Triplet-State Photoexcitation Dipole-Jump Relaxation Method To Observe Adsorption/Desorption Kinetics at a Reversed-Phase Silica/Solution Interface

Abstract

Electronic excitation of a probe chromophore can lead to a change in dipole moment that influences its activity or solubility in solution and changes its relative affinity for partitioning between two phases. Photoexcitation of a probe molecule can, therefore, perturb a sorption equilibrium, and the relaxation kinetics of the probe to the new equilibrium conditions can be monitored in a time-resolved luminescence experiment. The adsorption/desorption kinetics of rose bengal, distributed between a C-18 derivatized porous-silica surface and a liquid mobile-phase solution, were investigated. These kinetics were determined by observing their effect on the phosphorescence decay of the triplet state of rose bengal and its quenching by ferricyanide. The methanol/water solvent compositions were varied to alter the fraction of adsorbed rose bengal. The adsorption rate constant for the triplet state was determined from the dependence of the phosphorescence relaxation rate on dye concentration in solution. The results indicate that the adsorption kinetics are diffusion controlled and that the relaxation is influenced by efficient triplet-energy transfer between excited- and ground-state rose bengal at the C-18 silica/solution interface.

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

“…Slow intra-particle processes can include slow diffusion and/or slow binding and unbinding on the sorption sites. Techniques that have been used to study such intraparticle kinetics include column chromatography [3][4][5][6][7][8][9][10][11], luminescence methods involving pressure jump [12,13], temperature jump [14] and photon-induced dipole jump [15] and pulsed-gradient spin-echo NMR spectroscopy [16,17].…”

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

“…Spectroscopic methods for studying S/D kinetics include nuclear magnetic resonance 21,22,36,37,46-49 and luminescence 14,20,30,50-56 techniques. A limitation of these techniques is that they usually interrogate the rates of only one of the individual kinetic steps within the particle such as diffusion of nonretained solutes through pores, ,,,, surface diffusion, ,,− or the attachment/detachment step. − …”

“…Because they are difference measurements, they give accurate S/D rates when S/D processes dominate band broadening, but they give limited accuracy and potentially ambiguous results when non-S/D processes dominate. 3,8,11,24,45 Spectroscopic methods for studying S/D kinetics include nuclear magnetic resonance 21,22,36,37,[46][47][48][49] and luminescence 14,20,30,[50][51][52][53][54][55][56] techniques. A limitation of these techniques is that they usually interrogate the rates of only one of the individual kinetic steps within the particle such as diffusion of nonretained solutes through pores, 21,22,36,37,47 surface diffusion, 14,30,[54][55][56] or the attachment/ detachment step.…”

“…A limitation of these techniques is that they usually interrogate the rates of only one of the individual kinetic steps within the particle such as diffusion of nonretained solutes through pores, 21,22,36,37,47 surface diffusion, 14,30,[54][55][56] or the attachment/ detachment step. [50][51][52][53] Uptake/release methods for studying S/D kinetics involve monitoring the approach to equilibrium as a function of time after the concentration of solute surrounding the particle is changed abruptly. These methods measure directly the cumulative effects of steps i-iv above.…”

Thermodynamic and Kinetic Characterization of Polycyclic Aromatic Hydrocarbons in Reversed-Phase Liquid Chromatography

“…If these sources cannot be accurately measured or estimated, the resulting kinetic data will be in error. The nonchromatographic experiments have utilized pressure, temperature, and dipole jump methods, − as well as total-internal-reflection fluorescence correlation spectroscopy. , The jump methods require an abrupt perturbation in the equilibrium distribution of molecules between the mobile and stationary phases. This perturbation inherently changes the thermodynamic and kinetic behavior of the system that is being measured.…”