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. An apparatus comprising:
a fractionator configured to fractionate a sample solution comprising particles;
a fluid inlet coupled to an outlet of the fractionator and coupled to a measurement chamber,
wherein the fluid inlet is configured to introduce the sample solution into the measurement chamber;
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, resulting in a fluid flow;
a fluid outlet coupled to the measurement chamber,
wherein the fluid outlet is configured to allow the sample solution to exit the measurement chamber;
electrodes configured to generate an alternating electric field across the measurement chamber and essentially perpendicular to the direction,
thereby minimizing a Doppler component from the fluid flow; and
a concentration detector coupled to the fractionator and coupled to the measurement chamber,
wherein the concentration detector is configured to measure a concentration of each species in the sample solution, resulting in a measured concentration of the each species in the sample solution.
2. The apparatus of claim 1 wherein the fractionator comprises a field flow fractionation system.
3. The apparatus of claim 1 wherein the fractionator comprises a size exclusion chromatography system.
4. The apparatus of claim 1 wherein the fractionator comprises a reversed phase chromatography system.
5. The apparatus of claim 1 wherein the fractionator comprises a reversed phase chromatography system.
6. The apparatus of claim 1 wherein the concentration detector comprises a refractive index detector.
7. The apparatus of claim 1 further comprising a back pressure regulator configured to provide pressurization of the sample solution within the measurement chamber.