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Chemical characterization of domestic oral tobacco products : Total nicotine , pH , unprotonated nicotine and tobacco - specific N - nitrosamines .
 Chemical: nicotine; Chemical: nicotine; Chemical: N - nitrosamines
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: nicotine; Chemical: nicotine; Chemical: N - nitrosamines