Advantages and limitations of thermal lens spectrometry over conventional spectrophotometry for absorbance measurements.

This review considers the advantages and the limitations that thermal lens spectrometry has over conventional spectrophotometry for the measurement of optical absorption in specific applications. The photothermal method is characterized by its intrinsic sensitivity resulting from the indirect nature of the measurement and amplified by physical and thermo-optical parameters which are not effective in absorbance measurements. Other advantages include a weak dependence on light scattering and the complementary nature of photothermal spectra with respect to absorption and emission spectra for speciation studies at very low concentrations. The main drawbacks are the convective noise, the background absorbance and the complexity of the experimental set-up, especially when differential or wavelength scanning measurements are required.