Liquid scintillation counting of Ca in geochemical studies

A simplified method for the use of radioactive calcium in experimental geochemistry is described. The technique accomodates aqueous samples from 1.0 to 3.5 ml with high and constant efficiency (50%). Solutions containing sea water, HCl, and organic complexing agent have been assayed for ⁴⁵Ca with a precision of ±3% for one standard deviation. The use of Triton X-100 in the two-phase emulsion liquid-scintillation method noted here reduced self absorption and sample-preparation problems usually associated with the counting of aqueous samples of beta emitters such as ⁴⁵Ca. With this technique the application of radioisotope methodology to the study of calcium is facilitated.