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 p rocess in the inductively coupled plasma (ICP). The influence of the matrix on the analyte ion number density was evaluated by using laser-excited ato mic fluorescence spectroscopy (LEAFS). The results suggest that the presenc e of 0.1 M NaCl enhances the ionization of the analyte species. With the ad dition of the NaCl, the spatially integrated Ba(II) signal decreases, appar ently due to enhanced production of Ba2+. Added NaCl accelerates the appear ance of Sc+, but does not affect the spatially integrated signal once ioniz ation is complete. The possible effects on the fluorescence signal of quenc hing caused by the presence of the NaCl were evaluated by comparison of tim e-resolved and time-integrated detection. Quenching makes a small contribut ion to the fluorescence intensity change produced by the matrix but does no t account for large Loss in signal from singly ionized Ba.