On-line dilution, steady-state concentrations for inductively coupled plasma atomic emission and mass spectrometry achieved by tandem injection and merging-stream flow injection
Abstract
Steady-state concentrations have been achieved by on-line dilution, flow injection techniques with conventional instrumentation. An approach employing tandem injection for on-line dilution was applied to obtain a steady-state concentration. The deviation from signal stability resulting from concentration variations or ripples hampered exploitation of this approach for on-line dilution except over a limited range. However, when tandem injection was coupled with a single- or, especially, a double-confluence for the diluent, dilution was achieved over a wide range (up to 900-fold). Further, steady-state concentrations were obtained without concentration ripples. With the combined tandem injection and merging stream the emission signal variation with inductively coupled plasma (ICP) spectrometry compares well with that obtained for direct sample nebulisation. Simple relationships for calculation of the anticipated dilution have been derived and validated experimentally. Flow configurations were designed to implement on-line dilution approaches under optimum conditions. Although these developments for on-line dilution are initially intended for sequential multi-element ICP spectrometric analysis, they should prove to be of general use.