Sentence:  When 1 ml of conjugate was passed through a column ( * * f ) , the first and second milliliter fractions collected were the most <WSD>specific</WSD> and gave no nonspecific staining in some experiments , and very little in others . 
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