1561
The optimal chromatographic conditions were achieved on a C18 column with gradient elution using acetonitrile and 1 mmol . L ( - 1 ) KH2PO4 buffer solution at 203 nm .
 Chemical: KH2PO4
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: KH2PO4