Determination of Trace Cadmium in Biological Materials by Neutron and Photon Activation Analyses

Abstract

Two nuclear activation techniques have been applied for the determination of trace cadmium residues in a variety of Canadian foodstuffs, soils, and other biological materials. A neutron activation procedure based on radiochemical isolation of 115Cd has been used for p.p.b. concentrations in foods, vegetables, and scalp hair whereas an instrumental photon activation method employing assay of 111mCd with a solid state Ge(Li) detector has been useful for soil, fertilizer, and a few vegetation samples at p.p.m. levels. For the latter technique, bombardment at either 15 or 35 MeV has been used, the higher energy bombardment gave a slightly higher sensitivity. However, in samples containing appreciable amounts of indium and tin, interference is minimized by irradiating at the lower energy.The cadmium content of most Canadian foods ranged from 2–70 p.p.b.; agricultural soils studied contained 0.5–2 p.p.m., some of which could be attributed to fertilizers containing up to 5 p.p.m. of cadmium, whereas vegetable crops grown on such soils generally contained 0.1–0.2 p.p.m. For scalp hair, cadmium concentrations ranged from 0.25–2.0 p.p.m.The accuracy of the nuclear activation techniques was assessed with standard reference materials and by comparison with atomic absorption and the agreement was generally in the range of 2–7%.