Separation Factor:

Solvent extraction is basically a separation technique. The main objective is to separate the desired constituent from the other substances present in the mixture. In order to achieve the objective, we look for a solvent extraction system which may quantitatively extract the required constituent with practically negligible amount of the impurities present. The other way to solve the problem is to quantitatively extract all the impurities leaving behind the desired constituent totally in the aqueous phase. The situation where none of the impurities or all the impurities may quantitatively transfer from one phase to the other is rarely encountered. We are likely to face situations where they differ only somewhat in their tendencies to pass from one solvent to another. In order to achieve a simple separation, it is necessary that the distribution ratio of the material of interest and the interference be sufficiently different. The effectiveness of separation is usually expressed by means of separation factor " β " which is related to the individual distribution ratios in the following way:

β = ((C₁ )_o  / (C₂  ))_o/((C₁ )_a  / (C₂  )_a)

= (C₁ )_o  / (C₁ )_a/(C₂  )_o  / (C₂  )_a                                                                               

=  D₁/D₂     

C₁ is the concentration of component 1 in the organic and aqueous phases further labeled by subscripts o and a, respectively and C₂ is the concentration of component 2 in the two phases.