2018-4-2

Typical Japanese Diet

This certified reference material (CRM) is intended for use in the quality assurance of the analysis of minor and trace elements in the Japanese diet and in similar food matrices. One unit of this CRM contains approximately 18 g of the material in an amber glass bottle.
It was produced by The National Institute for Environmental Studies (NIES), Ibaraki, Japan, and The National Institute of Radiological Sciences (NIRS), Chiba, Japan, and is distributed by NIES.

Preparation of Material

The starting material for this CRM was a composite stock of menus served in 29 households in Japan. The households were asked to duplicate all meals for 3 consecutive days in November 1997-January 1998 and for another 3 days in March-June 1998.

The meals were typical of Japanese households and consists primarily of traditional Japanese foodstuffs with some Western dishes. The meals were frozen in the households and transported to NIES in the frozen state.

The food materials were then homogenized, freeze-dried, pulverized to pass 250 μm nylon screen, blended and bottled. These procedures were compliant with ISO GUIDE 34. Then material was sterilized by 60Co irradiation (2.5 Mrad).

Homogeneity Assessment

The homogeneity of this CRM was assessed at NIES by measuring, by inductively coupled plasma atomic emission spectrometry, the concentrations of Na, Mg, P, K, Ca, Mn, Fe and Zn in four 500 mg-subsamples from each of 6 randomly selected bottles after HNO3/HClO4/HF digestion.

No significant between-bottle variation was detected for these elements. However, a small but significant within-bottle variation was found for Fe, and in the subsequent collaborative analysis, for other trace constituents (e.g., Cr). These elements were excluded from certification.

Certified Values and Reference Values

Certified Values were determined for Na, Mg, K, Ca, Mn, Cu, Zn, As, Se, Sr, Cd, Sn, Ba and U based on a collaborative analysis involving NIES, NIRS and 20 other laboratories. Certified Values are listed in Table 1. Means of the acceptable mean values from the collaborating laboratories were assigned as Certified Values (with their 95 % confidence intervals representing the uncertainty ranges) only when they were from 3 independent analytical methods based on different analytical principles, pursuant to ISO GUIDE 35.

Table 2 lists Reference Values for this CRM. Reference Values, rather than Certified Values, are reported when the collaborative analytical results were consistent among the laboratories but when within-bottle inhomogeneity was detected (Fe), when contamination during the preparation was suspected (Pb), or when the values resulted from only 2 independent analytical methods.

Note that, because of the above reasons, the Reference Values may include bias. Certified and Reference Values are expressed on a dry weight basis. Analytical values should be corrected for the measured moisture content to relate to the Certified and Reference Values. See below for the drying procedure.

Table 1. Certified Values

Element Unit Cerified Value*1,2 Method*3
Ca %  0.125±0.004 AAS,ICP,ICPMS,IDICPMS,INAA,PIXE
K %  0.550±0.015 AAS,FES,ICP,ICPMS,INAA,PGA,PIXE
Na %  1.00±0.04 AAS,FES,ICP,ICPMS,INAA,PGA
As mg/kg  0.60±0.04 AAS,ICPMS,INAA
Ba mg/kg  1.1±0.1 ICP,ICPMS,INAA
Cd mg/kg  0.069±0.009 AAS,ICPMS,IDICPMS,INAA
Cu mg/kg  2.8±0.1 AAS,ICP,ICPMS,IDICPMS,PIXE
Mg mg/kg 576±12 AAS,ICP,ICPMS
Mn mg/kg  8.9±0.2 AAS,ICP,ICPMS,INAA,PIXE
Se mg/kg  0.25±0.02 AAS,INAA,IDGCMS
Sn mg/kg  1.6±0.1 AAS,ICPMS,IDICPMS,INAA
Sr mg/kg  4.9±0.2 AAS,ICP,ICPMS,IDICPMS,INAA,RNAA
Zn mg/kg 20.9±0.9 AAS,ICP,ICPMS,IDICPMS,INAA
U mg/kg  0.0029±0.0004 ICPMS,INAA,RNAA

Certified Value*1
Expressed on a dry weight basis. Analytical values should be corrected to allow for the moisture content. See text for the method for moisture content measurement.

