Determination Of Urea In Serum Research Articles

Kinetic determination of urea in serum by stopped-flow spectrophotometry

The determination of urea based on its reaction with biacetyl in the presence of thiosemicarbazide and iron(III) has been studied kinetically by using a modular stopped-flow system. This study gave some new data about this coloured reaction and led to the development of a simple, fast method which overcomes some of the disadvantages (e.g., long analysis times, high temperatures and acid concentrations) of the conventional equilibrium method for the determination of urea, which hinder its application to routine analyses. The linear range (0.5–15 μg ml −1), detection limit, precision and selectivity of the proposed kinetic stopped-flow method are reported. The method has been satisfactorily applied to the analysis of serum samples without pretreatment. The results correlate well with those obtained by the urease method.

A chemiluminometric method for the determination of urea in serum using a three-enzyme bioreactor.

A flow injection chemiluminometric assay for urea has been developed based on a minicolumn bioreactor packed with immobilized enzyme-bearing glass beads. The reactor contains immobilized urease, L-glutamate dehydrogenase and L-glutamate oxidase, aligned in this order (upstream to the downstream). When the sample is introduced into the bioreactor, urea is first hydrolysed by urease to produce ammonia, which is then converted into L-glutamate by L-glutamate dehydrogenase. L-Glutamate is finally oxidized by L-glutamate oxidase to produce hydrogen peroxide, which is quantified by measuring chemiluminescence emitted upon admixing with luminol and potassium ferricyanide. One assay cycle is completed within 1 minute. The method is sensitive (detection limit 0.5 nmol) and is linear in the range 0-30 mmol/l. It can be readily applied to the determination of urea in human serum, and requires no blank corrections for ammonia and/or L-glutamate present in serum samples.

Enzyme sensor system for potentiometric urea determination in serum and milk

A potentiometric enzyme electrode system for rapid assay of urea in biological fluids such as serum and urine, using a dual pH electrode arrangement in differential measuring mode is described. Individual sample pH correction within a fixed-time measuring interval provides both a good correlation with the indophenol method (correlation coefficients r = 0.998 and r = 0.987 for serum and milk, respectively) and a reasonable sample throughput (20–25 samples/h). A linear response is obtained in the urea concentration range 1–20 mmol/1. Lyophilized soy urease (3 U/mg) is immobilized directly on the active surface of a pH glass electrode.

Simultaneous determination of serum cations, anions and uremic toxins by ion chromatography using an immobilized enzyme

A procedure is described for the analysis of serum cations and uremic toxins by simultaneous conductivity (CD) and ultraviolet (UV) photometric detection and using phosphoric acid as the eluent. In addition, studies were made on the determination of urea in serum using immobilized urease, and on the simultaneous determination of cationic and anionic compounds. The ammonium ion produced from urea by immobilized urease was determined by CD. No significant differences in amounts were found between the present method and conventional colorimetric methods. There was no significant reduction in immobilized urease activity after two months of continuous use. Simultaneous analysis of cationic and anionic compounds in serum was performed by switching valves in order to change the eluents and to change the channel to the analytical column. No marked baseline variation was observed and satisfactory recovery of anions was achieved.

Determination of serum urea by isotope dilution mass spectrometry as a candidate definitive method.

Determination of serum urea by isotope dilution mass spectrometry as a candidate definitive method.

Determination of urea in blood serum with use of immobilized urease and a microwave cavity ammonia monitor

The system for urea determination consists of urease immobilized on porous PVC coated on the inside of a test tube, and a dissolved ammonia monitor comprising a dialyzer and a Stark microwave cavity resonator. The total time required for the determination of urea in serum is 18 min (the enzymatic reaction requires 10 min) and the calibration graph for urea—nitrogen is linear from 10 to 750 mg l00 −1. The relative standard deviation is 5%; there are very few interferences.

Enzymatic determination of urea in serum based on pH measurement with the flow injection method.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEnzymic determination of urea in serum based on pH measurement with the flow injection methodJ. Ruzicka, E. H. Hansen, Animesh K. Ghose, and H. A. MottolaCite this: Anal. Chem. 1979, 51, 2, 199–203Publication Date (Print):February 1, 1979Publication History Published online1 May 2002Published inissue 1 February 1979https://doi.org/10.1021/ac50038a011RIGHTS & PERMISSIONSArticle Views132Altmetric-Citations71LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (691 KB) Get e-Alerts Get e-Alerts

Rapid-flow enthalpimetric determination of urea in serum, with use of an immobilized urease reactor.

We used a differential thermal detector in conjunction with an immobilized urease reactor to determine urea in serum. Samples (120 mul) are introduced into a flow stream and passed through an "adiabatic" column, which is packed with enough insolubilized urease to completely convert urea to ammonia and carbon dioxide. Measured temperature changes are directly proportional to the serum urea concentration. Urea in the presence of protein, bilirubin, and hemoglobin can thus be rapidly, simply, and inexpensively measured. Results correlate well with those obtained by the manual diacetyl monoxime and urease/indophenol methods.

Frequency distribution of errors in the determination of serum urea and eeectrolyte values with the autoanalyzer

The frequency distributions of urea, Na, K, Cl and CO 2 results, found by replicate analyses of pooled sera with the AutoAnalyzer, were sometimes non-Gaussian when the Technicon chart reader was used. The number of skewed and kurtotic distributions was increased by logarithmic transformation of the results, but reduced by employing a graphical peak analyser to read chart recordings. For tests such as potassium, with a small standard deviation, the error distribution was further improved by registering the concentration as three significant figures.