TY - JOUR
T1 - Simplifying silver isotope analysis of metallic samples
T2 - using silver nitrate precipitation to avoid perilous chloride formation
AU - McCoy-West, Alex J.
AU - Davis, Alison M.
AU - Wainwright, Ashlea N.
AU - Tomkins, Andrew G.
N1 - Funding Information:
We are very gratefully to Michael Brauns and Gerhard Brügmann for undertaking comparative Ag isotope analyses at CEZ, Manheim. AMW acknowledges ARC grants FL160100168 and DE210101395. AMD acknowledges receipt of an Australian Postgraduate Award PhD scholarship. AGT acknowledges ARC grant LP015100717. ANW acknowledges ARC grant FL160100168. Simon Hitchman, Wess Edgar, Nathan Phillips from Fosterville gold mine, then operated by Kirkland Lake Gold, are thanked for their assistance in obtaining gold samples. Tom Kapitany is thanked for providing native Ag samples. Massimo Raveggi, Yona Jacobson, and Oliver Nebel are thanked for technical assistance and discussions at Monash. We thank two anonymous journal reviewers for their constructive comments.
Publisher Copyright:
© 2024 The Royal Society of Chemistry.
PY - 2024/3/1
Y1 - 2024/3/1
N2 - Silver (Ag) isotopes have the potential to provide useful insights into a diverse range of geological, environmental, and archaeological processes. This manuscript presents a novel technique that provides a simple, time-efficient, and accurate method for obtaining Ag isotope compositions of metallic gold (Au) samples. Unlike previous methodologies that favoured multiple ion exchange columns to purify and isolate Ag in nitrate form. This technique instead uses a single anion-exchange column, followed by the chemical conversion of Ag from chloride to nitrate form using the widely available reagents, ammonium hydroxide and ascorbic acid. This chemical conversion not only speeds up and simplifies sample processing allowing increased sample throughput, but importantly also significantly reduces the risk of Ag loss (and therefore user-induced isotopic fractionation) while converting the samples into a medium suitable for mass spectrometry. In this study, both pure Ag and native Au samples have been investigated, with Ag isotope compositions given relative the NIST SRM978a Ag standard. The long-term reproducibility of the in-house Sigma MON Ag solution was ϵ109Ag = 1.32 ± 0.31 (2 s.d.; n = 34), which is comparable to the precision achievable for unprocessed high-purity Ag samples with replicate analyses generating an average precision of ϵ109Ag = ± 0.25 (2 s.d.; n = 5). Comparable levels of precision were also achieved for natural Au samples, indicating that this methodology has no resolvable effect on the precision of the Ag isotope measurements. The natural Au standard CEZAg was used to test the external reproducibility of the chemical separation and conversion technique, yielding an average value of ϵ109Ag = 0.34 ± 0.13 (2 s.d.; n = 6), which is within analytical uncertainty of the previous determinations, demonstrating the accuracy of the new methodology. Furthermore, analysis of natural Au gold nuggets from the Fosterville Au Mine using the chemical conversion process described herein and a previously published multiple column method at a different institution produced consistent Ag isotope compositions, confirming the accuracy of the measurements generated using this method.
AB - Silver (Ag) isotopes have the potential to provide useful insights into a diverse range of geological, environmental, and archaeological processes. This manuscript presents a novel technique that provides a simple, time-efficient, and accurate method for obtaining Ag isotope compositions of metallic gold (Au) samples. Unlike previous methodologies that favoured multiple ion exchange columns to purify and isolate Ag in nitrate form. This technique instead uses a single anion-exchange column, followed by the chemical conversion of Ag from chloride to nitrate form using the widely available reagents, ammonium hydroxide and ascorbic acid. This chemical conversion not only speeds up and simplifies sample processing allowing increased sample throughput, but importantly also significantly reduces the risk of Ag loss (and therefore user-induced isotopic fractionation) while converting the samples into a medium suitable for mass spectrometry. In this study, both pure Ag and native Au samples have been investigated, with Ag isotope compositions given relative the NIST SRM978a Ag standard. The long-term reproducibility of the in-house Sigma MON Ag solution was ϵ109Ag = 1.32 ± 0.31 (2 s.d.; n = 34), which is comparable to the precision achievable for unprocessed high-purity Ag samples with replicate analyses generating an average precision of ϵ109Ag = ± 0.25 (2 s.d.; n = 5). Comparable levels of precision were also achieved for natural Au samples, indicating that this methodology has no resolvable effect on the precision of the Ag isotope measurements. The natural Au standard CEZAg was used to test the external reproducibility of the chemical separation and conversion technique, yielding an average value of ϵ109Ag = 0.34 ± 0.13 (2 s.d.; n = 6), which is within analytical uncertainty of the previous determinations, demonstrating the accuracy of the new methodology. Furthermore, analysis of natural Au gold nuggets from the Fosterville Au Mine using the chemical conversion process described herein and a previously published multiple column method at a different institution produced consistent Ag isotope compositions, confirming the accuracy of the measurements generated using this method.
UR - http://www.scopus.com/inward/record.url?scp=85184075453&partnerID=8YFLogxK
U2 - 10.1039/d3ja00374d
DO - 10.1039/d3ja00374d
M3 - Article
AN - SCOPUS:85184075453
SN - 0267-9477
VL - 39
SP - 780
EP - 790
JO - Journal of Analytical Atomic Spectrometry
JF - Journal of Analytical Atomic Spectrometry
IS - 3
ER -