Development of rotating electrochemical detectors for capillary electrophoresis

Analysis of inorganic and small organic ions by CE with amperometric detection

Capillary electrophoresis has become a widely useful analytical technology. Amperometric detection is extensively employed in capillary electrophoresis for its many inherent virtues, such as rapid response, remarkable sensitivity, and low cost of both detectors and instrumentations. Analysis of inorganic and small organic ions by capillary electrophoresis is an important research field. This review focuses on the recent developments of capillary electrophoresis coupled with amperometric detection for analysis of inorganic and small organic ions. Advancements in electrophoresis separation modes, amperometric detection modes, working electrodes, and applications of inorganic ions, amino acids, phenols, and amines are discussed.

Effect of Change in Angle between Microelectrode Surface and Jet Direction in Flow System on Current Response in Solutions of Different Ionic Strength

The influence of stream orientation versus surface of microelectrode detector was examined in the range between vertical and parallel flow for various jet velocities and various levels of supporting electrolyte. The flow cell was equipped with a conical body Pt microdisk electrode, and the measurements involved voltammetry and chronoamperometry. Ferrocene, two its charged derivatives (sodium ferrocenylo sulfate and ferrocenylomethyltrimethylamino hexafluorophosphate) and sodium iodide were employed as the substrates in the experiments. The strongest convectional transport and the highest signal of the analytes was obtained for alpha = 60 degrees (alpha is the angle between the electrode surface and the stream direction). The measured current increased by up to 1.85 times versus the traditional setup, and therefore, this new geometry of the detector is analytically advantageous. The value of alpha corresponding to the highest signal tended to decrease to approximately 45 degrees in the absence of supporting electrolyte provided that either flow rate or analyte concentration was above a certain threshold value. The experiments indicated that the interplay of the convectional and migrational components in the analyte transport is different for the charge increase and the charge cancellation processes. These experimental facts were confirmed by digital simulation results.

Electroanalytical Flow Measurements

A review based on 94 cited original papers describes recent achievements in application of different electrochemical detection in flow analysis, injection techniques of flow analysis, liquid chromatography and capillary electrophoresis.

Investigation into the Applicability of the Centrifugal Microfluidics Platform for the Development of Protein−Ligand Binding Assays Incorporating Enhanced Green Fluorescent Protein as a Fluorescent Reporter

The incorporation of a protein-ligand binding assay into a centrifugal microfluidics platform is described. The platform itself is a disc-shaped polymer substrate, upon which a series of microfluidic channels and reservoirs have been machined. Centrifugal microfluidics platforms require no internal moving parts, and fluid propulsion is achieved solely through rotation of the disc. Fluid flow is controlled by passive valves, the opening of which is dependent on the angular frequency of the rotating platform, the channel dimensions, and the physical properties of the fluid. To evaluate the effectiveness of incorporating a protein-based assay onto the centrifugal microfluidics analytical platform, a class-selective, homogeneous assay for the detection of phenothiazine antidepressants was employed. This class of drugs is known to bind to calmodulin, a calcium binding protein. Specifically, a fusion protein between calmodulin and enhanced green fluorescent protein was utilized. Calmodulin undergoes a conformational change upon binding to phenothiazines that alters the fluorescence properties of the attached fluorescent protein, which can be correlated to the concentration of the drug present. Another important aspect of this work was to study the efficacy of the platform to perform reconstitution assays. To do this, the biological reagent was dried on the platform and rehydrated to carry out the assay. The ability to prealiquot reagents on the platform should enhance its versatility and portability. The integration of protein-based assays in this platform should be useful in the design of analytical systems for high-throughput screening of pharmaceuticals and clinical diagnostics.