An infrared isotope analyzer

Abstract

The shift in the infrared absorption bands of isotopic molecules is used in a new method for determining the isotope ratios in tracer experiments. The infrared absorption is measured with a non-dispersive filter instrument containing as selective detector a gas cell filled with a concentrated sample of the component to be measured. An instrument is devised according to this method, to measure the 13C/12C ratio in carbon dioxide. It permits the measurement of the 13C abundance in 30 mg carbon dioxide with an error of 0.005 at.% in the neighbourhood of the natural abundance of 1.1 at.%. This precision is sufficient for the majority of tracer experiments. A more detailed account of this study is to be found in the thesis 5) of one of us.