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Abstract: Most analytical applications of thermal lens spectrometry (TLS) and related theoretical models consider absorbance of the sample constant during a single excitation by the pump laser beam. For photolabile analytes intensive excitation light can cause photodegradation, which significantly affects the results of TLS measurements. Theoretical models have been developed to account for changes in concentration and consequent changes in absorbance, caused by chemical reactions of different orders. Furthermore, abnormal TLS signal transients were observed for fast photochemical reactions on millisecond time scale, and the contributions of photodegradation as well as molecular diffusion were analyzed in detail. It has also been demonstrated that such effects can be reduced by performing TLS measurements in flowing systems such as in the case of flow injection analysis (FIA) or microfluidics. These findings were utilized to study the kinetics of chemical reactions, processes such as photostability of the soybean oil and thermal stability of biodiesel, or to improve the sensitivity of TLS detection in case of photolabile analytes. Furthermore, in combination with the concept of biomolecular recognition, FIA-TLS was exploited to study the efficiency of photocatalytic degradation of some neurotoxic substances such as organophosphate insecticides and revealed the formation of even more toxic degradation products. High sensitivity of TLS has enabled discrimination between photocatalytic and photosensitization mechanisms in photocatalytic degradation of textile dyes as well as between photodegradation and photocatalysis as will be demonstrated by the results of latest research in this field.
Keywords: Spektrometrija TLS, fotolabilnost, CrIVI), fotokataliza, fotorazgradnja
Published in RUNG: 23.10.2023; Views: 1311; Downloads: 0
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