Thermally Stimulated Discharge TDS

Ai the end of the run. the aluminum electrode is covered with a deposit from the organic acid, necessitating polishing it before the start of the next run. The reproducibility of the TVD curves was demonstrated with malonic acid. Three curves, recorded under identical conditions, were within 3-- % of each 

The TVD curves of selected amino acids were determined by Contarini and Wendlandt (121). A comparison of the TVD and DSC peak temperature is shown in Table 11.8. The TVD peak temperatures are somewhat higher than those obtained by DSC. Obviously, the kinetics of the electrodedecomposition produces) reaction are different from those of the decomposition reaction. These electrode reactions probably involve one or more diffusion steps between the electrode surface and the amino acid or amino acid decomposition produces), which would be different from the decomposition kinetics themselves. The leading edge of the TVD curve peaks is reproducible to within +1-2%. However, after the peak maximum temperature is attained, the reproducibility falls to within +20% in some cases. This is related to the electrode-amino acid decomposition products interface, which, due to the nature of the reaction, would not be expected to be reproducible. The trailing edge portion of the curve also consists of several shoulder peaks that may be related to the consecutive and/or concurrent reactions previously described in the DSC curves. These reactions could produce decomposition products that would react with the aluminum metal electrode surface. 

The primary amino acid-electrode reaction is probably similar to that 

These would involve the primary electrode reactions with the amino acid a possible secondary reaction could involve deamination reactions of the amino acid such as 

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