Miniaturised separation techniques
Capillary electrophoresis (CE) is a widely employed separation technique and known as an orthogonal method to HPLC. Miniaturized CE (CE on chip) has proven the predictions of the scaling laws. For separations in preparative scale, free-flow electrophoresis is more suited due to its continuous operation mode. While in CE the electric field is applied along the capillary in FFE the electric field is applied perpendicular to a hydrodynamic flow through a separation compartment. Thus, all analyte molecules are affected by two velocity vectors (electrophoretic and hydrodynamic velocity) leading to a sum vector which is at an angle to the hydrodynamic flow. This results in a geometrically two-dimensional separation since the time domain is transformed into a spatial domain. Several separation modes known from CE like zone electrophoresis, isotachophoresis, or isoelectric focusing can be implemented in FFE. Also the use of a miniaturized FFE (µFFE) device has affirmed the validity of the scaling laws.
Performance enhancement of a miniaturized free-flow electrophoresis device by two-depth etching and multiple-outlet interface
The etching of the microfluidic structures of the miniaturized free-flow electrophoresis device in two different depths enhances the flow characteristics. In connection with a multiple outlet interface it provides a better separation performance.
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Label free detecion inside free-flow electrophoresis devices
The detection by surface enhanced Raman spectroscopy (SERS) inside a miniaturised free-flow electrophoresis (FFE) device is demonstrated for the first time.
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Electrospray-ionisation with electrostatic field induction
A non-conductive piezo ceramic plate is used to induce an electrical field to generate an electrospray as an ionisation method for mass spectrometric determination.
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Dielectric polarisation for electrospray-ionisation
Electrospray (ESI) is the interface of choice to ionise and to transfer substances from a microfluidic separation device into a mass spectrometer (MS).
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