Sentence:  In our work the best procedure for removing substances causing nonspecific staining in order to obtain specific conjugates was to pass the conjugates through a DEAE-cellulose column and in some cases to absorb the first and second milliliter <WSD>fractions</WSD> with sweet clover tissue powder . 
Meaning of the word marked with <WSD> tags:  a component of a mixture that has been separated by a fractional process