Study of Possible Polyatomic Interference in the Determination of Cr in Some Environmental Matrices by Inductively Coupled Plasma Mass Spectrometry

The effect of polyatomic interferences on the determination of Cr by quadrupole inductively coupled plasma mass spectrometry in various matrices of environmental interest was studied. The investigation was centered on the isotope52Cr, i.e., the most abundant one (83.79%) and, therefore, the one most frequently chosen for such determinations. Five candidate reference materials were investigated (partly already certified for other elements). These are based on beech leaves, fly ash, rye grass, sewage sludge, and the aquatic plantTrapa natans.Interference arises mainly because of the various combinations of the elements Ar, C, Cl, N, O, and S that are present in the relevant matrices, in the plasma gas, and in the reagents employed in the pretreatment of samples. Synthetic matrices simulating the five materials were analyzed to quantify the contribution of each individual interferent. In addition, for each spectral interference, the corresponding apparent analyte concentration was calculated for increasing concentrations of interfering species. In this way, it was possible to estimate the real contribution of all potential interferents. These have resulted to be in particular the biatomic ions ArC+and ClO+. The influence of the former was minimized by using a correction equation; in the case of the latter the blank of a matrix-simulating solution was subtracted from the analytical signal. The validity of the correction approach was confirmed by using inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization and graphite furnace atomic absorption spectrometry.