Simple and Sensitive Determination of Urea in Serum and Urine

1992 ◽  
Vol 38 (5) ◽  
pp. 619-623 ◽  
Author(s):  
J L Orsonneau ◽  
C Massoubre ◽  
M Cabanes ◽  
P Lustenberger
Keyword(s):  
Urine Samples ◽  
Ph Change ◽  
Low Concentrations ◽  
Analytical Recovery ◽  
Urea Determination ◽  
Sensitive Determination ◽  
Ph Increase ◽  
Clinically Significant ◽  
Hydrolysis Of

Abstract In this method for serum and urinary urea determination, the same reagent is used without predilution of urine samples. The method is based on the pH increase resulting from the ammonia released by urease hydrolysis of urea. o-Cresolphthalein complexone is used to monitor the pH change colorimetrically. Urea concentration and absorbance at 570 nm are linearly related for concentrations as great as 600 mmol/L for urine samples and 100 mmol/L for serum. There are no clinically significant interferences from physiological substances or drugs, and precision and accuracy are excellent (CV approximately 2%, except at very low concentrations in serum; analytical recovery was 99% in urine, 100% in serum). Results by this method (y) and by the Astra method (x) for urine correlated well (y = 0.991x - 2.87, Sy/x = 9.21, r = 0.994), as did the results by this method and by the total enzymatic method (x') for serum (y = 1.002x' + 0.192, Sy/x' = 0.598, r = 0.997). This method is applicable to automated as well as manual instruments, and one-reagent or two-reagent formats can be used.

Modification of the choriogonadotropin beta-subunit radioimmunoassay for determination of urinary choriogonadotropin.

1978 ◽  
Vol 24 (11) ◽  
pp. 1958-1961 ◽  
Author(s):  
J McCready ◽  
G D Braunstein ◽  
D Helm ◽  
M E Wade
Keyword(s):  
Pregnant Women ◽  
Radioreceptor Assay ◽  
Beta Subunit ◽  
Urine Samples ◽  
Human Choriogonadotropin ◽  
Analytical Recovery ◽  
Antibody Method ◽  
Serum And Urine ◽  
Serum And Urine Samples

Abstract The choriogonadotropin beta-subunit radioimminoassay has been used extensively to measure human choriogonadotropin in the sera of pregnant women and individuals with trophoblastic and nontrophoblastic tumors. Unmodified, this method cannot be used to measure choriogonadotropin in urine because of interfering substances. We circumvented the non-parallelism between the standards and serial dilutions of urine containing choriogonadotropin by adding pooled urine from men to the standard tubes and limiting the volume of urine to 100 microliter. This modified assay has a sensitivity of 3 int. units/liter of urine and is specific for choriogonadotropin concentrations of 40 int. units/liter of urine. Analytical recovery of choriogonadotropin added to urine ranged from 96 to 105%. The within-assay CV was 7.6%; the between-assay CV was 11.8%. Concentrations of choriogonadotropin in concurrently collected serum and urine samples from pregnant women correlated well. The test can be performed within 24 h by using the double-antibody method for separating bound from free hormone, or in 3 h with a dioxane method. The assay is about 20-fold more sensitive than the 2-min or 2-h slide and tube pregnancy tests, and seven-to 12-fold more sensitive than the radioreceptor assay.

Sensitive determination of psychotropic drugs in urine samples using continuous liquid-phase microextraction with an extraction solvent lighter than water

2018 ◽  
Vol 42 (6) ◽  
pp. 4450-4456 ◽  
Author(s):  
Lida Haghnazari ◽  
Hamid Nomani ◽  
Nazir Fattahi ◽  
Kiomars Sharafi ◽  
Masoud Moradi
Keyword(s):  
Liquid Phase ◽  
Psychotropic Drugs ◽  
Urine Samples ◽  
Liquid Phase Microextraction ◽  
Extraction Solvent ◽  
Sensitive Determination ◽  
First Time

A novel extraction vessel was employed, for the first time, in continuous liquid-phase microextraction (CLPME) with an extraction solvent lighter than water for the extraction of psychotropic drugs from urine samples.

