SOURCES OF ERRORS IN THE USE OF CALORIMETRIC REFERENCES FOR PHOTOTHERMAL SPECTROSCOPIC METHODS

The measurement of absolute quantities, such as fluorescence quantum y ields, by laser photothermal spectroscopy requires the use of referenc e compounds in order to determine the relationship between the signal and the amount of thermal energy released. Care has to be taken to avo id errors which may arise when the sample signal is compared to the re ference signal. Differences in the amount of energy absorbed can origi nate from absorbance mismatches when the sample and the reference comp ounds exhibit different absorption features and from optical saturatio n. Errors can also occur from variations in the thermo-optical propert ies of the solvent when internal references based on quenching reactio ns are used instead of external references.