Atomic absorption analyzer compensated for background absorption

Claim 2

A radiant energy analyzer of the type particularly adapted for atomic absorption analysis and compensated for background absorption comprising: the source of primary resonance radiation of an element to be analyzed; a source of auxiliary radiation having a bandwidth that is broad compared to said primary resonance source and which includes radiation at the primary resonance wavelength; a radiant energy detector for producing an electrical signal having an output proportional to the instantaneous intensity impinging thereon; wavelength selection means positioned between said sources and said detector for selecting a narrow band of wavelength including said primary resonance wavelength; mean for directing pulses of radiant energy from said auxiliary radiation source and from said primary resonance source alternately along reference and sample beam paths to said detector whereby said detector produces an electrical output signal having a first component AR proportional to the intensity of auxiliary radiation passing said reference beam path, a second component AS proportional to the intensity of auxiliary radiation passing said sample beam path, a third componenT PR proportional to resonance radiation passing said reference beam path, and a fourth component PS proportional to resonance radiation passing said sample beam path; and electrical circuit means coupled to said detector and producing an electrical signal proportional to log PR - log PS - log AR + log AS whereby said produced electrical signal is proportional to the absorbance of free atoms in the sample beam path having a resonance frequency at the frequency of said resonance wavelength.

Claim 3

A radiant energy analyzer of the type particularly adapted for atomic absorption analysis and compensated for background absorption comprising: a source of primary resonance radiation of an element to be analyzed; a source of auxiliary radiation having a bandwidth that is broad compared to said primary resonance source and which includes radiation at the primary resonance wavelength; a radiant energy detector for producing an electrical signal having an amplitude proportional to the instantaneous intensity impinging thereon; wavelength selection means positioned between said sources and said detector for selecting a narrow band of wavelengths including said primary resonance wavelength; means for directing pulses of radiation from said auxiliary source and from said primary resonance source alternately along reference and sample beam paths to said detector whereby said detector produces an electrical output signal having a first component proportional to the intensity of auxiliary radiation passing said reference beam path, a second component proportional to the intensity of auxiliary radiation passing said sample beam path a third component proportional to resonant radiation passing said reference beam path and a fourth component proportional to resonance radiation passing said sample beam path; first electrical circuit means coupled to said detector and receiving said first and second components and producing a first electrical signal related to background absorptions in said sample beam path in the resonant wavelength region; second electrical circuit means coupled to said detector and receiving said third and fourth components and producing a second electrical signal related to the total absorption in said sample beam path at said resonant wavelength; and third electrical circuit means coupled to said first and second electrical circuit means for producing an electrical output signal related only to the absorption in said sample beam path due to an element to be analyzed.

Claim 4

A radiant energy analyzer of the type particularly adapted for atomic absorption analysis and compensated for background absorption comprising: a source of primary resonance radiation of an element to be analyzed; a source of auxiliary radiation having a bandwidth that is broad compared to said primary resonance source and which includes radiation at the primary resonance wavelength; a radiant energy detector for producing an electrical signal having an amplitude proportional to the instantaneous intensity impinging thereon; wavelength selection means positioned between said sources and said detector for selecting a narrow band of wavelengths including said primary resonance wavelength; means for directing pulses of radiation from said auxiliary source and from said primary resonance source alternately along reference and sample beam paths to said detector whereby said detector produces an electrical output signal having a first component proportional to the intensity of auxiliary radiation passing said reference beam path, a second component proportional to the intensity of auxiliary radiation passing said sample beam path a third component proportional to resonant radiation passing said reference beam path and a fourth component proportional to resonance radiation passing said sample beam path; first electrical circuit means coupled to said detector and receiving said first and second components and producing a first electrical signal related to background absorptions in said sample beam path in the resonant wavelength region; second electrical circuit means coupled to said detector and receiving said third and fourth components and producing a second electrical signal related to the total absorption in said sample beam path at said resonant wavelength; and third electrical circuit means coupled to said first and second electrical circuit means for producing an electrical output signal related only to the absorption in said sample beam path due to an element to be analyzed.

Claim 5

The radiant energy analyzer according to claim 2 wherein said first and second electrical circuit means each include logarithmic amplification means whereby each of said electrical output signal components are converted to logarithmic functions, said first electrical circuit means differencing said first and second components and said second electrical circuit means differencing said third and fourth components.

