Abstract

In ICP-HRMS, signal enhancements of analytes are often observed in the presence of the matrix. These signal behaviours are quite different from those in ICP-QMS. In order to explain the mechanism of signal enhancement in ICP-HRMS, effects of accelerating voltage added to the MS interface region on the shape of response curve of analytes (analyte signals plotted against their m/z) and on the ratio of analyte signal with matrix to that without matrix (analyte signal recovery) were investigated. The shape of the response curve was independent of the accelerating voltage over the range investigated, whereas the analyte signal recovery increased as the accelerating voltage increased, suggesting that the signal enhancement would be related to changes in physical properties of micro-plasmas after the sampler and the skimmer because the composition of the ICP is affected by the dissociation of the matrix element. In addition the factor was dependent only on mass and ionization potential (IP) of the matrix element; the presence of a matrix element with larger mass and smaller IP caused more remarkable signal enhancement of analytes. This result means that higher transportation and/or ionization efficiencies of analytes were attained in the micro-plasma after the sampler and/or the micro-plasma after the skimmer.