CHARACTERIZATION OF COLLOIDAL PARTICLES BY LASER-INDUCED PLASMA SPECTROSCOPY (LIPS)

To study the nature and abundance of colloids in aquifer systems Laser -Induced Plasma Spectroscopy (LIPS) was used for elemental analysis of heavy metal colloids with particle diameters between 0.1 and 1 mu m. Different experimental approaches to the qualitative and quantitative characterization of inorganic colloids are examined. Some of the inher ent problems associated with a direct detection are discussed. A direc t detection of colloids in water or a liquid jet without separation be tween solvent and particles yielded only inadequate spectral resolutio n and detection limits in the order of mg l(-1) Utilization of a minia turized ultrafiltration system with a 0.1 mu m membrane filter gave ab solute limits of detection in the ng-range with good reproducibility. Figures of merit are given for representative heavy metal colloids. Th e filtration device used in this work is suitable for subsurface sampl ing under flow conditions, which minimizes sampling artifacts. A sligh tly modified LIPS system will be used for field screening and monitori ng.