Speciation through evolved gas analysis using spectroscopic detection techniques

Abstract

Methods utilizing thermal separation and atomic emission detection which are capable of speciating inorganic compounds in solid samples are described. Inorganic samples are gradually heated to 2300(DEGREES)C in a graphite sample probe that is moved in a controlled manner into an inductively coupled plasma (ICP) discharge or in a resistance wire heated tube furnace. As the sample is heated its components vaporized at characteristic temperatures. The vapors are swept into the supporting Ar of an ICP which acts as an atomic emission source from which the characteristic emission of the evolved vapors can be detected. Identification of a given compound is based upon the position of the sample cup at the time of evolution of the element and by standard addition techniques. Problems which can complicate identification and speciation include chemical reactions within the sample itself and reactions between the sample and its surroundings. The speciation of several mixtures of solid inorganic compounds are described. Binary and ternary mixtures of V, Pb, Cd and Hg were qualitatively and quantitatively determined. The dynamics of the thermal vaporization process were studied and modeled.