Abstract
An indirect method for determining biuret in mixed fertilizers and urea has been developed. An alcoholic solution of biuret and copper is treated with a strong base to form a biuret-copper complex and to precipitate the excess copper. After separation of the precipitate, the complexed copper in solution is determined by atomic absorption spectrophotometry. Even though a stoichiometric ratio did not exist, a linear relationship between copper and biuret was obtained and was utilized for the determination of biuret. The proposed method is accurate and proved rugged for the range of biuret normally found in mixed fertilizers and urea when subjected to Youden’s ruggedness test.
Abstract
An uncomplicated, indirect method is described for the determination of α-amino nitrogen in plasma. Plasma is deproteinized with trichloroacetic acid and the protein-free filtrate is neutralized with alkali. The α-amino groups complex with and solubilize copper from insoluble copper phosphate. The solubilized copper, measured by atomic absorption spectrophotometry, is proportional to the amount of α-amino nitrogen present in the plasma.
Abstract
The atomic absorption method studied last year was re-examined and extended to include calcium and sodium. The procedures were submitted to 16 collaborators for determination of Ca, Cu, Fe, Mg, Mn, Na, and Zn. Results for Ca and Na were discouraging; further study is recommended.
Abstract
The official first action AOAC method for the spectrophotometric determination of biuret in urea, 2.072—2.074, was compared with official first action AOAC method 2.C01-2.C03 (atomic absorption spectrophotometry), 2 simplified versions of 2.072-2.074, and modified versions of 2 alternative procedures of the International Organization for Standardization. Three synthetic urea samples (0.3, 1.4, and 3.0% biuret) and 1 commercial urea sample (1.0% biuret) were analyzed. The methods proved to be equivalent and none showed a definite advantage over 2.072-2.074. The purification of biuret and the interference by ammonia are also discussed.
Determination of Trace Amounts of Arsenic(III) and Arsenic(V) in Drinking Water and Arsenic(III) Vapor in Air by Graphite-Furnace Atomic Absorption Spectrophotometry Using 2,3-Dimercaptopropane-1-sulfonate as a Complexing Agent.