Sensitivity

Because it is possible to use well established rotational spectroscopy theory to calculate absolute absorption as a function of concentration, it would be possible to establish the sensitivity of the sensor from these calculations and an engineering evaluation of the noise in the system. However, we chose to establish the sensitivity of the system by actual measurement of a dilute sample. Since very dilute samples are difficult to prepare and transport, we chose to look at the deuterium isotope CH₂DCN so that we could take advantage of the isotopic dilution of deuterium.

Figure: Acetonitrile Isotope Spectrum. shows a spectrum of CH₂DCN from which a detection limit of 2 ppt for CH₃CN was derived.