Portable lead detector

• US 5,437,772 A
• Filed: 11/01/1993
• Issued: 08/01/1995
• Est. Priority Date: 11/01/1993
• Status: Expired due to Fees

• Current Assignee: Electrosynthesis Co., Inc. (RWE AG)
• Original Assignee: Electrosynthesis Co., Inc. (RWE AG)
• Inventors: De Castro, Emory S., Genders, John D.
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US08/144,342
• Time in Patent Office: 638 Days
• Field of Search: 204/413, 204/434, 204/406, 204/407, 204/412, 204/416, 204/400, 204/153.13, 204/153.14, 204/153.16, 204/153.19, 204/153.1, 422/82.03
• US Class Current: 205/775
• CPC Class Codes: G01N 27/34 Dropping-mercury electrodes
• CPC Class Codes: G01N 27/42 Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte

Abstract

Apparatus and methods for quickly and easily detecting trace amounts of metallic or non-metallic, electro-active substances, and in particular trace amounts of metals, such as lead in a portable, hand-held detector system with single potential control.

Claims

1. A method of trace substance analysis, comprising the steps of:

introducing a solution having a low concentration of at least one metallic or non-metallic, electro-active substance into a chamber containing a transducer having a collector electrode array interdigitated with a detector electrode array;

applying a first reducing potential to said collector electrode array for a first period of time whereby ions of said at least one metallic or non-metallic, electro-active substance are reduced from said solution and concentrated on said collector electrode array;

applying a first oxidizing potential to said collector electrode array for a second period of time and simultaneously applying a detecting potential to said detector electrode array for said second period of time whereby said at least one metallic or non-metallic, electro-active substance concentrated on said collector array is stripped as ions from said collector electrode array back into said solution; and

measuring a current across said detector electrode array during said second period of time to determine the amount of said at least one metallic or non-metallic, electro-active substance within said solution.

2. The method of claim 1 including the step of interposing spaced digits of a monolithic, digitated array forming said collector electrode array between spaced digits of a monolithic, digitated array forming said detector electrode array so that adjacent digits are spaced a distance of about 5 μ

m to about 15 μ

m.

3. The method of claim 2 including the step of coating one or more of said digits of both said collector electrode array and said detector electrode array with a layer of mercury.

4. The method of claim 2 including the step of constructing said spaced digits of said collector electrode array and said detector electrode array from a material selected from the group consisting of gold, platinum, iridium, indium, tin oxide, indium on tin oxide, Ebonex™

, silver graphite glassy carbon, and conductive carbon.

5. The method of claim 1 including the step of selecting said at least one metallic or non-metallic electro-active substance from a neutral or charged species consisting essentially of carbon, nitrogen, oxygen, sulfur, phosphorous, halides, trace metals, or a combination thereof.

6. The method of claim 5 including the step of selecting said at least one metallic or non-metallic, electro-active species from compounds consisting of sulfites or cyanides.

7. The method of claim 5 including the step of selecting said at least one metallic or non-metallic, electro-active species from compounds consisting ionic or neutral organic compounds.

8. The method of claim 1 including the step of selecting said at least one electro-active substance from a low concentration of at least one trace metal.

9. The method of claim 8 including the step of selecting said at least one trace metal from the group consisting of lead, cadmium, silver, copper, zinc, arsenic, cobalt, chromium, iron, manganese, mercury, molybdenum, nickel, selenium, thallium, vanadium, and tin.

10. The method of claim 9 including the step of selecting said at least one trace metal as lead.

11. The method of claim 7 including the steps of:

applying said first reducing potential of about -0.4 to about -1.2 volts versus Ag/AgCl reference to said collector array for said first period of time;

applying said first oxidizing potential of about 0.10 to about -0.35 volts versus Ag/AgCl reference to said collector electrode array for said second period of time; and

applying said detecting potential of about -0.40 to about -0.70 volts versus Ag/AgCl reference to said detector electrode array for said second period of time.

12. The method of claim 11 including the steps of:

applying a first cleaning potential of about 0.10 to about -0.20 volts versus Ag/AgCl reference to said collector electrode array for a third period of time of about 0.5 to about 20 minutes to clean said collector electrode array; and

applying a second cleaning potential of about 0.10 to about -0.20 volts versus Ag/AgCl reference to said detector electrode array for said third period of time to clean said detector electrode array.

13. The method of claim 12 including the steps of:

selecting said first period of time between about 0.5 and about 20 minutes;

selecting said second period of time between about 0.5 and about 20 minutes; and

selecting said third period of time between about 0.5 and about 20 minutes.

14. A method of trace substance analysis, comprising the steps of:

introducing a solution having a low concentration of at least one electro-active substance into a chamber containing a transducer having a collector electrode array interdigitated with a detector electrode array;

applying a first oxidizing potential to said collector electrode array for a first period of time whereby ions of said at least one electro-active substance are oxidized from said solution and concentrated on said collector electrode array;

applying a first reducing potential to said collector electrode array for a second period of time and simultaneously applying a detecting potential to said detector electrode array for said second period of time whereby said at least one electro-active substance concentrated on said collector electrode array is stripped from said collector electrode array back into said solution; and

measuring the current across said detector electrode array during second period of time to determine the amount of said at least one electro-active substance within said solution.

