Kev sim tshuaj extraction siv qhov sib txawv ntawm solubility los yog muab faib coefficients ntawm ib yam khoom nyob rau hauv ob immiscible (los yog me ntsis soluble) cov kuab tshuaj, tso cai rau cov tshuaj hloov los ntawm ib tug hnyav mus rau lwm yam. Cov txheej txheem ntawm kev rov muab rho tawm feem ntau ntawm ib qho chaw hu ua extraction. Extraction feem ntau yuav tsum muaj tsawg kawg yog peb yam: lub extractant, lub solute, thiab cov diluent. Cov kuab tshuaj thiab diluent (thawj cov kuab tshuaj) yog sib sau ua ke hu ua cov tshuaj noj.
Cov txheej txheem rho tawm cov khoom siv feem ntau yog rho tawm, ntxuav, thiab rov qab- rho tawm. Cov txheej txheem ntawm kev rho tawm cov kua dej los ntawm cov txheej txheem organic mus rau theem aqueous feem ntau hu ua extraction; cov txheej txheem ntawm tshem tawm impurities los ntawm cov organic theem mus rau hauv lub aqueous theem yog hu ua ntxuav; thiab cov txheej txheem ntawm desorbing lub solute los ntawm cov organic theem mus rau lub aqueous theem yog hu ua rov qab -extraction.