Laser-induced breakdown detection (LIBD) of aquatic colloids with different laser systems

The Laser-Induced Breakdown Detection (LIBD) is a new, sensitive method for the quantification of aquatic colloids of lower range nanometer size in very low concentration, which can not be detected by conventional light scattering methods. The method is investigated by two different laser setups: an excimer pumped dye laser system and a Nd-YAG laser system. In this paper these two different setups for the LIBD are described and compared. Polystyrene reference particles with diameter from 1000 nm down to 19 nm are used for the investigation. The experimental data can be described by a model based on binomial statistics. The Nd-YAG laser system leads to a significant technical improvement in colloid measurement and the limit of detection for particle concentration is better than for the excimer-dye laser system. The model calculation on the experimental data results in a minimum detectable particle radius of rmin=0.6±0.3 nm, which is significantly lower than the value of rmin=9.8±2.0 nm found for the excimer-dye laser system. Such an improvement makes LIBD an even more powerful analytical tool for the investigation of aquatic colloids in the size range <50 nm.