VALIDATION OF THE CALIBRATION PROCEDURE IN ATOMIC-ABSORPTION SPECTROMETRIC METHODS

A general strategy for the validation of the calibration procedure in AAS was developed. In order to accomplish this, the suitability of dif ferent 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 web as randomization tests were considere d. 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 dis tributed over three or four concentration levels. In order to check th e goodness-of-fit, the significance of the quadratic term should be in vestigated. A lack-of-fit to a second degree model is better detected when the measurement points are distributed over more than four concen tration levels. For an unweighted second degree model, an analysis of variance (ANOVA) lack-of-fit can be used, while a randomization test i s proposed for a weighted model. A one-tailed F-test or an alternative randomization test should be used to trace a non-constant variance.