Heavy
metals in sediments of Yangzonghai Lake, China
Zhang yuxi,Liu jingtao,Liu junjian
Abstract
In stable isotope
ratio mass spectrometry (IRMS), the stable isotopic composition of samples is
measured relative to the isotopic composition of a working gas. This measured
isotopic composition must be converted and reported on the respective
international stable isotope reference scale for the accurate interlaboratory
comparison of results.
This data conversion
procedure, commonly called normalization. In this paper, we present a
discussion and mathematical formulation of several existing routinely used
normalization procedures. By utilizing laboratory analytical data, the accuracy
of the various normalization methods (given by the difference between the true
and the normalized isotopic composition) has been compared. Our computations
suggest that single-point anchoring produces normalization errors, that it must
not be used for routinely anchoring stable isotope measurement results to the
appropriate international scales. Using two or more certified reference
standards produces a smaller normalization error provided that the isotopic
composition of the standards brackets the isotopic composition of unknown samples.