Systems and methods for monitoring relative concentrations of different isotopic forms of a chemical species

A system for monitoring relative concentrations of a chemical species, the system comprising:

• a sample including first and second isotopic forms of the chemical species;
• a source emitting a broad band of electromagnetic radiation including first and second wavelength bands, the first wavelength band corresponding to an absorption band of the first isotope, the second wavelength band corresponding to an absorption band of the second isotope;
• first and second filters for filtering the broad band of radiation emitted by the source to define the first and second wavelength bands;
• a device for modulating the first and second wavelength bands of radiation emitted by the source;
• a waveguide cell defining a sample cell and having a pathlength of from about 30 centimeters to about 100 centimeters and an inner diameter of from about 0.3 millimeters to about 2.0 millimeters;
• and
• a detector for detecting electromagnetic radiation at the first and second wavelengths,
• wherein the system is arranged such that electromagnetic radiation emitted by the source is modulated by the device and filtered by the filters, impinges upon the sample, and at least 10% of the first and second wavelengths of electromagnetic radiation that enters the waveguide cell passes through the waveguide cell and impinges upon the detector.

A method of measuring relative concentrations of a sample including first and second isotopic forms, the method comprising the steps of:

• simultaneously emitting electromagnetic radiation at first and second wavelength bands;
• modulating the first and second wavelength bands of electromagnetic radiation;
• impinging at least a portion of the modulated first and second wavelengths of electromagnetic radiation upon the sample, the first wavelength band corresponding to an absorption band of the first isotopic form, the second wavelength band corresponding to an absorption band of the second isotopic form, the sample being contained within a waveguide cell having a pathlength of from about 30 centimeters to about 100 centimeters and an inner diameter of from about 0.3 millimeters to about 2.0 millimeters and transmitting at least about 10% of the first wavelength band and the second wavelength band of the portion of the electromagnetic radiation that entered the waveguide;
• and
• measuring absorption of the modulated electromagnetic radiation at the first and second wavelength bands by the first and second isotopic forms of the chemical species, respectively.

A system for monitoring relative concentrations of a chemical species, the system comprising:

• a sample including first and second isotopic forms of the chemical species;
• an electromagnetic radiation source emitting first and second wavelength bands, the first wavelength band corresponding to an absorption band of the first isotopic form, the second wavelength band corresponding to an absorption band of the second isotopic form;
• a device for modulating the electromagnetic radiation emitted by the source at the first and second wavelength bands;
• a waveguide defining a sample cell,
• said waveguide having a first window at one end and a second window at the opposite end and a pathlength from about 30 cm to about 100 cm;
• and
• a detector,
• wherein the system is arranged such that at least a portion of the electromagnetic radiation emitted by the source is modulated by the device, enters the waveguide through said first window, impinges upon the sample contained within the waveguide cell, at at least 10% of the first and second wavelength bands of electromagnetic radiation that enters the waveguide is transmitted through the waveguide sample cell and said second window and impinges upon the detector.

A system for monitoring relative concentrations of a chemical species, the system comprising:

• a sample including first and second isotopic forms of the chemical species;
• an electromagnetic radiation source, said source emitting broad band electromagnetic radiation including first and second wavelength bands, the first wavelength band corresponding to an absorption band of the first isotope, the second wavelength band corresponding to an absorption band of the second isotope;
• a first bandpass filter, passing a wavelength band corresponding to said first wavelength band;
• a second bandpass filter, passing a wavelength band corresponding to said second wavelength band;
• a device for modulating the first and second wavelength bands of radiation emitted by the source;
• a waveguide, said waveguide having a path length of about 30 cm to about 100 cm;
• and
• a detector;
• wherein the system is arranged such that at least a portion of electromagnetic radiation emitted by the source is modulated by the device and filtered by the filters, then enters the waveguide and impinges upon the sample, and at least 10% of the first wavelength and second wavelength of the portion of the electromagnetic radiation entering the waveguide are transmitted through the waveguide cell and impinges upon the detector.

A method of measuring relative concentrations of a sample including first and second isotopic forms, the method comprising the steps of:

• introducing said sample into a waveguide sample cell having a pathlength of about 30 cm to about 100 cm;
• simultaneously emitting electromagnetic radiation at first and second wavelength bands;
• modulating the first and second wavelength bands of electromagnetic radiation;
• impinging at least a portion of the modulated first and second wavelengths of electromagnetic radiation upon the sample in said waveguide sample cell, the first wavelength band corresponding to an absorption band of the first isotopic form, the second wavelength band corresponding to an absorption band of the second isotopic form;
• and
• measuring absorption of the modulated electromagnetic radiation at the first and second wavelength bands by the first and second isotopic forms of the chemical species, respectively.