Sentence:  ( 4 ) The conjugates were passed through a diethylaminoethyl ( DEAE - ) cellulose column equilibrated with neutral phosphate buffer ( PBS ) containing * * f <WSD>potassium</WSD> phosphate and * * f . 
Meaning of the word marked with <WSD> tags:  a light soft silver-white metallic element of the alkali metal group; oxidizes rapidly in air and reacts violently with water; is abundant in nature in combined forms occurring in sea water and in carnallite and kainite and sylvite