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The certified values and uncertainties are expressed as mass fraction.

All certified values were determined on an “as received” basis, without drying the material. The uncertainty attached to the certified values is the expanded uncertainty using a coverage factor k=2, corresponding to a confidence interval of approximately 95 %.
AAS, atomic absorption spectroscopy; ICP-OES, inductively coupled plasma optical emission spectrometry; ICP-MS, inductively coupled plasma mass spectrometry; INAA, instrumental neutron activation analysis; PIXE, proton induced X-ray emission spectrometry; XRF, X-ray fluorescence spectroscopy.

The referece values are expressed as mass fraction.

All certified values were determined on an “as received” basis, without drying the material.
ICP-OES, inductively coupled plasma optical emission spectrometry; ICP-MS, inductively coupled plasma mass spectrometry; INAA, instrumental neutron activation analysis; XRF, X-ray fluorescence spectroscopy.

The property values of the material were statistically determined based on chemical analyses by 8 organizations (including 13 laboratories) using a wide range of methods. A property value satisfying the following conditions was accepted as a certified value: 1) the relative standard deviation associated with the mean of the laboratory means was 5 % or less; 2) the number of laboratories contributing to the mean of the laboratory means was at least eight; 3) the number of analytical methods contributing to the mean of the laboratory means was at least two. The uncertainty attached to the certified values is the expanded uncertainty using a coverage factor k=2, corresponding to a confidence interval of approximately 95 %. A property value failing to satisfy one or two of the NIES criteria for certification but supplying valuable additional information about the material is given as a reference value. All certified and reference values were determined on an “as received” basis, that is, the values were determined without drying the material.

The CRM is supplied as fine powder in an amber glass bottle. It is pale grayish-yellow in color similar to wind-borne kosa dust has been reported from Japan, and it contains about 1 % carbonate carbon originating mainly from calcite (kosa dust characteristically contains calcite).

This CRM was produced from surface soil collected at four sampling sites (around 44 oN, 109 oE) in the south-western Gobi Desert in May 2011. Dust and sandstorms occur frequently in this area each spring. The collected surface soil (1200 kg) was fractionated in a controlled dust generation chamber in the Sainshand Meteorological Center, Mongolia, using a cyclone-type classification apparatus and the fine dust particles (<10 μm diameter) were collected. This material (about 2 kg) was further refined and homogenized at NIES to yield 1.2 kg suitable for the CRM. The final fine dust was placed in amber glass bottles (2 g in each bottle, 500 bottles), and sterilized by 60Co irradiation (25 kGy). All procedures complied with ISO GUIDE 34.

Mass fractions of multi-elements, including those for which certified values are given, were determined by XRF in material taken from 10 bottles selected from the total 500 bottles by stratified random sampling. The between-bottle variation evaluated by a one-way analysis of variance (ANOVA) showed the relative standard deviations between bottles for the analytes to be less than 1 %. The material, therefore, is sufficiently homogeneous for its intended use as a reference material.

1. Care should be taken to avoid contamination when opening the bottles. It is desirable to use up the contents as quickly as possible after opening.
2. This CRM should be kept tightly closed in its original bottle and stored in a desiccator at room temperature (≤30 oC).
3. Prior to weighing portions for analysis, the contents of the bottle should be shaken gently.
4. It is recommended that a sample intake of 0.02 g is the minimum for convenient handling.
5. Precautions should be taken to avoid inhalation of the material.
6. This CRM should not be used for purposes other than research. When disposing of the material, local laws concerning processing and disposal of waste materials should be strictly adhered to.
7. The mass fractions of elements in this CRM are reported on an “as received” basis without drying. This CRM, as received, has an average moisture content of 3.2 % as measured in NIES by drying 14 separate sub-samples for 4 h at 105 oC.
8. This CRM contains approximately 2 % carbon. An appropriate analytical method should be selected.

The expiry date for the certified values of this CRM is September 2022 assuming that the recommended storage conditions are adhered to. NIES will notify via its website if any changes in the contents are recognized within the term of validity.

The certified and reference values for this CRM were based on analytical values from the following eight participating organizations: 
National Institute for Environmental Studies; China Institute of Atomic Energy; Elemental Analysis, Inc.; Green Blue Corporation; IDEA Consultants, Inc.; Murata Keisokuki Service Co. Ltd; Nittech Research Inc.; Shimadzu Techno-Research Inc.

The raw and secondary materials of the CRM were obtained under the international collaboration by Institute of Meteorology and Hydrology, National Agency for Meteorology and Environment Monitoring and Sainshand Meteorological Center, Mongolia.