Fig. 1a, only one inflection point

Fig. 1a, only one inflection point of carboxylic
acids was obtained when following ASTM D664, while Fig. 1b indicated
that three inflection points can be obtained with the method
herein proposed. In this method, the mixture of tert-butanol and
acetone was used to dissolve bio-oil, and the potassium hydroxide
recommended by ASTM D664 was replaced with an organic base of
tetramethylammonium hydroxide, which are the keys for the sensitivity
of this method.