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Abstract

Suitable Mn-Fe rich microanalytical reference materials (MRMs) as calibration material for laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) have not been available. The United States Geological Survey (USGS) in collaboration with the Max Planck Institute for Chemistry has prepared a synthetic MRM, FeMnOx-1, with elevated mass fractions of MnO (25 g/100 g), Fe2O3 (8.5 g/100 g) and high mass fractions of 25 trace elements varying between 200 and 5000 mg/kg. This new MRM has been designed as calibration material for a wide range of different Mn-Fe deposits, such as desert/rock varnish, ocean crusts and nodules as well as Mn accumulations in soils and lakes. Small-scale and large-scale homogeneity of FeMnOx-1 were tested with three LA systems (200 nm femtosecond, and 193 nm and 213 nm nanosecond lasers) using different spot sizes and fluences. Our results demonstrate that FeMnOx-1 is homogeneous in the pg to mu g and nm to mu m range and therefore well suited for microanalytical applications. The relative standard deviation (RSD) values obtained from repeated measurements are about 2-3% for test portion masses of 5-100 ng, and are comparable to those of the homogeneous NIST SRM610 and USGS GSE-1G reference glasses. Homogeneity of FeMnOx-1 was also verified for a test portion of 0.1 ng. Seven laboratories using five different bulk and microanalytical techniques were involved in the characterization of FeMnOx-1. Small amounts of this MRM can be obtained on request from the authors. (C) 2016 Elsevier B.V. All rights reserved.