Claim 6

The radiant energy analyzer according to claim 2 wherein said first and second electrical circuit means each include logarithmic differential amplification means.

Claim 7

A radiant energy analyzer of the type particularly adapted for atomic absorption analysis and compensated for background absorption comprising: a source of primary resonance radiation of an element to be analyzed; a source of auxiliary radiation having a bandwidth that is broad compared to said primary resonance source and which includes radiation at the primary resonant wavelength; a radiant energy detector for producing an electrical signal having an amplitude proportional to the instantaneous intensity impinging thereon; wavelength selection means positioned between said sources and said detector for selecting a narrow band of wavelengths including said primary resonant wavelength; beam modulation means for directing pulses of radiant energy from said auxiliary radiation source and from said primary resonance source alternately Along reference and sample beam paths; beam recombining means for directing radiation from said reference and sample beam paths along a common path to said radiant energy detector whereby said detector produces an electrical output signal having a first component proportional to the intensity of auxiliary radiation passing said reference beam path, a second component proportional to the intensity of auxiliary radiation passing said sample beam path, a third component proportional to resonant radiation passing said reference beam path, and a fourth component proportional to resonant radiation passing said sample beam path; signal demodulation and logarithmic amplification means producing a first electrical signal which is a logarithmic function of said first component, a second electrical signal which is a logarithmic function of said second component, a third electrical signal which is a logarithmic function of said third component and a fourth electrical signal which is a logarithmic function of said fourth component; differential amplifier means connected to said demodulation and logarithmic amplification means for receiving at its input said first and second electrical signals and producing a first difference signal proportional to the difference between said first electrical signal and said second electrical signal; second differential amplifier means connected to said demodulation and logarithmic amplification means and receiving at its inputs said third and fourth electrical signals and producing a second difference signal proportional to the difference between said third electrical signal and said fourth electrical signal; third differential amplifier means connected to said first and second differential amplifier means and receiving at its input said first and second difference signals and producing at its output a signal proportional to the difference between said second differential signal and said first differential signal thereby to produce an output signal proportional to the absorbance of a sample in said sample beam path due to an element to be analyzed; and readout means coupled to said third differential amplifier means to provide a readout of said output signal.

Claim 8

A radiant energy analyzer of the type particularly adapted for atomic absorption analysis and compensated for background absorption comprising: a source of primary resonance radiation of an element to be analyzed; a source of auxiliary radiation having a bandwidth that is broad compared to said primary resonance source and which includes radiation at the primary resonant wavelength; a radiant energy detector for producing an electrical signal having an amplitude proportional to the instantaneous intensity impinging thereon; wavelength selection means positioned between said sources and said detector for selecting a narrow band of wavelengths including said primary resonant wavelength; beam modulation means for directing pulses of radiant energy from said auxiliary radiation source and from said primary resonance source alternately Along reference and sample beam paths; beam recombining means for directing radiation from said reference and sample beam paths along a common path to said radiant energy detector whereby said detector produces an electrical output signal having a first component proportional to the intensity of auxiliary radiation passing said reference beam path, a second component proportional to the intensity of auxiliary radiation passing said sample beam path, a third component proportional to resonant radiation passing said reference beam path, and a fourth component proportional to resonant radiation passing said sample beam path; signal demodulation and logarithmic amplification means producing a first electrical signal which is a logarithmic function of said first component, a second electrical signal which is a logarithmic function of said second component, a third electrical signal which is a logarithmic function of said third component and a fourth electrical signal which is a logarithmic function of said fourth component; differential amplifier means connected to said demodulation and logarithmic amplification means for receiving at its input said first and second electrical signals and producing a first difference signal proportional to the difference between said first electrical signal and said second electrical signal; second differential amplifier means connected to said demodulation and logarithmic amplification means and receiving at its inputs said third and fourth electrical signals and producing a second difference signal proportional to the difference between said third electrical signal and said fourth electrical signal; third differential amplifier means connected to said first and second differential amplifier means and receiving at its input said first and second difference signals and producing at its output a signal proportional to the difference between said second differential signal and said first differential signal thereby to produce an output signal proportional to the absorbance of a sample in said sample beam path due to an element to be analyzed; and readout means coupled to said third differential amplifier means to provide a readout of said output signal.