Pressure driven microfluidic injection for chemical separations

Patent metadata

Field	Value
Publication number	US-9255905-B1
Application number	US-201514708906-A
Country	US
Kind code	B1
Filing date	May 11, 2015
Priority date	May 11, 2015
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

Methods, systems and devices that allow independently applied pressures to a BGE reservoir and a sample reservoir for pressure-driven injection that can inject a discrete sample plug into a separation channel that does not require voltage applied to the sample reservoir and can allow for in-channel focusing methods to be used. The methods, systems and devices are particularly suitable for use with a mass spectrometer.

First claim

That which is claimed:

1. A method of sample processing, comprising:
providing a microfluidic device with at least one separation channel in fluid communication with a background electrolyte (BGE) reservoir and a sample reservoir having a sample channel that merges into the separation channel;
injecting a fluid sample from the sample reservoir into the separation channel downstream of the BGE reservoir by concurrently applying a defined pressure to the BGE reservoir and a defined pressure to the sample reservoir; then
clearing a trailing end of the sample from the sample channel and flowing fluid from the BGE reservoir to deliver a plug of the sample in the separation channel in response to reducing or removing the pressure applied to the sample reservoir while applying pressure to the BGE reservoir so that pressure applied to the BGE reservoir is greater than pressure then applied to the sample reservoir; and then
electrophoretically separating the delivered sample in the separation channel by-applying a voltage to the BGE reservoir and a downstream location of the separation channel.

2. The method of claim 1 , wherein the injecting, clearing and electrophoretic separation are carried out without applying a voltage to the sample reservoir.

3. The method of claim 1 , wherein the electrophoretic separation is carried out by further reducing or removing pressure applied to the BGE reservoir while applying the voltage to the BGE reservoir.

4. The method of claim 1 , wherein the electrophoretic separation comprises removing pressure applied to the BGE reservoir while applying the voltage to the BGE reservoir.

5. The method of claim 1 , further comprising electronically adjusting a duration of the pressure applied to at least one of the sample reservoir and the BGE reservoir for the injecting step.

6. The method of claim 1 , further comprising controlling a duration and magnitude of the pressure applied to the BGE reservoir to adjust a size of the plug of the sample delivered to the separation channel.

7. The method of claim 1 , wherein the clearing the trailing end of the sample to deliver the plug of the sample into the separation channel is carried out by removing the pressure applied to the sample reservoir while applying the pressure to the BGE reservoir.

8. The method of claim 1 , further comprising discharging the electrophoretically separated sample from the microfluidic device via at least one emitter on the microfluidic device toward at least one of a collection device for subsequent analysis or an entrance of a mass spectrometer.

9. The method of claim 8 , further comprising using at least one electro-osmotic (EO) pump held on the microfluidic device to drive the discharging.

10. The method of claim 1 , wherein the pressures applied to the BGE reservoir and the sample reservoir during the injecting step are each between 0.1 and 30 psi.

11. The method of claim 1 , wherein the pressure applied to the sample reservoir during the injecting step is between 1 and 10 psi, and wherein reducing or removing the pressure applied to the sample reservoir during the clearing step comprises venting pressurized gas from the sample reservoir.

12. The method of claim 1 , wherein the pressure applied to the BGE reservoir and the pressure applied to the sample reservoir during the injecting step is between 2 and 10 psi, wherein no pressure is applied to the sample reservoir during the clearing step, and wherein the pressure applied to the BGE reservoir during the clearing step is between 1-5 psi.

13. The method of claim 1 , wherein the injecting step is carried out by applying the defined pressures for between 1 and 30 seconds.

14. The method of claim 1 , further comprising:
providing a first pressure supply tube in communication with a pressurized gas supply and a first valve to the BGE reservoir;
providing a second pressure supply tube in communication with a pressurized gas supply and a second valve to the sample reservoir; and
electronically opening and closing the first and second valves in a defined sequence to carry out the injecting.

15. The method of claim 1 , wherein the BGE reservoir is in fluid communication with a BGE channel that merges into an end of the separation channel and the sample channel is downstream of the BGE channel and extends laterally from the sample reservoir to merge into the separation channel across from a laterally extending sample waste channel that is connected to a, sample waste reservoir.

16. The method of claim 1 , wherein the microfluidic device comprises a sample waste channel that is connected to a sample waste reservoir, and wherein the sample channel and sample waste channel define an orthogonal flow path across the separation channel downstream from the BGE reservoir.

17. The method of claim 1 , further comprising detecting analyte peak signals of the sample using a mass spectrometer and generating electropherograms of the sample.

18. The method of claim 1 , wherein the electrophoretic separation is completely free of injection bias so that peak areas in electropherograms generated during the electrophoretic separation are consistent for later eluting analytes in the delivered sample.

19. The method of claim 1 , wherein the delivered sample comprises an electrolyte that has greater electrophoretic mobility than analyte ions in the sample for transient isotachophoresis.

20. The method of claim 1 , wherein the sample comprises one or more of amino acids, polar metabolites, charged molecules, molecules with electrophoretic mobility, peptides, proteins, and molecules extracted from one or more of biofluids, blood, serum, urine, dried blood, cell growth media, lysed cells, environmental samples, beverages and food.

21. A microfluidic analysis system, comprising:
a microfluidic device comprising at least one separation channel in fluid communication with a background electrolyte (BGE) reservoir, a sample reservoir having a sample channel that merges into the separation channel and a sample waste channel that merges into the separation channel;
a first pressure supply tube in communication with a pressurized gas supply and a first valve, the first pressure supply tube comprising a voltage input attached to the BGE reservoir;
a second pressure supply tube in communication with a pressurized gas supply and a second valve attached to the sample reservoir; and
a controller in communication with a voltage source and with the first and second valves to direct the first and second valves to open and close to carry out a sample injection into the at least one separation channel followed by electrophoretic separation, wherein sample injection is carried out only using pressure applied to the BGE reservoir and the sample reservoir from the first and second supply tubes without any electrokinetic voltage.

22. The system of claim 21 , wherein the controller is configured to have a defined timing sequence for applying pressures between 0.1 and 30 psi to a headspace of the BGE reservoir via the first supply tube and to a headspace of the sample reservoir via the second supply tube for defined durations between 1 and 30 seconds to inject a sample into the at least one separation channel.

23. The system of claim 21 , wherein the controller is configured to independently apply a defined pressure to the sample reservoir and a defined pressure to the BGE reservoir, and wherein the microfluidic device further comprises at least one electro-osmotic (EO)

Assignees

• Univ North Carolina

Inventors

• Mellors John Scott
• Redman Erin Anne
• Ramsey John Michael

Classifications

• G01N27/44721 Primary

  by optical means · CPC title

• H01J49/167 Primary

  Capillaries and nozzles specially adapted therefor; (electrostatic spraying per se B05B5/00) · CPC title

• G01N27/44791

  Microapparatus (sample containers with integrated microfluidic structures B01L3/5027) · CPC title

• B01L3/50273

  characterised by the means or forces applied to move the fluids · CPC title

• B01L3/502715

  characterised by interfacing components, e.g. fluidic, electrical, optical or mechanical interfaces · CPC title