EFFECT OF COLLOIDAL STABILITY OF CERAMIC SUSPENSIONS ON NEBULIZATION OF SLURRIES FOR INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

The direct solid analysis of ceramic powders can be carried out by inductively coupled plasma atomic emission spectrometry (ICP-AES) using slurry sample introduction. However, a highly stable suspension is needed in order to obtain a representative aerosol for introduction into the ICP. In this work, the importance of the effect of the rheology and the stability of the ceramic suspensions on the analytical results provided by slurry nebulization ICP-AES is demonstrated. The basic concepts involved in the stabilization and homogenization of ceramic slurries are discussed. A general overview of the stabilizing mechanisms (electrostatic, steric and electrosteric) and the role of the different stabilizing additives, and the most adequate use of them, is described. Alumina (Al2O3) slurries, as a case study, are discussed. The rheological parameters, such as zeta potential, viscosity and sedimentation have been studied by changing the pH of the slurry and by introducing different dispersing additives (Dolapix PC-33, Darvan-7, Darvan-C, sodium hexametaphosphate, glycerol plus Kodak photoflow, Triton X-100 and Produkt PKV-5088). Their effect on stability is discussed, as well as the relationship between the stability of the slurry and the intensity and precision of the measurements provided by ICP-AES. It is clearly demonstrated that higher intensities and lower relative standard deviation values are obtained for a well-dispersed, stable slurry.