Sources of errors in the use of calorimetric references for photothermal spectroscopic methods

The measurement of absolute quantities, such as fluorescence quantum yields, by laser photothermal spectroscopy requires the use of reference compounds in order to determine the relationship between the signal and the amount of thermal energy released. Care has to be taken to avoid errors which may arise when the sample signal is compared to the reference signal. Differences in the amount of energy absorbed can originate from absorbance mismatches when the sample and the reference compounds exhibit different absorption features and from optical saturation. Errors can also occur from variations in the thermo-optical properties of the solvent when internal references based on quenching reactions are used instead of external references.