Ion mobility spectrometer and method for operation

1. A method, comprising:

supplying an analyte substance into a reaction chamber of an ion mobility spectrometer having a closed internal gas circuit and at least one membrane inlet having an inner membrane chamber;

changing at least one of flow resistances and gas paths in the closed internal gas circuit; and

controlling at least one of a quantity and a concentration of analyte-containing gas flowing from the inner membrane chamber to the reaction chamber.

2. The method of claim 1 , further comprising:

changing least one of the quantity, the concentration and a dispersion of the analyte-containing gas; and

adapting the measuring range of the ion mobility spectrometer to change concentrations of the analyte substance in a sample gas.

3. The method of claim 2 , wherein the changing of least one of the quantity, the concentration and the dispersion is controlled by feed-back from the result of an analytical measurement.

4. The method of claim 1 , further comprising:

circulating analyte-containing gas from one of several membrane inlets to the reaction chamber during a metering mode; and

circulating analyte-containing gas from the other membrane inlets to a filter during an isolation mode.

5. The method of claim 4 , further comprising:

switching the membrane inlets from the isolation mode to the metering mode at predetermined times and for predetermined periods; and

switching the membrane inlets from the metering mode to the isolation mode after each predetermined period.

6. The method of claim 1 , further comprising:

automatically reversing a direction of the flow in the inner membrane chamber; and

preventing analyte-containing gas from flowing to the reaction chamber when a measurement signal from the ion mobility spectrometer exceeds a specified limit.

7. The method of claim 1 , further comprising automatically reducing at least one of the quantity of gas or the concentration of analyte substances in the gas flowing to the reaction chamber and the dispersion of the analyte-containing gas inside the reaction chamber, to prevent a measurement signal from the ion mobility spectrometer from exceeding a specified limit.

8. The method of claim 1 , further comprising diverting a controllable proportion of the analyte-containing gas to a filter through a branching point in the gas circuit between the inner membrane chamber and the reaction chamber.

9. The method of claim 1 , further comprising:

introducing analyte-containing gas into the reaction chamber through at least one gas inlet;

removing the analyte-containing gas from the reaction chamber through at least one gas outlet; and

changing at least one of a quantity of the gas flowing in at least one of the gas inlets and a quantity of the gas flowing out of the gas outlets.

10. The method of claim 1 , further comprising adding a controllable portion of cleaned circulating gas before the analyte-containing gas is fed into the reaction chamber.

11. An ion mobility spectrometer, comprising:

a measuring tube having a reaction chamber;

a transport system;

a filter coupled between the measuring tube and the transport system;

a membrane inlet having an inner membrane chamber coupled to the reaction chamber, the inner membrane chamber configured and positioned in a diagonal branch of a bridge circuit comprising at least a first and a second flow elements, where the flow resistance of at least one of the first and the second flow elements is controllable; and

where the measuring tube, the membrane inlet, the transport system, the bridge circuit and the flow elements define a closed internal gas circuit.

12. The ion mobility spectrometer of claim 11 , wherein

the measuring tube further comprises a drift chamber;

the transport system is configured as a gas pump having a pressure side and a suction side;

the filter further comprises a first side and a second side, the first side is coupled to the pressure side of the gas pump, the second side is coupled to the drift chamber and a center connection of a changeover valve;

the reaction chamber is coupled to the suction side of the gas pump through a plurality of gas connections;

the inner membrane chamber of the membrane inlet is configured between the center connection of the changeover valve and the reaction chamber; and

the center connection is coupled to the suction side of the gas pump through at least one of a first flow element and a second flow element.

13. An ion mobility spectrometer, comprising:

a measuring tube having a reaction chamber;

a first membrane inlet having a first inner membrane chamber coupled to the reaction chamber through a first branching point;

a gas pump having a pressure side and a suction side, the pressure side is coupled to at least one of the measuring tube and the membrane inlet; and

at least one control element configured and positioned to have a variable flow resistance in a gas path from the first branching point to at least one of the pressure side and the suction side of the gas pump; and

where the measuring tube, the first membrane inlet, the gas pump and the control element define the closed internal gas circuit.

14. The ion mobility spectrometer of claim 13 , wherein

the reaction chamber further comprises a first gas connection and a second gas connection, the first gas connection coupling the first inner membrane chamber and the reaction chamber, the second gas connection coupled to the suction side of the gas pump through a second branching point;

the measuring tube further comprises a drift chamber;

the pressure side of the gas pump is coupled to the first inner membrane chamber and the drift chamber through a filter; and

the first and the second branching points coupled together through a control element.

15. The ion mobility spectrometer of claim 13 , wherein

the measuring tube further comprises a drift chamber;

the pressure side of the gas pump is coupled to the first inner membrane chamber and the drift chamber through a filter;

a second branching point is configured and positioned between the filter and the drift chamber;

the reaction chamber further comprises a first gas connection and a second gas connection, the first gas connection is coupled to the first inner membrane chamber through a third branching point, the second gas connection is coupled to the suction side of the gas pump and is positioned relatively close to the first gas connection; and

the second and the third branching points are coupled together through a control element.

16. The ion mobility spectrometer of claim 13 , wherein the control element is at least one of an electrically controllable throttle valve and a combination of an electrically operated gas switching valve and a constant flow element.

17. The ion mobility spectrometer of claim 13 , further comprises a second membrane inlet having an second inner membrane chamber, wherein

the measuring tube further comprises a drift chamber;

the pressure side of the gas pump is coupled to the drift chamber and the first inner membrane chambers through a filter, the inner membrane chambers configured in parallel;

the reaction chamber further comprises a first and a second gas connection;

the first inner membrane chamber is coupled to a first switch valve and the first gas connection;

the second inner membrane chamber is coupled a second switch valve and the first gas connection; and

the second gas connection is coupled to the reaction chamber and the first and the second switching valves, where the first and the second switching valves are coupled to the suction side of the gas pump.

18. The ion mobility spectrometer of claim 13 , further comprises a second membrane inlet having an second inner membrane chamber, wherein

the measuring tube further comprises a drift chamber;

the pressure side of the gas pump is coupled to the drift chamber and the inner membrane chambers through a filter, the inner membrane chambers are configured in parallel;

the reaction chamber further comprises a first and a second gas connection;

the first inner membrane chamber is coupled to the first gas connection and to a first end connection of a changeover valve through a first branching point;

the second inner membrane chamber is coupled to the second gas connection and a second end connection of the changeover valve through a second branching point; and

the suction side of the gas pump is coupled to a center connection of the changeover valve.

19. An ion mobility spectrometer, comprising:

a measuring tube having a reaction chamber, the reaction chamber includes at least one of a plurality of gas inlets and a plurality of gas outlets;

a membrane inlet having an inner membrane chamber coupled to the reaction chamber through a branching point;

a gas pump having a pressure side and a suction side, the pressure side coupled to at least one of the measuring tube and the membrane inlet;

a control element configured and positioned within a close internal gas circuit to change a flow rate in at least one of the gas inlets and the gas outlets;

at least one control element configured and positioned to have a variable flow resistance in a gas path from the branching point to at least one of the pressure side and the suction side of the gas pump; and

where the measuring tube, the membrane inlet, the gas pump and the control element define the closed internal gas circuit.

20. The ion mobility spectrometer of claim 19 , wherein at least one of the gas inlets and the gas outlets have a maximum possible distance between them.