Theoretical and experimental examination of recovery in the context of trueness of analytical results

In the report of the International Union of Pure and Applied Chemistry (IUPAC) estimation of analyte recovery (RV) is recommended as one of the ways for assessment of trueness of analytical results. RV is usually estimated with the use of samples spiked with known amount of analyte. However, neither the IUPAC guidelines, nor the available literature take into consideration various effects of different nature that may occur along the sample preparation steps prior and during measurements. Hence, in this work the attempt was made to classify these effects and to evaluate their influence on the analyte recovery. For this purpose a mathematical model has been developed, enabling to judge usefulness of the recovery test in objective estimation of trueness, and the results predicted by the model were checked experimentally. Trueness was estimated on the basis of analytical results obtained by both interpolative and extrapolative ways. The experiments were performed with the use of a dedicated flow injection system coupled to UV/VIS spectrometer and covered determination of chromium(III) as chromium(III) nitrate at a wavelength of 590 nm.