Ultrasensitive determination of gold in geogas by laser excited atomic fluorescence spectrometry

Ultratrace gold (Au) in geogas samples has been determined by means of laser excited atomic fluorescence spectrometry combined with graphite electrothermal atomization anc: time-gate technique. Gold atoms were excited from the ground state to the 6p(2)P(3/2) State by a pulsed laser beam with a wavelength of 242.8 nm. Fluorescence photons with a wavelength of 312.3 nm were measured by a photon-counting unit. The time-gate technique was used to reduce the background radiation caused by the furnace. This method has proved to be highly sensitive with minimal background interference. Eighty-two geogas samples were analysed and the Au contents obtained were in the range of 0.002-0.182 ng l(-1). The study of Au concentration of geogas in soil is of great interest in prospecting gold deposits. (C) 1997 Elsevier Science B.V. All rights reserved.