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The difficulties to analyse prostaglandins ( PG ) by gas - liquid chromatography are mainly due to the lack of sensitivity of the gas - chromatograph itself ( higher than 200 ng ) and to the poor resolution of the packed columns .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 None