System and method for optically monitoring the concentration of a gas in a sample vial using photothermal spectroscopy to detect sample growth

Abstract

A system and method for monitoring the concentration of a medium in at least one container using photothermal spectroscopy. The medium can be a gas, such as oxygen or carbon dioxide, or a solid or liquid. The system and method each employs an energy emitting device, such as a laser or any other suitable type of light emitting device, which is adapted to emit a first energy signal toward a location in the container. The first energy signal has a wavelength that is substantially equal to a wavelength at which the medium absorbs the first energy signal so that absorption of the first energy signal changes a refractive index of a portion of the medium. The system and method each also employs a second energy emitting device, adapted to emit a second energy signal toward the portion of the medium while the refractive index of the portion is changed by the first energy signal, and a detector, adapted to detect a portion of the second energy signal that passes through the portion of the medium. The system and method each further employs a signal analyzer, adapted to analyze the detected portion of the second energy signal to determine an amount of a sample in the container based on a concentration of the medium in the container. In particular, the signal analyzer can analyze the detection portion of the second energy signal to determine whether the sample includes an organism which consumes or emits the medium.

What is claimed is:  
     
         1 . A system for monitoring the concentration of a medium in at least one container, comprising: 
 an energy emitting device, adapted to emit a first energy signal toward a location in said container, said first energy signal having a wavelength that is substantially equal to a wavelength at which said medium absorbs said first energy signal so that absorption of said first energy signal changes a refractive index of a portion of said medium or an adjoining medium;    a second energy emitting device, adapted to emit a second energy signal toward said portion of said medium while said refractive index of said portion of said medium is changed by said first energy signal; and    a detector, adapted to detect a portion of said second energy signal that passes through said portion of said medium.    
     
     
         2 . A system as claimed in  claim 1 , further comprising: 
 a signal analyzer, adapted to analyze said detected portion of said second energy signal to determine an amount of a sample in said container based on a concentration of said medium in said container.    
     
     
         3 . A system as claimed in  claim 1 , wherein: 
 said medium or adjoining medium includes a gas; and    said first energy emitting device is adapted to emit said first energy signal at said wavelength at which said gas absorbs said first energy signal.    
     
     
         4 . A system as claimed in  claim 1 , wherein: 
 said medium or adjoining medium includes a liquid; and    said first energy emitting device is adapted to emit said first energy signal at said wavelength at which said liquid absorbs said first energy signal.    
     
     
         5 . A system as claimed in  claim 1 , wherein: 
 said medium or adjoining medium includes a solid; and    said first energy emitting device is adapted to emit said first energy signal at said wavelength at which said solid absorbs said first energy signal.    
     
     
         6 . A system as claimed in  claim 1 , wherein: 
 said medium includes oxygen; and    said first energy emitting device is adapted to emit said first energy signal at said wavelength at which oxygen absorbs said first energy signal.    
     
     
         7 . A system as claimed in  claim 1 , wherein: 
 said medium includes carbon dioxide; and    said first energy emitting device is adapted to emit said first energy signal at said wavelength at which carbon dioxide absorbs said first energy signal.    
     
     
         8 . A system as claimed in  claim 1 , wherein: 
 said medium includes one of NH 3 , H 2 S, CH 4  or SO 2 ; and    said first energy emitting device is adapted to emit said first energy signal at said wavelength at which said one of NH 3 , H 2 S, CH 4  or SO 2  absorbs said first energy signal.    
     
     
         9 . A system as claimed in  claim 1 , wherein: 
 said first energy emitting device includes a laser which is adapted to emit laser light as said first energy signal.    
     
     
         10 . A system as claimed in  claim 1 , wherein: 
 said second energy emitting device includes a laser which is adapted to emit laser light as said second energy signal.    
     
     
         11 . A method for monitoring the concentration of a medium in at least one container, comprising: 
 emitting a first energy signal toward a location in said container, said first energy signal having a wavelength that is substantially equal to a wavelength at which said medium absorbs said first energy signal so that absorption of said first energy signal changes a refractive index of a portion of said medium or an adjoining medium;    emitting a second energy signal toward said portion of said medium or adjoining medium while said refractive index of said portion of said medium is changed by said first energy signal; and    detecting a portion of said second energy signal that passes through said portion of said medium or adjoining medium.    
     
     
         12 . A method as claimed in  claim 11 , further comprising: 
 analyzing said detected portion of said second energy signal to determine an amount of a sample in said container based on a concentration of said medium in said container.    
     
     
         13 . A method as claimed in  claim 11 , wherein: 
 said medium includes a gas; and    said first energy signal is emitted at said wavelength at which said gas absorbs said first energy signal.    
     
     
         14 . A method as claimed in  claim 11 , wherein: 
 said medium includes a liquid; and    said first energy signal is emitted at said wavelength at which said liquid absorbs said first energy signal.    
     
     
         15 . A method as claimed in  claim 11 , wherein: 
 said medium includes a solid; and    said first energy signal is emitted at said wavelength at which said solid absorbs said first energy signal.    
     
     
         16 . A method as claimed in  claim 11 , wherein: 
 said medium includes oxygen; and    said first energy signal is emitted at said wavelength at which oxygen absorbs said first energy signal.    
     
     
         17 . A method as claimed in  claim 11 , wherein: 
 said medium includes carbon dioxide; and    said first energy signal is emitted at said wavelength at which carbon dioxide absorbs said first energy signal.    
     
     
         18 . A method as claimed in  claim 11 , wherein: 
 said medium includes one of NH 3 , H 2 S, CH 4  or SO 2 ; and    said first energy signal is emitted at said wavelength at which said one of NH 3 , H 2 S, CH 4  or SO 2  absorbs said first energy signal.    
     
     
         19 . A method as claimed in  claim 11 , wherein: 
 said first energy emitting step includes energizing a laser to emit laser light as said first energy signal.    
     
     
         20 . A method as claimed in  claim 11 , wherein: 
 said second energy emitting step includes energizing a laser to emit laser light as said second energy signal.