Matrix effect studies in the inductively coupled plasma with monodisperse droplets. Part II: The influence of matrix on spatially integrated ion density

Monodisperse droplet sample introduction was used to study the ionization process in the inductively coupled plasma (ICP). The influence of the matrix on the analyte ion number density was evaluated by using laser-excited atomic fluorescence spectroscopy (LEAFS). The results suggest that the presence of 0.1 M NaCl enhances the ionization of the analyte species. With the addition of the NaCl, the spatially integrated Ba(II) signal decreases, apparently due to enhanced production of Ba2+. Added NaCl accelerates the appearance of Sc+, but does not affect the spatially integrated signal once ionization is complete. The possible effects on the fluorescence signal of quenching caused by the presence of the NaCl were evaluated by comparison of time-resolved and time-integrated detection. Quenching makes a small contribution to the fluorescence intensity change produced by the matrix but does not account for large Loss in signal from singly ionized Ba.