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 q uadrupole inductively coupled plasma mass spectrometry in various matr ices of environmental interest was studied. The investigation was cent ered on the isotope Cr-52, i.e., the most abundant one (83.79%) and, t herefore, the one most frequently chosen for such determinations. Five candidate reference materials were investigated (partly already certi fied for other elements). These are based on beech leaves, Ay ash, rye grass, sewage sludge, and the aquatic plant Trapa natans. Interferenc e 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 sampl es. 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 co ncentration was calculated for increasing concentrations of interferin g species. In this way, it was possible to estimate the real contribut ion of all potential interferents. These have resulted to be in partic ular the biatomic ions ArC+ and ClO+. The influence of the former was minimized by using a correction equation; in the case of the latter th e blank of a matrix-simulating solution was subtracted from the analyt ical signal. The validity of the correction approach was confirmed by using inductively coupled plasma atomic emission spectrometry with ult rasonic nebulization and graphite furnace atomic absorption spectromet ry. (C) 1998 Academic Press.