4. Final comments

Uncertainty is a measure of the quality of a measurement. It is of vital importance in many sectors of analytical chemistry to introduce quality control and quality assurance in production, complying with and enforcing laws and regulations; calibrating standards and instruments or developing and comparing international and national reference standards among others.

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One of the best-known approaches to estimate the uncertainty of analytical procedures is the ISO/ GUM. However, from an analytical viewpoint, this approach is sometimes tedious, timeconsuming and unrealistic. One way to overcome these limitations is the procedure for evaluating uncertainty of analytical assays in routine analysis using the GUM approach together with the data from in-house validation based on the cause and effect diagram coming from the analytical specification function. Expressions to calculate the different contributions of uncertainty have to be carefully adapted in order to avoid double counting. The procedure is illustrated with a case study on fluorimetric determination of quinine in tonic water showing that it is very suitable for evaluating the uncertainty of the analyte content of future samples in routine analysis.

Finally, a summary including modern reviews on the estimation of measurement uncertainty of analytical assays by GUM is outlined in tabular form, which can be a useful guide for those interested in the subject. Moreover, selected application ranging from volumetric glassware, analytical balance, calibration curves, as well as the evaluation of the measurement uncertainty in classical and instrumental techniques in a wide variety of fields are given. Graphs on the number of references cited (over 200) per year and the number of papers by most cited journals are also included.
