Temperature-Programmed Evolution of Gases TPE

The thermal treatment in this technique is similar to that applied in TGA (vide supra). However, the solid-state reaction may be carried out in a quartz glass oven or in a stainless-steel device. The gases evolved, e. g., HCl or H2O, are determined by mass spectrometry (MS) or with a thermal conductivity detector (TCD). A suitable device including MS is seen in Fig. 1 and is described in more detail elsewhere [29]. 

Application of MS to monitor SSIE has the advantage that several simultaneously evolved gases can be separately analyzed, for instance, NHj, HCl and HjO. In the case of evolved anhydrous acids such as HCl, the vapor can be transferred by a stream of N2 or He into a trap containing an aqueous solution of a base (e.g., NaOH). When the reaction is complete, the degree of exchange can be determined via back-titration of the residual base. Also, the procedure can be designed such that a continuous titration of the HCl evolved and trapped in water is possible. 

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