Sentence:  In our work the best procedure for removing substances causing <WSD>nonspecific</WSD> 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 fractions with sweet clover tissue powder . 
Meaning of the word marked with <WSD> tags:  not caused by a specific agent; used also of staining in making microscope slides