Leakage current sense circuit for error detection in an improved capillary electrophoresis-electrospray ionization-mass spectrometry system

Patent metadata

Field	Value
Publication number	US-9500621-B2
Application number	US-201313908861-A
Country	US
Kind code	B2
Filing date	Jun 3, 2013
Priority date	Jun 4, 2012
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

Aspects of the present innovations relate to improved systems that may perform capillary electrophoresis (CE) and CE in conjunction with electrospray ionization (ESI) as an input to a mass spectrometry system (MS). Embodiments may use a current sense circuit at a high voltage output from an MS-ESI power supply in conjunction with additional elements to identify fault conditions associated with leakage current, to confirm the continuity of CE connections, and to provide improved system protection.

First claim

What is claimed is:

1. A capillary electrophoresis system for use in conjunction with electrospray ionization mass spectrometry systems comprising:
a capillary electrophoresis (CE) high voltage power supply having an output and an input;
a CE output current detector at the output of the CE high voltage power supply to detect a delivered current;
a CE return current detector at the input of the CE high voltage power supply to detect a return current;
a mass spectrometry (MS) power supply that connects to a high voltage input of a current sense circuit,
wherein the CE high voltage power supply and the MS power supply are electrically coupled to a system ground;
a current sense circuit coupled to a MS power supply terminal, such that the MS power supply terminal provides a potential that is electrically coupled to the input of the CE high voltage power supply via the current sense circuit, a conductive fluid capillary, and a return electrode, and wherein the potential provided by the MS power supply terminal is further electrically coupled to the output of the CE high voltage power supply via the current sense circuit, a separation capillary, and an inlet electrode; and
a comparison circuit that compares the delivered current, the return current, and a current sensed by the current sense circuit to detect a leakage current.

2. The system of claim 1 wherein the current sense circuit comprises a sense resistor and buffer amplifier coupled to an absolute value amplifier.

3. The system of claim 2 wherein the current sense circuit further comprises a DC/DC converter coupled to the absolute value amplifier and powering the buffer and absolute value amplifiers;
wherein an isolated side of the current sense circuit is floating.

4. The system of claim 3 further comprising a voltage protection device coupled from a system ground to a floating ground of the current sense circuit.

5. The system of claim 4 wherein the voltage protection device comprises a gas discharge tube.

6. The system of claim 2 further comprising a current sense signal path from the sense resistor to a controller.

7. The system of claim 6 wherein the controller is a microprocessor of a CE analysis system.

8. The system of claim 6 wherein the current sense signal path comprises the sense resistor coupled to the buffer amplifier, the absolute value amplifier, an isolated communication path, and a current sense output.

9. The system of claim 8 wherein the isolated communication path is an analog channel through a DC/DC converter that transmits analog signals to and from an isolated and a grounded side of the DC/DC converter.

10. The system of claim 8 wherein the isolated communication path comprises a wireless signal.

11. The system of claim 8 further comprising a conductive fluid current sensor coupled to the current sense circuit via a capillary junction and to the return electrode, wherein a conductive fluid current signal is offset from a current sense signal to create a leakage signal.

12. The system of claim 11 wherein the CE input current detector creates a return current signal.

13. The system of claim 12 wherein the CE output current detector creates a delivered current signal.

14. The system of claim 13 wherein the controller comprises an offset current signal that is associated with a system inaccuracy.

15. The system of claim 14 wherein the controller calculates a leakage current by subtracting the return current signal, the current sense signal, and the offset current signal from the delivered current signal.

16. The system of claim 15 wherein the controller creates an error signal if the leakage current exceeds a predetermined threshold.

17. The system of claim 16 wherein the controller initiates an automatic system shutdown when a number of leakage current readings above the predetermined threshold exceeds a number of leakage current readings below the predetermined threshold for a number of readings by an error flag number.

18. The system of claim 13 wherein the current sense circuit comprises a Hall Effect Sensor, a Rogowski Coil Sensor, or a combination thereof.

19. The system of claim 1 wherein a current sense input terminal is directly coupled to the system ground.

20. The system of claim 1 wherein the current sense circuit further comprises a limit resistor coupled from a sense resistor to an electrospray terminal or capillary junction.

21. The system of claim 20 wherein the limit resistor comprises a value selected from a group consisting of a resistor value of from 1 megaOhm to 200 megaOhms (inclusive), of from 1 megaOhm to 100 megaOhms (inclusive), of from 1 megaOhm to 50 megaOhms (inclusive), and from 1 megaOhm to 20 megaOhms (inclusive).

22. A capillary electrophoresis electrospray ionization mass spectrometry (CE-ESI-MS) system comprising:
a mass spectrometry (MS) high voltage power supply having a first output, a first return and a first ground;
a capillary electrophoresis (CE) high voltage power supply having a second output, a second return and a second ground, said second ground including a connection to the first ground;
a CE output current detector at the output of the CE high voltage power supply to detect a delivered current;
a CE return current detector at the input of the CE high voltage power supply to detect a return current;
a MS electrical path that provides the MS high voltage power supply first return from the first output to the first ground via a MS load;
a CE electrical path that provides the CE high voltage power supply second return from the second output to the second ground via a separation capillary, wherein a resistive electrical path of the separation capillary is connected to the first output and wherein the first output is electrically coupled to the second return via the separation capillary;
a current sense circuit coupled to the first output and to the separation capillary via a capillary junction; and
a comparison circuit that compares the delivered current, the return current, and a current sensed by the current sense circuit to detect a leakage current.

23. A method of operating a capillary electrophoresis electrospray ionization mass spectrometry system comprising:
measuring a sense current from an electrospray capillary junction to a mass spectrometry (MS) DC high voltage power supply at a MS supply terminal of the MS DC high voltage power supply;
measuring a delivered current at a capillary electrophoresis (CE) output of a CE high voltage power supply;
measuring a return current at a CE return of the CE high voltage power supply,
wherein the CE return and the CE output are electrically coupled to the electrospray capillary junction, and the MS DC high voltage power supply and CE high voltage power supply are coupled to a ground;
comparing the sense current, the delivered current, and the return current to calculate a leakage current; and
creating a fault error when the calculated leakage current exceeds a threshold.

24. A method comprising
measuring a delivered current at an output of a capillary electrophoresis (CE) power supply;
measuring a return current at a return of the CE power supply;
identifying an offset current associated with system inaccuracy;
measuring a sense current at a current sense circuit at a terminal of a mass spectrometry (MS) high voltage power supply,
wherein the terminal of the MS high voltage power supply, the return of the CE power supply, and t

Assignees

• Beckman Coulter Inc

Inventors

• Kotowski Peter S
• Deliwala Sunil S
• Frye Stephen A

Classifications

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title

• G01R31/50 Primary

  Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58) · CPC title

• G01N27/44713

  Particularly adapted electric power supply · CPC title

• H01J49/165

  Electrospray ionisation · CPC title

• H01J49/022 Primary

  Circuit arrangements, e.g. for generating deviation currents or voltages (regulating electric or magnetic variables in general, e.g. current, magnetic field G05F); Components associated with high voltage supply (high voltage supply per se H02M) · CPC title