Detection limit for silver by energy-dispersion X-ray analysis using radioisotopes

Abstract

The purpose of this study was to determine the sensitivity for silver in silica using radioisotopic X-ray sources, electronic discrimination with a single-channel analyzer, and scintillation detectors. The sensitivity for silver was determined as a function of excitation energy. Using monoenergetic K-spectra X-ray sources Sb, Te, and Ba, a normalized detection limit ranging from 21 to 13 ppm was obtained for 100-sec counting intervals. With an annular 125I source a detection limit of 15 ppm silver was measured. The effect on the detection limit of heavy metals common to silver ores was also investigated. A detection limit of 25 ppm or less was still obtained when 5 percent concentrations were present in the silica matrix provided X-ray interferences with the Ag Kα radiation did not exist. The need for accurate background measurements for analysis in the parts-per-million range was emphasized. The sensitivities found in this work indicate that a portable radioisotopic X-ray analyzer could be designed for low-grade silver ores.