Universität zu Köln

Pfeifer, M., Lloyd, N. S., Peters, S. T. M., Wombacher, F., Elfers, B. -M., Schulz, T. and Munker, C. (2017). Tantalum isotope ratio measurements and isotope abundances determined by MC-ICP-MS using amplifiers equipped with 10(10), 10(12) and 10(13) Ohm resistors. J. Anal. At. Spectrom., 32 (1). S. 130 - 144. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 1364-5544

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Abstract

Due to analytical difficulties related to the low abundance of Ta-180 (about 0.012%), the absolute isotope composition of tantalum is not well known and possible natural variations in Ta-180/Ta-181 are so far unconstrained. Improved precision is required in order to evaluate the homogeneity of Ta isotope distributions among solar system materials and whether natural Ta stable isotope variations exist on Earth. Using a Neptune (TM) multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) system and different resistors in the Faraday cup amplifier feedback loops (a 10(10) Omega for Ta-181; 10(12) or newly developed 10(13) Omega resistors for Ta-180 and Hf interference monitor isotopes) now allows relative analyses of Ta-180/Ta-181 with an intermediate precision of ca. +/- 4 epsilon (epsilon refers to one part in 10 000) using 25 to 100 ng Ta and thus even for sample sizes available from meteorites (e.g., 1 g). The 10(13) Omega amplifier resistors proved to be of paramount importance for high-precision Ta isotope ratio measurements of low amounts of material. Tailing effects from the large 181Ta beam have previously been underestimated. A thorough assessment of this effect revealed a tailing contribution of similar to 2.5% on the currently recommended IUPAC ratio. Potential systematic biases in the mass discrimination correction are assumed being of minor importance compared to an uncertainty of similar to 0.4% achieved for the estimate of the true Ta-180/Ta-181 ratio. We propose a new Ta-180/Ta-181 isotope ratio of 0.00011705(41), equivalent to Ta-181/Ta-180 = 8543(30), yielding isotope abundances of 0.011704(41) % for Ta-180 and 99.988296(41) % for Ta-181, and an absolute atomic weight for tantalum of 180.9478787(38) u (all uncertainties with k = 2).

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Pfeifer, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lloyd, N. S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Peters, S. T. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wombacher, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Elfers, B. -M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schulz, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Munker, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-247845
DOI:	10.1039/c6ja00329j
Journal or Publication Title:	J. Anal. At. Spectrom.
Volume:	32
Number:	1
Page Range:	S. 130 - 144
Date:	2017
Publisher:	ROYAL SOC CHEMISTRY
Place of Publication:	CAMBRIDGE
ISSN:	1364-5544
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PLASMA-MASS SPECTROMETRY; MULTIPLE FARADAY COLLECTORS; ATOMIC-WEIGHT; SOLAR-SYSTEM; CARBONACEOUS CHONDRITES; OMEGA AMPLIFIERS; PRECISE; NEBULA; EARTH; TIMS Multiple languages Chemistry, Analytical; Spectroscopy Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/24784