US3881997A
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Method for voltammetric determination of nitrate and nitrite
Assignee: Iowa State University Research Foundation Inc
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Filing: 1974-03-27
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Granted: 1975-05-06
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Expires: 1994-03-27
Abstract
Abstract Nitrate and/or nitrite in water are determined by a cadmium electrode maintained at a critical negative potential and with the test solution at a hydrogen ion concentration favoring the reduction of nitrate and nitrite to hydroxylamine, the detected current being linearly proportional to the nitrate or nitrite concentration. Interfering metal ions are replaced with hydrogen ions by cation exchange, and the nitrate, nitrite, and dissolved oxygen components of the test solution are chromatographically separated in an anion exchange column. For effective separation of the dissolved oxygen and the nitrite, the chromatographic adsorption is preferably made from a solution stream at a lower hydrogen concentration than the hydrogen ion concentration used during the voltammetric determination. The method can be carried out by an analyzer apparatus producing a chromatogram.
Inventors
- 👤 Dennis C Johnson
- 👤 Ronald J Davenport
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 03:17
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/26; G01N27/403; G01N27/404; G01N27/4045; G01N30/00; G01N30/96; G01N30/02; G01N30/84; G01N2030/8429; G01N2030/8435
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
98 words
THE VOLTAMMETRIC METHOD OF DETERMINING THE CONCENTRATION OF SMALL AMOUNTS OF NITRATE AND/OR NITRITE IN WATER, CHARACTERIZED BY THE STEP OFL: A. MAINTAINING A CADMIUM ELECTRODE AT A NEGATIVE POTENTIAL IN THE RANGE OF -0.80 TO -1.15 VOLTS WITH REFERENCE TO A SATURATED CALOMEL ELECTRODE; B. CONTACTING AN AQUEOUS TEST SOLUTION WITH SAID CADMIUM ELECTRODE, SAID SOLUTION CONTAINING UP TO ABOUT 15 PPM NITROGEN AS AN UNKNOWN CONCENTRATION OF NITRATE AND/OR NITRITE, SAID SOLUTION HAVING A HYDROGEN ION CONCENTRATION IN THE RANGE OF 0.001 TO 5 MOLAR FAVORING THE REDUCTION OF SAID NITROGEN OXIDE ION TO HYDROXYLAMINE; AND
Claim 2
Dependent Claim
98 words
THE VOLTAMMETRIC METHOD OF DETERMINING THE CONCENTRATION OF SMALL AMOUNTS OF NITRATE AND/OR NITRITE IN WATER, CHARACTERIZED BY THE STEP OFL: A. MAINTAINING A CADMIUM ELECTRODE AT A NEGATIVE POTENTIAL IN THE RANGE OF -0.80 TO -1.15 VOLTS WITH REFERENCE TO A SATURATED CALOMEL ELECTRODE; B. CONTACTING AN AQUEOUS TEST SOLUTION WITH SAID CADMIUM ELECTRODE, SAID SOLUTION CONTAINING UP TO ABOUT 15 PPM NITROGEN AS AN UNKNOWN CONCENTRATION OF NITRATE AND/OR NITRITE, SAID SOLUTION HAVING A HYDROGEN ION CONCENTRATION IN THE RANGE OF 0.001 TO 5 MOLAR FAVORING THE REDUCTION OF SAID NITROGEN OXIDE ION TO HYDROXYLAMINE; AND
Claim 3
Dependent Claim
35 words
The method steps of claim 1 further characterized in that said cadmium electrode is maintained at a constant negative potential in the range of -0.90 to -1.05 volts with referenee to a saturated calomel electrode.
Claim 4
Dependent Claim
23 words
The method steps of claim 1 further characterized in that said test solution has a hydrogen ion concentration of 0.01 to 1.0 molar.
Claim 5
Dependent Claim
35 words
The method steps of claim 1 further characterized in the said cadmium electrode is in the form of a tube and said test solution is passed continuously at a uniform rate through said electrode tube.
Claim 6
Dependent Claim
104 words
The voltammetric method of determining the concentration of small amounts of nitrate and/or nitrite in water, characterized by the steps of: a. maintaining a cadmium electrode at a negative potential in the range of -0.90 to -1.05 volts with reference to a saturated calomel electrode; b. contacting an aqueous test solution with said cadmium electrode, said solution containing up to about 15 ppm nitrogen as an unknown concentration of nitrate and/or nitrite, said solution having a hydrogen ion concentration from 0.01 to 1.0 molar; and c. detecting the current flow between said cadmium electrode and a counter electrode in contact with said test solution.
