[Measurement of calcium content in the blood and other biological fluids by Arsenazo III complexone]

A method of photometric measurement of total calcium in the serum and other biological liquids using Arsenazo III color complexone is offered. Physicochemical characteristics of Arsenazo III (mol extinction, affinity for other ions, spectral characteristics, and its complex with calcium) are described. Calcium was measured in 750 normal subjects, its reference value was 2.15-2.75 mmol/liter, the mean value 2.47 mmole/liter. In semiautomated measurement CV% was about 5%. The reagent is convenient, particularly for automated analyzers; no other reagent are needed, it can be stored for a long time at room temperature, and gives stable results.