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Current Analytical Chemistry


ISSN (Print): 1573-4110
ISSN (Online): 1875-6727

General Research Article

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

Author(s): Wenshan Ni, Xiangju Mao*, Hongli Zhang, Lu Liu, Xiaorui Guo and Qiliang Sun

Volume 17, Issue 4, 2021

Published on: 15 July, 2020

Page: [552 - 563] Pages: 12

DOI: 10.2174/1573411016999200715160650

open access plus


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 a fire assay collector to reduce the melting temperature from 1250°C to 1050°C, 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 was 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 was 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.

Keywords: Chinese certified reference materials, ICP-MS, microwave digestion, platinum group elements, tin fire assay, tin powder.

Graphical Abstract
Kang, C.; Richard, J.W.; Roberta, L.R.; Shan, G.; Richard, M.G.; Igor, S.P.; Ming, T.; Zhao, C.H. Platinum-group element abundances and Re-Os isotopic systematics of the upper continental crust through time: Evidence from glacial diamictites. Geochim. Cosmochim. Acta, 2016, 191(15), 1-16.
Barefoot, R. R. Determination of platinum group elements and gold in geological materials: A review of recent magnetic sector and laser ablation applications. Anal Chim Acta., 2004, 509(2,3), 119-125.,
Noreen, J.E.; Jeffrey, J.D.; John, P.B.; David, F. Contamination-free preparation of geological samples for ultra-trace gold and platinum-group element analysis. J. Geochem. Explor., 2003, 80(1), 19-24.
Barefoot, R.R.; Van Loon, J.C. Recent advances in the determination of the platinum group elements and gold. Talanta, 1999, 49(1), 1-14.
[] [PMID: 18967568]
Shazali, I.; Dack, L.V.; Gijbels, R. Determination of precious metals in ores and rocks by thermal neutron activation/γ-spectrometry after preconcentration by nickel sulfide fire assay and coprecipitation with tellurium. Anal. Chim. Acta, 1987, 196, 49-58.
McDonald, I.; Hart, R.J.; Tredoux, M. Determination of the platinum-group elements in South African kimberlites by nickel sulphide fire-assay and neutron activation analysis. Anal. Chim. Acta, 1994, 289(2), 237-247.
Jackson, S.E.; Fryer, B.J.; Gosse, W. Determination of the precious metals in geological materials by inductively coupled plasma-mass spectrometry (ICP-MS) with nickel sulphide fire-assay collection and tellurium coprecipitation. Chem. Geol., 1990, 83(1-2), 119-132.
Juvonen, R.; Lakomaa, T.; Soikkeli, L. Determination of gold and the platinum group elements in geological samples by ICP-MS after nickel sulphide fire assay: Difficulties encountered with different types of geological samples. Talanta, 2002, 58(3), 595-603.
[ ] [PMID: 18968787]
Shinotsuka, K.; Suzuki, K. Simultaneous determination of platinum group elements and rhenium in rock samples using isotope dilution inductively coupled plasma mass spectrometry after cation exchange separation followed by solvent extraction. Anal. Chim. Acta, 2007, 603(2), 129-139.
[] [PMID: 17963832]
Jarvis, K.E.; Williams, J.G.; Parry, S.J.; Bertalan, E. Quantitative determination of the platinum-group elements and gold using NiS fire assay with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Chem. Geol., 1995, 124(1-2), 37-46.
Renata, K. Recent advances in the preconcentration and determination of platinum group metals in environmental and biological samples. TrAC-Trend. Anal. Chem., 2020, 122115708
Hoffman, E.L.; Naldrett, A.J.; Van Loon, J.C. The determination of all the platinum-group elements and gold in rocks and ore by neutron activation analysis after preconcentration by a nickel sulfide fire assay technique on large samples. Anal. Chim. Acta, 1978, 102, 157-166.
Oguri, K.; Shimoda, G.; Tatsumi, Y. Quantitative determination of gold and platinum-group elements in geological samples using improved Nis fire-assay and tellium coprecipitation with inductively coupled plasma-mass spectrometry (ICP-MS). Chem. Geol., 1999, 157, 189-197.
Reddi, G.S.; Rao, C.R.M.; Rao, T.A.S.; Lakshmi, S.V.; Prabhu, R.K.; Mahalingam, T.R. Nickel suiphide fire assay-ICPMS method for the determination of platinum-group elements: A detailed study on the recovery and losses at different stages. Fresenius J. Anal. Chem., 1993, 348, 350-352.
Sun, Y.L.; Guan, X.Y.; Du, A.D. Determination of platinum group elements by inductively coupled plasma-mass spectrometry combined with nickel sulphide fire assay and tellurium coprecipitation. Spectrochim. Acta B At. Spectrosc., 1998, 53(10), 1463-1467.
Yi, Y.V.; Masuda, A. Simultaneous determination of ruthenium, palladium, iridium and platinum at ultratrace levels by isotope dilution inductively coupled plasma mass spectrometry in geological samples. Anal. Chem., 1996, 68(8), 1444-1450.
Ni, W.S.; Mao, X.J.; Zhang, H.L. Determination of ultra-trace platinum, palladium, ruthenium, rhodium, and iridium in rocks and minerals by inductively coupled–plasma mass spectrometry following nickel sulfide fire assay preconcentration and open mixed acid digestion. Anal. Lett., 2019, 52(11), 1699-1710.
Ni, W.S.; Mao, X.J.; Zhang, H.L.; Liu, L.; Gao, X.F.; Xiao, F. Lead fire assay preconcentration and high resolution continuum source graphite furnace atomic absorption spectrometry for the determination of ultra-trace amounts of Au, Ir, Pd, Pt and Rh in rocks and minerals. Spectrochim. Acta B At. Spectrosc., 2019, 158105643
Moloughney, P.E.; Graham, J.A. Determination of silver in ores and metallurgical concentrates by a combination of fire-assay preconcentration (using tin as collector) and atomic-absorption spectrophotometry. Talanta, 1971, 18(5), 475-479.
[] [PMID: 18960908]
Moloughney, P.E.; Faye, G.H. A rapid fire-assay/atomic-absorption method for the determination of platinum, palladium and gold in ores and concentrates: A modification of the tin-collection scheme. Talanta, 1976, 23(5), 377-381.
[] [PMID: 18961877]

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