The present study explores the possibility to use the sensorgram methodology, which is very common in surface plasmon resonance (SPR), in potentiometry. Can we obtain information on rates of adsoption/ion exchange of ionized organic molecules from their response behavior on a potentiometric sensor? And do we see changes in this behavior if we add a (e.g. protein) biomolecule in the sensor coating? The answer is yes. Sensorgrams were  obtained by injection of square concentration pulses in a flow injection (FIA) setup with a flow-through system. The compounds studied include metabolic acids, environmental contaminants, basic drugs plus alkaloids, and oligonucleotides. As potentiometric sensor coatings we compare a soft, hydrophilic gelatin based coating with a classical lipophilic rubber based coating. The substrate (contact layer) of these coated wire type sensors was a conductive composite. The “on” and “off” kinetics (k_on and k_off) were studied as a function of analyte characteristics, analyte concentration, contact time, hydrodynamics, sensing layer type, and addition of biomolecules  to the sensing layer. The figure in this abstract shows sensorgrams for promazine on a classical rubber membrane injected at concentrations 10^-7, 10^-6, 10^-5 and 10^-4 M. It will be discussed in relation to analogous SPR sensorgrams. Adsorption on- and diffusion in the sensor’s coating materials are shown to be active during the contact times which varied between 10 and 40s. Large flexible analyte molecules with high interaction with the surface (components) yield the slowest “on” (phase transfer) kinetics. In the soft gelatin material, diffusion becomes more predominant as compared to the hard rubber materials. This gelatin material can be easily doped with a (protein or DNA) biomolecule. This is very promising in view of future qualitative and quantitative use of potentiometric sensor response dynamics in analyte/biomolecule and analyte/surface studies. Compatibility of the sensors with separation methods is also briefly discussed.

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