Automatic Titration of Calcium or Magnesium in Blood Serum

Abstract

Direct automatic derivative spectrophotometric EDTA titration procedures for Ca and Mg in blood serum are described. Calcium is automatically titrated in the Sargent-Malmstadt "Spectro" titrator at pH 13 using Calcon as indicator. The results obtained by the automatic method are of the same degree of accuracy and reproducibility as those obtained by the classic permanganate titration of precipitated calcium oxalate. Total Ca and Mg can be titrated automatically at pH 10 with Eriochrome Black T as indicator, and magnesium is calculated by difference between total Ca and Mg and Ca only. The average automatic titration time for each Ca determination is about 10 seconds and about 15 seconds for total Ca and Mg. The total time for the complete procedure for each Ca or Mg determination is about 5 minutes.