Abstract
A developed method was designed for gold determination directly in organic medium in some sedimentary rocks (fine sandstone, carbonates), pyrite, serpentine and international standard gold sample (MA-1a) using flame atomic absorption spectroscopy (FAAS). Instrumental parameters; burner angle, fuel flow rate, band pass and burner height together with chemical parameters; different media, leaching and interference effect were optimized to improve gold determination. Selective leaching using a new mixture (5% KCN, 5% Na2S2O3 and hydrogen peroxide) offered maximum leaching percentage of gold (>99%) with minimal concentration of accompanying elements. Extraction parameters using methyl isobutyl ketone (MIBK) from 3 M HCl were optimized for more than 99% gold extraction, followed by scrubbing using 0.1 M HCl. Gold was determined directly in organic phase. Beer’s law was obeyed from 0.01 μg/ml to 10 μg/ml. Standard deviation (from 0.017 to 1.05) and percentage error (from 1.5% to 2.5%) using the present developed AAS method were calculated.
Highlights
Gold belongs to the group of elements which occur on the Earth with very low natural abundances
Many techniques were available for gold determination using either the classical methods, such as fire assay (FA) or modern instrumental methods such as flame atomic absorption spectrometry (FAAS) [4]-[7], graphite furnace atomic absorption spectrometry (GFAAS) [8], inductively coupled plasma atomic emission spectrometry (ICP-AES) [9], inductively coupled plasma mass spectrometry (ICP-MS) [10] [11] and neutron activation analysis (NAA) [12], where these techniques were coupled with solvent extraction, ion exchange, or coprecipitation methods, which gave reliable results even from rock matrix, rich in the interfering species especially iron, present in appreciable quantity in sulfide faces banded iron formations (SBIF) [13]
For successful development of the present studied method, several certified samples must be available to evaluate the efficacy of the method, there was a lack in the certified samples and this was overcome by analyzing several types of rocks bearing gold using the established accurate, but time consuming, fire assay method to be used as certified samples, Table 1
Summary
Gold belongs to the group of elements which occur on the Earth with very low natural abundances. (2015) The Application of Flame Atomic Absorption Spectrometry for Gold Determination in Some of Its Bearing Rocks. Many techniques were available for gold determination using either the classical methods, such as fire assay (FA) or modern instrumental methods such as flame atomic absorption spectrometry (FAAS) [4]-[7], graphite furnace atomic absorption spectrometry (GFAAS) [8], inductively coupled plasma atomic emission spectrometry (ICP-AES) [9], inductively coupled plasma mass spectrometry (ICP-MS) [10] [11] and neutron activation analysis (NAA) [12], where these techniques were coupled with solvent extraction, ion exchange, or coprecipitation methods, which gave reliable results even from rock matrix, rich in the interfering species especially iron, present in appreciable quantity in sulfide faces banded iron formations (SBIF) [13]. By scrubbing the loaded organic phase, the interfering ions were washed away and gold was determined in the organic phase directly using flame atomic absorption spectroscopy
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