Influence of Microwave Irradiation on the Mass-Transfer Kinetics of Propylbenzene in Reversed-Phase Liquid Chromatography

Abstract

The effect of microwave irradiation on the kinetics of mass transfer in reversed-phase liquid chromatography (RPLC) was studied by measuring its influence on the band profile of propylbenzene in a C 18 -silica column eluted with an aqueous solution of methanol and placed inside a microwave oven. The elution peaks were measured by the pulse-response method, under linear conditions. The amount of microwave energy induced into the column was varied based on the microwave input power. The experimental data were analyzed using the conventional method of moment analysis and the lumped pore diffusion model. With input powers of 15 and 30 W, the effluent temperatures were 25 ( 1 and 30 ( 1°C, respectively. The effect of microwave irradiation on the mass transfer of the studied solute was determined by comparing the band profiles obtained under the same experimental conditions, at the same temperature, with and without irradiation. The values of the intraparticle diffusion coefficient, D e , measured with microwave irradiation were ca. 20% higher than those obtained without irradiation. Derived from the method of moments, the values of D e at 15 W (25 ( 1°C) and 0 W (25 ( 1°C) were 8.408 × 10 -6 cm 2 s -1 and 6.947 × 10 -6 cm 2 s -1 , respectively, while these values at 30 W (30 ( 1°C) and 0 W (30 ( 1°C) were 9.389 × 10 -6 cm 2 s -1 and 7.848 × 10 -6 cm 2 s -1 , respectively. The values of the surface diffusivity, D S , also increased with increasing power of the microwave irradiation. It is assumed that the increase in intraparticle diffusion for propylbenzene was caused by the molecular excitation of the organic modifier that has a higher dielectric loss than the solute. The values of D e were also analyzed and determined using the POR model. There was an excellent agreement between the results of the two independent methods. These preliminary results suggest that microwave irradiation may have a considerable influence on the mass transfer kinetics in RPLC.

Microwave high performance liquid chromatography with UV-visible detection. Application to vitamins determination

“…This phenomenon disappears as the radiation ceases.As a result of all these processes, the intraparticle and the surface diffusivity coefficients are higher in presence than in the absence of the microwave field. 10 In the present study already for thiamine, narrower peaks were obtained when the microwave field was on, in spite of the fact that the mobile phase heating was negligible (i.e., a 2 C increase in the temperature was noticed). Additional processes such as the effect of microwave on the ionization of the stationary phase could be considered as negligible because perchloric acid was present in the mobile phase.…”

“…As the temperature increase was more remarkable at 84 W than at 21 W, the drop in system pressure was also more significant (Fig.2c).Fig.3shows that the retention factor decreased with the MW applied power for biotin and riboflavin. The reason that can be argued to explain this trend was that the diffusivity of the analyte increased because the radiation improved this physical property10 and the mobile phase temperature rose (with a concomitant decrease in the viscosity) as a result of the absorption of microwave radiation. Another interesting observation was that the modification in retention times with MW application depended on the evaluated vitamin.…”

Recent Progress and Prospects in Catalytic Water Treatment

“…The last type of heating under MW can be attributed to magnetic loss occurring in magnetic materials, as Fe, Ni and Co, affected by both electric field and magnetic field, and some metal oxides such as ferrites or nickel oxides 237 . Finally, it was demonstrated that there can be a positive, but non-thermal, effect of microwaves on the intra-particle diffusion and mass transfer coefficients in surface modified porous silica due to the molecular excitation of organic molecules with a higher dielectric loss than the aqueous solution 238 .…”

“…237 Finally, it was demonstrated that there can be a positive, but nonthermal, effect of microwaves on the intraparticle diffusion and mass transfer coefficients in surface modified porous silica due to the molecular excitation of organic molecules with a higher dielectric loss than the aqueous solution. 238 Consequently, MW irradiation can be an efficient way for wastewater treatment due not only to the heating of water or polar pollutants but more importantly to possible beneficial interactions with oxidants and catalysts. In fact, the direct treatment of wastewater under MW irradiation leads to an increase in temperature, which causes the removal from water of volatile or semivolatile pollutants by evaporation but is not sufficient for breaking chemical bonds and decompose organic pollutants.…”

Efficient oxidation of high levels of soil-sorbed phenanthrene by microwave-activated persulfate: implication for in situ subsurface remediation engineering

“…In addition, microwave-specific effect (non-thermal effect) may further enhance the intra-particle diffusion and mass transfer coefficients in a heterogeneous system (Galinada et al 2005;Galinada and Guiochon 2007), which may facilitate the persulfate oxidation of soil-sorbed organic contaminants. As there is no reported application of microwave-activated persulfate for in situ subsurface remediation, this study aimed to evaluate the potential of microwave-activated persulfate for subsurface remediation.…”