Chemometrics on thermochromatography of inorganic salts: decomposition of thermochromatograms to chromatograms and thermograms using EFA and peak shape constraints

A low volume thermal furnace, interfaced to a capillary gas chromatograph ( GC) via a computer controlled, pneumatic sample inlet device, permits tempe rature resolved high speed GC analysis of the evolved components. The metho d is called thermochromatography (ThGC), The results of such an evolved gas analysis (EGA) can be conveniently represented as a thermochromatogram: a two-way detector response surface in the axes of sample temperature and chr omatographic retention time, It is demonstrated that such thermochromatogra ms, if subjected to the specific chemometrics analysis - evolving factor an alysis (EFA) - provide information about independent thermal processes that happened during the sample heating. The data is decomposed to matrixes of chromatograms and thermal evolution curves, thermograms, in a manner which connects each thermal decomposition step to the products evolved at that te mperature region. Chromatographic peak shapes of the evolved gases are used as additional constraints in the analysis, The EFA performance is evaluate d by ThGC of several inorganic salts and apatites. As a reference to EFA th e direct deconvolution of thermochromatograms to the gas chromatograms and temperature dependent thermograms was performed. This comparison demonstrat ed that EFA gives confident results if essential constraints of non-negativ ity to chromatograms and thermograms have been applied. (C) 1999 Elsevier S cience B.V. All rights reserved.