The determination of fluorine in rock materials by γ-activation and radiochemical separation

Abstract

A technique is described for the determination of fluorine in rock materials involving irradiation in a source of high energy γ-photons to induce the ¹⁹F (γ,n)¹⁸F reaction. Fluorine-18 is then separated from the radioactive matrix by distillation and its activity measured either in the distillate or as precipitated calcium fluoride and compared with that of irradiated calcium fluoride standards. The technique has been applied to the analysis of standard rock materials G1 (638 p.p.m.), W1 (221 p.p.m.), T1 (476 p.p.m.) and to Apollo 11 lunar fines (76 p.p.m.). Precautions are taken to eliminate interferences. The results obtained for the standard rocks are in good agreement with those of conventional methods but disagree with other activation results. The limit of detection of the method is 0·002 µg.