A method is described for the determination of urea in plasma and urine. The effects of variations in the experimental conditions are examined and the results of recovery experiments and other tests of precision and accuracy are reported. In comparison with other methods in current use, this method has distinct advantages in sensitivity, simplicity, and precision, thus economizing in time, samp...

Elevation in one or more compounds in exhaled breath condensate (EBC) has been reported to be related to one or another lung disease. The increased concentration might be caused by increased chemicals in the airway surface liquid. However, it might also be due to an increased delivery of liquid samples into the airstream. Being evenly distributed throughout the body, urea is a likely candidate ...

In connection with other studies in this laboratory (1, 2),’ it became necessary to determine the concentration of urea in the blood of individual new-born rats. In view of the small quantities of blood available and the need for a considerable number of analyses, the calorimetric method developed by Archibald (3) appeared to be particularly suitable. This method is based upon the formation of ...

A new method has been developed for measuring the permeability coefficient, omega, of small nonelectrolytes. The method depends upon a mathematical analysis of the time course of cell volume changes in the neighborhood of the minimum volume following addition of a permeating solute to an isosmolal buffer. Coefficients determined by the minimum volume method agree with those obtained using radio...

In connection with other studies in this laboratory (1, 2),’ it became necessary to determine the concentration of urea in the blood of individual new-born rats. In view of the small quantities of blood available and the need for a considerable number of analyses, the calorimetric method developed by Archibald (3) appeared to be particularly suitable. This method is based upon the formation of ...

A sequential injection system was proposed to accomplish the potentiometric determination of urea. This procedure used an ammonium tubular selective electrode to assess ammonium concentration produced by enzymatic hydrolysis of urea from Jack bean meal (Canavalia ensiformis DC) crude extract. A gaseous diffusion device was coupled to the flow set-up allowing on-line sampling and suitable select...

A miniaturizedflow-injected thermal biosensor was developed for the determination of urea and L-lactate in undilutedblood in 1-L samples. The sensor employed a smallenzyme column constructedof stainlesssteeltubing and microbead thermistors. Urease and lactate oxidase/catalase were separately immobilized onto controlled-pore glass beads, which, in turn, were charged into the enzyme column. With ...

The method of Parsons et al. (1984) for measuring dissolved free amino acids (DFAA) in coastal seawater was modified. We found considerable interference in DFAA determination from ammonia dissolved in coastal seawater, although the interference of urea could be ignored. For DFAA analysis for coastal seawater samples, ammonia determinations for the same sample are needed to correct DFAA values. ...

Empty body composition of 68 mixed-breed and 50 Angus steers was determined by chemical analysis of the right half-carcass and entire noncarcass fraction of each steer. Chemical composition was used to develop prediction equations for empty body protein (EBPRO) and fat (EBFAT) in steers using urea space (US) and body weight measurements. Previous research showed a significant positive correlati...

In 1935 one of us described micromethods for ammonia, urea, total nitrogen, uric acid, creatinine, and allantoin (1). These methods are adapted for the analysis of 1 to 2 ml. aliquots of dilute solutions, e.g. 0.1 mg. per cent of ammonia or urea, and for carrying out a large number of analyses simultaneously. These methods all end in a calorimetric measurement. In the present communication meth...