Universität zu Köln

Schnabel, Christiane, Muenker, Carsten and Strub, Erik ORCID: 0000-0002-4136-2871 (2017). La-Ce isotope measurements by multicollector-ICPMS. J. Anal. At. Spectrom., 32 (12). S. 2360 - 2371. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 1364-5544

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Abstract

The La-138-Ce-138 decay system (half-life 1.02 x 10(11) years) is a potentially highly useful tool to unravel information about the timing of geological processes and about the interaction of geological reservoirs on earth, complementing information from the more popular Sm-147-Nd-143 and Lu-176-Hf-176 isotope systems. Previously published analytical protocols were limited to TIMS. Here we present for the first time an analytical protocol that employs MC-ICPMS, with an improved precision and sensitivity. To perform sufficiently accurate La-Ce measurements, an efficient ion-chromatographic procedure is required to separate Ce from the other rare earth elements (REE) and Ba quantitatively. This study presents an improved ion-chromatographic procedure that separates La and Ce from rock samples using a three-step column separation. After REE separation by cation exchange, Ce is separated employing an Ln Spec column and selective oxidation. In the last step, a cation clean-up chemistry is performed to remove all remaining interferences. Our MC-ICPMS measurement protocol includes all stable Ce isotopes (Ce-136, Ce-138, Ce-140 and Ce-142), by employing a 10(10) ohm amplifier for the most abundant isotope 140Ce. An external reproducibility of +/-0.253-units (2 r. s. d) has been routinely achieved for Ce-138 measurements for as little as 150-600 ng Ce, depending on the sample-skimmer cone combinations being used. Because the traditionally used JMC-304 Ce reference material is not commercially available anymore, a new reference material was prepared from AMES laboratory Ce metal (Cologne-AMES). In order to compare the new material with the previously reported isotopic composition of AMES material prepared at Mainz (Mainz-AMES), Cologne-AMES and JMC-304 were measured relative to each other in the same analytical session, demonstrating isotope heterogeneity between the two AMES and different JMC-304 batches used in the literature. To enable sufficiently precise age correction of radiogenic Ce-138 and to perform isochron dating, a protocol was developed where La and Ce concentrations are determined by isotope dilution (ID), using an isotope tracer enriched in La-138 and Ce-142. The new protocols were applied to determine the variations of Ce isotope compositions and La-Ce concentrations of certified geochemical reference materials (CRMs): BCR-2, BCR-1, BHVO-2, JR-1, JA-2, JB-3, JG-1, JR-1, JB-1b, AGV-1 and one in-house La Palma standard.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Schnabel, Christiane UNSPECIFIED UNSPECIFIED UNSPECIFIED Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED Strub, Erik UNSPECIFIED orcid.org/0000-0002-4136-2871 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-209532
DOI:	10.1039/c7ja00256d
Journal or Publication Title:	J. Anal. At. Spectrom.
Volume:	32
Number:	12
Page Range:	S. 2360 - 2371
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 RARE-EARTH-ELEMENTS; REE ABUNDANCES; MC-ICPMS; SM-ND; GEOCHEMICAL SAMPLES; PRECISE MEASUREMENT; WEST GREENLAND; CE/ND ISOTOPE; CERIUM; SYSTEMATICS Multiple languages Chemistry, Analytical; Spectroscopy Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/20953