Derivation Of Adsorption Capacity And Adsorption Isotherm By A Single Adsorbate Concentration In Liquid-solid System

Based on the adsorption of adsorbates on adsorbents,a novel approach was presented for the derivation of adsorption capacity and adsorption isotherm by a single adsorbate concentration in liquid-solid system.The aim is to solve the problem of large amount of samples but difficult to obtain in the study of the properties of the active components with small content in Chinese medicinal materials.As a proof-of-concept application of this strategy,frontal chromatography?FC?was used as an example in the current work.Through the binding interaction between adsorbates in feed solution and adsorption sites on stationary phase,a break-through curve equation was presented to show the dependence of adsorbate concentration in feed solution on time in FC.By this equation,three characteristic binding parameters n?the number of the adsorbates bound to an adsorption site?,K?the adsorption equilibrium constant of adsorbates on the stationary phase?and n_a?the total number of the adsorption sitesdistributed over the surface of the stationary phase?can be simultaneously derived and further,the adsorption capacity and adsorption isotherm can be derived by a single even part of a single break-through curve.This equation was tested and verified with the break-through curves of some aromatic hydrocarbons and proteins on reversed-phase,ion-exchange,hydrophobic and affinity media.The results showed that this equation could be used to fit these break-through data well,and the adsorption data derived by it were consistent with those derived by static method and elution peak method respectively.In addition,all these adsorption data were of the type I adsorption and deferred to the Langmuir isothermal equation.This work provides a possible way for the determination of characteristic binding parameters and adsorption data for very rare substances on different interfaces.And it may provide some perspective for the determination of physico-chemical property and performance study of very rare substances.The full text consists of two parts:?1?A new method is proposed to derive the adsorption capacity and adsorption isotherm from the concentration of a single adsorbent in the liquid-solid system.According to the interaction between solute molecules and adsorption sites,the conservation of adsorption sites on the surface of the stationary phase,the mass conservation of solute in the incoming column and the mass conservation of solute out of the column,the breakthrough curve equation was established.The equation reflects the relationship between the solute concentration[S]and time t at the exit of the column in the frontier chromatography?FC?.?2?This equation and its different linear forms were tested and verified with the break-through curves of some aromatic hydrocarbons and proteins in RP-C₁₈reversed-phase FC,and some proteins in WCX weak cation-exchange FC,PEG-400 hydrophobic FC and Chelating Sepharose Fast-flow chelated with Zn²⁺affinity FC,and their three characteristic binding parameters and adsorption isotherms were determined respectively.The adsorption data obtained are compared with static method and elution peak method.