Computer processing of thermogravimetric-mass spectrometric and high pressure thermogravimetric data. Part 1. Smoothing and differentiation

High quality data smoothing is frequently required in the thermal analysis. Though the mathematical methods for smoothing are well known, the selectio n of the proper smoothing parameters cannot be based on statistical checks alone in thermal analysis. Many times a compromise must be found between th e effective removal of the various experimental error components and the di stortion of the curves by too strong smoothing. The following topics are di scussed from a practical point of view: (i) the determination of the deriva tive thermogravimetric (DTG) curves at low sample masses; (ii) the eliminat ion of the noise and flutter from the results of high-pressure TG experimen ts; (iii) the evaluation of the noisy, low intensity mass spectrometric sig nals arising from the minor volatile products of decomposition or oxidation . The performance of the methods is shown in two applications: (1) Evaluati on 0.25-0.5 mg mass loss steps in high-pressure thermogravimetry; (2) Study of NOx formation by atmospheric pressure thermogravimetry-mass spectrometr y during the temperature programmed combustion of 0.4 mg coal char. (C) 199 9 Elsevier Science B.V. All rights reserved.