Reference Sheet - Trace Elements And Methylmercury In Estuarine Sediment

Homogeneity

Extensive homogeneity tests were carried out on this material in order to ensure its

suitability as an intercomparison sample. A preliminary test was performed before final bottling

and sample dispatch and did not detect any inhomogeneity in the material. A final homogeneity

test was conducted after completion of the bottling of sample material. The between-bottle

homogeneity was tested by the determination of the concentration of some typical elements (Cu,

Fe, Mn, Zn) on sample intakes of 100 mg and 200 mg taken from 15 bottles which were set aside

at regular intervals during the whole period of bottling. The within-bottle homogeneity was

assessed by 15 replicate determinations on the re-homogenized content of one bottle. A F-test at a

significance level of 0.05 was performed for the different metals and did not reveal significant

differences between the within- and between-bottle variances for 100 mg intakes. On the basis of

these results, no inhomogeneities in the material were suspected. It was concluded that the

material is homogeneous at an analytical portion of 100 mg and above for trace elements and,

therefore, suitable for use as an intercomparison sample [1].

Dry weight determination

The average moisture content of the lyophilized sample after bottling, determined by

drying to a constant weight at 105°C, was found to be 2.5 %. Since the moisture content can vary

with the ambient humidity and temperature, it was recommended that the water content of this

material be determined in a separate subsample (not used for analysis) by drying to a constant

weight (~24 hours) at 105°C just prior to analysis. Final results should always be reported on a dry

weight basis.

Stability of the material

The stability of several trace metals was tested to determine the suitability of this material as

a candidate CRM. Five bottles of the IAEA-405 material were stored in the dark at +20 °C, –20 °C

and +60 °C, respectively, over a period of 17 months (starting in September 1998) and the

measurement of total Hg, Cu, Fe, Mn and Zn was performed at regular intervals during the storage

period. On the basis of these results, it was concluded that no instability of the material could be

demonstrated [1].

Instructions for use

The recommended minimum sample size for analysis is 100 mg. Analysts are reminded to

take appropriate precautions in order to avoid contaminating the remaining material in the bottle.

The bottle should be thoroughly mixed by shaking before use and tightly resealed immediately

after use. The material should be stored in the dark and kept below 25 ºC.

Legal disclaimer

The IAEA makes no warranties, expressed or implied, with respect to the data contained in

this reference sheet and shall not be liable for any damage that may result from the use of such

data.

References

[1]

Coquery M., Azemard S. and de Mora S. J., Report on the World-wide Intercomparison

Exercise for the Determination of Trace Elements and Methylmercury in Estuarine Sediment

IAEA-405, IAEA/AL/127 (IAEA/MEL/70), IAEA, Monaco, 2000.

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Reference Sheet - Trace Elements And Methylmercury In Estuarine Sediment - 2000 Page 3