Laser doppler electrophoresis using a diffusion barrier
In one general aspect, an electrophoretic measurement method is disclosed that includes providing a vessel that holds a dispersant, providing a first electrode immersed in the dispersant, and providing a second electrode immersed in the dispersant. A sample is placed at a location within the dispersant between the first and second electrodes with the sample being separated from the electrodes, an alternating electric field is applied across the electrodes, and the sample is illuminated with temporally coherent light. A frequency shift is detected in light from the step of illuminating that has interacted with the sample during the step of applying an alternating electric field, and a property of the sample is derived based on results of the step of detecting.
1. An electrophoretic measurement method, comprising:
providing an upright u-shaped vessel that holds a dispersant,
providing a first electrode immersed in the dispersant,
providing a second electrode immersed in the dispersant,
placing a sample at a location within the dispersant between the first and second electrodes with the sample being separated from the electrodes,
applying an alternating electric field across the electrodes,
illuminating the sample with temporally coherent light,
detecting a frequency shift in light from the step of illuminating that has interacted with the sample during the step of applying an alternating electric field, and
deriving a property of the sample based on results of the step of detecting.
2. The method of claim 1 wherein the step of placing the sample includes injecting the sample.
3. The method of claim 1 wherein the step of placing the sample is part of a process of drawing the sample through the vessel.
4. The method of claim 1 further including a step of recovering the sample.
5. The method of claim 1 wherein the sample is a soft sample.
6. The method of claim 1 wherein the sample is a protein sample.
7. The method of claim 1 wherein the step of placing the sample places the sample at a location separated from the electrodes by dispersant.
8. The method of claim 1 wherein the step of placing the sample places the sample at a location separated from the electrodes by a barrier different from the dispersant.
9. The method of claim 1 wherein the step of deriving includes deriving a zeta potential value from an electrophoretic mobility value for the sample.
10. The method of claim 1 wherein the step of detecting takes place in a time that is shorter than a time during which a significant amount of the sample can diffuse to either of the first and second electrodes with the alternating current applied.
11. The method of claim 1 wherein the step of illuminating employs a laser.
12. The method of claim 1 further including a step of recovering the sample before the sample has fully diffused into the dispersant.
13. The method of claim 1 wherein the step of placing includes placing the sample around the bottom of the u-shaped vessel.