Method and apparatus for analyzing mixtures of gases

• US 6,849,239 B2
• Filed: 04/05/2002
• Issued: 02/01/2005
• Est. Priority Date: 10/16/2000
• Status: Expired due to Fees

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Morris, Patricia A.
• Primary Examiner(s): Warden, Jill
• Assistant Examiner(s): Sines, Brian J.
• Application Number:
  US10/117,472
• Publication Number:
  US 20040013571A1
• Time in Patent Office: 1,033 Days
• Field of Search: 422/50, 422/83, 422/88, 422/94, 422/95, 422/96, 422/97, 422/98, 436/43, 436/149, 73/10.1, 73/10.2, 73/232, 73/233.1, 73/310.6
• US Class Current: 422/98
• CPC Class Codes: G01N 33/0031 comprising two or more sensors, e.g. a sensor array electrochemical electrode arrays G01N27/27
• CPC Class Codes: Y10T 436/11 Automated chemical analysis

Abstract

Disclosed herein is a method and apparatus for analyzing, sensing and measuring information related to the concentrations of various gases, including NO_x, hydrocarbons, carbon monoxide and oxygen, in a multi-component gas system using chemical sensors and chemical sensor arrays. The sensors and sensor arrays use chemo/electro-active materials to analyze and detect the presence of gases.

Claims

1. An apparatus for analyzing a multi-component gas mixture, comprising:

(a) an array of at least two chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials, the electrical response characteristic of at least one material being quantifiable as value, wherein the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from the electrical responses of the chemo/electro-active materials inputted thereto, but not from a baseline response value, comparison response value or reference gas value inputted thereto.

2. An apparatus according to claim 1 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

3. An apparatus according to claim 1 wherein the gas mixture is an emission from a combustion process.

4. An apparatus according to claim 1 further comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

5. An apparatus according to claim 1 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

6. An apparatus according to claim 1 wherein at least one chemo/electro-active material is a metal oxide.

7. An apparatus according to claim 1 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

8. An apparatus according to claim 1 wherein the component gases in the gas mixture are not separated.

9. An apparatus according to claim 1 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

10. An apparatus according to claim 1 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

11. An apparatus according to claim 1 wherein the gas mixture has a temperature of less than 400°

C.

12. An apparatus according to claim 6 wherein the chemo/electro-active materials comprise:

an array of first and second chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials, wherein the chemo/electro-active materials are selected from the pairings in the group consisting of

(a) the first material is M¹O_x, and the second material is M¹_aM²_bO_x;

(b) the first material is M¹O_x, and the second material is M¹_aM²_bM³_cO_x;

(c) the first material is M¹_aM²_bO_x, and the second material is M¹_aM²_bM³_cO_x;

(d) the first material is a first M¹O_x, and the second material is a second M¹O_x;

(e) the first material is a first M¹_aM²_bO_x, and the second material is a second M¹_aM²_bO_x; and

(f) the first material is a first M¹_aM²_bM³_cO_x, and the second material is a second M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

13. An apparatus according to claim 6 wherein the chemo/electro-active materials comprise an array of chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials,

wherein at least one chemo/electro-active material is selected from the group consisting of M¹O_x, M¹_aM²_bO_x and M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

14. An apparatus according to claim 1 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

15. An apparatus according to claim 1 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

16. An apparatus according to claim 1 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

17. An apparatus according to claim 1 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

18. An apparatus according to claim 1 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

19. An apparatus for analyzing a multi-component gas mixture, comprising:

(a) an array of first and second chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo-electro-active materials, wherein the chemo/electro-active materials are selected from the pairings in the group consisting of

(i) the first material is M¹O_x, and the second material is M¹_aM²_bO_x;

(ii) the first material is M¹O_x, and the second material is M¹_aM²_bM³_cO_x;

(iii) the first material is M¹_aM²_bO_x, and the second material is M¹_aM²_bM³_cO_x;

(iv) the first material is a first M¹O_x, and the second material is a second M¹O_x;

(v) the first material is a first M¹_aM²_bO_x, and the second material is a second M¹_aM²_bO_x; and

(vi) the first material is a first M¹_aM²_bM³_cO_x, and the second material is a second M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

is a number sufficient so that the oxygen present balances the charges of the other elements in the compound;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from the electrical responses of the chemo/electro-active materials inputted thereto, but not from a baseline response value, comparison response value or reference gas value inputted thereto.

