Method and apparatus to measure electrophoretic mobility of a flowing sample
When measuring electrophoretic mobility it is customary to apply an electric field and determine the electrophoretic velocity while minimizing all other contributions to the particle movement. A method and apparatus for the measurement of mobility while the sample is flowing is disclosed. Combined with a fractionation system, this approach further enables the direct measurement of individual species' mobility within a multi-modal sample. Other advantages of this new mobility measurement approach include the ability to easily pressurize the sample to suppress electrolysis, mitigation of oxidation-reduction effects and efficient heat dissipation.
1. A sample cell comprising:
a measurement chamber configured to allow a sample solution comprising particles to flow in a direction essentially parallel to a path of a laser beam transmitted through the measurement chamber;
a fluid inlet coupled to the measurement chamber and configured to introduce the sample solution into the measurement chamber;
a fluid outlet coupled to the measurement chamber and configured to allow the sample solution to exit the measurement chamber; and
electrodes configured to generate an alternating electric field across the measurement chamber and essentially perpendicular to the direction.
2. The sample cell of claim 1 further comprising
a back pressure regulator configured to provide pressurization of the sample solution within the measurement chamber.
3. The sample cell of claim 2 wherein the sample cell is capable of sustaining a back pressure of greater than 50 bars.
4. A method comprising:
flowing a sample solution comprising particles through a sample cell comprising
a measurement chamber configured to allow the sample solution to flow in a direction essentially parallel to a path of a laser beam transmitted through the measurement chamber,
a fluid inlet coupled to the measurement chamber and configured to introduce the sample solution into the measurement chamber, and
a fluid outlet coupled to the measurement chamber and configured to allow the sample solution to exit the measurement chamber; and
generating, via electrodes, an alternating electric field across the measurement chamber and essentially perpendicular to the direction.
5. The method of claim 4 further comprising
applying a back pressure to the sample cell.
6. The method of claim 4 further comprising
fractionating the sample solution.
7. The method of claim 6 wherein the fractionating comprises
fractionating the sample solution via a field flow fractionation system.
8. The method of claim 6 wherein the fractionating comprises
fractionating the sample solution via a size exclusion chromatography system.
9. The method of claim 6 wherein the fractionating comprises
fractionating the sample solution via a reversed phase chromatography system.