Marine Sediment

The National Institute for Environmental Studies (NIES) announces the availability of NIES Certified Reference Material No.12, Marine Sediment.* This Certified Reference Material (CRM) is intended for use in the quality assurance of the analysis of organotin and elements.

* NIES CRM No.12 Marine Sediment is not available overseas.

1. Preparation of Material

The starting material for NIES CRM No.12 Marine Sediment was sampled in 1989 at the center of Bay of Tokyo. Approximately 200 kg (wet weight) of surface sediment was sampled by an Eckman-Burge sampler. It was transported to NIES and seawater was removed by filtration.

The material was further air-dried for 2 weeks. After removing visible external materials (e.g., shell), it was pulverized in a 7-L high-purity alumina ball-mill to pass 100 μm nylon sieve. The < 100 μm fraction was homogenized in one lot using a V-blender for 3 hrs. Then, 30 g aliquot of the homogenized material was doubly vacuum-packaged into a polyethylene laminate bag with oxygen absorbent to prepare 700 packages.

It should be mentioned that NIES CRM No.12 Marine Sediment has not been sterilized to prevent possible decomposition of the organotin compounds by Co irradiation, a standard procedure for sterilization. Instead, they have been vacuum-packaged and stored at -20℃ in a freezer to reduce any bacterial activities.

2. Homogeneity Assessment

The homogeneity of the prepared material was assessed by analyzing the major and trace element concentrations.   Three 300 mg-subsamples were taken from each of 3 randomly selected packages, and were decomposed with HNO3/HCLO4/HF.   The major and trace element concentrations ( Na, Mg, Al, K, Ca, V, Cr, Fe, Mn, Cu, Zn, and Sr) were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

The within- and between-package variation was calculated by a one-way analysis of variance (ANOVA). ANOVA did not find any statistically significant between-package variation in the element concentrations in this material. These results indicate that prepared material has a homogeneous element composition.

3. Moisture Content

Since the certified and reference values are expressed on a dry-weight basis, the moisture content of this CRM has to be corrected to relate the analytical values to the certified/reference values. A moisture content of 6% was obtained from repetitive measurements at NIES each time the new package was opened.

Therefore, it is essential to measure the moisture content prior to measuring any analytes of this CRM if the package had been opened. The stability of the analytes in this CRM was not intensively examined once the package seal had been broken.

4. Certified Values and Reference Values

The certified values for tributyltin and total tin are based on results of determinations by at least three independent analytical techniques from collaborative laboratories. The uncertainties of the certified values were estimated based on consideration of 2 times the standard deviation of the mean of the acceptable values and of the 95% confidence intervals for the mean of individual methods.

Certified Values

Constituent Unit Certified Value*1 Method*2
Tributyltin mg TBT/kg 0.19±0.03 a,b,c,d
Total tin mg/kg 10.7±1.4 e,f,g,h,i
Constituent Unit Reference Value*1
Triphenyltin mg TPT/kg 0.008

Certified Value and Reference Value*1
Certified values and reference values are on dry weight basis.

Method*2

a: Gas chromatography electron capture detection
b: Gas chromatography-flame photometric detection
c: Gas chromatography-mass spectrometry
d: High performance liquid chromatography-ICP-MS detection
e: Instrumental neutron activation analysis
f: Electrothermal atomic absorption spectrometry
g: Hydride generation atomic absorption spectrometry
h: Inductively coupled plasma mass spectrometry
i: Isotope dilution inductively coupled plasma mass spectrometry

Seven laboratories provided analytical results of TPT for this material. However, the reported mean values ranged from 0.006 to 0.010 mg TPT/kg dry wt., making it difficult to determine a certified value. So a simple mean of the reported values is designated as the reference value.

And the reference values for major and trace elements contents of this CRM were determined by intensive analysis at NIES. These are based on results of determinations by at least two independent analytical techniques.

Reference Values

Element Unit Reference Value*1 Element Unit Reference Value*1
Na % 3.25 Co ppm 16.6
Mg % 1.46 Ni ppm 57.6
Al % 7.22 Cu ppm 104
Si % 24.2 Zn ppm 738
K % 1.56 Rb ppm 69
Ca % 1.06 Sr ppm 126
Ti % 0.34 Cd ppm 3.0
V ppm 134 Ba ppm 254
Cr ppm 201 Hg ppm 1.16
Mn ppm 837 Pb ppm 101
Fe % 4.31 - - -

Reference Value*1
Reference values are on dry weight basis.

5. Storage

The material should be stored in a freezer at -20℃. Exposure to light should be avoided.

6. Use

  1. The package should be left at room temperature for at least 30 min before weighing samples. The minimum sample of 300 mg of the material should be used.
  2. This CRM contains 6% moisture at the time of the preparation. The moisture content of the sample should be measured at the time of each use in order to correct the analytical value to dry weight basis value. Moisture content of this CRM is to measured by the following procedure.
    (1) Weigh accurately aliquot (1 g) of the material.
    (2) Dry at 110℃ for 4 hrs in a conventional electric oven followed by cooling for 30 min in a silicagel dessicator at room temperature.
    (3) Weigh again.
    (4) The difference in two weight measurements is assigned as moisture content.
    In order to avoid possible loss/degradation of analytes by heating, use separate aliquot for moisture measurement from aliquots for analyte determination.
  3. Certified values and Reference values are based on complete decomposition. We recommend to use an acid mixture(HNO3, HF, HCLO4) to decompose completely. When acids do not work (for example Cr, Sn), alkari fusion1 will be recommended.

7. Reference

1 Element Concentrations in NIES Candidate Marine Sediment Certified Reference Material. Reference Values for Major and trace Elements
Anal. Sci., 12: 993-995(1996)
Jun Yoshinaga, Atsushi Tanaka, Takejiro Takamatsu, Masatoshi Morita, Kensaku Okamoto
2 Determination of total tin in sediment reference materials by isotope dilution inductively coupled plasma mass spectrometry after alkali fusion
Analyst, 124: 257-261(1999)
Jun Yoshinaga, Atsuko Nakama, Kyoko Tanaka
3 Integrative assessment of organotin contamination in a southern European estuarine system (Ria de Aveiro, NW Portugal): Tracking temporal trends in order to evaluate the effectiveness of the EU ban
Mar. Pollut. Bull., 54: 1645-1653(2007)
Ana Sousa, Chiho Matsudaira, Shin Takahashi, Shinsuke Tanabe, Carlos Barroso