Evaluation of measurement uncertainty after optimization of the method for potentiometric titration of glycine

Abstract

Accuracy and repeatability of the results obtained by potentiometric determination mostly depend on the stoichiometric ratio between the quantity of titrant used and the quantity of sample to be examined. During the optimization of the method, care should be taken to adjust the sample amount to provide suitable volume of titrant, in order to avoid the titration error with consumption above 90% of the total burette volume. In this study suitable approach for optimization of method for potentiometric titration of glycine with 0.1 M perchloric acid was demonstrated, followed by evaluation of measurement uncertainty of the results. The results obtained from the method validation study (statistical error as estimate for precision, and proportional systematic error and additional systematic error as estimates of bias) were used for estimation of uncertainty of measurement of the result, using top-down approach. Comparable estimates for combined (0.5%) and expanded uncertainty (1.0%) were also obtained using two different approaches: bottom-up approach and top-down approach using data from participation in proficiency testing studies. Key words: potentiometric titration, measurement uncertainty, bottom-up / top-down approach