ELECTROCHEMICAL METHODS FOR MONITORING THE VOLATILE PYROLYSIS PRODUCTS OF PINUS-HALEPENSIS PINE-NEEDLES

Various electrochemical methods such as oxidation-reduction potentiome try, pH-metry and conductometry were used for monitoring the volatile pyrolysis products of Pinus halepensis pine-needles. The study was car ried out under non-isothermal conditions (ambient to 400 degrees C) wi th a heating rate of 10 degrees C min(-1), in nitrogen atmosphere. Pro ducts with the lowest redox potential values, such as aldehydes and al cohols, were evolved between 180 and 230 degrees C. Products with the highest conductivity values such as carboxylic acids, were evolved in the temperature range of 240-320 degrees C, whilst those with the lowe st pH values, such as phenols and acids were evolved in the temperatur e range of 220-300 degrees C. The results of this study are in agreeme nt with those obtained previously by DI-MS, Py-GC-FID and Py-GC-MS. Th e electrochemical methods have the advantage of being simple, fast and low cost methods for monitoring the pyrolysis products. The redox pot ential value is examined as a measure of the chemical stability (i.e. the reducing properties increase as the redox values decrease) correla ted with the flammability of the pyrolysis products. (C) 1997 Elsevier Science B.V.