Slurry sampling for the determination of silver and gold in soils and sediments using electrothermal atomic absorption spectrometry

Procedures for determining silver and gold in soil and sediment samples using electrothermal atomic absorption spectrometry are discussed. Slurries are prepared from the samples and fast-program methodology is used for the heating cycle. To determine silver, suspensions are prepared by weighing 5–200 mg of sample and adding 25 ml of a solution containing 3% v/v concentrated nitric acid, 50% v/v concentrated hydrogen peroxide and 25% v/v concentrated hydrofluoric acid. For gold determination, slurries are prepared by weighing up to 200 mg of sample and then adding 1 ml of concentrated hydrofluoric acid. For both cases, the slurries are submitted to a 10 min mild heating stage. After cooling to ambient temperature, the suspensions are introduced directly into the atomizer. No modifier other than hydrofluoric acid and hydrogen peroxide (for silver determination) are required and calibration is carried out using aqueous standards. The detection limits are 0.02 and 0.01 mg kg−1 for silver and gold, respectively.