Measurements of Carbon-14 With Cavity Ring-Down Spectroscopy

Accelerator Mass Spectrometry (AMS) is the most sensitive method for quantitation of ¹⁴C in biological samples. This technology has been used in a variety of low dose, human health related studies over the last 20 years when very high sensitivity was needed. AMS helped pioneer these scientific methods, but its expensive facilities and requirements for highly trained technical staff have limited their proliferation. Quantification of ¹⁴C by cavity ring-down spectroscopy (CRDS) offers an approach that eliminates many of the shortcomings of an accelerator-based system and would supplement the use of AMS in biomedical research. Our initial prototype, using a non-ideal wavelength laser and under suboptimal experimental conditions, has a 3.5-modern, 1-σ precision for detection of milligram-sized, carbon-14-elevated samples. These results demonstrate proof of principle and provided a starting point for the development of a spectrometer capable of biologically relevant sensitivities.