https://pure.tue.nl/ws/files/2459317/620232.pdf

High-performance zone electrophoresis

A microchip laboratory system and method provide fluid manipulations for a variety of applications, including sample injection for microchip chemical separations. The microchip is fabricated using standard photolithographic procedures and chemical wet etching, with the substrate and cover plate joined using direct bonding. Capillary electrophoresis and electrochromatography are performed in channels formed in the substrate. Analytes are loaded into a four-way intersection of channels by electrokinetically pumping the analyte through the intersection, followed by switching of the potentials to force an analyte plug into the separation channel.

Apparatus and method for performing microfluidic manipulations for chemical analysis and synthesis

A microscale fluid handling system (10) that permits the efficient transfer of nanoliter to picoliter quantities of a fluid sample from the spatially concentrated environment of a microfabricated chip to 'off-chip' analytical or collection devices (23) for further off-chip sample manipulation and analysis is disclosed. The fluid handling system (10) is fabricated in the form of one or more channels (12), in any suitable format, provided in a microchip body or substrate of silica, polymer or other suitable non-conductive material, or of stainless steel, noble metal, silicon or other suitable conductive or semi-conductive material. The microchip fluid handling system (10) includes one or more exit ports (16) integral with the end of one or more of the channels (12) for consecutive or simultaneous off-chip analysis or collection of the sample. The exit port or ports (16) may be configured, for example, as an electrospray interface for transfer of a fluid sample to a mass spectrometer (23).

Microscale fluid handling system

Capillary zone electrophoretic separations of proteins have been achieved by using nonionic surfactant coated capillaries. Capillaries were prepared by derivatization of the silica surface with octadecylsilane followed by the deposition of a layer of nonionic surfactant from an aqueous solution above the critical micelle concentration. This coating is of sufficient thickness and hydrophilicity to reduce both protein adsorption and electroosmotic pumping. This hydrophilic coating reduces electroosmotic pumping 5-8-fold while resolving proteins quickly and efficiently with good recovery. The coating provides a stable and reproducible means of deactivation, while the rate of electroosmotic pumping stays relatively constant throughout the pH range 4-11. This allows the pH to be varied to enhance selectivity without adversely affecting the flow rate.

Capillary electrophoretic separations of proteins using nonionic surfactant coatings.

Low molecular weight carboxylic acids are separated and quantitated by capillary zone electrophoresis (CZE) with an on-column conductivity detector. The addition of 0.2-0.5 mM TTAB (tetradecyltrimethylammonium bromide) controls the electroosmotic flow so that all carboxylate anions pass through the detector. Unlike other CZE detection methods, conductivity detection shows a direct relationship between retention time and peak area. This confers on conductivity detection, in CZE, the unique advantage that use of an internal standard allows accurate determination of absolute concentrations in a mixture without separate calibration of response for each component.

Quantitative determination of low molecular weight carboxylic acids by capillary zone electrophoresis/conductivity detection

The contributions of diffusion, Joule heating, sampling and electroosmotic flow to the dispersion of zones separated by capillary zone electrophoresis were evaluated theoretically and verified experimentally. The theoretical model predicts that an optimum electric field strength, E, exists at which the number of theoretical plates, N, is a maximum. Both open and closed capillaries were considered and a simple formula was derived for the calculation of a maximumm with a given experimental arrangement. The theoretical efficiency curves, N vs. E, were calculated and compared with those obtained experimentally in capillaries of various I.D.'s and filled with background electrolytes of various conductivities. The possibilities of minimization of some dispersion factors are discussed.

Capillary Zone Electrophoresis

Simple detection cells for on-line UV absorbance and conductivity detection in capillary zone electrophoresis are described. The UV detection system employs a commercial photometer and optical fibers which are in direct contact with the outer walls of the separation capillary and conduct the light beam perpendicularly across the migrating zones. The conductivity detection cell consists of platinum wires protruding the wall of the separation capillary and thus in direct contact with the electrolytes inside. The electronic system is adopted from a commercially available conductivity detector for isotachophoresis.

Mirko Deml

Papers

Capillary Zone Electrophoresis

On-line fiber optic UV detection cell and conductivity cell for capillary zone electrophoresis

Determination of nitrate, chloride and sulphate in drinking water by capillary free-zone electrophoresis

Use of complex formation equilibria in the analytical isotachophoresis of strong electrolyte ions

Electric sample splitter for capillary zone electrophoresis