20. An apparatus according to claim 19 wherein

(a) M¹O_x is selected from the group consisting of Ce_aO_x, CoO_x, CuO_x, FeO_x, GaO_x, NbO_x, NiO_x, PrO_x, RuO_x, SnO_x, Ta_aO_x, TiO_x, TmO_x, WO_x, YbO_x, ZnO_x, ZrO_x, SnO_x with Ag additive, ZnO_x with Ag additive, TiO_x with Pt additive, ZnO_x with frit additive, NiO_x with frit additive, SnO_x with frit additive, or WO_x with frit additive;

(b) M¹_aM²_bO_x is selected from the group consisting of Al_aCr_bO_x, Al_aFe_bO_x, Al_aMg_bO_x, Al_aNi_bO_x, Al_aTi_bO_x, Al_aV_bO_x, Ba_aCu_bO_x, Ba_aSn_bO_x, Ba_aZn_bO_x, Bi_aRu_bO_x, Bi_aSn_bO_x, Bi_aZn_bO_x, Ca_aSn_bO_x, Ca_aZn_bO_x, Cd_aSn_bO_x, Cd_aZn_bO_x, Ce_aFe_bO_x, Ce_aNb_bO_x, Ce_aTi_bO_x, Ce_aV_bO_x, Co_aCu_bO_x, Co_aGe_bO_x, Co_aLa_bO_x, Co_aMg_bO_x, Co_aNb_bO_x, Co_aPb_bO_x, Co_aSn_bO_x, Co_aV_bO_x, Co_aW_bO_x, Co_aZn_bO_x, Cr_aCu_bO_x, Cr_aLa_bO_x, Cr_aMn_bO_x, Cr_aNi_bO_x, Cr_aSi_bO_x, Cr_aTi_bO_x, Cr_aY_bO_x, Cr_aZn_bO_x, Cu_aFe_bO_x, Cu_aGa_bO_x, Cu_aLa_bO_x, Cu_aNa_bO_x, Cu_aNi_bO_x, Cu_aPb_bO_x, Cu_aSn_bO_x, Cu_aSr_bO_x, Cu_aTi_bO_x, Cu_aZn_bO_x, Cu_aZr_bO_x, Fe_aGa_bO_x, Fe_aLa_bO_x, Fe_aMo_bO_x, Fe_aNb_bO_x, Fe_aNi_bO_x, Fe_aSn_bO_x, Fe_aTi_bO_x, Fe_aW_bO_x, Fe_aZn_bO_x, Fe_aZr_bO_x, Ga_aLa_bO_x, Ga_aSn_bO_x, Ge_aNb_bO_x, Ge_aTi_bO_x, In_aSn_bO_x, K_aNb_bO_x, Mn_aNb_bO_x, Mn_aSn_bO_x, Mn_aTi_bO_x, Mn_aY_bO_x, Mn_aZn_bO_x, Mo_aPb_bO_x, Mo_aRb_bO_x, Mo_aSn_bO_x, Mo_aTi_bO_x, Mo_aZn_bO_x, Nb_aNi_bO_x, Nb_aNi_bO_x, Nb_aSr_bO_x, Nb_aTi_bO_x, Nb_aW_bO_x, Nb_aZr_bO_x, Ni_aSi_bO_x, Ni_aSn_bO_x, Ni_aY_bO_x, Ni_aZn_bO_x, Ni_aZr_bO_x, Pb_aSn_bO_x, Pb_aZn_bO_x, Rb_aW_bO_x, Ru_aSn_bO_x, Ru_aW_bO_x, Ru_aZn_bO_x, Sb_aSn_bO_x, Sb_aZn_bO_x, Sc_aZr_bO_x, Si_aSn_bO_x, Si_aTi_bO_x, Si_aW_bO_x, Si_aZn_bO_x, Sn_aTa_bO_x, Sn_aTi_bO_x, Sn_aW_bO_x, Sn_aZn_bO_x, Sn_aZr_bO_x, Sr_aTi_bO_x, Ta_aTi_bO_x, Ta_aZn_bO_x, Ta_aZr_bO_x, Ti_aV_bO_x, Ti_aW_bO_x, Ti_aZn_bO_x, Ti_aZr_bO_x, V_aZn_bO_x, V_aZr_bO_x, W_aZn_bO_x, W_aZr_bO_x, Y_aZr_bO_x, Zn_aZr_bO_x, Al_aNi_bO_x with frit additive, Cr_aTi_bO_x with frit additive, Fe_aLa_bO_x with frit additive, Fe_aNi_bO_x with frit additive, Fe_aTi_bO_x with frit additive, Nb_aTi_bO_x with frit additive, Nb_aW_bO_x with frit additive, Ni_aZn_bO_x with frit additive, Ni_aZr_bO_x with frit additive, Sb_aSn_bO_x with frit additive, Ta_aTi_bO_x with frit additive, or Ti_aZn_bO_x with frit additive; and

