Please summarize "Part II-Concentration" in the following article.
In doing so, please fulfill the following conditions.

#Condition#.
1. refer to this article only.
2. provide a factual response.
3．optimize your description to be detailed.

#Article#
https://www.accesstoinsight.org/NAME_1/authors/nanamoli/PathofPurification2011.pdf Provide the entire answer in JSON format.
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