Infrared spectrometer for the measurement of isotopic ratios

摘要

An infrared spectrometer for the determination of isotopic ratios of gaseous compounds includes a broad-band infrared light source, a spectral selector, a sample compartment, an infrared detector, and a processor. The spectral selector selectively transmits a wavelength window of infrared light covering a range of wavelengths in which the wavelength window can be selected alternatively to overlap with a wavelength range primarily absorbed by a compound with a first isotope or by the compound with a second isotope. The sample compartment holds a gas sample and includes a gas inlet and a gas outlet. The infrared spectrometer can be used to detect isotopic ratios of carbon dioxide, where enhancement of ¹³CO₂ can indicate metabolic activity of an infection, for example by H. pylori, or of specific enzymes. Preferred embodiments use a particular multipass optical cell that includes a field mirror and a multi-segment objective mirror.