/or

(c) M¹_aM²_bM³_cO_x is selected from the group consisting of Al_aMg_bZn_cO_x, Al_aSi_bV_cO_x, Ba_aCu_bTi_cO_x, Ca_aCe_bZr_cO_x, Co_aNi_bTi_cO_x, Co_aNi_bZr_cO_x, Co_aPb_bSn_cO_x, Co_aPb_bZn_cO_x, Cr_aSr_bTi_cO_x, Cu_aFe_bMn_cO_x, Cu_aLa_bSr_cO_x, Fe_aNb_bTi_cO_x, Fe_aPb_bZn_cO_x, Fe_aSr_bTi_cO_x, Fe_aTa_bTi_cO_x, Fe_aW_bZr_cO_x, Ga_aTi_bZn_cO_x, La_aMn_bNa_cO_x, La_aMn_bSr_cO_x, Mn_aSr_bTi_cO_x, Mo_aPb_bZn_cO_x, Nb_aSr_bTi_cO_x, Nb_aSr_bW_cO_x, Nb_aTi_bZn_cO_x, Ni_aSr_bTi_cO_x, Sn_aW_bZn_cO_x, Sr_aTi_bV_cO_x, Sr_aTi_bZn_cO_x, or Ti_aW_bZr_cO_x.

21. An apparatus according to claim 19 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

22. An apparatus according to claim 19 wherein the gas mixture is an emission from a combustion process.

23. An apparatus according to claim 19 wherein the component gases in the gas mixture are not separated.

24. An apparatus according to claim 19 wherein the electrical responses of the chemo/electro-active materials are determined upon exposure to only the multi-component gas mixture.

25. An apparatus according to claim 19 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

26. An apparatus according to claim 19 further comprising means for measuring the temperature of the gas mixture, and means for digitizing the electrical responses and the temperature measurement.

27. An apparatus according to claim 19 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

28. An apparatus according to claim 19 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute.

29. An apparatus according to claim 19 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

30. An apparatus according to claim 19 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

31. An apparatus according to claim 19 wherein the gas mixture has a temperature of less than 400°

C.

32. An apparatus according to claim 19 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

33. An apparatus according to claim 19 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

34. An apparatus according to claim 19 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

35. An apparatus according to claim 19 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

36. An apparatus according to claim 19 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

37. An apparatus for analyzing a multi-component gas mixture, comprising:

(a) an array of chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo-electro-active materials, wherein at least one chemo/electro-active materials is selected from the group consisting of M¹O_x, M¹_aM²_bO_x and M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, e, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0 05 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from the electrical responses of the chemo/electro-active materials, but not a baseline response value, a comparison response value or a reference gas value.