15. A method of claim 14 including the step of selecting said electro-active substance from at least one metallic or non-metallic substance selected from the group of neutral or charged species consisting essentially of carbon, nitrogen, oxygen, sulfur, phosphorous, halides, the metals, or a combination thereof.

16. A system for trace substance analysis, comprising:

means for introducing a solution having a low concentration of at least one electro-active substance into a chamber containing a transducer having a collector electrode array interdigitated with a detector electrode array;

means for applying a first reducing potential to said collector electrode array for a first period of time whereby ions of said at least one electro-active substance are reduced from said solution and concentrated on said collector electrode array;

means for applying a first oxidizing potential to said collector electrode array for a second period of time;

means for applying a detecting potential to said detector electrode array during said second period of time whereby said at least one electro-active substance on said collector electrode array is stripped from said collector electrode array back into said solution; and

means for measuring current across said detector electrode array during said second period of time to determine the amount of said at least one electro-active substance within said solution.

17. The system of claim 16 wherein said collector electrode array and said detector electrode array are each constructed of a monolithic, digitated array having a plurality of spaced digits.

18. The system of claim 17 wherein at least one of said plurality of spaced digits is coated with a layer of mercury.

19. The system of claim 18 wherein said spaced digits of said collector electrode array and said detector electrode array are constructed from a material selected from the group consisting of gold, platinum, iridium, indium tin oxide, indium and tin oxide Ebonex™

, silver, graphite, glassy carbon, and conductive carbon.

20. The system of claim 19 wherein said at least one electro-active substance is a neutral or charged species consisting essentially of carbon, nitrogen, oxygen, sulfur, phosphorous, halides, trace metals, or a combination thereof.

21. The system of claim 20 wherein said at least one electro-active substance is a low concentration of at least one trace metal.

22. The system of claim 21 wherein said at least one trace metal is from the group consisting of lead, cadmium, silver, copper, zinc, arsenic, cobalt, chromium, iron, manganese, mercury, molybdenum, nickel, selenium, thallium, vanadium, and tin.

23. The system of claim 20 wherein said at least one trace metal is lead.

24. A system for trace substance analysis, comprising:

means for introducing a solution having a low concentration of at least one electro-active substance into a chamber containing a transducer formed of a collector electrode array interdigitated with a detector electrode array;

means for applying a first oxidizing potential to said collector electrode array for a first period of time whereby said species of said at least one electro-active substance are oxidized from said solution and concentrated on said collector electrode array;

means for applying a first reducing potential to said collector electrode array for a second period of time;

means for applying a detecting potential to said detector electrode array during said second period of time whereby said at least one electro-active substance concentrated on said collector array is stripped from said collector electrode array back into said solution; and

means for measuring current across said detector electrode array during said second period of time to determine the amount of said at least one electro-active substance within said solution.

25. The system of claim 24 including means for selecting said electro-active species from at least one metallic or non-metallic, neutral or charged species consisting essentially of carbon, nitrogen, oxygen, sulfur, phosphorous, halides, the metals, or a combination thereof.

26. The system of claim 25 including:

means for applying said first reducing potential of about -0.4 to about -1.2 volts versus Ag/AgCl reference to said collector electrode array for said first period of time;

means for applying said first oxidizing potential of about 0.10 to about -0.35 volts versus Ag/AgCl reference to said collector electrode array for said second period of time; and

means for applying said detection potential of about -0.40 to about -0.70 volts versus Ag/AgCl reference to said detector electrode array for said second period of time.

27. The system of claim 25 including:

means for applying a first cleaning potential of about 0.10 to about -0.20 volts versus Ag/AgCl reference to said collector electrode array for a third period of time of about 0.5 to about 20 minutes to clean said collector electrode array; and

means for applying a second cleaning potential of about 0.10 to about -0.20 volts versus Ag/AgCl reference to said detector electrode array for said third period of time to clean said detector electrode array.

28. An interdigitated array constructed of a first electrode array and a second electrode array, each of said first and second electrode arrays being constructed of a monolithic, digitated array having a plurality of spaced digits each coated with a layer of mercury, said spaced digits are constructed of a material selected from the group consisting of gold, platinum, iridium, indium, tin oxide, indium and tin oxide, Ebonex™

, silver graphite glass, carbon, and conductive carbon.

29. The interdigitated array of claim 28 wherein said layer of mercury is less than about 1000 nm thick.

30. The interdigitated array of claim 29 wherein said layer of mercury is preferably from about 100 nm to about 500 nm thick.

31. The interdigitated array of claim 28 wherein each of said monolithic, digitated arrays has four electrodes, and two of said electrodes on said monolithic, digitated array are reference and auxiliary electrodes.