Radiometric determination of trace amounts of zinc using liquid scintillation counting

A sensitive and selective radiometric method of substoichiometric isotope dilution analysis for the determination of trace amounts of zinc is described. The activity of (65)Zn used as a tracer in this method was measured by liquid scintillation counting and its counting efficiency was found to be 76+/-2.7%. The method is based on the extraction of the ion-association complex of zinc from thiocyanate medium at pH 7.9 using substoichiometric amount of Aliquat-336 in toluene. The method is sensitive to 20 ng of Zn(II) in an aqueous phase volume of up to 15 ml and its reliability was tested by applying it to a certified reference material-magnesium alloy and pharmaceutical samples.