Determination of Trace Gold in Plant Samples from a Gold Mining Area by Graphite Furnace Atomic Absorption Spectrometry with Ascorbic Acid as the Matrix Modifier

Abstract

Determination of low-level gold in geochemical samples by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) has good accuracy. However, this method is limited to the determination of trace gold in plants due to the large sample amount of > 20 g required, incomplete ashing in the muffle furnace, and a high detection limit of 0.29 ng/g. A revised method of determining trace gold in plant samples from a gold mining area by GFAAS is proposed. The heating process in a graphite furnace Involves ashing and atomization temperatures of 1000℃ and 2000℃, respectively, and ascorbic acid is used as the matrix modifier. Sample ashing temperature of 500℃ and an ashing time of 2.0 h in a porcelain crucible can guarantee the complete ashing of samples and avoid volatilization loss. This method uses small weight samples of 5.0g, the detection limit is 0.03 ng/g, the precision is 6.8%-11.9%, and standard addition recoveries are 83.8%-104.7%. It was also found that different plants have different capacities of gold enrichment with maize containing the highest enrichment.

Keywords

• plant samples in gold mining area
• trace gold
• graphite furnace atomic absorption spectrometry
• ascorbic acid
• porcelain crucible