Method and apparatus to measure electrophoretic mobility of a flowing sample

Patent metadata

Field	Value
Publication number	US-2018299405-A1
Application number	US-201515521255-A
Country	US
Kind code	A1
Filing date	Nov 6, 2015
Priority date	Nov 6, 2014
Publication date	Oct 18, 2018
Grant date	—

Abstract

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.

First claim

1 . An apparatus to measure the electrophoretic mobility of particles in flowing sample solution comprising
A) a light beam source; B) a non-conductive sample cell comprised of
1. a fluid inlet through which said sample solution is introduced into
2. a measurement chamber wherein the direction of fluid flow is essentially parallel to the path of said light beam;
3. a fluid outlet through which said sample exits said measurement chamber;
4. electrodes, between which a voltage may be applied, and said voltage polarity may be alternated, across said sample contained within said chamber, said voltage being applied essentially perpendicularly to said direction of fluid flow; and
5. optical windows in said chamber through which
a) said light beam enters said measurement chamber and scatters light from particles contained within said flowing sample;
b) said light beam and a fraction of the light scattered from said particles in said flowing sample leave said sample cell;

C) an array of photo detector elements onto which said scattered and unscattered light is incident, with each said detector element producing time varying signals therefrom; and D) electronic means to convert said signals into digital representations and transmit said resultant digital signals to a computer; E) said computer containing algorithms whereby the optical signal contribution of movement of said particles due to convective flow and externally imposed flow is decoupled from signal due electrophoresis, leaving the contribution from the imposed electric field created by the voltage applied across said measurement cell by said electrodes, and to calculate therefrom said electrophoretic mobility.

2 . The apparatus of claim 1 further comprising
A) a beam splitter to divide said light beam into
1. a sample beam that will pass through said flowing sample, and
2. a reference beam;

B) an optical means to collect and collimate said sample beam leaving said measurement cell unscattered and said fraction of said sample beam light scattered from said particles and leaving said measurement cell;
C) means to modulate the optical phase of said reference beam relative to the optical phase of said sample beam; and
D) an optical means in free space to combine said reference beam with said collimated fraction of light scattered from said particles, forming thereby a third coherent beam which is incident upon said array of photodetector elements.

3 . The apparatus of claim 1 where said photo detector elements are photodiodes.

4 . The apparatus of claim 1 where said array of photo detector elements is one dimensional.

5 . The apparatus of claim 1 where said array of photo detector elements are two dimensional.

6 . The apparatus of claim 1 where said light beam source is a laser.

7 . The apparatus of claim 2 where said means to collect and collimate said sample beam comprises a converging lens.

8 . The apparatus of claim 1 further comprising a back pressure regulator to provide pressurization of the sample within said measurement chamber.

9 . The apparatus of claim 8 where said measurement cell is capable of sustaining a back pressure of greater than 50 bars.

10 . A method to measure the electrophoretic mobility of particles in a flowing sample solution comprising the steps of
A) generating light beam; B) flowing said sample through a non-conductive sample cell comprised of
1. a fluid inlet through which said sample solution is introduced into
2. a measurement chamber wherein the direction of fluid flow is essentially parallel to the path of said light beam;
3. a fluid outlet through which said sample exits said measurement chamber;
4. electrodes, between which a voltage may be applied, and said voltage polarity may be alternated, across said sample contained within said chamber, said voltage being applied essentially perpendicularly to said direction of fluid flow; and
5. optical windows in said chamber through which
c) said light beam enters said measurement chamber and scatters light from particles contained within said flowing sample;
d) said light beam and a fraction of the light scattered from said particles in said flowing sample leave said sample cell;

C) collecting said scattered and unscattered light upon an array of photo detector elements, with each said detector element producing time varying signals therefrom; and D) converting said time varying signals into digital representations; E) transmitting said resultant digital signals to a computer; F) decoupling, by computer means, the optical signal contribution of movement of said particles due to convective flow and externally imposed flow from signal due electrophoresis, leaving the contribution from the imposed electric field created by the voltage applied across said measurement cell by said electrodes; G) calculating therefrom said electrophoretic mobility.

11 . The method of claim 10 comprising the further step of applying a back pressure to the measurement cell.

12 . The method of claim 10 further comprising the step fractionating said sample solution by fractionation means.

13 . The method of claim 12 wherein said fractionation means is a field flow fractionation system.

14 . The method of claim 13 wherein said fractionation means is a size exclusion chromatography system.

15 . The method of claim 14 wherein said fractionation means is a reversed phase chromatography system.

Assignees

• Wyatt Tech Corp

Inventors

• Hsieh Hung-Te
• Trainoff Steven P

Classifications

• G01N30/02

  Column chromatography · CPC title

• B01D15/325

  Reversed phase · CPC title

• G01N27/44721 Primary

  by optical means · CPC title

• G01N27/44769

  Continuous electrophoresis, i.e. the sample being continuously introduced, e.g. free flow electrophoresis [FFE] · CPC title

• B01D15/34

  Size-selective separation, e.g. size-exclusion chromatography; Gel filtration; Permeation · CPC title