Direct Colorimetric Determination of Serum Calcium witho-Cresolphthalein Complexon

Abstract

A simple, rapid colorimetric procedure for measuring calcium with a single, stable o-cresolphthalein complexon reagent is described. The procedure is accurate (r² = 0.96; recovery = 98.8%), precise (C.V. = 1.9%) and sensitive (absorptivity = 740). The color developed is stable for several hours. The procedure does not require deproteinization, and phosphorus, magnesium, bilirubin, hemoglobin, and albumin do not interfere. Linearity extends to 18 mg. per dl.