Direct Determination of High Grade Gold in Ore by Flame Atomic Absorption Spectrometry with Aqua Regia Sampling Preparation

Atomic absorption spectrometry (AAS) was applied to the determination of gold in ores with high grade gold, effectively avoiding the problems caused by the fire assay gravimetric and volumetric method with forcyanide quinone, such as the large amount of toxic chemical reagents required and limits of measurement conditions. Foam enrichment-Flame Atomic Absorption Spectrometry (FAAS) can determine the grade of gold reached up to 500 μg/g in gold ore, but this method adds the filter residue separation, diluted and foam ashing, redissolving process based on the conventional FAAS method. Due to the increase in time of the operation process, the analysis efficiency is not high with increasing probability of error. In this paper, a fast analysis method for high grade gold ore is described. The gold ore sample was dissolved by aqua regia, followed by filtering of the residue. The filtrate with constant volume without preconcentration and separation was determined with FAAS. The precision of the method (RSD) is 1.6%, which is an improvement on the precision of FAAS itself and meets the monitoring requirements of rapid analysis for high grade gold ore samples. The gold ore sample collected from Heilongjiang province (a production monitoring samples), an inspection gold ore sample and a national standard gold ore sample were selected to study the established method in this paper, foam adsorption-FAAS method, cyanide quinone capacity method and fire assay gravimetric method. The results show that the accuracy of the iron content directly affects the high grade gold determination. When the gold sample size was 50-110 μg/g, 110-164 μg/g and 164-218 μg/g, the amount of iron content allowed in the samples was no more than 10%, 20% and 25%, respectively. Based on these studies, this presented method is suitable for gold ore samples with more than 50 μg/g gold and less than 10% Fe. The average content of iron in the earth's crust is 5.63%, and the iron content of most national standard reference gold ore materials are close to the average value. The iron content in general gold ores are rarely at a higher level. Therefore, this method is highly suitable. Compared with the method of foam adsorption-FAAS, the operation processes of foam adsorption-ashing-redissolving were eliminated, which greatly improved the analysis efficiency.