Colloid analysis by single particle inductively coupled plasma-mass spectroscopy: a feasibility study

The feasibility of single particle analysis of colloids in water has been studied by inductively coupled plasma-mass spectroscopy (ICP-MS). The transient signal induced by the flash of ions due to the ionisation of a colloidal particle in the plasma torch can be detected and measured for a selected ion mass by the mass spectrometer. The intensity of the MS signal is recorded in time scan, and the peaks recorded are analysed as a function of the particle size and the fraction of the studied element in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. After developing the theory on detection, composition and intensity of ion flashes generated by colloid ionisation in the plasma torch, tests were performed on model colloids (rutile, alumina, goethite) and on a natural clay (montmorillonite). This feasibility study also describes the experimental conditions and the choice of isotopes to detect natural colloids in a single particle analysis mode. (C) 2002 Elsevier Science B.V. All rights reserved.