INVESTIGATION OF BACKGROUND SIGNALS FROM NA AS A SOURCE OF INTERFERENCE IN LASER-ENHANCED IONIZATION SPECTROMETRY IN FLAMES

Laser-Enhanced Ionization (LEI signals from Na have been investigated by the one-step excitation scheme in flames in the UV region (220-410 nm). This knowledge is of importance for the applicability of the LEI technique since Na often exists as a matrix in a number of samples and gives rise to background signals. It is shown that the analyte-versus-Na selectivity decreases considerably as a function of increased laser intensity. It is concluded that there exists an optimum laser intensity for the most efficient detection of a particular element in a certain Na matrix. This optimum intensity, however, is determined by factors which are specific to each experimental setup.