Devices, methods and kits for sample characterization

1. A method for electrophoretic introduction of a mobilization electrolyte into a separation channel comprising one or more isoelectrically focused analyte bands, the method comprising:

a) performing isoelectric focusing of a sample comprising one or more analytes within the separation channel by applying a first electric field between a first electrode and a second electrode, thereby separating the sample into one or more isoelectrically focused analyte bands, wherein the first electrode is in electrical contact with a proximal end of the separation channel, and wherein the second electrode is in electrical contact with a distal end of the separation channel; and

b) electrophoretically introducing a mobilization electrolyte from a mobilization channel into the separation channel to initiate mobilization of the one or more isoelectrically focused analyte bands, wherein the mobilization channel is distinct from the separation channel and a distal end of the mobilization channel intersects the separation channel at a single point at the distal end of the separation channel, by automatically switching off the first electric field and automatically switching on a second electric field applied between the first electrode and a third electrode that is in electrical contact with a proximal end of the mobilization channel.

2. The method of claim 1 , wherein the separation channel is a microchannel in a microfluidic device.

3. The method of claim 1 , wherein the separation channel is a capillary.

4. The method of claim 1 , wherein the electrophoretic introduction of the mobilization electrolyte leads to improved separation resolution after mobilization compared to that attained at the completion of the isoelectric focusing and prior to the electrophoretic introduction of the mobilization electrolyte.

5. The method of claim 4 , wherein the improvement in separation resolution is at least 20%.

6. The method of claim 4 , wherein the improvement in separation resolution is at least 40%.

7. The method of claim 4 , wherein the improvement in separation resolution is at least 60%.

8. The method of claim 4 , wherein the improvement in separation resolution is at least 80%.

9. The method of claim 1 , wherein the mobilization electrolyte comprises acetic acid, formic acid, carbonic acid, or any combination thereof.

10. The method of claim 1 , wherein the mobilization electrolyte comprises ammonium hydroxide, diethylamine, dimethyl amine, piperidine, or any combination thereof.

11. The method of claim 1 , wherein the automatic switching of the first electric field and the second electric field occurs at a user-specified time following initiation of the isoelectric focusing by applying the first electric field.

12. The method of claim 1 , wherein the automatic switching of the first electric field and the second electric field is triggered by monitoring a current flowing through the separation channel during the isoelectric focusing and detecting when the current drops below a specified current threshold.

13. The method of claim 1 , wherein the one or more isoelectrically focused analyte bands are mobilized towards an electrospray ionization interface with a mass spectrometer.

14. The method of claim 13 , wherein a nebulizing gas is used to facilitate electrospray ionization.

15. The method of claim 1 , further comprising acquiring images of all or a portion of the separation channel during both the isoelectric focusing in (a) and the mobilization in (b).

16. The method of claim 15 , wherein data derived from the images enables more accurate isoelectric point (pI) determinations for the one or more isoelectrically focused analyte bands.

17. The method of claim 15 , wherein data derived from the images is used to correlate isoelectric point (pI) data for the one or more isoelectrically focused analyte bands with mass spectrometer data.

18. The method of claim 15 , further comprising processing the images, wherein data derived from the processed images is used to trigger the automatic switching of the first electric field and the second electric field.

19. The method of claim 15 , wherein the images are processed to monitor the presence or absence of an isoelectrically focused analyte band of the one of more isoelectrically focused analyte bands in the separation channel.

20. The method of claim 19 , wherein the first electric field is maintained in an “on” state if no isoelectrically focused analyte band is detected in the separation channel.

21. The method of claim 19 , wherein the images are processed to monitor changes in position of the one or more isoelectrically focused analyte bands over time or changes in the width of the one or more isoelectrically focused analyte bands over time.

22. The method of claim 21 , wherein an absence of change or a reduction in a rate of change in isoelectrically focused analyte band position or band width for the one or more isoelectrically focused analyte bands over a time period of at least 20 seconds triggers the automatic switching of the first electric field and the second electric field.

23. The method of claim 15 , wherein the images are acquired using light transmitted through the separation channel.

24. The method of claim 15 , wherein the images are UV absorbance images or fluorescence images.

25. The method of claim 24 , wherein the fluorescence images are native fluorescence images.

26. The method of claim 15 , wherein the images are acquired at a rate of at least 1 image every 15 seconds.

27. The method of claim 1 , wherein the one or more analytes are proteins.

28. The method of claim 27 , wherein the proteins are intact proteins.

29. The method of claim 1 , wherein the method is implemented by a system used to generate data to establish biosimilarity between a candidate biological drug and a reference biological drug.