The protein content of dry biomass of the microalgae Porphyridium cruentum, Scenedesmus almeriensis, and Muriellopsis sp. and of the cyanobacteria Synechocystis aquatilis and Arthrospira platensis was measured by the Lowry method following disruption of the cells by milling with inert ceramic particles. The measurements were compared with the Kjeldahl method and by elemental analysis. The nitro...

In 1883, in Fresenius' Zeitschrift fur analytische Chemie, there appeared a paper by Johan Kjeldahl of the Carlsberg Laboratory in Copenhagen entitled "A new method for the determination of nitrogen in organic substances."35 This contribution has had an effect upon analytical chemistry in general and especially upon the application of analytical chemistry to agricultural and physiological chemi...

We evaluated four spectrophotometric methods for suitability in determining total protein in human milk samples. Results were compared with those by an established method for the determination of total nitrogen (micro-Kjeldahl). Values for total protein by all four methods significantly correlated with micro-Kjeldahl. For the biuret assay, Lowry-Peterson assay, Bio-Rad Coomassie Blue assay, and...

This instrumental method for total urinary nitrogen (TUN) is based on the principle of gas-phase chemiluminescence. Results correlate well with measurements of TUN by the Kjeldahl method, which has long provided the means to calculate nitrogen balances for nutritional management. In recent years, because of speed and convenience of measurement, determination of urinary urea nitrogen (UUN) has b...

Quantitative estimations of total protein in biological fluids may be performed by the micro Kjeldahl reaction with or without distillation (Rappaport and Lasowski, 1943), by a colorimetric method such as the biuret (Weichselbaum, 1946; Kingsley, 1940), by measuring the specific gravity according to the method of Phillips, Van Slyke, Emerson, Hamilton, and Archibald (1944), by the turbidimetric...