A correction method for thermogravimetric wood analysis under pyrolytic conditions using autosampler and a vertical balance system

Thermogravimetric analysis is a quick method for identifying the material composition of polymers and wood composites through differences in the thermal stability of their components. Scots pine stemwood usually exhibits an average ash content of 0.5 %. However, a large variation in ash content was found when analyzing the composition of Scots pine sapwood sampled with an autosampler and analyzed with a PerkinElmer Thermogravimetric analyzer Pyris 1 TGA, which was equipped with a vertical balance system. An increase in ash content was found with increasing order of analysis due to tar accumulation on the weighing system during pyrolysis in an inert and subsequent combustion in an oxidative atmosphere. This mass increase falsifies the individual ash content and initial sample mass readings. Uncorrected, the method can therefore give a biased interpretation of the composition of wood compounds. A method that provides a mathematical correction of the false ash contents and adjusts for a false initial mass of the sample is presented in this paper. The ash content could be calculated by this correction method to a close approximation.