US3873269A
Expired / Lapsed
US
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Indicator for the determination of urea
Assignee: Merck Patent GmbH
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Filing: 1973-06-07
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Granted: 1975-03-25
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Expires: 1993-06-07
Abstract
Abstract A colorimetric indicator for the determination of urea, comprising a reaction system containing urease and a colorimetric pH indicator system arranged one above the other on absorbent supports. The reaction system is characterized by containing alkali carbonate and/or hydroxide and optionally one or more organic acids, and by having a pH range of about 8 to 10.
Inventors
- 👤 Friedrich Kraffczyk
- 👤 Roland Helger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:39
CPC Classifications
C; C12; C12Q; C12Q1/00; C12Q1/58; Y; Y10; Y10S; Y10S435/00; Y10S435/805; Y10T; Y10T436/00; Y10T436/10; Y10T436/107497; Y10T436/17; Y10T436/171538
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
110 words
A COLORIMETRIC INDICATOR SUITABLE FOR THE RAPID SEMIQUANTITATIVE DETECTION OF UREA IN SOLUTION, SAID INDICATOR COMPRISING: A. A REACTION ZONE CONTAINING AN ABSORBENT CARRIER IMPREGNATED WITH AN ENZYME CAPABLE OF HYDROLYZING UREA INTO AMMONIA AND CARBON DIOXIDE AND AT LEAST ONE ALKALI METAL CARBONATE OR ALKALI METAL HYDROXIDE IN AN AMOUNT SUFFI CIENT TO PROVIDE PH OF 8 - 10 WHEN SAID REACTION ZONE IS MOISTENED WITH WATER AND TO RAISE THE VAPOR PRESSURE OF AMMONIA RELEASED BY ENZYMATIC HYDROLYSIS OR UREA, AND B. A PH INDICATOR ZONE SEPARATE FROM THE REACTION ZONE CONTAINING AN ABSORBENT CARRIER IMPREGNATED WITH A COLORIMETRIC INDICATOR RESPONSIVE TO AMMONIA LIBERATED BY SAID REACTION ZONE.
Claim 2
Dependent Claim
110 words
A COLORIMETRIC INDICATOR SUITABLE FOR THE RAPID SEMIQUANTITATIVE DETECTION OF UREA IN SOLUTION, SAID INDICATOR COMPRISING: A. A REACTION ZONE CONTAINING AN ABSORBENT CARRIER IMPREGNATED WITH AN ENZYME CAPABLE OF HYDROLYZING UREA INTO AMMONIA AND CARBON DIOXIDE AND AT LEAST ONE ALKALI METAL CARBONATE OR ALKALI METAL HYDROXIDE IN AN AMOUNT SUFFI CIENT TO PROVIDE PH OF 8 - 10 WHEN SAID REACTION ZONE IS MOISTENED WITH WATER AND TO RAISE THE VAPOR PRESSURE OF AMMONIA RELEASED BY ENZYMATIC HYDROLYSIS OR UREA, AND B. A PH INDICATOR ZONE SEPARATE FROM THE REACTION ZONE CONTAINING AN ABSORBENT CARRIER IMPREGNATED WITH A COLORIMETRIC INDICATOR RESPONSIVE TO AMMONIA LIBERATED BY SAID REACTION ZONE.
Claim 3
Dependent Claim
19 words
An indicator according to claim 1, wherein said enzyme is urease having an activity of at least 5 U/mg.
Claim 4
Dependent Claim
17 words
An indicator according to claim 1, wherein said alkali metal is potassium, rubidium, cesium or mixtures thereof.
Claim 5
Dependent Claim
15 words
An indicator according to claim 3, wherein said alkali metal is present as cesium carbonate.
Claim 6
Dependent Claim
18 words
An indicator according to claim 1, wherein said reaction zone further contains an organic carboxylic or sulfonic acid.
Claim 7
Dependent Claim
33 words
An indicator accOrding to claim 5, wherein said acid is at least one member selected from the group consisting of phthalic acid, isophthalic acid, salicylic acid, 5-sulfosalicylic acid, 5-nitrosalicylic acid and mellitic acid.
Claim 8
Dependent Claim
25 words
An indicator according to claim 1, wherein said reaction zone further contains an oxidation-inhibiting amount of an organic compound containing at least one -SH group.
Claim 9
Dependent Claim
23 words
An indicator according to claim 1, wherein said colorimetric indicator has a color change in the pH range of 6.8 - 3.0, inclusive.
Claim 10
Dependent Claim
26 words
An indicator according to claim 8, wherein said colorimetric indicator is selected from the group consisting of bromcresol green, bromphenol red, bromcresol purple and iron rhodanate.
Claim 11
Dependent Claim
27 words
An indicator according to claim 1, wherein said reaction zone and said indicator zone are spaced 1 - 20 mm. from each other on a common support.
Claim 12
Dependent Claim
24 words
An indicator according to claim 1, wherein said reaction zone is prepared by impregnation with an aqueous solution containing, per liter of distilled water,
Claim 13
Dependent Claim
66 words
A process for the semiquantitative colorimetric determination of urea in solution which comprises moistening the reaction zone of an indicator according to claim 1 with a solution to be tested, subjecting the moistened indicator to conditions which permit urea hydrolysis and ammonia absorption to take place, and measuring the ascension level of the reacted indicator system as a function of urea content in the test solution.
References Cited (Backward Citations)
US3531254A
Cited
US3427225A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-24 | 1978-09-23 | 1979-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-24 | 1982-09-23 | 1983-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-24 | 1986-09-23 | 1987-03-25 | $7700.00 | Window Closed / Lapsed |