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Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
41, Number 8, September 2003, pp. 439-443
Measurement Uncertainty of Liquid Chromatographic Analyses Visualized
by Ishikawa Diagrams
Veronika R. Meyer
EMPA St. Gallen, Swiss Federal Laboratories for Materials Testing and Research,
Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland
Ishikawa, or cause-and-effect diagrams, help to visualize the
parameters that influence a chromatographic analysis. Therefore, they facilitate
the set up of the uncertainty budget of the analysis, which can then be expressed
in mathematical form. If the uncertainty is calculated as the Gaussian sum
of all uncertainty parameters, it is necessary to quantitate them all, a task
that is usually not practical. The other possible approach is to use the intermediate
precision as a base for the uncertainty calculation. In this case, it is at
least necessary to consider the uncertainty of the purity of the reference
material in addition to the precision data. The Ishikawa diagram is then very
simple, and so is the uncertainty calculation. This advantage is given by the
loss of information about the parameters that influence the measurement uncertainty.
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