FeMnOx-1: A new microanalytical reference material for the investigation of Mn–Fe rich geological samples

• There is a need for Mn-rich microanalytical reference materials.
• The Mn-rich microanalytical reference material FeMnOx-1 is useful for calibration.
• FeMnOx-1 is homogeneous in the pg to μg and nm to μm range, respectively.
• Different analytical techniques were involved in the characterization of FeMnOx-1.

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 μg and nm to μm 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 SRM 610 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.

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