Certified Value*2
Certified Values are the means of the acceptable mean values obtained in the collaborative analysis. Uncertainty is represented by the 95% confidence interval of the mean. The minimum sample on which the Certified Values are based was 500 mg.

Method*3

AAS: Atomic absorption spectrometry
FES: Flame emission spectrometry
ICP: Inductively coupled plasma atomic emission spectrometry
ICPMS ICP mass spectrometry
IDICPMS: Isotope dilution ICPMS
INAA: Instrumental neutron activation analysis
RNAA Radiochemical neutron activation analysis
PGA: Prompt gamma ray analysis
PIXE Particle induced X-ray emission spectrometry
IDGCMS: Isotope dilution gas chromatography-mass spectrometry

Table 2. Reference Values

Element Unit Reference Value*1,2 Element Unit Reference Value*1,2
Br mg/kg 24 Mo mg/kg 0.43
Cl % 1.5 Ni mg/kg 0.39
Co mg/kg 0.022 P % 0.26
Cs mg/kg 0.020 Pb mg/kg 0.62
Fe mg/kg 18 Rb mg/kg 4.7
I mg/kg 1.9 Th mg/kg 0.002
Reference Value*1
Expressed on a dry weight basis. Analytical values should be corrected to allow for the moisture content. See text for the method for moisture content measurement.


Reference Value
*2
Recommended minimum sample weight is 500 mg.

Instruction for Use

  • (a) Storage
    The bottle should be tightly capped and stored at 4 ℃ or below. Avoid excess exposure to light and UV.
  • (b) Use
    Allow the bottle to come to room temperature and gently shake before opening to ensure homogeneity. A minimum sample weight of 500 mg is recommended for analysis.
  • (c) Drying
    Approximately 1 g of the material is to be accurately weighed into a dry glass or metal vessel of known weight. After that the vessel with the material stands under vacuum below room temperature for 24 hours, the resulting weight loss is to be assigned as moisture content. Moisture content of the material in freshly opened bottles, measured at NIES by this method, was 0.6 %. However moisture content of the material may vary with storage conditions.

    All analytical values should be corrected for moisture content measured immediately prior to analysis. Drying at a higher temperature (e.g.,oven drying) will result in a greater weight loss, probably because of evaporation of volatile constituents, and thus should be avoided. Subsample used to determine the moisture content should not be used for element analysis.
  • (d) Warning
    This CRM is for laboratory use only and is not for human consumption.techniques. A minimum sample weight of 100 mg is recommended for the analysis.

Expiration of Certification

The certification of this CRM is valid until July 2025, under the appropriate storage conditions specified above.

Reference

1 Certified Reference Material for Analytical Quality Assurance of Minor and Trace Elements in Food and Related Matrixes Based on a typical Japanese Diet: Interlaboratory Study
J. AOAC Int., 84:1202-1208(2001)
Jun Yoshinaga, Masatoshi Morita, Masae Yukawa, Kunio Shiraishi, Hisao Kawamura

Collaborating Laboratories

The certified values for this CRM(No.27) have been determined with faithful contributions of the following participating laboratories.

University of Massachusetts, Bhabha Atomic Research Centre, International Atomic Energy Agency, Shimadzu Co., The Japan Radioisotope Association, Musashi Institute of Technology, Hokkaido Institute of Environmental Studies, Seiko Instruments Inc., National Institute of Radiological Sciences, Chiba Institute of Technology, Kagoshima University, Iwate Medical College, National Food Research Institute, Kyoto University, Konan University, Tokyo Metropolitan Industrial Technology Research Institute, Beltsville Human Nutrition Research Center, Tohoku National Agricultural Experiment Station, Japan Atomic Energy Research Institute, National Institute for Environmental Studies