High temperature methods for decomposition of solid samples

The initial and principal topic of this thesis was hazardous waste destruction by inductively coupled plasma (ICP) assisted post-combustion. As an aside, direct solid sample analysis (DSSA) on powdered sample was to be studied. To perform this double task, an "analytical chamber", described in chapter 2, was designed and made. The project was still at the preliminary studies stage on the usefulness of Swann bands as a probe for the presence of carbon to carbon bonds (Chapter 2), when the lack of funding forced a reorientation on the DSSA project as the main topic for the thesis. Since ICPs are known to be poor particle digesters, a suitable solid-gas reactor had to be found. From this study (Chapter 3), the cyclone reactor appeared to be the best-suited type of reactor for this task. Unfortunately, micro-engineering and gas flow rate constraints imposed by the ICP forced the abandonment of the concept for a simpler one.In parallel with the quest for a suitable DSSA reactor, a new calibration method, the tandem calibration method (TCM) was developed. The objective of the TCM was to achieve calibration of any sample introduction system with the use of classical liquid standards. The study showed clearly that not only did the TCM not bias the results, but it also automatically corrected for physico-chemical matrix effects in a manner similar to standard additions. Despite the fact that results presented in Chapter 4 were obtained on liquid samples, the TCM is equally applicable to solid samples introduced into the plasma by other means. The TCM was used on an electrothermal vaporizer (ETV) (see Appendix 3).The first DSSA system studied was modified direct sample insertion (MDSI). The MDSI used halogen-assisted sample vaporization and demonstrated that quantitative vaporization of solids could be achieved using the ICP as the thermal energy source (Chapter 5). The next step was to design a reactor along the same fines, but capable of operating under continuous sample feed from an appropriate powder feeder. This intraplasmic reactor, the pseudo fluidized-bed reactor (PFBR) did not perform as well as expected (Chapter 6). Still, it allowed the demonstration of the usefulness of a baffle placed in the path of the particles inside the reactor to achieve longer solid residence time. The results obtained on the PFBR indicated that although the general concept was good, the source of most problems came from inefficient energy transfer from the plasma to the reactor. This drawback was eliminated by replacing plasma heating with Ohmic (resistive) heating. Called the ohmically heated PFBR (OPFBR), this reactor imposed severe design constraints, principally in terms of electrode cooling and protection of the hot graphite reactor against attack from oxygen. The design required a series of modifications, described in Chapter 7, before reaching its final form (Chapter 8). Transport losses were a problem with the OPFBR. The introduction of a quenching gas through tangential holes in the upper body of the reactor faded to eliminate transport losses; however, these losses were sufficiently small and reproducible to allow quantitative analysis on real samples (SO-4 sod CRM and 1646 Estuarine sediment CRM) fed continuously into the reactor. These results fulfill the goal of this thesis, which was to develop a method for steady-state feed DSSA