Sentence:  The deep concave gradient employed ( fig. 2 ) was obtained with a nine chambered gradient <WSD>elution</WSD> device ( `` Varigrad '' , reference ( 8 ) ) and has been described elsewhere . 
Meaning of the word marked with <WSD> tags:  the process of extracting one material from another by washing with a solvent to remove adsorbed material from an adsorbent (as in washing of loaded ion-exchange resins to remove captured ions); used to obtain uranium ions