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Patent US4273556A successfully refreshed from Google Patents.
US4273556A
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Determination of urea
Assignee: Covidien AG
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Filing: 1979-12-19
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Granted: 1981-06-16
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Expires: 1999-12-19
Abstract
Abstract Colorimetric urea determination method and reagent in which urea in a liquid sample reacts with o-phthalaldehyde and chromotropic acid or one of its salts to produce an intensely colored reaction product whose concentration is linearly related to the concentration of urea in the sample and which follows Beer's law over a wide range of urea concentrations.
Inventors
- 👤 E. Melvin Gindler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:26
CPC Classifications
G; G01; G01N; G01N33/00; G01N33/48; G01N33/50; G01N33/62; Y; Y10; Y10T; Y10T436/00; Y10T436/17; Y10T436/171538
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
87 words
A method of determining the urea concentration of a liquid sample comprising the steps of: (a) adding o-phthalaldehyde and a chromogenic compound to said liquid sample, said chromogenic compound being chosen from the group consisting essentially of chromotropic acid and its salts; (b) maintaining said sample at a temperature at which said chromogenic compound, said o-phthalaldehyde and said urea in said sample react to produce a colored reaction product; (c) obtaining a colorimetric absorbance reading for said sample; and (d) comparing said absorbance reading with calibration means.
Claim 2
Independent Claim
87 words
A method of determining the urea concentration of a liquid sample comprising the steps of: (a) adding o-phthalaldehyde and a chromogenic compound to said liquid sample, said chromogenic compound being chosen from the group consisting essentially of chromotropic acid and its salts; (b) maintaining said sample at a temperature at which said chromogenic compound, said o-phthalaldehyde and said urea in said sample react to produce a colored reaction product; (c) obtaining a colorimetric absorbance reading for said sample; and (d) comparing said absorbance reading with calibration means.
Claim 3
Dependent Claim
12 words
The method of claim 1 wherein said chromogenic compound comprises chromotropic acid.
Claim 4
Dependent Claim
16 words
The method of claim 1 wherein said chromogenic compound comprises the disodium salt of chromotropic acid.
Claim 5
Dependent Claim
23 words
The method of claim 1 wherein the formation of said colored reaction product is carried out at approximately 25° C. to 37° C.
Claim 6
Dependent Claim
20 words
The method of claim 1 wherein the formation of said colored reaction product is carried out in slightly acidic solution.
Claim 7
Independent Claim
142 words
A method of determining the urea concentration of a liquid sample comprising the steps of (a) adding said liquid sample to a sample container; (b) adding equal amounts of o-phthalaldehyde to said sample container and to a blank container; (c) adding equal amounts of a chromogenic compound to the contents of each of said sample and blank containers, said chromogenic compound being chosen from the group consisting essentially of chromotropic acid and its salts; (d) maintaining the contents of each of said sample and blank containers in a temperature at which said chromogenic compound, said o-phthalaldehyde and said urea in said sample react to produce a colored reaction product; (e) obtaining colorimetric absorbance readings for the contents of each of said sample and blank containers; (f) computing the difference between said obtained absorbance readings; and (g) comparing said difference with calibration means.
Claim 8
Independent Claim
142 words
A method of determining the urea concentration of a liquid sample comprising the steps of (a) adding said liquid sample to a sample container; (b) adding equal amounts of o-phthalaldehyde to said sample container and to a blank container; (c) adding equal amounts of a chromogenic compound to the contents of each of said sample and blank containers, said chromogenic compound being chosen from the group consisting essentially of chromotropic acid and its salts; (d) maintaining the contents of each of said sample and blank containers in a temperature at which said chromogenic compound, said o-phthalaldehyde and said urea in said sample react to produce a colored reaction product; (e) obtaining colorimetric absorbance readings for the contents of each of said sample and blank containers; (f) computing the difference between said obtained absorbance readings; and (g) comparing said difference with calibration means.
Claim 9
Dependent Claim
23 words
The method of claim 6 wherein the formation of said colored reaction product is carried out at approximately 25° C. to 37° C.
Claim 10
Dependent Claim
20 words
The method of claim 6 wherein the formation of said colored reaction product is carried out in slightly acidic solution.
Claim 11
Dependent Claim
34 words
A reagent for colorimetric urea determination, said reagent consisting essentially of an acidic solution of (1) o-phthalaldehyde and (2) a chromogenic compound selected from the group consisting essentially of chromotropic acid and its salts.
Claim 12
Dependent Claim
34 words
A reagent for colorimetric urea determination, said reagent consisting essentially of an acidic solution of (1) o-phthalaldehyde and (2) a chromogenic compound selected from the group consisting essentially of chromotropic acid and its salts.
Claim 13
Dependent Claim
12 words
The reagent of claim 9 wherein said chromogenic compound comprises chromotropic acid.
Claim 14
Dependent Claim
16 words
The reagent of claim 9 wherein said chromogenic compound comprises the disodium salt of chromotropic acid.
Claim 15
Dependent Claim
9 words
The reagent of claim 9 further including a surfactant.
Claim 16
Independent Claim
51 words
A method of indicating the presence of urea in a sample, said method comprising the steps of mixing said sample with a reagent comprising o-phthalaldehyde and a chromogenic compound to produce a colored reaction product, said chromogenic compound being selected from the group consisting essentially of chromotropic acid and its salts.
Claim 17
Independent Claim
51 words
A method of indicating the presence of urea in a sample, said method comprising the steps of mixing said sample with a reagent comprising o-phthalaldehyde and a chromogenic compound to produce a colored reaction product, said chromogenic compound being selected from the group consisting essentially of chromotropic acid and its salts.
Claim 18
Dependent Claim
12 words
The method of claim 13 wherein said chromogenic compound comprises chromotropic acid.
Claim 19
Dependent Claim
16 words
The method of claim 13 wherein said chromogenic compound comprises the disodium salt of chromotropic acid.
Claim 20
Dependent Claim
56 words
A reagent kit for colorimetric determination of urea, said reagent kit consisting essentially of a package containing a first container containing a first solution comprising a colorimetric amount of a chromogen chosen from the group consisting of chromotropic acid and its salts, and a second container containing a second solution comprising a colorimetric amount of o-phthalaldehyde.
Claim 21
Dependent Claim
56 words
A reagent kit for colorimetric determination of urea, said reagent kit consisting essentially of a package containing a first container containing a first solution comprising a colorimetric amount of a chromogen chosen from the group consisting of chromotropic acid and its salts, and a second container containing a second solution comprising a colorimetric amount of o-phthalaldehyde.
Claim 22
Dependent Claim
11 words
The kit of claim 16 wherein said chromogen is chromotropic acid.
Claim 23
Dependent Claim
15 words
The kit of claim 16 wherein said chromogen is the disodium salt of chromotropic acid.
Claim 24
Dependent Claim
17 words
The kit of claim 16 wherein said first solution comprises an acidic aqueous solution of said chromogen.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-06-15 | 1984-12-15 | 1985-06-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-06-15 | 1988-12-15 | 1989-06-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-06-15 | 1992-12-15 | 1993-06-16 | $7700.00 | Window Closed / Lapsed |