Solid-phase dispersive microextraction using reduced graphene oxide for the sensitive determination of cadmium and lead in waters

2019 ◽  
Vol 11 (5) ◽  
pp. 635-641 ◽  
Author(s):  
Ignacio López-García ◽  
Juan José Marín-Hernández ◽  
Manuel Hernández-Córdoba
Keyword(s):  
Graphene Oxide ◽  
Cloud Point Extraction ◽  
Solid Phase ◽  
Lead And Cadmium ◽  
Low Concentrations ◽  
Reduced Graphene ◽  
Dispersive Microextraction ◽  
Sensitive Determination ◽  
Cadmium And Lead

The combination of cloud point extraction with ETAAS measurement allows very low concentrations of lead and cadmium to be determined.

Screening for microalbuminuria in patients with diabetes mellitus: frozen storage of urine samples decreases their albumin content.

1989 ◽  
Vol 35 (2) ◽  
pp. 308-310 ◽  
Author(s):  
L D Elving ◽  
J A Bakkeren ◽  
M J Jansen ◽  
C M de Kat Angelino ◽  
E de Nobel ◽  
...  
Keyword(s):  
Frozen Storage ◽  
Urine Samples ◽  
Diabetic Patients ◽  
Albumin Concentration ◽  
Low Concentrations ◽  
Albumin Content ◽  
Patients With Diabetes ◽  
The Difference ◽  
Urinary Albumin Concentration

Abstract The influence of storage on urinary albumin concentration was prospectively studied with use of overnight urine specimens (Albustix negative) from 73 diabetic patients. From each urine sample four aliquots were taken. One was stored at 4 degrees C and assayed within two weeks, the other three were stored at -20 degrees C and assayed within two weeks and after two and six months. Albumin concentration was measured with laser immunonephelometry. The detection limit, 1 mg/L, suffices for the screening of diabetic patients for microalbuminuria. After storage for two and six months at -20 degrees C, significantly lower albumin concentrations were found. The difference was mainly caused by lower concentrations found in urine samples in which a precipitate had formed, which was the case in 22 and 25 samples, respectively. Thus, freezing of urine samples for determination of low concentrations of albumin may yield falsely low results. Urine samples are best stored at 4 degrees C and assayed within two weeks.

METHOD JUSTIFICATION OF Β-GALACTOSIDASE ACTIVITY OF ENZYME PREPARATION

1970 ◽  
pp. 65-68
Author(s):  
Е. М. Serba ◽  
М. B. Overchenko ◽  
N. I. Ignatova ◽  
М. Е. Medrish ◽  
L. V. Rimareva
Keyword(s):  
Glucose Oxidase ◽  
Performance Studies ◽  
Enzyme Hydrolysis ◽  
Hydrolysis Time ◽  
Enzyme Preparations ◽  
Optimum Parameters ◽  
Low Concentrations ◽  
Reliable Performance ◽  
Hydrolysis Of

Enzyme preparations - sources of β-galactosidase, are widely used in the dairy industry. However, there is no standardized methods to determine their activity. Existing methods differ by the type of substrate used, conditions of analysis and how to define the products of the hydrolysis. The aim of this work is to study the process of conversion biocatalytic milk sugar and experimental substantiation of methods of analysis of hydrolysis products, providing reliable results determine activity of β-galactosidase. Found that of chemical methods glucose oxidase showed a greater sensitivity towards low concentrations of the product of hydrolysis is glucose formed in the conversion process lactose. The results of testing showed that the mass concentration of the glucose formed in hydrolysis of lactose, HPLC tested, consistent with data obtained using the glucose oxidase method. Set optimum range, which was observed directly proportional to the level of glucose concentration rise in reaction mixture from the lengthy process and the concentration of enzyme:  hydrolysis time - from 10 to 20 min, produced   glucose - from 20 µcg to 40 mcg, while the mass of enzyme - 25.0·10-6, and from 40 mcg to 80 mcg, when mass -5,0·10-5 g.  When the values of absorbance of the reaction mixture ranged 0,045-0,300 to ensure reliable performance. Studies on determination of the activity of the enzyme preparations confirmed received experimental data and allowed to choose optimum parameters and conditions analysis for introducing them to the method for determining the activity β-galactosidase using glucose oxidase reagent: time of inactivation enzyme (control) -10 min.  in a boiling water bath, substrate - 2% solution of lactose, pH of the substrate-6,0, hydrolysis time 15 min. at 30° c.

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