Measurement of the Isotopic Composition of Molybdenum in Geological Samples by MC‐ICP‐MS using a Novel Chromatographic Extraction Technique

Abstract

A novel preconcentration method is presented for the determination of M o isotope ratios by multi‐collector inductively coupled plasma‐mass spectrometry ( MC ‐ ICP ‐ MS ) in geological samples. The method is based on the separation of M o by extraction chromatography using N‐benzoyl‐N‐phenylhydroxylamine ( BPHA ) supported on a microporous acrylic ester polymeric resin (Amberlite CG ‐71). By optimising the procedure, M o could be simply and effectively separated from virtually all matrix elements with a single pass through a small volume of BPHA resin (0.5 ml). This technique for separation and enrichment of M o is characterised by high selectivity, column efficiency and recovery (~ 100%), and low total procedural blank (~ 0.18 ng). A 100 M o‐ 97 M o double spike was mixed with samples before digestion and column separation, which enabled natural mass‐dependent isotopic fractionation to be determined with a measurement reproducibility of < 0.09‰ (δ 98/95 M o, 2 s ) by MC ‐ ICP ‐ MS . The mean δ 98/95 Mo SRM 3134 ( NIST SRM 3134 Mo reference material; Lot No. 891307) composition of the IAPSO seawater reference material measured in this study was 2.00 ± 0.03‰ (2 s , n = 3), which is consistent with previously published values. The described procedure facilitated efficient and rapid Mo isotopic determination in various types of geological samples.