Claim 7
Dependent Claim
104 words
The voltammetric method of determining the concentration of small amounts of nitrate and/or nitrite in water, characterized by the steps of: a. maintaining a cadmium electrode at a negative potential in the range of -0.90 to -1.05 volts with reference to a saturated calomel electrode; b. contacting an aqueous test solution with said cadmium electrode, said solution containing up to about 15 ppm nitrogen as an unknown concentration of nitrate and/or nitrite, said solution having a hydrogen ion concentration from 0.01 to 1.0 molar; and c. detecting the current flow between said cadmium electrode and a counter electrode in contact with said test solution.
Claim 8
Dependent Claim
35 words
The method steps of claim 5 further characterized in that said calmium electrode is in the form of a tube and said test solution is passed continuously at a uniform rate through said electrode tube.
Claim 9
Dependent Claim
134 words
The voltammetric method of determining the concentration of small amounts of nitrate and/or nitrite in water, characterized by the steps of: a. maintaining a cadmium electrode at a constant negative potential in the range of -0.90 to -1.05 volts with reference to a saturated calomel electrode, said cadmium electrode being in the form of a tube; b. passing an aqueous test solution at a constant flow rate through said tubular cadmium electrode, said solution containing up to about 15 ppm nitrogen as an unknown concentration of nitrate and/or nitrite, said solution having a hydrogen ion concentration in the range of 0.001 to 5 molar favoring the reduction of said nitrogen oxide ion to hydroxylamine; and c. detecting the current flow between said cadmium electrode and a counter electrode in contact with said test solution.
Claim 10
Dependent Claim
134 words
The voltammetric method of determining the concentration of small amounts of nitrate and/or nitrite in water, characterized by the steps of: a. maintaining a cadmium electrode at a constant negative potential in the range of -0.90 to -1.05 volts with reference to a saturated calomel electrode, said cadmium electrode being in the form of a tube; b. passing an aqueous test solution at a constant flow rate through said tubular cadmium electrode, said solution containing up to about 15 ppm nitrogen as an unknown concentration of nitrate and/or nitrite, said solution having a hydrogen ion concentration in the range of 0.001 to 5 molar favoring the reduction of said nitrogen oxide ion to hydroxylamine; and c. detecting the current flow between said cadmium electrode and a counter electrode in contact with said test solution.
Claim 11
Dependent Claim
129 words
In a method of determining the concentration of small amounts of nitrate and/or nitrite in an aqueous test solution containing metal ions and dissolved oxygen, the steps comprising: a. removing the metal cations from said test solution and replacing them with hydrogen ions; b. chromatographically separating said nitrate, nitrite, and oxygen components by successive adsorption and elution in a column of a strong cation exchange resin to provide an eluent containing up to about 15 ppm nitrogen as an unknown concentration of nitrate and/or nitrite; and c. voltammetrically determining the concentration of the separated nitrate and/or nitrite in the eluent by flowing said eluent through a tubular cadmium electrode maintained at a negative potential in the range of -0.80 to -1.15 volts with reference to a saturated calomel electrode.
Claim 12
Dependent Claim
129 words
In a method of determining the concentration of small amounts of nitrate and/or nitrite in an aqueous test solution containing metal ions and dissolved oxygen, the steps comprising: a. removing the metal cations from said test solution and replacing them with hydrogen ions; b. chromatographically separating said nitrate, nitrite, and oxygen components by successive adsorption and elution in a column of a strong cation exchange resin to provide an eluent containing up to about 15 ppm nitrogen as an unknown concentration of nitrate and/or nitrite; and c. voltammetrically determining the concentration of the separated nitrate and/or nitrite in the eluent by flowing said eluent through a tubular cadmium electrode maintained at a negative potential in the range of -0.80 to -1.15 volts with reference to a saturated calomel electrode.
Claim 13
Dependent Claim
28 words
The method steps of claim 8 in which said voltammetric determination is carried out at a hydrogen ion concentration in said tubular electrode of 0.01 to 1.0 molar.
Claim 14
Dependent Claim
26 words
The method steps of claim 8 in which said cadmium electrode is maintained at a constant negative potential in the range of -0.90 to -1.05 volts.
References Cited (Backward Citations)
US3262051A
Cited
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1978-05-05 | 1978-11-04 | 1979-05-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-05 | 1982-11-04 | 1983-05-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-05 | 1986-11-04 | 1987-05-06 | $7700.00 | Window Closed / Lapsed |