Sentence:  In our work the best procedure for removing substances causing nonspecific staining in order to obtain <WSD>specific</WSD> conjugates was to pass the conjugates through a DEAE-cellulose column and in some cases to absorb the first and second milliliter fractions with sweet clover tissue powder . 
Meaning of the word marked with <WSD> tags:  (sometimes followed by `to') applying to or characterized by or distinguishing something particular or special or unique