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

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1778
Author(s):  
Yan-hong Liu ◽  
Bo Wan ◽  
Ding-shuai Xue
Keyword(s):  
Inductively Coupled Plasma ◽  
Direct Determination ◽  
Important Indicator ◽  
Fire Assay ◽  
Sample Digestion ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry ◽  
Solid Adsorbents ◽  
Exchange Resins

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.

Simultaneous determination of ultra-trace Pt, Pd, Rh and Ir in geochemical samples by inductively coupled plasma mass spectrometry following tin fire assay preconcentration and microwave digestion

2020 ◽  
Vol 16 ◽  
Author(s):  
Wenshan Ni ◽  
Xiangju Mao ◽  
Hongli Zhang ◽  
Lu Liu ◽  
Xiaorui Guo ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Nickel Oxide ◽  
Inductively Coupled Plasma ◽  
Lead Oxide ◽  
Microwave Digestion ◽  
Fire Assay ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry ◽  
Ultra Trace

Background: Platinum (Pt), palladium (Pd), rhodium (Rh) and iridium (Ir) are platinum group elements (PGEs) and also important elements of geochemistry and environmental chemistry with the similar physic-chemical properties, which have been widely used in industry and laboratory. However, due to the low abundance and inhomogeneous distribution in natural ore as well as the nugget effect, the accurate determination of PGEs has been a challenge to analytical chemistry. Methods: In this work, a novel fire assay method was reported for the determination of ultra-trace Pt, Pd, Rh and Ir in geochemical samples. Tin powder (Sn) instead of stannic oxide (SnO2) was used as fire assay collector to reduce the melting temperature from 1250 oC to 1050 oC, the escape of molten material caused by high temperature was successfully avoided. Tin bead was compressed into thin slice and dissolved by HCl. For the target Pt, Pd, Rh and Ir, HCl insoluble substance such as PtSn4, PdSn4, RhSn4 and Ir3Sn7 were formed and separated from matrix by filtering. The metal compounds precipitate together with filter paper were microwave-assisted completely digested by aqua regia (50%, v/v), thence the sample solution were determined by inductively coupled plasma mass spectrometry (ICP-MS). Results: Compared with nickel oxide and lead oxide in nickel sulfide /lead fire assay, the reagent blank of tin powder were relatively low and could be directly employed in tin fire assay to collect Pt, Pd, Rh and Ir without purifying. Moreover, the harm of nickel oxide and lead oxide to the analyst and environment was avoided by using the non-toxic tin powder. The decomposition method of chromite and black shale were investigated as well as the amount of tin powder and flour, microwave digestion program for the determination of Pt, Pd, Rh and Ir were optimized. Besides, the influence of mass spectrum interference of co-existing elements was discussed and the standard mode and kinetic energy discrimination collision pool mode were compared. Under the optimal conditions, excellent curve fitting of Pt, Pd, Rh and Ir were obtained between 0.01～100 ng mL-1 , with the correlation coefficients exceeding 0.9996. The detection limits were from 0.003 ng g -1 to 0.057 ng g -1 . Conclusion: The developed method was applied to analyze the Chinese Certified Reference Materials and the determined values were in good agreement with the certified values.

scholarly journals Slurry nebulisation ICP-MS direct determination of high field strength elements (Nb, Ta, Zr, and Hf) in silicate rocks

RSC Advances ◽  
2019 ◽  
Vol 9 (56) ◽  
pp. 32435-32440 ◽  
Author(s):  
Rui Tong ◽  
Wei Guo
Keyword(s):  
Field Strength ◽  
Inductively Coupled Plasma ◽  
High Field ◽  
Direct Determination ◽  
High Field Strength ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
Silicate Rocks

A simple, rapid, and reliable method based on slurry nebulisation inductively coupled plasma mass spectrometry (ICP-MS) was developed for the direct determination of four high field strength elements (HFSEs, namely, Nb, Ta, Zr, and Hf) in refractory silicate rocks.

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