Continuous desorption rate measurement from a shallow-bed of poly(styrene–divinylbenzene) particles with correction for experimental artifacts

Abstract

A 0.50 mm high bed, containing ca. 3 mg of the nominally non-porous poly(styrene-divinylbenzene) (PS-DVB) sorbent Hamilton PRP-infinity, is located in a valve. After the bed is pre-equilibrated with a (7/3) methanol/water solution of naphthalene (NA), the valve is switched and (7/3) methanol/water solvent flows continuously through the bed at a high linear velocity. This causes NA to desorb into a constantly refreshed solvent, creating a "shallow-bed" contactor with an "infinite bath" kinetic condition. The effluent from the bed passes through a UV-absorbance detector which generates the observed instantaneous desorption rate curve for NA. The same experiment is performed using the solute phloroglucinol (PG), which is not sorbed by PRP-infinity and serves as an "impulse response function marker" (IRF-Marker). The resulting peak-shaped IRF curve is used in two ways (i.e. subtraction and deconvolution) in order to correct the observed instantaneous rate curve of NA for the following experimental artifacts: hold-up volume of the bed and valve, transit-delay time between the bed and the detector and instrument bandbroadening of the NA zone. The cumulative desorption rate curve, which is a plot of moles NA desorbed versus time, is obtained by integration. It is found to be accurately described by the theoretical equation for homogeneous spherical diffusion. The diffusion coefficient of NA inside the PRP-infinity particles (5.0+/-0.6) x 10(-11) cm2/s, agrees with the literature value that was obtained from the sorption rate of NA into the same particles. This constitutes virtually conclusive evidence for diffusion control of intra-particle kinetics of NA in the PS-DVB matrix of PRP-infinity and related polymers. The influence of both sorbent and solute properties on the method is evaluated.

External and Intraparticle Diffusion of Coumarin 102 with Surfactant in the ODS-silica Gel/water System by Single Microparticle Injection and Confocal Fluorescence Microspectroscopy

“…[1][2][3][4] The mass transfer in the porous material/solution system has been often analyzed in terms of diffusion in pores of the material. [5][6][7][8][9][10] However, analysis of the mass transfer mechanism is generally difficult. As an example, mass transfer in a porous particle/ solution system consists of several elementary processes such as adsorption/desorption at the pore walls, mass transfer in the surrounding solution (external mass transfer), and diffusion in the pore solution (pore diffusion) and along the pore walls (surface diffusion).…”

Measurement of Desorption Rates from Octadecylsilyl Bonded-Phase HPLC Particles and Its Characterization in Terms of Pore, Surface, and Film Diffusion

“…These methods measure directly the cumulative effects of steps i−iv above. They have been briefly reviewed in a recent paper . The shallow-bed method (SB method) of performing uptake/release rate measurements employs a very short bed (i.e., <1 mm) of particles and a high linear velocity of mobile phase flowing through it. ,− …”

“…In a recent study, the desorption rate curve was measured for the solute compound naphthalene from a 0.50-mm-long bed of 20-μm-diameter particles of the nominally nonporous poly(styrene−divinylbenzene) sorbent Hamilton PRP-∞, using a SB instrument of simple design. Flow through the instrument components that are located between the bed and the detector (e.g., bed outlet frit, connecting tubing, detector flow cell, and detector time constant) causes instrument band broadening , of the solute zone.…”

Mass Transfer in Mesoporous Microparticles Studied by Confocal Fluorescence Recovery after Photobleaching

“…2,5 These processes consist of diffusion through the pore solution (pore diffusion), diffusion along the pore walls (surface diffusion), adsorption/desorption and chemical reactions at the pore walls, and so on; 1,6,7 further, quantitative measurements of intraparticle mass transfer rates are generally difficult to obtain. Pore and surface diffusion have been kinetically analyzed using sophisticated high-performance liquid chromatography, 8,9 microspectroscopy for single microparticles, [10][11][12][13][14][15][16][17] and so forth. [18][19][20] We have reported on intraparticle diffusion in silica gel and octadecylsilyl (ODS) silica gel in aqueous solutions, using microspectroscopy for single microparticles.…”