Colorimetric urea determination in presence of long hydrocarbon chain amidobetaine
AssigneeSherwood Medical Industries Inc.
InventorsE. Melvin Gindler, Olga Daskalakis
Life of this patent
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Abstract
A colorimetric urea determination method, reagent, and reagent kit useful in end point and kinetic urea determination. Urea in a liquid sample reacts with o-phthalaldehyde and chromotropic acid or one of its salts in the presence of a linear long hydrocarbon chain amidobetaine to produce an intensely colored reaction product, the concentration of which is linearly related to the urea concentration in the sample.
Claims16
A method of demonstrating the presence of urea in a liquid sample, said method comprising the step of mixing said sample with a reagent comprising o-phthalaldehyde, a chromogenic compound selected from the group consisting of chromotropic acid and its salts, and a long hydrocarbon chain amidobetaine to produce a colored reaction product.
A method of demonstrating the presence of urea in a sample of a human body fluid comprising the step of mixing said sample with o-phthalaldehyde and a chromogenic compound selected from the group consisting of chromotropic acid and its salts, under slightly acidic conditions in the presence of an amidobetaine having either of the following structures:
- ##STR6## where R is a straight chain coconut oil residue having between about 10 and 14 carbon atoms in said chain,
- to produce a colored reaction product.
A method of determining the urea concentration is a liquid sample comprising the steps of:
- (a) adding o-phthalaldehyde, a chromogenic compound selected from the group consisting of chromotropic acid and its salts, and a long hydrocarbon chain amidobetaine to said liquid sample;
- (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.
In a method of determining the urea concentration in a liquid sample comprising the steps of mixing said sample with o-phthalaldehyde and a chromogenic compound selected from the group consisting of chromotropic acid and its salts under slightly acidic conditions to form a colored reaction product, obtaining a colorimetric absorbance reading of said sample and comparing said absorbance reading with calibration means, the improvement wherein said colored reaction product is formed in the presence of a long hydrocarbon chain amidobetaine.
A method of determining the urea concentration of a liquid sample, said method comprising the steps of:
- (a) adding said sample to a sample container;
- (b) adding equal amounts of a reagent comprising a solution of o-phthalaldehyde, a chromogenic compound selected from the group consisting of chromotropic acid and its salts, and a long hydrocarbon chain amidobetaine to said sample container and a blank container;
- (c) maintaining the contents of each said container at a temperature at which said o-phthalaldehyde and said urea in said sample react to produce a colored reaction product;
- (d) obtaining first colorimetric absorbance readings for each of said blank and sample containers at the end of a first time period;
- (e) obtaining second colorimetric absorbance readings for each of said blank and sample containers at the end of a second time period;
- (f) computing the difference between said first and second absorbance readings for each of said sample and blank containers;
- and,
- (g) comparing said differences with calibration means.
A reagent for colorimetric urea determination consisting essentially of a solution of (a) o-phthalaldehyde, (b) a chromogenic compound selected from the group consisting of chromotropic acid and its salts, and (c) a long hydrocarbon chain amidobetaine.
A reagent for colorimetric urea determination consisting essentially of an acidic solution of (a) o-phthalaldehyde, (b) a chromogenic compound selected from the group consisting of chromotropic acid and its salts, and (c) a long hydrocarbon chain amidobetaine selected from the group consisting of compounds of the formula ##STR10## where R is a straight chain coconut oil residue having between about 10 and 14 carbon atoms in said chain.
A reagent kit for colorimetric determination of urea, said reagent kit consisting of a package containing a first container containing a first solution comprising a colorimetric amount of a chromogen selected 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, one of said first and second solutions further comprising a long hydrocarbon chain amidobetaine.
Dependencies are inferred from the claim text.