The certified values and uncertainties are expressed as mass fraction.

AAS: atomic absorption spectroscopy
ICP-OES: inductively coupled plasma optical emission spectrometry
ICP-MS: inductively coupled plasma mass spectrometry
ID-ICP-MS: isotope dilution-ICP-MS
INAA: instrumental neutron activation analysis
XRF: X-ray fluorescence spectroscopy

The referece values are expressed as mass fraction.

The certified values and uncertainties are expressed as mass fraction.

AAS: atomic absorption spectroscopy
ICP-OES: inductively coupled plasma optical emission spectrometry
ICP-MS: inductively coupled plasma mass spectrometry

The referece values are expressed as mass fraction.

The property values of the material were statistically determined based on chemical analyses by 13 organizations (including 20 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 under 10 %; 2) the number of laboratories contributing to the mean of the laboratory means was at least ten; 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 the half-width of 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 based on dry mass.

The CRM is supplied as fine powder in an amber glass bottle. It is dark grayish-yellow in color.

The origin of this material is sediment collected at Lake Kasumigaura, Japan in February 1999. The raw sediment was dried in the sun at NIES and the clods that formed were crushed, sieved through a 2 mm sieve, and dried at 105 ºC overnight. This dry material was then ground in an alumina ball mill, and passed first through a 212 µm sieve and then through a 75 µm sieve. The sieved material was homogenized with a V-blender to yield 12.2 kg of powder suitable for use as the CRM. The final material was placed in amber glass bottles (20 g in each bottle, 560 bottles), and sterilized by 60Co irradiation (20 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 560 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 0.05 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 a dry mass basis. This CRM, as received, has less than 1 % water as measured in NIES by drying for 4 h at 105 ºC. Correction to dry mass should be determined by drying a separate sub-sample.

The expiry date for the certified values of this CRM is December 2024 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 13 participating organizations: 
National Institute for Environmental Studies; China Institute of Atomic Energy; Elemental Analysis, Inc.; Environmental Control Center Co., Ltd.; Environmental Research Center Co., Ltd.; IDEA Consultants, Inc.; Japan Environment Sanitation Center; Japan Food Research Laboratories; Kanagawa Industrial Technology Center; Murata Keisokuki Service Co., Ltd.; Naitoh Environmental Science Co., Ltd.; Nippon Steel & Sumikin Technology Co., Ltd.; Shimadzu Techno-Research Inc. 

Appendix Fig.1
Schematic flow-chart of the HCl/HNO3/HClO4 extraction method according to “The Methods for Sediment surveillance” (in Japanese) of the Ministry of the Environment, Japan (public notice, August 2012). 

Appendix Table 1
Information values of Mass fractions of C, N, Si and S in NIES CRM No.31 Lake Sediment

EA: elemental analysis
XRF: X-ray fluorescence spectroscopy
ICP-OES: inductively coupled plasma optical emission spectrometry