Infrared emission detection

Apparatus for detecting and making quantitative measurements of at least one selected component in a sample, in which at least one selected component of the sample, or at least one selected substance produced from the at least one selected component in the sample and characteristic of the at least one selected component, is introduced into an exciting means, and when the at least one selected component is present in the sample, gas-phase, infrared-active molecules emit infrared radiation at at least one characteristic wavelength in proportion to the quantity of the at least one selected component in the sample, comprising:

• a. flame means for exciting the gas-phase, infrared-active molecules with a flame to emit radiation along a first path, wherein when the at least one selected component is present in the sample, the gas-phase, infrared-active molecules emit radiation at at least one characteristic wavelength with an intensity proportional to the quantity of the at least one selected component in the sample, and wherein the exciting means simultaneously emits fluctuating background radiation along said first path at the at least one characteristic wavelength of the gas-phase, infrared-active molecules and at other wavelengths,
• b. beam splitting means disposed on said first path for directing a portion of the emitted radiation over a second path;
• c. first and second infrared detector means located on said first and second paths respectively, wherein said first detector means generates a first electrical signal responsive to emitted radiation at the at least one characteristic wavelength, and said second detector means generates a second electrical signal responsive to the simultaneously emitted background radiation;
• d. first wavelength discriminating means located on said first path between said beam splitting means and said first detector means, and second wavelength discriminating means located on said second path between said beam splitting means and said second detector means, wherein said first wavelength discriminating means allows passage of radiation at the at least one characteristic wavelength and inhibits the passage of other wavelengths, and said second wavelength discriminating means allows passage of the emitted background radiation and inhibits the passage of radiation at the at least one characteristic wavelength;
• and
• e. means connected to said first and second detector means for combining the first and second electrical signals to thereby cause a cancellation of fluctuations in intensity at the at least one characteristic wavelength caused by fluctuations in the background radiation.