Dry mass determination: what role does it play in combined measurement uncertainty? |
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Authors: | E Zeiller E Benetka M Koller R Schorn |
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Institution: | 1.Chemistry Unit, PCI Agency’s Laboratories Seibersdorf,International Atomic Energy Agency,Vienna,Austria;2.Austrian Research Centre Seibersdorf,Seibersdorf,Austria |
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Abstract: | Elemental mass fractions are normally reported on a dry-mass basis. In addition, producers of reference material state their
property values for dry masses and relate them to a defined dry mass determination method. This paper describes how biases
and uncertainties in dry mass correction factors may affect values reported as ‘concentration per dry mass’. The influence
of the use of different drying methods, accuracy of drying temperature, length of drying, environmental humidity, and the
sample mass used for dry mass determination have been evaluated using two candidate International Atomic Energy Agency reference
materials. Deviation from proposed drying methods was observed to lead to differences of up to 5% in dry mass correction factors.
In addition, the heterogeneity of sample moisture as well as hygroscopic behaviour during weighing play an important role
in the uncertainty estimation. Proposals are made regarding which sources of uncertainty arising from dry mass determination
should be considered and included in the combined uncertainty of analytical results. |
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Keywords: | Reference material Uncertainty dry mass Standard uncertainty Dry mass determination |
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