38. An apparatus according to claim 37 wherein

(a) M¹O_x is selected from the group consisting of Ce_aO_x, CoO_x, CuO_x, FeO_x, GaO_x, NbO_x, NiO_x, PrO_x, RuO_x, SnO_x, Ta_aO_x, TiO_x, TmO_x, WO_x, YbO_x, ZnO_x, ZrO_x, SnO_x with Ag additive, ZnO_x with Ag additive, TiO_x with Pt additive, ZnO_x with frit additive, NiO_x with frit additive, SnO_x with frit additive, or WO_x with frit additive;

(b) M¹_aM²_bO_x is selected from the group consisting of Al_aCr_bO_x, Al_aFe_bO_x, Al_aMg_bO_x, Al_aNi_bO_x, Al_aTi_bO_x, Al_aV_bO_x, Ba_aCu_bO_x, Ba_aSn_bO_x, Ba_aZn_bO_x, Bi_aRu_bO_x, Bi_aSn_bO_x, Bi_aZn_bO_x, Ca_aSn_bO_x, Ca_aZn_bO_x, Cd_aSn_bO_x, Cd_aZn_bO_x, Ce_aFe_bO_x, Ce_aNb_bO_x, Ce_aTi_bO_x, Ce_aV_bO_x, Co_aCu_bO_x, Co_aGe_bO_x, Co_aLa_bO_x, Co_aMg_bO_x, Co_aNb_bO_x, Co_aPb_bO_x, Co_aSn_bO_x, Co_aV_bO_x, Co_aW_bO_x, Co_aZn_bO_x, Cr_aCu_bO_x, Cr_aLa_bO_x, Cr_aMn_bO_x, Cr_aNi_bO_x, Cr_aSi_bO_x, Cr_aTi_bO_x, Cr_aY_bO_x, Cr_aZn_bO_x, Cu_aFe_bO_x, Cu_aGa_bO_x, Cu_aLa_bO_x, Cu_aNa_bO_x, Cu_aNi_bO_x, Cu_aPb_bO_x, Cu_aSn_bO_x, Cu_aSr_bO_x, Cu_aTi_bO_x, Cu_aZn_bO_x, Cu_aZr_bO_x, Fe_aGa_bO_x, Fe_aLa_bO_x, Fe_aMo_bO_x, Fe_aNb_bO_x, Fe_aNi_bO_x, Fe_aSn_bO_x, Fe_aTi_bO_x, Fe_aW_bO_x, Fe_aZn_bO_x, Fe_aZr_bO_x, Ga_aLa_bO_x, Ga_aSn_bO_x, Ge_aNb_bO_x, Ge_aTi_bO_x, In_aSn_bO_x, K_aNb_bO_x, Mn_aNb_bO_x, Mn_aSn_bO_x, Mn_aTi_bO_x, Mn_aY_bO_x, Mn_aZn_bO_x, Mo_aPb_bO_x, Mo_aRb_bO_x, Mo_aSn_bO_x, Mo_aTi_bO_x, Mo_aZn_bO_x, Nb_aNi_bO_x, Nb_aNi_bO_x, Nb_aSr_bO_x, Nb_aTi_bO_x, Nb_aW_bO_x, Nb_aZr_bO_x, Ni_aSi_bO_x, Ni_aSn_bO_x, Ni_aY_bO_x, Ni_aZn_bO_x, Ni_aZr_bO_x, Pb_aSn_bO_x, Pb_aZn_bO_x, Rb_aW_bO_x, Ru_aSn_bO_x, Ru_aW_bO_x, Ru_aZn_bO_x, Sb_aSn_bO_x, Sb_aZn_bO_x, Sc_aZr_bO_x, Si_aSn_bO_x, Si_aTi_bO_x, Si_aW_bO_x, Si_aZn_bO_x, Sn_aTa_bO_x, Sn_aTi_bO_x, Sn_aW_bO_x, Sn_aZn_bO_x, Sn_aZr_bO_x, Sr_aTi_bO_x, Ta_aTi_bO_x, Ta_aZn_bO_x, Ta_aZr_bO_x, Ti_aV_bO_x, Ti_aW_bO_x, Ti_aZn_bO_x, Ti_aZr_bO_x, V_aZn_bO_x, V_aZr_bO_x, W_aZn_bO_x, W_aZr_bO_x, Y_aZr_bO_x, Zn_aZr_bO_x, Al_aNi_bO_x with frit additive, Cr_aTi_bO_x with frit additive, Fe_aLa_bO_x with frit additive, Fe_aNi_bO_x with frit additive, Fe_aTi_bO_x with frit additive, Nb_aTi_bO_x with frit additive, Nb_aW_bO_x with frit additive, Ni_aZn_bO_x with frit additive, Ni_aZr_bO_x with frit additive, Sb_aSn_bO_x with frit additive, Ta_aTi_bO_x with frit additive, or Ti_aZn_bO_x with frit additive; and

