Capillary electrophoresis-electrospray ionization-mass spectrometry system

Abstract

Aspects of the innovations presented herein relate to improved systems that in some embodiments perform capillary electrophoresis (CE) and CE in conjunction with electrospray ionization (ESI) as an input to a mass spectrometry system (MS). Some embodiments use a high voltage isolated CE power supply that is configured to float on the high voltage output of an ESI-MS power supply, with a protective resistance in the ESI-MS path, as well as DC/DC converter isolation and communication system isolation for the isolated CE power supply. Some embodiments additionally use a cartridge assembly integrating separation and conductive fluid capillaries with fluid cooling and protective retractable housings for the capillary end portions and for the ESI output. The protective housing may further be used with an adapter for interfacing with different MS systems.

What is claimed is: 
     
         1 . An electrical circuit comprising:
 a first dc power supply having a first output and a first input;   a first resistive electrical path connected to a ground that provides a first dc power supply return from the first output to the first input;   a second dc power supply having a second output and a second input;   a second resistive electrical path that provides a second dc power supply return from the second output to the second input, wherein the second resistive electrical path is isolated from the ground, and wherein the first output is electrically coupled with the second input;   an isolated control circuit that is electrically coupled with the second dc power supply and is isolated from the ground, wherein the isolated control circuit is communicatively coupled with an interface board via a communication link, and wherein the communication link maintains isolation from the ground; and   a DC/DC converter that provides isolated input power to the second dc power supply and the isolated control circuit.   
     
     
         2 . The electrical circuit of  claim 1  wherein the second resistive electrical path is electrically coupled to an electro-spray (ES) assembly. 
     
     
         3 . The electrical circuit of  claim 2  wherein the ES assembly is electrically coupled to an adapter, and
 wherein the ES assembly comprises a sprayer housing, and wherein the sprayer housing comprises a needle, a spring wound around the needle, and a retracting protective sheath coupled to the spring. 
 
     
     
         4 . The electrical circuit of  claim 3  wherein the ES assembly is coupled to a mass spectrometer via the adapter. 
     
     
         5 . The electrical circuit of  claim 2  wherein the ES assembly comprises a conductive slug portion that provides a resistive electrical ES assembly path from an external surface of the ES assembly to a conductive fluid contact area inside the ES assembly; and
 wherein the second resistive electrical path comprises the resistive electrical ES assembly path. 
 
     
     
         6 . The electrical circuit of  claim 5  wherein the second resistive electrical path further comprises a resistive electrical adapter path as part of an adapter that couples the ES assembly to a mass spectrometer. 
     
     
         7 . The electrical circuit of  claim 5  wherein the first output is electrically coupled with the second input via the resistive electrical ES assembly path. 
     
     
         8 . The electrical circuit of  claim 1  wherein the second resistive electrical path comprises a sample capillary path that is part of a capillary electrophoresis (CE) analysis system. 
     
     
         9 . The electrical circuit of  claim 8  wherein the interface board is part of the CE analysis system, and wherein the CE analysis system communicates with the isolated control circuit via the interface board to control the second DC power supply. 
     
     
         10 . The electrical circuit of  claim 1  wherein the interface board is part of the CE analysis system;
 wherein the communications link is an optical communications link; 
 wherein the interface board receives an analog control signal, converts the analog control signal to a digital logic pulse stream which is routed to the isolated control circuit; and 
 wherein the isolated control circuit converts the digital logic pulse stream back into the analog control signal and controls the second DC power supply using the analog control signal. 
 
     
     
         11 . The electrical circuit of  claim 1  further comprising a voltage limit resistor coupled directly with the first dc power supply, wherein said voltage limit resistor is in the first resistive electrical path and is not in the second resistive electrical path. 
     
     
         12 . The electrical circuit of  claim 11  wherein the communication link and the DC/DC converter each is able to withstand a voltage greater than or equal to a maximum output voltage of the first dc power supply, a maximum output voltage of the second dc power supply, or a voltage that is a sum of said maximum output voltages. 
     
     
         13 . The electrical circuit of  claim 12  wherein the maximum output voltage of the first dc power supply is a value between −10 kV and +10 kV, inclusive. 
     
     
         14 . The electrical circuit of  claim 12  wherein the maximum output voltage of the second dc power supply is a value between −30 kV and +30 kV, inclusive. 
     
     
         15 . The electrical circuit of  claim 11  wherein the voltage limit resistor has a resistive value between 10 megaOhms and 500 megaOhms, inclusive. 
     
     
         16 . The electrical circuit of  claim 11  further comprising a leakage detection circuit operably coupled with the voltage limit resistor that measures leakage current. 
     
     
         17 . The electrical circuit of  claim 16  wherein the leakage detection circuit comprises:
 a sense resistor coupled directly to the voltage limit resistor; and 
 an amplifier coupled with the sense resistor and the voltage limit resistor; 
 
       wherein the sense resistor and the amplifier are disposed in the first resistive electrical path and are not disposed in the second resistive electrical path. 
     
     
         18 . The electrical circuit of  claim 16  wherein the leakage detection circuit comprises:
 a sense resistor coupled indirectly with the voltage limit resistor; and 
 an amplifier coupled directly with the sense resistor, 
 wherein the amplifier is indirectly coupled with a first side of the voltage limit resistor via the first DC power supply and is indirectly coupled with a second side of the voltage limit resistor via a mass spectrometer load and the sense resistor; and 
 wherein the sense resistor and the amplifier are disposed in the first resistive electrical path and are not disposed in the second resistive electrical path. 
 
     
     
         19 . The electrical circuit of  claim 17  wherein the resistive value of the sense resistor is a value between 1 kOhm and 503 kOhms, inclusive. 
     
     
         20 . The electrical circuit of  claim 18  wherein the resistive value of the sense resistor is a value between 1 kOhm and 503 kOhms, inclusivey.