Rapid dissolution of larger amounts of rock and ore samples by microwave digestion for the estimation of gold by ICP-MS for geochemical prospecting studies

National Geophysical Research Institute, Hyderabad-500 007, India

Manuscript received 14 December 1998, revised 28 April 1999. accepted 29 June 1999

A microwave dissolution method for the determination of gold in sample weight as high as 10 g has been described. The gold concentrations in several field samples and gold reference samples are estimated using ICP-MS after microwave dissolution. ¹⁰³Rh is used as an internal standard. The gold values obtained compare well with the certified values. The average values obtained on the replicate determinations are within 10% RSD with comparable accuracy. The efficiencies of the microwave dissolution and the open-acid-digestion for the extraction of gold in a few field samples are compared. Microwave dissolution is found to be more efficient apart from giving faster dissolution. The detection limit of gold is found to be 0.02 ng/g using this method.