Validation of the calibration procedure in atomic absorption spectrometric methods

Abstract

A general strategy for the validation of the calibration procedure in AAS was developed. In order to accomplish this, the suitability of different experimental designs and statistical tests, to trace outliers, to examine the behaviour of the variance and to detect a lack-of-fit, was evaluated. Parametric as well as randomization tests were considered. For these investigations, simulated data were used, which are based on real measurements. The results obtained indicate that to validate a straight-line model, the measurement points should preferably be distributed over three or four concentration levels. In order to check the goodness-of-fit, the significance of the quadratic term should be investigated. A lack-of-fit to a second degree model is better detected when the measurement points are distributed over more than four concentration levels. For an unweighted second degree model, an analysis of variance (ANOVA) lack-of-fit can be used, while a randomization test is proposed for a weighted model. A one-tailed F-test or an alternative randomization test should be used to trace a non-constant variance.