Automated and manual direct methods for the determination of urea in blood or serum are described. These methods determine urea by the colored product formed when urea, in relatively weak acid solution, reacts with diacetyl monoxime in the presence of thiosemicarbazide and ferric ion. Results are compared with those obtained by urease conversion of urea to ammonia and measurement of the ammonia by nesslerization.

Automated and Manual Direct Methods for the Determination of Blood Urea

1. Unstimulated whole saliva and parotid saliva stimulated at a constant flow rate of 1·0 ml./min were collected from eight subjects at about 07.00, 11.00, 14.00, 17.00 and 22.00 hr and oral temperature was recorded several times daily for time spans of between 4 and 26 days. A least-squares cosine wave was fitted to the data to test for the presence and characteristics of circadian rhythms.

2. Estimates of mean level, amplitude, acrophase and period were obtained for different components and the results were subjected to cosinor analysis.

3. Unstimulated whole saliva showed significant circadian rhythms in flow rate and in the concentrations of sodium and chloride but not in protein, potassium, calcium, phosphate or urea.

4. Stimulated parotid saliva showed significant circadian rhythms in the concentrations of protein, sodium, potassium, calcium and chloride but not in phosphate or urea

5. Oral temperature showed a circadian rhythm which, like the salivary rhythms, was of a 24.0 hr periodicity.

Circadian rhythms in human salivary flow rate and composition

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Improvements in the determination of urea using diacetyl monoxime; methods with and without deproteinisation

Optimization of conditions for the colorimetric determination of citrulline, using diacetyl monoxime

Differential analyses of glyoxylate derivatives

A new simple and rapid method for quantitative semimicro determination of blood urea is presented. Diacetyl monoxime and thiosemicarbazide form in acid medium with urea a red color complex with a maximum adsorption at 530 mµ stable at room temperature and requiring 0.2 ml. of 1:10 blood filtrate.

L. Favreau

Papers

A New Simple Semimicro Method for Colorimetric Determination of Urea