Determination of serum calcium by glyoxal bis (2-hydroxyanil) chelation.

A simple micro (0.1 ml.) colorimetric method is described for the determination of serum calcium. This method employs the differential chelating characteristic of glyoxyl bis (2-hydroxyanil) in the presence of other divalent cations. The serum sample is placed in a colorimetric tube followed by additions of water, glyoxyl bis (2-hydroxyanil) reagent, and alkaline carbonate color developer. Chloroform is added to extract the chromogen, and its transmittance at 535 m s is determined.