/or

(c) M¹_aM²_bM³_cO_x is selected from the group consisting of Al_aMg_bZn_cO_x, Al_aSi_bV_cO_x, Ba_aCu_bTi_cO_x, Ca_aCe_bZr_cO_x, Co_aNi_bTi_cO_x, Co_aNi_bZr_cO_x, Co_aPb_bSn_cO_x, Co_aPb_bZn_cO_x, Cr_aSr_bTi_cO_x, Cu_aFe_bMn_cO_x, Cu_aLa_bSr_cO_x, Fe_aNb_bTi_cO_x, Fe_aPb_bZn_cO_x, Fe_aSr_bTi_cO_x, Fe_aTa_bTi_cO_x, Fe_aW_bZr_cO_x, Ga_aTi_bZn_cO_x, La_aMn_bNa_cO_x, La_aMn_bSr_cO_x, Mn_aSr_bTi_cO_x, Mo_aPb_bZn_cO_x, Nb_aSr_bTi_cO_x, Nb_aSr_bW_cO_x, Nb_aTi_bZn_cO_x, Ni_aSr_bTi_cO_x, Sn_aW_bZn_cO_x, Sr_aTi_bV_cO_x, Sr_aTi_bZn_cO_x, or Ti_aW_bZr_cO_x.

39. An apparatus according to claim 37 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

40. An apparatus according to claim 37 wherein the gas mixture is an emission from a combustion process.

41. An apparatus according to claim 37 wherein the component gases in the gas mixture are not separated.

42. An apparatus according to claim 37 wherein the electrical responses of the chemo/electro-active materials are determined upon exposure to only the multi-component gas mixture.

43. An apparatus according to claim 37 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

44. An apparatus according to claim 37 further comprising means for measuring the temperature of the gas mixture, and means for digitizing the electrical responses and the temperature measurement.

45. An apparatus according to claim 37 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

46. An apparatus according to claim 37 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute.

47. An apparatus according to claim 37 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

48. An apparatus according to claim 37 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

49. An apparatus according to claim 37 wherein the gas mixture has a temperature of less than 400°

C.

50. An apparatus according to claim 37 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

51. An apparatus according to claim 37 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

52. An apparatus according to claim 37 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

53. An apparatus according to claim 37 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

54. An apparatus according to claim 37 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

55. A gas-sensitive apparatus, comprising:

(a) an array of at least three chemo/electro-active materials, each chemo/electro-active material exhibiting a change in electrical resistance upon exposure to a multi-component gas mixture, wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (i) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (ii) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from the electrical responses of the chemo/electro-active materials, but not a baseline response value, a comparison response value or a reference gas value.

