Comparison of Calculated Detection Limits in Molecular Absorption, Molecular Luminescence, Raman, Molecular Ionization, and Photothermal Spectrometry*

Detection limits for absorption, luminescence, photoionization, Raman, and photothermal molecular spectrometric methods are calculated from signal-to-noise expressions. The detection limits (in m −3 ) represent the best possible values by the various methods, since the limiting noises in each case were chosen. Molecular luminescence methods, with laser excitation, approach 1 species/cm 3 . Methods relying upon two (or more) laser wavelengths generally have much poorer detection limits than the simpler single-wavelength methods.