22300
In total , 55 samples of semi - skimmed milk were purchased from five supermarkets over the course of a year and the proportions of the A1 , A2 , B and C casein variant proteins were measured , using high resolution HPLC - MS .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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