56. An apparatus according to claim 55 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute.

57. An apparatus according to claim 55 further comprising means for determining the temperature of the array.

58. An apparatus according to claim 55 wherein at least one chemo/electro-active material is a metal oxide.

59. An apparatus according to claim 55 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

60. An apparatus according to claim 55 wherein the gas mixture has a temperature of less than 400°

C.

61. An apparatus according to claim 55 wherein the component gases in the gas mixture are not separated.

62. An apparatus according to claim 55 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

63. An apparatus according to claim 55 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

64. An apparatus according to claim 58 wherein the chemo/electro-active materials comprise:

an array of first and second chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials, wherein the chemo/electro-active materials are selected from the pairings in the group consisting of

(a) the first material is M¹O_x, and the second material is M¹_aM²_bO_x;

(b) the first material is M¹O_x, and the second material is M¹_aM²_bM³_cO_x;

(c) the first material is M¹_aM²_bO_x, and the second material is M¹_aM²_bM³_cO_x;

(d) the first material is a first M¹O_x, and the second material is a second M¹O_x;

(e) the first material is a first M¹_aM²_bO_x, and the second material is a second M¹_aM²_bO_x; and

(f) the first material is a first M¹_aM²_bM³_cO_x, and the second material is a second M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

65. An apparatus according to claim 58 wherein the chemo/electro-active materials comprise an array of chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials,

wherein at least one chemo/electro-active material is selected from the group consisting of M¹O_x, M¹_aM²_bO_x and M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

66. An apparatus according to claim 55 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

67. An apparatus according to claim 55 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

68. An apparatus according to claim 55 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

69. An apparatus according to claim 55 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

70. An apparatus according to claim 55 wherein the gas mixture is an emission from a combustion process.

71. An apparatus according to claim 55 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

72. An apparatus according to claim 55 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

73. An apparatus for analyzing a multi-component gas mixture, comprising:

(a) an array of at least two chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials, the electrical response characteristic of at least one material being quantifiable a value, wherein the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from only the electrical responses of the chemo/electro-active materials.

74. An apparatus according to claim 73 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

75. An apparatus according to claim 73 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

76. An apparatus according to claim 73 wherein the gas mixture has a temperature of less than 400°

C.

77. An apparatus according to claim 73 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

78. An apparatus according to claim 73 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for period of at least about one minute.

79. An apparatus according to claim 73 wherein the component gases in the gas mixture are not separated.

80. An apparatus according to claim 73 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

81. An apparatus according to claim 73 wherein the chemo/electro-active materials comprise an array of first and second chemo/electro-active materials, each chemo/electro active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials, wherein the chem/electro-active materials are selected from the pairings in the group consisting of

(a) the first material is M¹O_x, and the second material is M¹_aM²_bO_x;

(b) the first material is M¹O_x, and the second material is M¹_aM²_bM³_cO_x;

(c) the first material is M¹_aM²_bO_x, and the second material is M¹_aM²_bM³_cO_x;

(d) the first material is a first M¹O_x, and the second material is a second M¹O_x;

(e) the first material is a first M¹_aM²_bO_x, and the second material is a second M¹_aM²_bO_x; and

(f) the first material is a first M¹_aM²_bM³_cO_x, and the second material is a second M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

82. An apparatus according to claim 73 wherein the chemo/electro-active materials comprise an array of chemo/electro-active materials, each chemo/electro active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials,

wherein at least one chem/electro-active materials is selected from the group consisting of M¹O_x, M¹_aM²_bO_x and M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

83. An apparatus according to claim 73 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

84. An apparatus according to claim 73 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

85. An apparatus according to claim 73 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

86. An apparatus according to claim 73 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

87. An apparatus according to claim 73 wherein the gas mixture is an emission from a combustion process.

88. An apparatus according to claim 73 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

89. An apparatus according to claim 73 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

90. An apparatus for analyzing a multi-component gas mixture, comprising:

(a) an array of first and second chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo-electro-active materials, wherein the chemo/electro-active materials are selected from the pairings in the group consisting of

