Apparatus and method for controlling an electrostatically induced liquid spray

1. A system for controlling an electrostatically induced liquid spray comprising:

an electrostatic spray device for generating a liquid spray from a liquid sample;

a spray current sensing means placed in relation to the spray device and configured to generate a current output signal that represents a current of the liquid spray;

a mechanism that receives the current output signal and compares it to a pre-selected current value, with a difference between the two representing a control signal tat is sent to one of (1) a pump that regulates the flow rate of the liquid sample and (2) a power supply to regulate an electric field associated with the spray device that generates the liquid spray according to a set level of current; and

a mass spectrometer having an inlet for receiving the liquid spray, the current sensing means being disposed between an opening of the spray device though which the liquid spray is discharged and having a ring-shaped structure with an orifice through which the liquid spray passes.

2. The system of claim 1 , wherein the electrostatic spray device includes an injection-molded nozzle with an opening of about 20 microns through which the liquid spray is discharged.

3. The system of claim 1 , wherein the electrostatic spray device includes a microfabricated nozzle though which the liquid spray is discharged.

4. The system of claim 1 , wherein the electrostatic spray device comprises one of an electrode and an electrical conducting element.

5. The system of claim 1 , wherein the spray current sensing means comprises one of an electrode disposed proximate but behind a nozzle opening of the spray device and an electrical conducting element placed in front of the spray device.

6. The system of claim 1 , wherein the spray current sensing means is disposed proximate but behind an opening of the spray device through which the liquid spray is discharged.

7. The system of claim 1 , further comprising:

an inlet associated with a device that receives the liquid spray, wherein the current sensing means is disposed in front of an opening of the spray device though which the liquid spray is discharged, the opening of the spray device being oriented perpendicular to the inlet.

8. The system of claim 7 , wherein the inlet is pan of a mass spectrometer.

9. A system for controlling an electrostatically induced liquid spray comprising:

an electrostatic spray device for generating a liquid spray from a liquid sample;

a spray current sensing means placed in relation to the spray device and configured to generate a current output signal that represents a current of the liquid spray;

a mechanism that receives the current output signal and compares it to a pre-selected current value, with a difference between the two representing a control signal that is sent to one of (1) a pump that regulates the flow rate of the liquid sample and (2) a power supply to regulate an electric field associated with the spray device that generates the liquid spray according to a set level of current; and

a mass spectrometer having an inlet for receiving the liquid spray, the current sensing means enclosing the inlet and further acting as an electrostatic lens.

10. The system of claim 1 , wherein the mechanism includes a current amplifier and a negative feedback element for receiving the current output signal and comparing it to the pre-selected current value for generating the output signal.

11. A method for controlling an electrostatically induced liquid spray comprising the steps of:

generating a liquid spray from a liquid sample with an electrostatic spray device;

providing a mass spectrometer including an inlet that receives the liquid spray;

sensing a current the liquid spray with a spray current sensing disposed between an opening of the spray device, the current sensing means having a ring-shaped structure with an orifice through which the liquid spray passes; through which the liquid spray is discharged and the inlet the liquid spray passing through an opening formed through the current sensing means;

comparing the sensed current of the liquid spray with a pre-selected current value, with a difference between the two representing a control signal; and

delivering the control signal to one of (1) a pump that regulates the flow rate of the liquid sample and (2) a power supply to regulate an electric field associated with the spray device according to a set level of current.