IAEA Reference Materials
Reference
Sheets
IAEA-392
TRACE, MINOR and MAJOR ELEMENTS IN NATURALLY GROWN ALGAE
Intended
Use
This reference material is intended to be used for quality assurance
purposes, basically as a quality control material for the measurement
of the elemental composition of biological materials especially of
biomonitors, for the assessment of a laboratory’s analytical work
and for the validation of analytical methods.
Origin
and preparation of the material
The
IAEA-392 Algae material was prepared by the Analytical Quality Control
Services of the International Atomic Energy Agency in co-operation with
the Institute of Microbiology, Academy of Sciences of the Czech
Republic in Trebon, during 1995. The IAEA-392 algae material (type:
Scenedesmus obliquus 208) was produced under standard outdoor culture
conditions [2, 3]. Mineral nutrients were prepared from p.a. chemicals
and added as required to maintain the optimum balanced composition of
the nutrient medium in the growing culture. After harvesting, the algae
were stored in a coupled tank and continuously spray dried at moderate
venting and temperature avoiding a damage of the cell structure. The
bulk algae material and the sealed bottles were treated with gamma ray
irradiation with a total dose of 25 kGy using a Co-60 source to improve
long-term stability of the material by reducing microbial action.
|
Date of Release:
December 2005
|
Unit Price:
130 Euro
|
Unit Size:
20 g
|
| Producer:
Reference Materials Group (RMG) Chemistry Unit, PCI International Atomic Energy Agency AAgency's Laboratories, Seibersdorf, A-2444 Seibersdorf, Austria |
Supplier:
Analytical Quality Control Services Agency's Laboratories, Seibersdorf A-2444 Seibersdorf, Austria |
|
|
Reference Sheet:
 IAEA-392(.pdf) |
||
(Based on dry weight)
|
|
||||
|
|
Mass fraction [mg/kg] |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
(Based on dry weight)
|
|
||||
|
|
Mass fraction [mg/kg] |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| * |
number of accepted laboratory means which were used to calculate the recommended or information values
|
The
recommended and information values are the unweighted means of n
laboratory means. The uncertainties were calculated following
recommendations given in ISO Guide 35 and include the uncertainty
components derived from the sample heterogeneity at masses between 100
to 200 mg and the between laboratory variability. For the expanded
uncertainty a coverage factor of two was applied (95% confidence
interval). The uncertainty related to long- and short-term stability
was not considered. The property values assigned to the algae reference
material are element mass fractions, expressed in the derived SI unit
mg/kg. The utmost care was taken regarding the metrological
traceability of the property values assigned to this reference material
already at the planning phase and during the entire characterization
process. Laboratories participating in the characterization campaign
have been requested to carefully choose the calibrants and to provide
the IAEA with all related information, including certificates. However,
the selection of measurement methods and measurement procedures, as
well as respective calibrants, was based on a decision of the
participating laboratory. A consequence of the use of different
calibrants, is the fact that the metrological chain(s) for each of the
assigned quantity values respectively (combined from number of
results), cannot not easily be described. Therefore, the assigned
property values – the element mass fractions – although
expressed in the derived SI unit, are not intended for calibration
purposes, and the reference material as such is not to be used as a
calibrant.
Further details on the characterisation and calculation of property and
uncertainty values can be found in the report IAEA/AL/149 ‘Report
on the characterisation of the naturally grown algae reference material
IAEA 392’ [1].
Homogeneity
The natural cell particle size of the algae reference material IAEA 392
is about 8 µm. This small particle size by itself is a good basis
for high sample homogeneity. During several homogeneity studies the
uncertainty due to sample heterogeneity for sample masses between 100
to 200 mg was evaluated for all elements. The uncertainty was found not
to exceed 2% for all elements except for Cu (2.8%). These values are
already conservative since the uncertainty due to method repeatability
was still partly included. Details can be found in the characterisation
report [1]. No systematic attempt was made to evaluate the minimum
representative sample size for IAEA-392. However, subsequent analysis
for some elements by INAA indicates that even lower sample masses as
100 to 200 mg give comparable results.
Dry
weight determination
All
recommended and information values are expressed on a dry weight basis.
Therefore the analytical results need to be corrected for the humidity
content of the sample at the time of analysis. It is recommended to dry
a separate sample of at least 500 mg for 4 hours at 80oC.
If smaller sample intake masses are used, or the drying procedure is
modified, the uncertainty on the dry weight factor is increased and
should be taken into account for the total uncertainty calculation. An
indication on the magnitude of the dry mass uncertainties and their
influence on the final results can be found in a related publication .
Instructions
for use
The
recommended minimum sample intake is 200 mg. Before each subsampling,
the bottle should be thoroughly shaken for 5 minutes to re-homogenise
the sample again. Analysts are reminded to take appropriate precautions
to avoid contamination of the sample and the remaining material in the
bottle. It is recommended to store the material after opening of the
bottle in a refrigerator (at 4 to 8oC) or in a dessicator. Exposure to sunlight should be avoided. Storage at room temperature and even temperatures up to 40oC did not show degradation of the originally sealed algae material.
References:
| [1] | |
| [2] |
Doucha
J. et al.: Report on preparation of microalgae biomass with different
content of heavy metals, Trebon, Czech Republic, 1996.
|
| [3] |
Doucha
J., Lívansky K.: Novel outdoor thin layer high density
microalgae culture system: Productivity and operational parameters,
Arch. Hydrobiol. 106/Algolog. Stud. 76, 129-147 (1995).
|
| [4] |
Zeiller
E., Benetka E., Koller M., Schorn R.: Dry mass determination - which
role does it play for the combined measurement uncertainty in IAEA
algae reference materials (presented at the IUPAC Symposium on
‘Trace elements in food’ Oct 2004, paper submitted for
publication)
|
Last updated 06 December 2007
