherein the insulating sleeve is made of an inert polymer.

21. The electrode as set forth in claim 20 wherein the ductile sleeve is made of stainless steel.

22. The electrode as set forth in claim 19 wherein the electrically conductive thermal expansion connection assembly includes:

a bore defined in the electrically conductive element which is sized and shaped to receive the carbon rod slidably therein.

23. The electrode as set forth in claim 22 further including:

an electrically conductive spring disposed in the bore in a compressed state to make mechanical and electrical contact with the electrically conductive element and the carbon rod.

24. The electrode as set forth in claim 22 wherein a second end of the ductile sleeve is compressed against an insulator sleeve to support and form a fluid-tight seal with the electrically connective element.

25. The electrode as set forth in claim 19 wherein the carbon is an amorphous carbon.

26. The electrode as set forth in claim 25 wherein the carbon is a glassy carbon.

27. An electrode comprising:

a rod of an amorphous form of carbon;

a compressible insulating sleeve surrounding the carbon rod, the compressible insulating sleeve compressing at a pressure lower than a compressive pressure at which the carbon rod fractures;

a ductile sleeve surrounding the insulating sleeve, the ductile sleeve being compressed, compressing the insulating sleeve and providing a fluid-tight seal between the ductile sleeve, the insulating sleeve, and the carbon rod;

an electrical connector supported by the ductile sleeve, a bore defined in the electrically conductive element which is sized and shaped to receive the carbon rod slidably therein; and

a spring, intermediate the electrical connector and the carbon rod, which electrically connects the electrical connector and the carbon rod.

28. An electrochemical method comprising:

surrounding an electrode in the form of a carbon rod with an insulating sleeve;

surrounding the insulating sleeve with a ductile metal sleeve;

compressing the ductile metal sleeve forming a fluid-tight compression seal with the insulating sleeve and the carbon rod;

making an electrical connection with the carbon rod which compensates for thermal expansion of the metallic sleeve;

connecting the electrical connection with an electrochemical analysis system;

immersing at least a face of the carbon rod into a fluid to be analyzed.

29. The method as set forth in claim 28 further including, prior to making an electrochemical measurement, applying alternating conditioning voltage pulses to the carbon electrode.

30. The method as set forth in claim 29 wherein the alternating pulses have magnitudes of +2.5 volts and −

2.0 volts.