Sheathless interface for capillary electrophoresis/electrospray ionization-mass spectrometry
Provided herein are capillaries for use in an electrophoretic separations. The capillaries can comprise an elongated tubular wall defining a path for fluid flow from an inlet to a tapered outlet; and a decoupler junction positioned within the elongated tubular wall upstream of the tapered outlet. The decoupler junction can comprise a plurality of microchannels penetrating through the elongated tubular wall and an ion-permeable polymer coating the plurality of microchannels. Also provided are sheathless interfaces for coupling capillary electrophoresis (CE) with mass spectrometry that employ these capillaries.
1. A capillary for use in an electrophoretic separation, the capillary comprising:
(a) an elongated tubular wall defining a path for fluid flow from an inlet to a tapered outlet; and
(b) a decoupler junction positioned within the elongated tubular wall upstream of the tapered outlet;
wherein decoupler junction comprises a plurality of microchannels penetrating through the elongated tubular wall and an ion-permeable polymer coating the plurality of microchannels.
2. The capillary of claim 1 , wherein the ion-permeable polymer comprises a non-ionic polymer.
3. The capillary of claim 1 , wherein the ion-permeable polymer comprises a hydrophilic polymer.
4. The capillary of claim 1 , wherein the ion-permeable polymer comprises an ion-exchange polymer.
5. The capillary of claim 1 , wherein the ion-permeable polymer comprises cellulose acetate, nafion, or a combination thereof.
6. The capillary of claim 1 , wherein the ion-permeable polymer coating the plurality of microchannels has a thickness of 100 microns or less.
7. The capillary of claim 6 , wherein the ion-permeable polymer coating the plurality of microchannels has a thickness of from 25 microns to 100 microns.
8. The capillary of claim 1 , wherein the plurality of microchannels comprises 5 or more microchannels.
9. The capillary of claim 8 , wherein the plurality of microchannels comprises from 5 to 30 microchannels.
10. The capillary of claim 1 , wherein each of the plurality of microchannels are spaced apart by a distance of from 10 microns to 50 microns.
11. The capillary of claim 1 , wherein the plurality of microchannels comprises at least three microchannels, and wherein each of the plurality of microchannels are spaced apart by substantially equal distances.
12. The capillary of claim 1 , wherein the plurality of microchannels provide a surface area of from 2500 μm 2 to 15000 μm 2 .
13. The capillary of claim 1 , wherein the plurality of microchannels are axially spaced apart along the elongated tubular wall.
14. The capillary of claim 1 , wherein the plurality of microchannels are aligned along the elongated tubular wall.
15. The capillary of claim 1 , wherein each of the plurality of microchannels has a characteristic cross-sectional dimension of from 5 microns to 50 microns.
16. The capillary of claim 1 , wherein the decoupler junction is positioned from 0.1 cm to 10 cm upstream of the tapered outlet.
17. A sheathless interface for coupling capillary electrophoresis (CE) with mass spectrometry, the interface comprising:
(a) the capillary of claim 1 ;
(b) a buffer reservoir in liquid contact with the decoupler junction of the capillary and filed with a reservoir liquid; and
(c) an electrode in contact with the reservoir liquid.
18. A method of characterizing a sample, the method comprising:
(a) providing a sheathless interface for coupling capillary electrophoresis (CE) with mass spectrometry, the interface comprising:
(i) the capillary of claim 1 ;
(ii) a buffer reservoir in liquid contact with the decoupler junction of the capillary and filed with a reservoir liquid;
(iii) an electrode in contact with the reservoir liquid;
(iv) a mass spectrometer comprising an entrance and a detector, wherein the tapered outlet of the capillary is directed towards the entrance of a mass spectrometer; and
(v) a power supply electrically connected to the electrode, wherein the power supply is configured to apply a potential across the capillary;
(b) injecting the sample into the inlet of the capillary;
(c) electrophoretically separating the sample;
(d) directing the separated sample into the entrance of the mass spectrometer.
19. A method of forming a capillary for use in an electrophoretic separation, the method comprising:
(a) providing an electrophoretic capillary comprising an elongated tubular wall defining a path for fluid flow from a capillary inlet to a capillary outlet;
(b) modifying the capillary outlet to form a tapered outlet;
(c) laser ablating a plurality of microchannels penetrating through the elongated tubular wall; and
(d) coating the plurality of microchannels with an ion-permeable polymer.
20. The method of claim 19 , wherein modifying the capillary outlet comprises sharpening the capillary outlet to form the tapered outlet.