Quality IssuesThe Concept of Uncertainty as Applied to Chemical Measurements

Abstract

The calculation of uncertainty as recommended for physical measurements cannot be transferred readily to chemical measurements. Physical measurements and chemical measurements have entirely different error patterns that behave differently on replication. Correctable local bias predominates in physical systems and random error is minor; random error predominates in chemical systems and bias is difficult to identify and eradicate. Therefore bias must be monitored by randomizing in the interlaboratory environment, a concept not handled by the conventional ISO treatment of uncertainty.

References

1. J. K. Taylor, Handbook for SRM Users, NBS Special Publication 260-100, National Institute of Standards and Technology, Gaithersburg MD 20899, 1985.
2. M. H. Hansen, W. N. Hurwitz and W. G. Madow, Sample Survey Methods and Theory, Wiley, New York, 1953, p. 58.
3. R. Albert and W. Horwitz, Anal. Chem., 1997, 69, 789.
4. Quantifying Uncertainty in Analytical Measurements, Eurachem Secretariat, PO Box 46, Teddington, Middlesex TW11 0LY, UK, 1995.
5. Analytical Methods Committee, Analyst, 1995, 120, 2303.
6. International Organization for Standardization, Guide to the Expression of Uncertainty in Measurement, ISO, Geneva, 1995, p. 53.