(i) the first material is M¹O_x, and the second material is M¹_aM²_bO_x;

(ii) the first material is M¹O_x, and the second material is M¹_aM²_bM³_cO_x;

(iii) the first material is M¹_aM²_bO_x, and the second material is M¹_aM²_bM³_cO_x;

(iv) the first material is a first M¹O_x, and the second material is a second M¹O_x;

(v) the first material is a first M¹_aM²_bO_x, and the second material is a second M¹_aM²_bO_x; and

(vi) the first material is a first M¹_aM²_bM³_cO_x, and the second material is a second M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the up consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

is a number sufficient so that the oxygen present balances the charges of the other elements in the compound;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from only the electrical responses of the chemo/electro-active materials.

91. An apparatus according to claim 90 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

92. An apparatus according to claim 90 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

93. An apparatus according to claim 90 wherein the gas mixture has a temperature of less than 400°

C.

94. An apparatus according to claim 90 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

95. An apparatus according to claim 90 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute.

96. An apparatus according to claim 90 wherein the component gases in the gas mixture are not separated.

97. An apparatus according to claim 90 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

98. An apparatus according to claim 90 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

99. An apparatus according to claim 90 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

100. An apparatus according to claim 90 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

101. An apparatus according to claim 90 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

102. An apparatus according to claim 90 wherein the gas mixture is an emission from a combustion process.

103. An apparatus according to claim 90 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

104. An apparatus according to claim 90 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

105. An apparatus for analyzing a multi-component gas mixture, comprising:

(a) an array of chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo-electro-active materials, wherein at least one chemo/electro-active materials is selected from the group consisting of M¹O_x, M¹_aM²_bO_x and M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr, M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from only the electrical responses of the chemo/electro-active materials.

106. An apparatus according to claim 105 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

107. An apparatus according to claim 105 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

108. An apparatus according to claim 105 wherein the gas mixture has a temperature of less than 400°

C.

109. An apparatus according to claim 105 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

110. An apparatus according to claim 105 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for a period of at least about one minute.

111. An apparatus according to claim 105 wherein the component gases in the gas mixture are not separated.

112. An apparatus according to claim 105 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

113. An apparatus according to claim 105 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

114. An apparatus according to claim 105 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

115. An apparatus according to claim 105 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

116. An apparatus according to claim 105 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

117. An apparatus according to claim 105 wherein the gas mixture is an emission from a combustion process.

118. An apparatus according to claim 105 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

119. An apparatus according to claim 105 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.

120. A gas-sensitive apparatus, comprising:

(a) an array of at least three chemo/electro-active materials, each chemo/electro-active material exhibiting a change in electrical resistance upon exposure to a multi-component gas mixture, wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (i) has an electrical resistivity in the range of about 1 ohm-cm to bout 10⁶ ohm-cm, and (ii) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure;

(b) a heater that heats the array to a temperature above 500°

C.;

(c) means for determining the electrical response of each chemo/electro-active material upon exposure of the array to the gas mixture; and

(d) means for detecting the presence of, or calculating the actual concentration of, one or more individual component gases and/or subgroups within the gas mixture from only the electrical responses of the chemo/electro-active materials.

121. An apparatus according to claim 120 wherein the electrical response is selected from the group consisting of resistance, impedance, capacitance, voltage or current.

122. An apparatus according to claim 120 wherein the array is situated within the gas mixture, and the gas mixture has a temperature of about 400°

C. or more.

123. An apparatus according to claim 120 wherein the gas mixture has a temperature of less than 400°

C.

124. An apparatus according to claim 120 wherein at least one chemo/electro-active material, when at a temperature of about 400°

C. or more, (a) has an electrical resistivity in the range of about 1 ohm-cm to about 10⁶ ohm-cm, and (b) exhibits a change in electrical resistance of at least about 0.1 percent upon exposure of the material to the gas mixture, as compared to the resistance before exposure.

