Detection limits versus matrix effects: analysis of solutions with high amounts of dissolved solids by flow injection inductively coupled plasma mass spectrometry

Flow injection inductively coupled plasma mass spectrometry (FI-ICP-MS) has been used for the analysis of high-purity nickel (>99.99% m/m). The advantage of analysing solutions with high amounts of dissolved solids (i.e., 3% m/m Ni) offered by FI-ICP-MS compared with conventional solution nebulization with 0.05% Ni solutions results in detection limits in the ng of analyte per g of Ni range because of the small dilution factor. Stable operating conditions can be maintained with the injection of 200 µl sample volumes in a carrier stream of 1% HNO3 with a relative standard deviation of less than 2% and 5% drift on 13 consecutive injections in 15 min. For certain elements severe matrix effects caused by the high Ni concentrations were found when the signal depression was compared with 1% HNO3 solutions, it varied between less than 5% for Rb and 80% for B. This depression is a function of the degree of ionization of the analyte element: the smaller the degree of ionization the higher the matrix effect. For quantitative analysis an automated standard additions procedure was applied because it was impossible to compensate for the different matrix effects by internal standards.