matter was measured as weight loss after burning in muffle furnace
at 950 C following procedures given in ASTM E872-82. The
ash content was determined as the residue after burning to constant
weight in a muffle furnace at 575 C according to ASTM
E1755-01. This process allows removal of the volatiles and fixed
carbon. Fixed carbon was determinate using the data previously
obtained in the proximate analysis and according García et al.
[10] using the formula % FC = 100–(% Ash–% VM). All analyses were
performed in triplicate.