125. An apparatus according to claim 120 wherein the electrical response characteristic of at least one material upon exposure to the gas mixture at a selected temperature is quantifiable as a value, and the value of the response of that material is constant or varies by no more than about twenty percent during exposure of the material to the gas mixture at the selected temperature for period of at least about one minute.

126. An apparatus according to claim 120 wherein the component gases in the gas mixture are not separated.

127. An apparatus according to claim 120 comprising means for calculating the concentration within the gas mixture of at least one individual gas component.

128. An apparatus according to claim 120 wherein the chemo/electro-active materials comprise an array of first and second chemo/electro-active materials, each chemo/electro active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials, wherein the chem/electro-active materials are selected from the pairings in the group consisting of

(a) the first material is M¹O_x, and the second material is M¹_aM²_bO_x;

(b) the first material is M¹O_x, and the second material is M¹_aM²_bM³_cO_x;

(c) the first material is M¹_aM²_bO_x, and the second material is M¹_aM²_bM³_cO_x;

(d) the first material is a first M¹O_x, and the second material is a second M¹O_x;

(e) the first material is a first M¹_aM²_bO_x, and the second material is a second M¹_aM²_bO_x; and

(f) the first material is a first M¹_aM²_bM³_cO_x, and the second material is a second M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same M¹ _aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

129. An apparatus according to claim 120 wherein the chemo/electro-active materials comprise an array of

chemo/electro-active materials, each chemo/electro-active material exhibiting a different electrical response characteristic, upon exposure at a selected temperature to the gas mixture, than each of the other chemo/electro-active materials,

wherein at least one chemo/electro-active material is selected from the group consisting of M¹O_x, M¹_aM²_bO_x;

and M¹_aM²_bM³_cO_x;

wherein M¹ is selected from the group consisting of Ce, Co, Cu, Fe, Ga, Nb, Ni, Pr, Ru, Sn, Ti, Tm, W, Yb, Zn, and Zr;

M² and M³ are each independently selected from the group consisting of Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, K, La, Mg, Mn, Mo, Na, Nb, Ni, Pb, Pr, Rb, Ru, Sb, Sc, Si, Sn, Sr, Ta, Ti, Tm, V, W, Y, Yb, Zn, and Zr, but M² and M³ are not the same in M¹_aM²_bM³_cO_x;

a, b and c are each independently about 0.0005 to about 1; and

x is a number sufficient so that the oxygen present balances the charges of the other elements in the compound.

130. An apparatus according to claim 120 wherein the gas mixture comprises one or more members of the group consisting of oxygen, carbon monoxide, a nitrogen oxide, a hydrocarbon, CO₂, H₂S, sulfur dioxide, a halogen, hydrogen, water vapor, ammonia, alcohol, a solvent vapor, an ether, a ketone, an aldehyde, a carbonyl, and a microorganism.

131. An apparatus according to claim 120 wherein the gas mixture comprises one or more members of the group consisting of oxygen, a nitrogen oxide, a hydrocarbon, and ammonia.

132. An apparatus according to claim 120 wherein the gas mixture comprises one or more members of the group consisting of a nitrogen oxide and ammonia.

133. An apparatus according to claim 120 wherein the gas mixture comprises one or more members of the group consisting of oxygen and a hydrocarbon.

134. An apparatus according to claim 120 wherein the gas mixture is an emission from a combustion process.

135. An apparatus according to claim 120 wherein the gas mixture is provided from a manufacturing process, a waste stream, environmental monitoring, or a medical, agriculture, food or beverage operation.

136. An apparatus according to claim 120 wherein the multi-component gas mixture is emitted by a process, or is a product of a chemical reaction that is transmitted to a device, and wherein the apparatus further comprises means for utilizing the electrical responses for controlling the process or the device.