Sample Digestion and Combined Preconcentration Methods for the Determination of Ultra-Low Gold Levels in Rocks

Abstract

The gold abundance in basic rocks, which normally varies between 0.5 and 5 ppb, has served as a very important indicator in many geoscience studies, including those focused on the planetary differentiation, redistribution of elements during the crustal process, and ore genesis. However, because gold is a monoisotopic element that exhibits a nugget effect, it is very difficult to quantify its ultra-low levels in rocks, which significantly limits our understanding of the origin of gold and its circulation between the Earth crust, mantle, and core. In this work, we summarize various sample digestion and combined preconcentration methods for the determination of gold amounts in rocks. They include fire assay, fire assay combined with Te coprecipitation and instrumental neutron activation analysis (INAA) or laser ablation inductively coupled plasma mass spectrometry, fusion combined with Te coprecipitation and anion exchange resins, dry chlorination, wet acid digestion combined with precipitation, ion exchange resins, solvent extraction, polyurethane foam, extraction chromatography, novel solid adsorbents, and direct determination by INAA. In addition, the faced challenges and future perspectives in this field are discussed.

Strategies to overcome interferences in elemental and isotopic geochemical analysis by quadrupole inductively coupled plasma mass spectrometry: A critical evaluation of the recent developments

“…Since these interferences originate from the sample matrix, removal of interference‐causing elements from the matrix is normally practiced by methods such as precipitation, 63 solvent extraction64 and ion‐exchange chromatography 65 . Fire‐assay separation and preconcentration methods are the best for the determination of precious metals in geological materials 66–68 . Agatemor and Beauchemin 28 discussed the advantages and limitations of some of these sample pretreatment analyte–matrix separation methods for the ICP‐MS analysis of some geological materials.…”

A new desorption method of polyurethane foam for the determination of gold and a comparative study on four desorption methods based on meta-analysis

“…The treatment methods before gold determination include dry ashing, [2][3][4] and wet acid digestion. Enrichment, such as precipitation, 5 ion exchange resin, 6 solvent extraction, [7][8][9] PUF adsorption, 10,11 extraction chromatography, 12 is followed. There are many testing methods for gold, including atomic absorption spectrometry, 13 inductively coupled plasma mass spectrometry 14,15 and so on.…”

Validación Del Método Para La Determinación De Oro Por Ensayo Al Fuego Combinado Con Espectrometría De Absorción Atómica en Muestras Geológicas Mineras Metalúrgicas

“…Los tamaños ideales de partícula de la muestra son los menores o iguales a 0,075 mm (Osman Ali Salih, 2018). En el análisis de oro mediante ensayo al fuego se debe considerar que las recuperaciones de oro cuando está presente el teluro suelen ser bajas (Liu et al,2019;Santos-Munguía et al, 2019).…”

“…Una variante del ensayo al fuego tradicional es el cambio del plomo por níquel, pero se reportan varios problemas y bajas recuperaciones (Liu et al, 2019). Dentro de las técnicas para determinar oro, luego de su recuperación y purificación, se encuentra la espectroscopia de absorción atómica con llama, la espectroscopia de absorción atómica con horno de grafito, y la es-pectrometría de masas con plasma acoplado inductivamente, el requisito para utilizarlas es que el oro se encuentre en solución.…”