Methods for determination of elements in various types of samples are generally considered to be very precise and highly accurate. For reliable analysis of elements Na, Mg and Ni in food samples is it worthwhile to perform an extensive method validation of high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) according to the principle of pooled calibrations (PoPC). Under routine laboratory conditions of analysis, elevated levels of relative uncertainty of measurement reaching values of more than 50% were detected, which jeopardized the validity of results, even when the measurements in the present study were performed with samples of tap water and borehole water. Comparison of relative uncertainties with corresponding literature results indicates that sample-signal differences may be due to detector noise rather than specimen variations.
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