Electro-Responsive Surface Composition and Kinetics of an Ionic Liquid in a Polar Oil.

The quartz crystal microbalance (QCM) has been used to study how the interfacial layer of an ionic liquid dissolved in a polar oil at low weight percentages responds to changes in applied potential. The changes in surface composition at the QCM gold surface depend on both the magnitude and sign of the applied potential. The time-resolved response indicates that the relaxation kinetics are limited by the diffusion of ions in the interfacial region and not in the bulk, since there is no concentration dependence.

Reliable Strategy for Analysis of Complex Biosensor Data.

When using biosensors, analyte biomolecules of several different concentrations are percolated over a chip with immobilized ligand molecules that form complexes with analytes. However, in many cases of biological interest, e.g.

Weighing the surface charge of an ionic liquid.

Electrochemical quartz crystal microbalance has been used to measure changes in the composition of the capacitive electrical double layer for 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate, an ionic liquid, in contact with a gold electrode surface as a function of potential. The mass difference between the cation and anion means that the technique can effectively "weigh" the surface charge accurately with high temporal resolution. This reveals quantitatively how changing the potential alters the ratio of cations and anions associated with the electrode surface, and thus the charge per unit area, as well as the kinetics associated with these interfacial processes.

Electroimmobilization of proinsulin C-peptide to a quartz crystal microbalance sensor chip for protein affinity purification.

Proinsulin C-peptide was electroimmobilized to a quartz crystal microbalance sensor chip, localizing this low-pI peptide for covalent attachment to activated surface carboxyl groups. The resulting chip was used in a continuous flow biosensor to capture anti-C-peptide antibodies, which could subsequently be eluted in 5% formic acid between air bubbles for efficient recovery and mass spectrometric identification. The method is reproducible through repeated cycles, providing affinity purification of proteins under real-time monitoring of the binding and elution processes.