Nitrogen, estimation

The quality control of immunoglobuhns includes potency tests and conventional tests of safety and sterihty. The potency tests consist of neutrahzation tests that parallel those used for the potency assay of immunosera, except that in the cases of some immimoglobulins the assays are made in vitro, fit addition to the safety and sterihty tests, total protein is determined by nitrogen estimations, the protein composition by... 

Nitrogenous Substances,—These consist mainly of proteins (casein, albumin) and to a small extent of other substances (lecithin, etc.). They may be determined together or separately from the nitrogen estimated by the Kjeldahl-Ulsch method (Vol. I, p. 122) ... 

Total nitrogen estimations were performed on the polyamino acid solutions before hydrolysis by a semimicro-Kjeldahl technique. Amide-like nitrogen was measured on samples of the polyamino acids after hydrolysis in 2N HC1 for 2 hours under reflux by the Conway microdiffusion technique using No. 2 units. Ammonia was absorbed in 0.5% boric acid solution and titrated with 0.01 N HC1 using a micrometer syringe. 

While low serum cholesterol levels have been observed in malnourished patients, largely as a result of decreased synthesis of lipoproteins in the liver, hypocholesterolemia occurs later in the course of malnutrition and is therefore not useful as a screening test. PEM usually results in low serum urea nitrogen (BUN), urinary urea, and total nitrogen. Estimation of 24-h urine creatinine excretion is also a valuable biochemical index of muscle mass (when there is no impairment in renal function). The urinary CHI is correlated to lean body mass and anthropometric measurements. In edematous patients, for whom the extracellular fluids contribute to body weight and spuriously high body mass index values, the decreased CHI values are especially useful in diagnosing malnutrition. 

Isopropanol (1) and water (2) are condensing in the presence of nitrogen (3) inside a vertical tube of 2.54 cm inside diameter. At the vapor inlet, the bulk composition of the gas phase is 11.23 mol% isopropanol, 42.46% water, and 46.31% nitrogen. The interfacial vapor composition is 14.57 mol% isopropanol, 16.40% water, and 69.03% nitrogen. Estimate the molar rates of condensation of isopropanol and water at that point. The following data apply ... 

In Van Slyke s method, the amino compound is added to a mixture of 30 per cent, sodium nitrite and glacial acetic acid contained in a special type of apparatus, which is shaken vigorously for five minutes. The evolved gas is expelled, treated with alkaline permanganate to absorb nitric oxide, which forms as a by-product, and the residual nitrogen estimated in a manometer. Under standard conditions, the a-amino groups lose all their nitrogen within five minutes. 

---